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Segment Anything Model (#552)

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* add segment anything model

* add readme

* reorg file structure

* update

* lint

* minor updates

* ack

* fix weight loading

* simplify

* fix to run notebooks

* amg in mlx

* remove torch dependency

* nit in README

* return indices in nms

* simplify

* bugfix / simplify

* fix bug'

* simplify

* fix notebook and remove output

* couple more nits

---------

Co-authored-by: Awni Hannun <awni@apple.com>
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1
ACKNOWLEDGMENTS.md
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@ -13,3 +13,4 @@ MLX Examples was developed with contributions from the following individuals:
- Gabrijel Boduljak: Implemented `CLIP`. - Gabrijel Boduljak: Implemented `CLIP`.
- Markus Enzweiler: Added the `cvae` examples. - Markus Enzweiler: Added the `cvae` examples.
- Prince Canuma: Helped add support for `Starcoder2` models. - Prince Canuma: Helped add support for `Starcoder2` models.
- Shiyu Li: Added the `Segment Anything Model`.

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# Segment Anything
An implementation of the Segment Anything Model (SAM) in MLX. See the original
repo by Meta AI for more details.[^1]
## Installation
```bash
pip install -r requirements.txt
```
## Convert
```bash
python convert.py --hf-path facebook/sam-vit-base --mlx-path sam-vit-base
```
The `safetensors` weight file and configs are downloaded from Hugging Face,
converted, and saved in the directory specified by `--mlx-path`.
The model sizes are:
- `facebook/sam-vit-base`
- `facebook/sam-vit-large`
- `facebook/sam-vit-huge`
## Run
See examples `notebooks/predictor_example.ipynb` and
`notebooks/automatic_mask_generator_example.ipynb` to try the Segment Anything
Model with MLX.
You can also generate masks from the command line:
```bash
python main.py --model <path/to/model> --input <image_or_folder> --output <path/to/output>
```
[^1]: The original Segment Anything [GitHub repo](https://github.com/facebookresearch/segment-anything/tree/main).

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import argparse
import json
import shutil
from pathlib import Path
from typing import Dict, Union
import mlx.core as mx
from huggingface_hub import snapshot_download
def save_weights(save_path: Union[str, Path], weights: Dict[str, mx.array]) -> None:
"""Save model weights into specified directory."""
if isinstance(save_path, str):
save_path = Path(save_path)
save_path.mkdir(parents=True, exist_ok=True)
total_size = sum(v.nbytes for v in weights.values())
index_data = {"metadata": {"total_size": total_size}, "weight_map": {}}
model_path = save_path / "model.safetensors"
mx.save_safetensors(str(model_path), weights)
for weight_name in weights.keys():
index_data["weight_map"][weight_name] = "model.safetensors"
index_data["weight_map"] = {
k: index_data["weight_map"][k] for k in sorted(index_data["weight_map"])
}
with open(save_path / "model.safetensors.index.json", "w") as f:
json.dump(index_data, f, indent=4)
def download(hf_repo):
return Path(
snapshot_download(
repo_id=hf_repo,
allow_patterns=["*.safetensors", "*.json"],
resume_download=True,
)
)
def convert(model_path):
weight_file = str(model_path / "model.safetensors")
weights = mx.load(weight_file)
mlx_weights = dict()
for k, v in weights.items():
if k in {
"vision_encoder.patch_embed.projection.weight",
"vision_encoder.neck.conv1.weight",
"vision_encoder.neck.conv2.weight",
"prompt_encoder.mask_embed.conv1.weight",
"prompt_encoder.mask_embed.conv2.weight",
"prompt_encoder.mask_embed.conv3.weight",
}:
v = v.transpose(0, 2, 3, 1)
if k in {
"mask_decoder.upscale_conv1.weight",
"mask_decoder.upscale_conv2.weight",
}:
v = v.transpose(1, 2, 3, 0)
mlx_weights[k] = v
return mlx_weights
if __name__ == "__main__":
parser = argparse.ArgumentParser(description="Convert Meta SAM weights to MLX")
parser.add_argument(
"--hf-path",
default="facebook/sam-vit-base",
type=str,
help="Path to the Hugging Face model repo.",
)
parser.add_argument(
"--mlx-path",
type=str,
default="sam-vit-base",
help="Path to save the MLX model.",
)
args = parser.parse_args()
model_path = download(args.hf_path)
mlx_path = Path(args.mlx_path)
mlx_path.mkdir(parents=True, exist_ok=True)
mlx_weights = convert(model_path)
save_weights(mlx_path, mlx_weights)
shutil.copy(model_path / "config.json", mlx_path / "config.json")

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import argparse
import json
import os
import sys
from typing import Any, Dict, List
import cv2
from segment_anything import SamAutomaticMaskGenerator, sam
parser = argparse.ArgumentParser(
description=(
"Runs automatic mask generation on an input image or directory of images, "
"and outputs masks as either PNGs or COCO-style RLEs. Requires open-cv, "
"as well as pycocotools if saving in RLE format."
)
)
parser.add_argument(
"--input",
type=str,
required=True,
help="Path to either a single input image or folder of images.",
)
parser.add_argument(
"--output",
type=str,
required=True,
help=(
"Path to the directory where masks will be output. Output will be either a folder "
"of PNGs per image or a single json with COCO-style masks."
),
)
parser.add_argument(
"--model",
type=str,
required=True,
help="The path to the SAM model to use for mask generation.",
)
parser.add_argument(
"--convert-to-rle",
action="store_true",
help=(
"Save masks as COCO RLEs in a single json instead of as a folder of PNGs. "
"Requires pycocotools."
),
)
amg_settings = parser.add_argument_group("AMG Settings")
amg_settings.add_argument(
"--points-per-side",
type=int,
default=None,
help="Generate masks by sampling a grid over the image with this many points to a side.",
)
amg_settings.add_argument(
"--points-per-batch",
type=int,
default=None,
help="How many input points to process simultaneously in one batch.",
)
amg_settings.add_argument(
"--pred-iou-thresh",
type=float,
default=None,
help="Exclude masks with a predicted score from the model that is lower than this threshold.",
)
amg_settings.add_argument(
"--stability-score-thresh",
type=float,
default=None,
help="Exclude masks with a stability score lower than this threshold.",
)
amg_settings.add_argument(
"--stability-score-offset",
type=float,
default=None,
help="Larger values perturb the mask more when measuring stability score.",
)
amg_settings.add_argument(
"--box-nms-thresh",
type=float,
default=None,
help="The overlap threshold for excluding a duplicate mask.",
)
amg_settings.add_argument(
"--crop-n-layers",
type=int,
default=None,
help=(
"If >0, mask generation is run on smaller crops of the image to generate more masks. "
"The value sets how many different scales to crop at."
),
)
amg_settings.add_argument(
"--crop-nms-thresh",
type=float,
default=None,
help="The overlap threshold for excluding duplicate masks across different crops.",
)
amg_settings.add_argument(
"--crop-overlap-ratio",
type=int,
default=None,
help="Larger numbers mean image crops will overlap more.",
)
amg_settings.add_argument(
"--crop-n-points-downscale-factor",
type=int,
default=None,
help="The number of points-per-side in each layer of crop is reduced by this factor.",
)
amg_settings.add_argument(
"--min-mask-region-area",
type=int,
default=None,
help=(
"Disconnected mask regions or holes with area smaller than this value "
"in pixels are removed by postprocessing."
),
)
def write_masks_to_folder(masks: List[Dict[str, Any]], path: str) -> None:
header = "id,area,bbox_x0,bbox_y0,bbox_w,bbox_h,point_input_x,point_input_y,predicted_iou,stability_score,crop_box_x0,crop_box_y0,crop_box_w,crop_box_h" # noqa
metadata = [header]
for i, mask_data in enumerate(masks):
mask = mask_data["segmentation"]
filename = f"{i}.png"
cv2.imwrite(os.path.join(path, filename), mask * 255)
mask_metadata = [
str(i),
str(mask_data["area"]),
*[str(x) for x in mask_data["bbox"]],
*[str(x) for x in mask_data["point_coords"][0]],
str(mask_data["predicted_iou"]),
str(mask_data["stability_score"]),
*[str(x) for x in mask_data["crop_box"]],
]
row = ",".join(mask_metadata)
metadata.append(row)
metadata_path = os.path.join(path, "metadata.csv")
with open(metadata_path, "w") as f:
f.write("\n".join(metadata))
return
def get_amg_kwargs(args):
amg_kwargs = {
"points_per_side": args.points_per_side,
"points_per_batch": args.points_per_batch,
"pred_iou_thresh": args.pred_iou_thresh,
"stability_score_thresh": args.stability_score_thresh,
"stability_score_offset": args.stability_score_offset,
"box_nms_thresh": args.box_nms_thresh,
"crop_n_layers": args.crop_n_layers,
"crop_nms_thresh": args.crop_nms_thresh,
"crop_overlap_ratio": args.crop_overlap_ratio,
"crop_n_points_downscale_factor": args.crop_n_points_downscale_factor,
"min_mask_region_area": args.min_mask_region_area,
}
amg_kwargs = {k: v for k, v in amg_kwargs.items() if v is not None}
return amg_kwargs
def main(args: argparse.Namespace) -> None:
print("Loading model...")
model = sam.load(args.model)
output_mode = "coco_rle" if args.convert_to_rle else "binary_mask"
amg_kwargs = get_amg_kwargs(args)
generator = SamAutomaticMaskGenerator(model, output_mode=output_mode, **amg_kwargs)
if not os.path.isdir(args.input):
targets = [args.input]
else:
targets = [
f
for f in os.listdir(args.input)
if not os.path.isdir(os.path.join(args.input, f))
]
targets = [os.path.join(args.input, f) for f in targets]
os.makedirs(args.output, exist_ok=True)
for t in targets:
print(f"Processing '{t}'...")
image = cv2.imread(t)
if image is None:
print(f"Could not load '{t}' as an image, skipping...")
continue
image = cv2.cvtColor(image, cv2.COLOR_BGR2RGB)
masks = generator.generate(image)
base = os.path.basename(t)
base = os.path.splitext(base)[0]
save_base = os.path.join(args.output, base)
if output_mode == "binary_mask":
os.makedirs(save_base, exist_ok=False)
write_masks_to_folder(masks, save_base)
else:
save_file = save_base + ".json"
with open(save_file, "w") as f:
json.dump(masks, f)
print("Done!")
if __name__ == "__main__":
args = parser.parse_args()
main(args)

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{
"cells": [
{
"cell_type": "markdown",
"metadata": {},
"source": [
"# Automatically generating object masks with SAM"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"This notebook walks through how to automatically segment objects in an image. It is modified from [original SAM GitHub repo](https://github.com/facebookresearch/segment-anything/).\n",
"\n",
"Since SAM can efficiently process prompts, masks for the entire image can be generated by sampling a large number of prompts over an image. This method was used to generate the dataset SA-1B. \n",
"\n",
"The class `SamAutomaticMaskGenerator` implements this. It samples single-point input prompts in a grid over the image, from each of which SAM then predicts multiple masks. The masks are filtered for quality and deduplicated using non-max suppression. Additional options allow for further improvement of mask quality and quantity, such as running prediction on multiple crops of the image or postprocessing masks to remove small disconnected regions and holes."
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Set-up"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"import numpy as np\n",
"import matplotlib.pyplot as plt\n",
"import cv2"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"def show_anns(anns):\n",
" if len(anns) == 0:\n",
" return\n",
" sorted_anns = sorted(anns, key=(lambda x: x['area']), reverse=True)\n",
" ax = plt.gca()\n",
" ax.set_autoscale_on(False)\n",
"\n",
" img = np.ones((sorted_anns[0]['segmentation'].shape[0], sorted_anns[0]['segmentation'].shape[1], 4))\n",
" img[:,:,3] = 0\n",
" for ann in sorted_anns:\n",
" m = ann['segmentation']\n",
" color_mask = np.concatenate([np.random.random(3), [0.35]])\n",
" img[m] = color_mask\n",
" ax.imshow(img)"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Example image"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"image = cv2.imread('images/dog.jpg')\n",
"image = cv2.cvtColor(image, cv2.COLOR_BGR2RGB)"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"plt.figure(figsize=(20,20))\n",
"plt.imshow(image)\n",
"plt.axis('off')\n",
"plt.show()"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Automatic mask generation"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"To run automatic mask generation, provide a SAM model to the `SamAutomaticMaskGenerator` class. Set the path below to the SAM checkpoint."
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"import sys\n",
"sys.path.append(\"..\")\n",
"from segment_anything import SamAutomaticMaskGenerator\n",
"from segment_anything.sam import load\n",
"\n",
"sam_checkpoint = \"../sam-vit-base\"\n",
"sam = load(sam_checkpoint)\n",
"\n",
"mask_generator = SamAutomaticMaskGenerator(sam)"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"To generate masks, run `generate` on an image."
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"masks = mask_generator.generate(image)"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Mask generation returns a list over masks. Each item is a dictionary with keys:\n",
"* `segmentation` : the mask\n",
"* `area` : the area of the mask in pixels\n",
"* `bbox` : the boundary box of the mask in XYWH format\n",
"* `predicted_iou` : the model's own prediction for the quality of the mask\n",
"* `point_coords` : the sampled input point that generated this mask\n",
"* `stability_score` : an additional measure of mask quality\n",
"* `crop_box` : the crop of the image used to generate this mask in XYWH format"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"print(len(masks))\n",
"print(masks[0].keys())"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Show all the masks overlayed on the image."
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"plt.figure(figsize=(20,20))\n",
"plt.imshow(image)\n",
"show_anns(masks)\n",
"plt.axis('off')\n",
"plt.show() "
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Automatic mask generation options"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"There are several tunable parameters in automatic mask generation that control how densely points are sampled and what the thresholds are for removing low quality or duplicate masks. Generation can be automatically run on crops of the image to get better results for smaller objects. Post-processing can remove stray pixels and holes. Here is an example configuration that samples more masks:"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"mask_generator_2 = SamAutomaticMaskGenerator(\n",
" model=sam,\n",
" points_per_side=32,\n",
" pred_iou_thresh=0.86,\n",
" stability_score_thresh=0.92,\n",
" crop_n_layers=1,\n",
" crop_n_points_downscale_factor=2,\n",
" min_mask_region_area=100, # Requires open-cv to run post-processing\n",
")"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"masks2 = mask_generator_2.generate(image)\n",
"len(masks2)"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"plt.figure(figsize=(20,20))\n",
"plt.imshow(image)\n",
"show_anns(masks2)\n",
"plt.axis('off')\n",
"plt.show() "
]
}
],
"metadata": {
"kernelspec": {
"display_name": "Python 3 (ipykernel)",
"language": "python",
"name": "python3"
},
"language_info": {
"codemirror_mode": {
"name": "ipython",
"version": 3
},
"file_extension": ".py",
"mimetype": "text/x-python",
"name": "python",
"nbconvert_exporter": "python",
"pygments_lexer": "ipython3",
"version": "3.9.17"
}
},
"nbformat": 4,
"nbformat_minor": 2
}

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{
"cells": [
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Segmenting from Prompts\n",
"\n",
"This notebook walks through predicting object segmentations from a provided prompt. It uses the `Predictor` class. It is modified from [original SAM GitHub repo](https://github.com/facebookresearch/segment-anything/).\n",
"\n",
"### Setup\n",
"Necessary imports and helper functions for displaying points, boxes, and masks."
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"import cv2\n",
"import matplotlib.pyplot as plt\n",
"import mlx.core as mx\n",
"import numpy as np"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"def show_mask(mask, ax, random_color=False):\n",
" if random_color:\n",
" color = np.concatenate([np.random.random(3), np.array([0.6])], axis=0)\n",
" else:\n",
" color = np.array([30/255, 144/255, 255/255, 0.6])\n",
" h, w = mask.shape[:2]\n",
" mask_image = np.array(mask).reshape(h, w, 1) * color.reshape(1, 1, -1)\n",
" ax.imshow(mask_image)\n",
" \n",
"def show_points(coords, labels, ax, marker_size=375):\n",
" pos_points = np.array(coords)[labels==1]\n",
" neg_points = np.array(coords)[labels==0]\n",
" ax.scatter(pos_points[:, 0], pos_points[:, 1], color='green', marker='*', s=marker_size, edgecolor='white', linewidth=1.25)\n",
" ax.scatter(neg_points[:, 0], neg_points[:, 1], color='red', marker='*', s=marker_size, edgecolor='white', linewidth=1.25) \n",
" \n",
"def show_box(box, ax):\n",
" box = box.tolist()\n",
" x0, y0 = box[0], box[1]\n",
" w, h = box[2] - box[0], box[3] - box[1]\n",
" ax.add_patch(plt.Rectangle((x0, y0), w, h, edgecolor='green', facecolor=(0,0,0,0), lw=2)) "
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Example image"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"image = cv2.imread('images/truck.jpg')\n",
"image = cv2.cvtColor(image, cv2.COLOR_BGR2RGB)"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"plt.figure(figsize=(10,10))\n",
"plt.imshow(image)\n",
"plt.axis('on')\n",
"plt.show()"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Selecting objects with SAM"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"First, load the SAM model and predictor. Change the path below to point to the SAM checkpoint."
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"import sys\n",
"sys.path.append(\"..\")\n",
"from segment_anything.sam import load\n",
"from segment_anything.predictor import SamPredictor\n",
"\n",
"sam_checkpoint = \"../sam-vit-base\"\n",
"sam = load(sam_checkpoint)\n",
"predictor = SamPredictor(sam)"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Process the image to produce an image embedding by calling `SamPredictor.set_image`. `SamPredictor` remembers this embedding and will use it for subsequent mask prediction."
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"predictor.set_image(image)"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"To select the truck, choose a point on it. Points are input to the model in (x,y) format and come with labels 1 (foreground point) or 0 (background point). Multiple points can be input; here we use only one. The chosen point will be shown as a star on the image."
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"input_point = mx.array([[500, 375]])\n",
"input_label = mx.array([1])"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"plt.figure(figsize=(10,10))\n",
"plt.imshow(image)\n",
"show_points(input_point, input_label, plt.gca())\n",
"plt.axis('on')\n",
"plt.show() "
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Predict with `SamPredictor.predict`. The model returns masks, quality predictions for those masks, and low resolution mask logits that can be passed to the next iteration of prediction."
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"masks, scores, logits = predictor.predict(\n",
" point_coords=input_point[None],\n",
" point_labels=input_label[None],\n",
" multimask_output=True,\n",
")"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"With `multimask_output=True` (the default setting), SAM outputs 3 masks, where `scores` gives the model's own estimation of the quality of these masks. This setting is intended for ambiguous input prompts, and helps the model disambiguate different objects consistent with the prompt. When `False`, it will return a single mask. For ambiguous prompts such as a single point, it is recommended to use `multimask_output=True` even if only a single mask is desired; the best single mask can be chosen by picking the one with the highest score returned in `scores`. This will often result in a better mask."
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"for i in range(masks.shape[-1]):\n",
" mask = masks[..., i]\n",
" score = scores[..., i].item()\n",
" plt.figure(figsize=(10,10))\n",
" plt.imshow(image)\n",
" show_mask(mask[0], plt.gca())\n",
" show_points(input_point, input_label, plt.gca())\n",
" plt.title(f\"Mask {i+1}, Score: {score:.3f}\", fontsize=18)\n",
" plt.axis('off')\n",
" plt.show() "
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Specifying a specific object with additional points"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"The single input point is ambiguous, and the model has returned multiple objects consistent with it. To obtain a single object, multiple points can be provided. If available, a mask from a previous iteration can also be supplied to the model to aid in prediction. When specifying a single object with multiple prompts, a single mask can be requested by setting `multimask_output=False`."
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"input_point = mx.array([[500, 375], [1125, 625]])\n",
"input_label = mx.array([1, 1])\n",
"mask_input = logits[..., mx.argmax(scores)] # Choose the model's best mask"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"masks, _, _ = predictor.predict(\n",
" point_coords=input_point[None],\n",
" point_labels=input_label[None],\n",
" mask_input=mask_input[..., None],\n",
" multimask_output=False,\n",
")"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"plt.figure(figsize=(10,10))\n",
"plt.imshow(image)\n",
"show_mask(masks[0], plt.gca())\n",
"show_points(input_point, input_label, plt.gca())\n",
"plt.axis('off')\n",
"plt.show() "
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"To exclude the car and specify just the window, a background point (with label 0, here shown in red) can be supplied."
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"input_point = mx.array([[500, 375], [1125, 625]])\n",
"input_label = mx.array([1, 0])\n",
"mask_input = logits[..., mx.argmax(scores)] # Choose the model's best mask"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"masks, _, _ = predictor.predict(\n",
" point_coords=input_point[None],\n",
" point_labels=input_label[None],\n",
" mask_input=mask_input[..., None],\n",
" multimask_output=False,\n",
")"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"plt.figure(figsize=(10, 10))\n",
"plt.imshow(image)\n",
"show_mask(masks[0], plt.gca())\n",
"show_points(input_point, input_label, plt.gca())\n",
"plt.axis('off')\n",
"plt.show() "
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Specifying a specific object with a box"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"The model can also take a box as input, provided in xyxy format."
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"input_box = mx.array([425, 600, 700, 875])"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"masks, _, _ = predictor.predict(\n",
" point_coords=None,\n",
" point_labels=None,\n",
" box=input_box[None, :],\n",
" multimask_output=False,\n",
")"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"plt.figure(figsize=(10, 10))\n",
"plt.imshow(image)\n",
"show_mask(masks[0, ..., 0], plt.gca())\n",
"show_box(input_box, plt.gca())\n",
"plt.axis('off')\n",
"plt.show()"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Combining points and boxes"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Points and boxes may be combined, just by including both types of prompts to the predictor. Here this can be used to select just the trucks's tire, instead of the entire wheel."
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"input_box = mx.array([425, 600, 700, 875])\n",
"input_point = mx.array([[575, 750]])\n",
"input_label = mx.array([0])"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"masks, _, _ = predictor.predict(\n",
" point_coords=input_point[None],\n",
" point_labels=input_label[None],\n",
" box=input_box,\n",
" multimask_output=False,\n",
")"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"plt.figure(figsize=(10, 10))\n",
"plt.imshow(image)\n",
"show_mask(masks[0, ..., 0], plt.gca())\n",
"show_box(input_box, plt.gca())\n",
"show_points(input_point, input_label, plt.gca())\n",
"plt.axis('off')\n",
"plt.show()"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Batched prompt inputs"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"`SamPredictor` can take multiple input prompts for the same image."
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"input_boxes = mx.array([\n",
" [75, 275, 1725, 850],\n",
" [425, 600, 700, 875],\n",
" [1375, 550, 1650, 800],\n",
" [1240, 675, 1400, 750],\n",
"])"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"masks, _, _ = predictor.predict(\n",
" point_coords=None,\n",
" point_labels=None,\n",
" box=input_boxes,\n",
" multimask_output=False,\n",
")"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"plt.figure(figsize=(10, 10))\n",
"plt.imshow(image)\n",
"for mask in masks:\n",
" show_mask(mask, plt.gca(), random_color=True)\n",
"for box in input_boxes:\n",
" show_box(box, plt.gca())\n",
"plt.axis('off')\n",
"plt.show()"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## End-to-end batched inference"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"If all prompts are available in advance, it is possible to run SAM directly in an end-to-end fashion. This also allows batching over images."
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"image1 = image # truck.jpg from above\n",
"image1_boxes = mx.array([\n",
" [75, 275, 1725, 850],\n",
" [425, 600, 700, 875],\n",
" [1375, 550, 1650, 800],\n",
" [1240, 675, 1400, 750],\n",
"])\n",
"\n",
"image2 = cv2.imread('images/groceries.jpg')\n",
"image2 = cv2.cvtColor(image2, cv2.COLOR_BGR2RGB)\n",
"image2_boxes = mx.array([\n",
" [450, 170, 520, 350],\n",
" [350, 190, 450, 350],\n",
" [500, 170, 580, 350],\n",
" [580, 170, 640, 350],\n",
"])"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Both images and prompts are input as mlx array that are already transformed to the correct frame. Inputs are packaged as a list over images, which each element is a dict that takes the following keys:\n",
"* `image`: The input image as a mlx array in HWC format.\n",
"* `original_size`: The size of the image before transforming for input to SAM, in (H, W) format.\n",
"* `point_coords`: Batched coordinates of point prompts.\n",
"* `point_labels`: Batched labels of point prompts.\n",
"* `boxes`: Batched input boxes.\n",
"* `mask_inputs`: Batched input masks.\n",
"\n",
"If a prompt is not present, the key can be excluded."
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"from segment_anything.utils.transforms import ResizeLongestSide\n",
"resize_transform = ResizeLongestSide(sam.vision_encoder.img_size)\n",
"\n",
"def prepare_image(image, transform, device):\n",
" image = transform.apply_image(image)\n",
" image = mx.array(image)\n",
" return image"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"batched_input = [\n",
" {\n",
" 'image': prepare_image(image1, resize_transform, sam),\n",
" 'boxes': resize_transform.apply_boxes(image1_boxes, image1.shape[:2]),\n",
" 'original_size': image1.shape[:2]\n",
" },\n",
" {\n",
" 'image': prepare_image(image2, resize_transform, sam),\n",
" 'boxes': resize_transform.apply_boxes(image2_boxes, image2.shape[:2]),\n",
" 'original_size': image2.shape[:2]\n",
" }\n",
"]"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Run the model."
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"batched_output = sam(batched_input, multimask_output=False)"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"The output is a list over results for each input image, where list elements are dictionaries with the following keys:\n",
"* `masks`: A batched mlx array of predicted binary masks, the size of the original image.\n",
"* `iou_predictions`: The model's prediction of the quality for each mask.\n",
"* `low_res_logits`: Low res logits for each mask, which can be passed back to the model as mask input on a later iteration."
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"fig, ax = plt.subplots(1, 2, figsize=(20, 20))\n",
"\n",
"ax[0].imshow(image1)\n",
"for mask in batched_output[0]['masks']:\n",
" show_mask(np.array(mask), ax[0], random_color=True)\n",
"for box in image1_boxes:\n",
" show_box(np.array(box), ax[0])\n",
"ax[0].axis('off')\n",
"\n",
"ax[1].imshow(image2)\n",
"for mask in batched_output[1]['masks']:\n",
" show_mask(np.array(mask), ax[1], random_color=True)\n",
"for box in image2_boxes:\n",
" show_box(np.array(box), ax[1])\n",
"ax[1].axis('off')\n",
"\n",
"plt.tight_layout()\n",
"plt.show()"
]
}
],
"metadata": {
"kernelspec": {
"display_name": "Python 3 (ipykernel)",
"language": "python",
"name": "python3"
},
"language_info": {
"codemirror_mode": {
"name": "ipython",
"version": 3
},
"file_extension": ".py",
"mimetype": "text/x-python",
"name": "python",
"nbconvert_exporter": "python",
"pygments_lexer": "ipython3",
"version": "3.9.17"
}
},
"nbformat": 4,
"nbformat_minor": 2
}

3
segment_anything/requirements.txt Normal file
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matplotlib
opencv-python
huggingface_hub

1
segment_anything/segment_anything/__init__.py Normal file
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from .automatic_mask_generator import SamAutomaticMaskGenerator

425
segment_anything/segment_anything/automatic_mask_generator.py Normal file
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from typing import Any, Dict, List, Optional, Tuple
import mlx.core as mx
import numpy as np
from .predictor import SamPredictor
from .sam import Sam
from .utils.amg import (
MaskData,
area_from_rle,
batch_iterator,
batched_mask_to_box,
box_xyxy_to_xywh,
build_all_layer_point_grids,
calculate_stability_score,
coco_encode_rle,
generate_crop_boxes,
is_box_near_crop_edge,
mask_to_rle_mlx,
remove_small_regions,
rle_to_mask,
uncrop_boxes_xyxy,
uncrop_masks,
uncrop_points,
)
class SamAutomaticMaskGenerator:
def __init__(
self,
model: Sam,
points_per_side: Optional[int] = 32,
points_per_batch: int = 64,
pred_iou_thresh: float = 0.88,
stability_score_thresh: float = 0.95,
stability_score_offset: float = 1.0,
box_nms_thresh: float = 0.7,
crop_n_layers: int = 0,
crop_nms_thresh: float = 0.7,
crop_overlap_ratio: float = 512 / 1500,
crop_n_points_downscale_factor: int = 1,
point_grids: Optional[List[mx.array]] = None,
min_mask_region_area: int = 0,
output_mode: str = "binary_mask",
) -> None:
"""
Using a SAM model, generates masks for the entire image.
Generates a grid of point prompts over the image, then filters
low quality and duplicate masks. The default settings are chosen
for SAM with a ViT-H backbone.
Arguments:
model (Sam): The SAM model to use for mask prediction.
points_per_side (int or None): The number of points to be sampled
along one side of the image. The total number of points is
points_per_side**2. If None, 'point_grids' must provide explicit
point sampling.
points_per_batch (int): Sets the number of points run simultaneously
by the model. Higher numbers may be faster but use more GPU memory.
pred_iou_thresh (float): A filtering threshold in [0,1], using the
model's predicted mask quality.
stability_score_thresh (float): A filtering threshold in [0,1], using
the stability of the mask under changes to the cutoff used to binarize
the model's mask predictions.
stability_score_offset (float): The amount to shift the cutoff when
calculated the stability score.
box_nms_thresh (float): The box IoU cutoff used by non-maximal
suppression to filter duplicate masks.
crop_n_layers (int): If >0, mask prediction will be run again on
crops of the image. Sets the number of layers to run, where each
layer has 2**i_layer number of image crops.
crop_nms_thresh (float): The box IoU cutoff used by non-maximal
suppression to filter duplicate masks between different crops.
crop_overlap_ratio (float): Sets the degree to which crops overlap.
In the first crop layer, crops will overlap by this fraction of
the image length. Later layers with more crops scale down this overlap.
crop_n_points_downscale_factor (int): The number of points-per-side
sampled in layer n is scaled down by crop_n_points_downscale_factor**n.
point_grids (list(mx.array) or None): A list over explicit grids
of points used for sampling, normalized to [0,1]. The nth grid in the
list is used in the nth crop layer. Exclusive with points_per_side.
min_mask_region_area (int): If >0, postprocessing will be applied
to remove disconnected regions and holes in masks with area smaller
than min_mask_region_area. Requires opencv.
output_mode (str): The form masks are returned in. Can be 'binary_mask',
'uncompressed_rle', or 'coco_rle'. 'coco_rle' requires pycocotools.
For large resolutions, 'binary_mask' may consume large amounts of
memory.
"""
assert (points_per_side is None) != (
point_grids is None
), "Exactly one of points_per_side or point_grid must be provided."
if points_per_side is not None:
self.point_grids = build_all_layer_point_grids(
points_per_side,
crop_n_layers,
crop_n_points_downscale_factor,
)
elif point_grids is not None:
self.point_grids = point_grids
else:
raise ValueError("Can't have both points_per_side and point_grid be None.")
assert output_mode in [
"binary_mask",
"uncompressed_rle",
"coco_rle",
], f"Unknown output_mode {output_mode}."
if output_mode == "coco_rle":
from pycocotools import mask as mask_utils # type: ignore # noqa: F401
if min_mask_region_area > 0:
import cv2 # type: ignore # noqa: F401
self.predictor = SamPredictor(model)
self.points_per_batch = points_per_batch
self.pred_iou_thresh = pred_iou_thresh
self.stability_score_thresh = stability_score_thresh
self.stability_score_offset = stability_score_offset
self.box_nms_thresh = box_nms_thresh
self.crop_n_layers = crop_n_layers
self.crop_nms_thresh = crop_nms_thresh
self.crop_overlap_ratio = crop_overlap_ratio
self.crop_n_points_downscale_factor = crop_n_points_downscale_factor
self.min_mask_region_area = min_mask_region_area
self.output_mode = output_mode
def generate(self, image: np.ndarray) -> List[Dict[str, Any]]:
"""
Generates masks for the given image.
Arguments:
image (np.ndarray): The image to generate masks for, in HWC uint8 format.
Returns:
list(dict(str, any)): A list over records for masks. Each record is
a dict containing the following keys:
segmentation (dict(str, any) or np.ndarray): The mask. If
output_mode='binary_mask', is an array of shape HW. Otherwise,
is a dictionary containing the RLE.
bbox (list(float)): The box around the mask, in XYWH format.
area (int): The area in pixels of the mask.
predicted_iou (float): The model's own prediction of the mask's
quality. This is filtered by the pred_iou_thresh parameter.
point_coords (list(list(float))): The point coordinates input
to the model to generate this mask.
stability_score (float): A measure of the mask's quality. This
is filtered on using the stability_score_thresh parameter.
crop_box (list(float)): The crop of the image used to generate
the mask, given in XYWH format.
"""
# Generate masks
mask_data = self._generate_masks(image)
# Filter small disconnected regions and holes in masks
if self.min_mask_region_area > 0:
mask_data = self.postprocess_small_regions(
mask_data,
self.min_mask_region_area,
max(self.box_nms_thresh, self.crop_nms_thresh),
)
# Encode masks
if self.output_mode == "coco_rle":
mask_data["segmentations"] = [
coco_encode_rle(rle) for rle in mask_data["rles"]
]
elif self.output_mode == "binary_mask":
mask_data["segmentations"] = [rle_to_mask(rle) for rle in mask_data["rles"]]
else:
mask_data["segmentations"] = mask_data["rles"]
# Write mask records
curr_anns = []
for idx in range(len(mask_data["segmentations"])):
ann = {
"segmentation": mask_data["segmentations"][idx],
"area": area_from_rle(mask_data["rles"][idx]),
"bbox": box_xyxy_to_xywh(mask_data["boxes"][idx]).tolist(),
"predicted_iou": mask_data["iou_preds"][idx].item(),
"point_coords": [mask_data["points"][idx].tolist()],
"stability_score": mask_data["stability_score"][idx].item(),
"crop_box": box_xyxy_to_xywh(mask_data["crop_boxes"][idx]).tolist(),
}
curr_anns.append(ann)
return curr_anns
def _generate_masks(self, image: np.ndarray) -> MaskData:
orig_size = image.shape[:2]
crop_boxes, layer_idxs = generate_crop_boxes(
orig_size, self.crop_n_layers, self.crop_overlap_ratio
)
# Iterate over image crops
data = MaskData()
for crop_box, layer_idx in zip(crop_boxes, layer_idxs):
crop_data = self._process_crop(image, crop_box, layer_idx, orig_size)
data.cat(crop_data)
# Remove duplicate masks between crops
if len(crop_boxes) > 1:
# Prefer masks from smaller crops
scores = 1 / box_area(data["crop_boxes"])
keep_by_nms = non_max_supression(
data["boxes"].astype(mx.float32),
scores,
iou_threshold=self.crop_nms_thresh,
)
data.filter(keep_by_nms)
data.to_numpy()
return data
def _process_crop(
self,
image: np.ndarray,
crop_box: List[int],
crop_layer_idx: int,
orig_size: Tuple[int, ...],
) -> MaskData:
# Crop the image and calculate embeddings
x0, y0, x1, y1 = crop_box
cropped_im = image[y0:y1, x0:x1, :]
cropped_im_size = cropped_im.shape[:2]
self.predictor.set_image(cropped_im)
# Get points for this crop
points_scale = mx.array(cropped_im_size[::-1])[None]
points_for_image = self.point_grids[crop_layer_idx] * points_scale
# Generate masks for this crop in batches
data = MaskData()
for (points,) in batch_iterator(self.points_per_batch, points_for_image):
batch_data = self._process_batch(
points, cropped_im_size, crop_box, orig_size
)
data.cat(batch_data)
del batch_data
self.predictor.reset_image()
# Remove duplicates within this crop.
keep_by_nms = non_max_supression(
data["boxes"].astype(mx.float32),
data["iou_preds"],
iou_threshold=self.box_nms_thresh,
)
data.filter(keep_by_nms)
# Return to the original image frame
data["boxes"] = uncrop_boxes_xyxy(data["boxes"], crop_box)
data["points"] = uncrop_points(data["points"], crop_box)
data["crop_boxes"] = mx.array([crop_box for _ in range(len(data["rles"]))])
return data
def _process_batch(
self,
points: np.ndarray,
im_size: Tuple[int, ...],
crop_box: List[int],
orig_size: Tuple[int, ...],
) -> MaskData:
orig_h, orig_w = orig_size
masks, iou_preds, _ = self.predictor.predict(
points[:, None, :],
mx.ones((points.shape[0], 1), dtype=mx.int64),
multimask_output=True,
return_logits=True,
)
masks = masks.transpose(0, 3, 1, 2)
# Serialize predictions and store in MaskData
data = MaskData(
masks=masks.flatten(0, 1),
iou_preds=iou_preds.flatten(0, 1),
points=mx.repeat(points, masks.shape[1], axis=0),
)
del masks
# Filter by predicted IoU
if self.pred_iou_thresh > 0.0:
keep_mask = data["iou_preds"] > self.pred_iou_thresh
data.filter(keep_mask)
# Calculate stability score
data["stability_score"] = calculate_stability_score(
data["masks"],
self.predictor.model.mask_threshold,
self.stability_score_offset,
)
if self.stability_score_thresh > 0.0:
keep_mask = data["stability_score"] >= self.stability_score_thresh
data.filter(keep_mask)
# Threshold masks and calculate boxes
data["masks"] = data["masks"] > self.predictor.model.mask_threshold
data["boxes"] = batched_mask_to_box(data["masks"])
# Filter boxes that touch crop boundaries
keep_mask = ~is_box_near_crop_edge(
data["boxes"], crop_box, [0, 0, orig_w, orig_h]
)
if not mx.all(keep_mask):
data.filter(keep_mask)
# Compress to RLE
data["masks"] = uncrop_masks(data["masks"], crop_box, orig_h, orig_w)
data["rles"] = mask_to_rle_mlx(data["masks"])
del data["masks"]
return data
@staticmethod
def postprocess_small_regions(
mask_data: MaskData, min_area: int, nms_thresh: float
) -> MaskData:
"""
Removes small disconnected regions and holes in masks, then reruns
box NMS to remove any new duplicates.
Edits mask_data in place.
Requires open-cv as a dependency.
"""
if len(mask_data["rles"]) == 0:
return mask_data
# Filter small disconnected regions and holes
new_masks = []
scores = []
for rle in mask_data["rles"]:
mask = rle_to_mask(rle)
mask, changed = remove_small_regions(mask, min_area, mode="holes")
unchanged = not changed
mask, changed = remove_small_regions(mask, min_area, mode="islands")
unchanged = unchanged and not changed
new_masks.append(mx.array(mask)[None])
# Give score=0 to changed masks and score=1 to unchanged masks
# so NMS will prefer ones that didn't need postprocessing
scores.append(float(unchanged))
scores = mx.array(scores)
# Recalculate boxes and remove any new duplicates
masks = mx.concatenate(new_masks, axis=0)
boxes = batched_mask_to_box(masks)
keep_by_nms = non_max_supression(
boxes.astype(mx.float32),
scores,
iou_threshold=nms_thresh,
)
# Only recalculate RLEs for masks that have changed
for i_mask, keep in enumerate(keep_by_nms):
if not keep:
continue
if scores[i_mask] == 0.0:
mask_mlx = masks[i_mask][None]
mask_data["rles"][i_mask] = mask_to_rle_mlx(mask_mlx)[0]
mask_data["boxes"][i_mask] = boxes[i_mask] # update res directly
mask_data.filter(keep_by_nms)
return mask_data
def box_area(boxes: mx.array) -> mx.array:
"""
Computes the area of a set of bounding boxes, which are specified by their
(x1, y1, x2, y2) coordinates.
Args:
boxes (mx.array[N, 4]): boxes for which the area will be computed. They
are expected to be in (x1, y1, x2, y2) format with
``0 <= x1 < x2`` and ``0 <= y1 < y2``.
Returns:
mx.array[N]: the area for each box
"""
return (boxes[:, 2] - boxes[:, 0]) * (boxes[:, 3] - boxes[:, 1])
def batched_iou(boxes_a: mx.array, boxes_b: mx.array) -> mx.array:
"""Compute IoU for batched boxes.
Args:
boxes_a (mx.array): [..., [x1, y1, x2, y2]] sized Mx4
boxes_b (mx.array): [..., [x1, y1, x2, y2]] sized Nx4
Returns:
mx.array: MxN
"""
area_a = box_area(boxes_a) # M
area_b = box_area(boxes_b) # N
top_left = mx.maximum(boxes_a[:, None, :2], boxes_b[:, :2])
bottom_right = mx.minimum(boxes_a[:, None, 2:], boxes_b[:, 2:])
area_inter = mx.prod(mx.clip(bottom_right - top_left, a_min=0, a_max=None), 2)
return area_inter / (area_a[:, None] + area_b - area_inter)
def non_max_supression(
boxes: mx.array, scores: mx.array, iou_threshold: float = 0.5
) -> mx.array:
sort_index = mx.argsort(-scores)
boxes = boxes[sort_index]
n_boxes = boxes.shape[0]
ious = batched_iou(boxes, boxes)
ious -= mx.eye(n_boxes)
ious = np.array(ious)
keep = np.ones(n_boxes, dtype=np.bool_)
for i, iou in enumerate(ious):
if not keep[i]:
continue
condition = iou <= iou_threshold
keep = keep & condition
return sort_index[mx.array(np.where(keep)[0])]

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from typing import Type
import mlx.core as mx
import mlx.nn as nn
class MLPBlock(nn.Module):
def __init__(
self,
embedding_dim: int,
mlp_dim: int,
act: Type[nn.Module] = nn.GELU,
) -> None:
super().__init__()
self.lin1 = nn.Linear(embedding_dim, mlp_dim)
self.lin2 = nn.Linear(mlp_dim, embedding_dim)
self.act = act()
def __call__(self, x: mx.array) -> mx.array:
return self.lin2(self.act(self.lin1(x)))
class LayerNorm2d(nn.Module):
def __init__(self, num_channels: int, eps: float = 1e-6) -> None:
super().__init__()
self.weight = mx.ones(num_channels)
self.bias = mx.zeros(num_channels)
self.eps = eps
def __call__(self, x: mx.array) -> mx.array:
u = x.mean(3, keepdims=True)
s = ((x - u) ** 2).mean(3, keepdims=True)
x = (x - u) / mx.sqrt(s + self.eps)
x = self.weight * x + self.bias
return x

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from typing import Optional, Tuple, Type
import mlx.core as mx
import mlx.nn as nn
from .common import LayerNorm2d, MLPBlock
class ImageEncoderViT(nn.Module):
def __init__(
self,
img_size: int = 1024,
patch_size: int = 16,
in_chans: int = 3,
embed_dim: int = 768,
depth: int = 12,
num_heads: int = 12,
mlp_ratio: float = 4.0,
out_chans: int = 256,
qkv_bias: bool = True,
norm_layer: Type[nn.Module] = nn.LayerNorm,
act_layer: Type[nn.Module] = nn.GELU,
use_abs_pos: bool = True,
use_rel_pos: bool = False,
rel_pos_zero_init: bool = True,
window_size: int = 0,
global_attn_indexes: Tuple[int, ...] = (),
) -> None:
"""
Args:
img_size (int): Input image size.
patch_size (int): Patch size.
in_chans (int): Number of input image channels.
embed_dim (int): Patch embedding dimension.
depth (int): Depth of ViT.
num_heads (int): Number of attention heads in each ViT block.
mlp_ratio (float): Ratio of mlp hidden dim to embedding dim.
qkv_bias (bool): If True, add a learnable bias to query, key, value.
norm_layer (nn.Module): Normalization layer.
act_layer (nn.Module): Activation layer.
use_abs_pos (bool): If True, use absolute positional embeddings.
use_rel_pos (bool): If True, add relative positional embeddings to the attention map.
rel_pos_zero_init (bool): If True, zero initialize relative positional parameters.
window_size (int): Window size for window attention blocks.
global_attn_indexes (list): Indexes for blocks using global attention.
"""
super().__init__()
self.img_size = img_size
self.patch_embed = PatchEmbed(
kernel_size=(patch_size, patch_size),
stride=(patch_size, patch_size),
in_chans=in_chans,
embed_dim=embed_dim,
)
if use_abs_pos:
# Initialize absolute positional embedding with pretrain image size.
self.pos_embed = mx.zeros(
[1, img_size // patch_size, img_size // patch_size, embed_dim]
)
else:
self.pos_embed = None
self.layers = []
for i in range(depth):
block = Block(
dim=embed_dim,
num_heads=num_heads,
mlp_ratio=mlp_ratio,
qkv_bias=qkv_bias,
norm_layer=norm_layer,
act_layer=act_layer,
use_rel_pos=use_rel_pos,
rel_pos_zero_init=rel_pos_zero_init,
window_size=window_size if i not in global_attn_indexes else 0,
input_size=(img_size // patch_size, img_size // patch_size),
)
self.layers.append(block)
self.neck = Neck(embed_dim, out_chans)
def __call__(self, x: mx.array) -> mx.array:
x = self.patch_embed(x)
if self.pos_embed is not None:
x = x + self.pos_embed
for blk in self.layers:
x = blk(x)
x = self.neck(x)
return x
class Neck(nn.Module):
def __init__(self, embed_dim, out_chans):
super().__init__()
self.conv1 = nn.Conv2d(
embed_dim,
out_chans,
kernel_size=1,
bias=False,
)
self.layer_norm1 = LayerNorm2d(out_chans)
self.conv2 = nn.Conv2d(
out_chans,
out_chans,
kernel_size=3,
padding=1,
bias=False,
)
self.layer_norm2 = LayerNorm2d(out_chans)
def __call__(self, x):
return self.layer_norm2(self.conv2(self.layer_norm1(self.conv1(x))))
class Block(nn.Module):
"""Transformer blocks with support of window attention and residual propagation blocks"""
def __init__(
self,
dim: int,
num_heads: int,
mlp_ratio: float = 4.0,
qkv_bias: bool = True,
norm_layer: Type[nn.Module] = nn.LayerNorm,
act_layer: Type[nn.Module] = nn.GELU,
use_rel_pos: bool = False,
rel_pos_zero_init: bool = True,
window_size: int = 0,
input_size: Optional[Tuple[int, int]] = None,
) -> None:
"""
Args:
dim (int): Number of input channels.
num_heads (int): Number of attention heads in each ViT block.
mlp_ratio (float): Ratio of mlp hidden dim to embedding dim.
qkv_bias (bool): If True, add a learnable bias to query, key, value.
norm_layer (nn.Module): Normalization layer.
act_layer (nn.Module): Activation layer.
use_rel_pos (bool): If True, add relative positional embeddings to the attention map.
rel_pos_zero_init (bool): If True, zero initialize relative positional parameters.
window_size (int): Window size for window attention blocks. If it equals 0, then
use global attention.
input_size (tuple(int, int) or None): Input resolution for calculating the relative
positional parameter size.
"""
super().__init__()
self.layer_norm1 = norm_layer(dim)
self.attn = Attention(
dim,
num_heads=num_heads,
qkv_bias=qkv_bias,
use_rel_pos=use_rel_pos,
rel_pos_zero_init=rel_pos_zero_init,
input_size=input_size if window_size == 0 else (window_size, window_size),
)
self.layer_norm2 = norm_layer(dim)
self.mlp = MLPBlock(
embedding_dim=dim, mlp_dim=int(dim * mlp_ratio), act=act_layer
)
self.window_size = window_size
def __call__(self, x: mx.array) -> mx.array:
shortcut = x
x = self.layer_norm1(x)
# Window partition
if self.window_size > 0:
H, W = x.shape[1], x.shape[2]
x, pad_hw = window_partition(x, self.window_size)
x = self.attn(x)
# Reverse window partition
if self.window_size > 0:
x = window_unpartition(x, self.window_size, pad_hw, (H, W))
x = shortcut + x
x = x + self.mlp(self.layer_norm2(x))
return x
class Attention(nn.Module):
"""Multi-head Attention block with relative position embeddings."""
def __init__(
self,
dim: int,
num_heads: int = 8,
qkv_bias: bool = True,
use_rel_pos: bool = False,
rel_pos_zero_init: bool = True,
input_size: Optional[Tuple[int, int]] = None,
) -> None:
"""
Args:
dim (int): Number of input channels.
num_heads (int): Number of attention heads.
qkv_bias (bool): If True, add a learnable bias to query, key, value.
rel_pos (bool): If True, add relative positional embeddings to the attention map.
rel_pos_zero_init (bool): If True, zero initialize relative positional parameters.
input_size (tuple(int, int) or None): Input resolution for calculating the relative
positional parameter size.
"""
super().__init__()
self.num_heads = num_heads
head_dim = dim // num_heads
self.scale = head_dim**-0.5
self.qkv = nn.Linear(dim, dim * 3, bias=qkv_bias)
self.proj = nn.Linear(dim, dim)
self.use_rel_pos = use_rel_pos
if self.use_rel_pos:
assert (
input_size is not None
), "Input size must be provided if using relative positional encoding."
# initialize relative positional embeddings
self.rel_pos_h = mx.zeros(shape=(2 * input_size[0] - 1, head_dim))
self.rel_pos_w = mx.zeros(shape=(2 * input_size[1] - 1, head_dim))
def __call__(self, x: mx.array) -> mx.array:
B, H, W, _ = x.shape
# qkv with shape (3, B, nHead, H * W, C)
qkv = (
self.qkv(x)
.reshape(B, H * W, 3, self.num_heads, -1)
.transpose(2, 0, 3, 1, 4)
)
# q, k, v with shape (B * nHead, H * W, C)
qkv = qkv.reshape(3, B * self.num_heads, H * W, -1)
q, k, v = qkv[0], qkv[1], qkv[2]
attn = (q * self.scale) @ k.transpose(0, 2, 1)
if self.use_rel_pos:
attn = add_decomposed_rel_pos(
attn, q, self.rel_pos_h, self.rel_pos_w, (H, W), (H, W)
)
attn = mx.softmax(attn, axis=-1)
x = (
(attn @ v)
.reshape(B, self.num_heads, H, W, -1)
.transpose(0, 2, 3, 1, 4)
.reshape(B, H, W, -1)
)
x = self.proj(x)
return x
def window_partition(x: mx.array, window_size: int) -> Tuple[mx.array, Tuple[int, int]]:
"""
Partition into non-overlapping windows with padding if needed.
Args:
x (mx.array): input tokens with [B, H, W, C].
window_size (int): window size.
Returns:
windows: windows after partition with [B * num_windows, window_size, window_size, C].
(Hp, Wp): padded height and width before partition
"""
B, H, W, C = x.shape
pad_h = (window_size - H % window_size) % window_size
pad_w = (window_size - W % window_size) % window_size
if pad_h > 0 or pad_w > 0:
x = mx.pad(x, ((0, 0), (0, pad_w), (0, pad_h), (0, 0)))
Hp, Wp = H + pad_h, W + pad_w
x = x.reshape(B, Hp // window_size, window_size, Wp // window_size, window_size, C)
windows = x.transpose(0, 1, 3, 2, 4, 5).reshape(-1, window_size, window_size, C)
return windows, (Hp, Wp)
def window_unpartition(
windows: mx.array,
window_size: int,
pad_hw: Tuple[int, int],
hw: Tuple[int, int],
) -> mx.array:
"""
Window unpartition into original sequences and removing padding.
Args:
windows (mx.array): input tokens with [B * num_windows, window_size, window_size, C].
window_size (int): window size.
pad_hw (Tuple): padded height and width (Hp, Wp).
hw (Tuple): original height and width (H, W) before padding.
Returns:
x: unpartitioned sequences with [B, H, W, C].
"""
Hp, Wp = pad_hw
H, W = hw
B = windows.shape[0] // (Hp * Wp // window_size // window_size)
x = windows.reshape(
B, Hp // window_size, Wp // window_size, window_size, window_size, -1
)
x = x.transpose(0, 1, 3, 2, 4, 5).reshape(B, Hp, Wp, -1)
if Hp > H or Wp > W:
x = x[:, :H, :W, :]
return x
def get_rel_pos(q_size: int, k_size: int, rel_pos: mx.array) -> mx.array:
"""
Get relative positional embeddings according to the relative positions of
query and key sizes.
Args:
q_size (int): size of query q.
k_size (int): size of key k.
rel_pos (mx.array): relative position embeddings (L, C).
Returns:
Extracted positional embeddings according to relative positions.
"""
max_rel_dist = int(2 * max(q_size, k_size) - 1)
# Interpolate rel pos if needed.
if rel_pos.shape[0] != max_rel_dist:
# Interpolate rel pos.
rel_pos_resized = rel_pos.reshape(1, rel_pos.shape[0], -1).transpose(0, 2, 1)
scale_factor = (
max_rel_dist[0] / rel_pos_resized.shape[1],
max_rel_dist[1] / rel_pos_resized.shape[2],
)
rel_pos_resized = nn.Upsample(scale_factor=scale_factor, mode="linear")(
rel_pos_resized
)
rel_pos_resized = rel_pos_resized.reshape(-1, max_rel_dist).transpose(1, 0)
else:
rel_pos_resized = rel_pos
# Scale the coords with short length if shapes for q and k are different.
q_coords = mx.arange(q_size)[:, None] * max(k_size / q_size, 1.0)
k_coords = mx.arange(k_size)[None, :] * max(q_size / k_size, 1.0)
relative_coords = (q_coords - k_coords) + (k_size - 1) * max(q_size / k_size, 1.0)
return rel_pos_resized[relative_coords.astype(mx.int64)]
def add_decomposed_rel_pos(
attn,
q,
rel_pos_h: mx.array,
rel_pos_w: mx.array,
q_size: Tuple[int, int],
k_size: Tuple[int, int],
) -> mx.array:
"""
Calculate decomposed Relative Positional Embeddings from :paper:`mvitv2`.
https://github.com/facebookresearch/mvit/blob/19786631e330df9f3622e5402b4a419a263a2c80/mvit/models/attention.py # noqa B950
Args:
attn (mx.array): attention map.
q (mx.array): query q in the attention layer with shape (B, q_h * q_w, C).
rel_pos_h (mx.array): relative position embeddings (Lh, C) for height axis.
rel_pos_w (mx.array): relative position embeddings (Lw, C) for width axis.
q_size (Tuple): spatial sequence size of query q with (q_h, q_w).
k_size (Tuple): spatial sequence size of key k with (k_h, k_w).
Returns:
attn (mx.array): attention map with added relative positional embeddings.
"""
q_h, q_w = q_size
k_h, k_w = k_size
Rh = get_rel_pos(q_h, k_h, rel_pos_h)
Rw = get_rel_pos(q_w, k_w, rel_pos_w)
B, _, dim = q.shape
r_q = q.reshape(B, q_h, q_w, dim)
# TODO: replace mx.einsum when its ready
# workaround for these einsum computations
# rel_h = torch.einsum("bhwc,hkc->bhwk", r_q, Rh)
# rel_w = torch.einsum("bhwc,wkc->bhwk", r_q, Rw)
rel_h = r_q @ Rh.transpose(0, 2, 1)
rel_w = (r_q.transpose(0, 2, 1, 3) @ Rw.transpose(0, 2, 1)).transpose(0, 2, 1, 3)
attn = (
attn.reshape(B, q_h, q_w, k_h, k_w)
+ rel_h[:, :, :, :, None]
+ rel_w[:, :, :, None, :]
).reshape(B, q_h * q_w, k_h * k_w)
return attn
class PatchEmbed(nn.Module):
"""
Image to Patch Embedding.
"""
def __init__(
self,
kernel_size: Tuple[int, int] = (16, 16),
stride: Tuple[int, int] = (16, 16),
padding: Tuple[int, int] = (0, 0),
in_chans: int = 3,
embed_dim: int = 768,
) -> None:
"""
Args:
kernel_size (Tuple): kernel size of the projection layer.
stride (Tuple): stride of the projection layer.
padding (Tuple): padding size of the projection layer.
in_chans (int): Number of input image channels.
embed_dim (int): Patch embedding dimension.
"""
super().__init__()
self.projection = nn.Conv2d(
in_chans, embed_dim, kernel_size=kernel_size, stride=stride, padding=padding
)
def __call__(self, x: mx.array) -> mx.array:
x = self.projection(x)
return x

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import math
from typing import List, Tuple, Type, Union
import mlx.core as mx
import mlx.nn as nn
from .common import LayerNorm2d
class MaskDecoder(nn.Module):
def __init__(
self,
*,
transformer_dim: int,
transformer: nn.Module,
num_multimask_outputs: int = 3,
activation: Type[nn.Module] = nn.GELU,
iou_head_depth: int = 3,
iou_head_hidden_dim: int = 256,
) -> None:
"""
Predicts masks given an image and prompt embeddings, using a
transformer architecture.
Args:
transformer_dim (int): the channel dimension of the transformer
transformer (nn.Module): the transformer used to predict masks
num_multimask_outputs (int): the number of masks to predict
when disambiguating masks
activation (nn.Module): the type of activation to use when
upscaling masks
iou_head_depth (int): the depth of the MLP used to predict
mask quality
iou_head_hidden_dim (int): the hidden dimension of the MLP
used to predict mask quality
"""
super().__init__()
self.transformer_dim = transformer_dim
self.transformer = transformer
self.num_multimask_outputs = num_multimask_outputs
self.iou_token = nn.Embedding(1, transformer_dim)
self.num_mask_tokens = num_multimask_outputs + 1
self.mask_tokens = nn.Embedding(self.num_mask_tokens, transformer_dim)
self.upscale_conv1 = ConvTranspose2d(
transformer_dim,
transformer_dim // 4,
kernel_size=2,
stride=2,
padding=1,
)
self.upscale_layer_norm = LayerNorm2d(transformer_dim // 4)
self.activation = activation()
self.upscale_conv2 = ConvTranspose2d(
transformer_dim // 4,
transformer_dim // 8,
kernel_size=2,
stride=2,
padding=1,
)
self.output_hypernetworks_mlps = [
MLP(transformer_dim, transformer_dim, transformer_dim // 8, 1)
for i in range(self.num_mask_tokens)
]
self.iou_prediction_head = MLP(
transformer_dim,
iou_head_hidden_dim,
self.num_mask_tokens,
iou_head_depth - 2,
)
def __call__(
self,
image_embeddings: mx.array,
image_pe: mx.array,
sparse_prompt_embeddings: mx.array,
dense_prompt_embeddings: mx.array,
multimask_output: bool,
) -> Tuple[mx.array, mx.array]:
"""
Predict masks given image and prompt embeddings.
Args:
image_embeddings (mx.array): the embeddings from the image encoder
image_pe (mx.array): positional encoding
sparse_prompt_embeddings (mx.array): the embeddings of the points and boxes
dense_prompt_embeddings (mx.array): the embeddings of the mask inputs
multimask_output (bool): Whether to return multiple masks or a single
mask.
Returns:
mx.array: batched predicted masks
mx.array: batched predictions of mask quality
"""
masks, iou_pred = self.predict_masks(
image_embeddings=image_embeddings,
image_pe=image_pe,
sparse_prompt_embeddings=sparse_prompt_embeddings,
dense_prompt_embeddings=dense_prompt_embeddings,
)
# Select the correct mask or masks for output
if multimask_output:
mask_slice = slice(1, None)
else:
mask_slice = slice(0, 1)
masks = masks[:, :, :, mask_slice]
iou_pred = iou_pred[:, mask_slice]
# Prepare output
return masks, iou_pred
def predict_masks(
self,
image_embeddings: mx.array,
image_pe: mx.array,
sparse_prompt_embeddings: mx.array,
dense_prompt_embeddings: mx.array,
) -> Tuple[mx.array, mx.array]:
"""Predicts masks. See '__call__' for more details."""
# Concatenate output tokens
output_tokens = mx.concatenate(
[self.iou_token.weight, self.mask_tokens.weight], axis=0
)
output_tokens = mx.broadcast_to(
output_tokens[None],
[
sparse_prompt_embeddings.shape[0],
output_tokens.shape[0],
output_tokens.shape[1],
],
)
tokens = mx.concatenate((output_tokens, sparse_prompt_embeddings), axis=1)
# Expand per-image data in batch direction to be per-mask
src = mx.repeat(image_embeddings, repeats=tokens.shape[0], axis=0)
src = src + dense_prompt_embeddings
b, h, w, c = src.shape
# Run the transformer
hs, src = self.transformer(src, image_pe, tokens)
iou_token_out = hs[:, 0, :]
mask_tokens_out = hs[:, 1 : (1 + self.num_mask_tokens), :]
# Upscale mask embeddings and predict masks using the mask tokens
src = src.reshape(b, h, w, c)
src = self.upscale_conv1(src)
src = self.upscale_layer_norm(src)
src = self.activation(src)
src = self.upscale_conv2(src)
upscaled_embedding = self.activation(src)
hyper_in_list: List[mx.array] = []
for i in range(self.num_mask_tokens):
hyper_in_list.append(
self.output_hypernetworks_mlps[i](mask_tokens_out[:, i, :])
)
hyper_in = mx.stack(hyper_in_list, axis=1)
b, h, w, c = upscaled_embedding.shape
masks = (
(hyper_in @ upscaled_embedding.reshape(b, h * w, c).transpose(0, 2, 1))
.transpose(0, 2, 1)
.reshape(b, h, w, -1)
)
# Generate mask quality predictions
iou_pred = self.iou_prediction_head(iou_token_out)
return masks, iou_pred
class MLP(nn.Module):
def __init__(
self,
input_dim: int,
hidden_dim: int,
output_dim: int,
num_layers: int,
sigmoid_output: bool = False,
) -> None:
super().__init__()
self.num_layers = num_layers
self.proj_in = nn.Linear(input_dim, hidden_dim)
self.layers = [nn.Linear(hidden_dim, hidden_dim) for _ in range(num_layers)]
self.proj_out = nn.Linear(hidden_dim, output_dim)
self.sigmoid_output = sigmoid_output
def __call__(self, x):
x = nn.relu(self.proj_in(x))
for i, layer in enumerate(self.layers):
x = nn.relu(layer(x))
x = self.proj_out(x)
if self.sigmoid_output:
x = mx.sigmoid(x)
return x
# TODO: Naive implem. Replace when mlx.nn support conv_transpose
class ConvTranspose2d(nn.Module):
def __init__(
self,
in_channels: int,
out_channels: int,
kernel_size: Union[int, tuple],
stride: Union[int, tuple] = 1,
padding: Union[int, tuple] = 0,
dilation: Union[int, tuple] = 1,
bias: bool = True,
):
super().__init__()
kernel_size, stride, padding = map(
lambda x: (x, x) if isinstance(x, int) else x,
(kernel_size, stride, padding),
)
scale = math.sqrt(1 / (in_channels * kernel_size[0] * kernel_size[1]))
self.weight = mx.random.uniform(
low=-scale,
high=scale,
shape=(out_channels, *kernel_size, in_channels),
)
if bias:
self.bias = mx.zeros((out_channels,))
self.padding = padding
self.stride = stride
self.dilation = dilation
def _extra_repr(self):
return (
f"{self.weight.shape[-1]}, {self.weight.shape[0]}, "
f"kernel_size={self.weight.shape[1:2]}, stride={self.stride}, "
f"padding={self.padding}, dilation={self.dilation}, "
f"bias={'bias' in self}"
)
def __call__(self, x):
y = mx.conv_general(
x,
self.weight,
stride=1,
padding=self.padding,
kernel_dilation=self.dilation,
input_dilation=self.stride,
flip=True,
)
if "bias" in self:
y = y + self.bias
return y

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from typing import Optional, Tuple
import mlx.core as mx
import numpy as np
from .sam import Sam
from .utils.transforms import ResizeLongestSide
class SamPredictor:
def __init__(
self,
sam_model: Sam,
) -> None:
"""
Uses SAM to calculate the image embedding for an image, and then
allow repeated, efficient mask prediction given prompts.
Args:
sam_model (Sam): The model to use for mask prediction.
"""
super().__init__()
self.model = sam_model
self.transform = ResizeLongestSide(sam_model.vision_encoder.img_size)
self.reset_image()
def set_image(
self,
image: np.ndarray,
image_format: str = "RGB",
) -> None:
"""
Calculates the image embeddings for the provided image, allowing
masks to be predicted with the 'predict' method.
Args:
image (np.ndarray): The image for calculating masks. Expects an
image in HWC uint8 format, with pixel values in [0, 255].
image_format (str): The color format of the image, in ['RGB', 'BGR'].
"""
self.reset_image()
assert image_format in [
"RGB",
"BGR",
], f"image_format must be in ['RGB', 'BGR'], is {image_format}."
if image_format != self.model.image_format:
image = image[..., ::-1]
# Transform the image to the form expected by the model
input_image = self.transform.apply_image(image)
input_image = mx.array(input_image)[None, :, :, :]
self.original_size = image.shape[:2]
self.input_size = input_image.shape[1:3]
input_image = self.model.preprocess(input_image)
self.features = self.model.vision_encoder(input_image)
self.is_image_set = True
def predict(
self,
point_coords: Optional[mx.array],
point_labels: Optional[mx.array],
box: Optional[mx.array] = None,
mask_input: Optional[mx.array] = None,
multimask_output: bool = True,
return_logits: bool = False,
) -> Tuple[mx.array, mx.array, mx.array]:
"""
Predict masks for the given input prompts, using the currently set image.
Input prompts are batched mlx tensors and are expected to already be
transformed to the input frame using ResizeLongestSide.
Args:
point_coords (mx.array or None): A BxNx2 array of point prompts to the
model. Each point is in (X,Y) in pixels.
point_labels (mx.array or None): A BxN array of labels for the
point prompts. 1 indicates a foreground point and 0 indicates a
background point.
box (mx.array or None): A size 4 array giving a box prompt to the
model, in XYXY format.
mask_input (mx.array): A low resolution mask input to the model, typically
coming from a previous prediction iteration. Has form BxHxWx1, where
for SAM, H=W=256. Masks returned by a previous iteration of the
predict method do not need further transformation.
multimask_output (bool): If true, the model will return three masks.
For ambiguous input prompts (such as a single click), this will often
produce better masks than a single prediction. If only a single
mask is needed, the model's predicted quality score can be used
to select the best mask. For non-ambiguous prompts, such as multiple
input prompts, multimask_output=False can give better results.
return_logits (bool): If true, returns un-thresholded masks logits
instead of a binary mask.
Returns:
(mx.array): The output masks in BxHxWxC format, where C is the
number of masks, and (H, W) is the original image size.
(mx.array): An array of shape BxC containing the model's
predictions for the quality of each mask.
(mx.array): An array of shape BxHxWxC, where C is the number
of masks and H=W=256. These low res logits can be passed to
a subsequent iteration as mask input.
"""
if not self.is_image_set:
raise RuntimeError(
"An image must be set with .set_image(...) before mask prediction."
)
# Transform input prompts
points = None
if point_coords is not None:
assert (
point_labels is not None
), "point_labels must be supplied if point_coords is supplied."
point_coords = self.transform.apply_coords(point_coords, self.original_size)
points = (point_coords, point_labels)
if box is not None:
box = self.transform.apply_boxes(box, self.original_size)
# Embed prompts
sparse_embeddings, dense_embeddings = self.model.prompt_encoder(
points=points,
boxes=box,
masks=mask_input,
pe_layer=self.model.shared_image_embedding,
)
# Predict masks
low_res_masks, iou_predictions = self.model.mask_decoder(
image_embeddings=self.features,
image_pe=self.model.shared_image_embedding(
self.model.prompt_encoder.image_embedding_size
),
sparse_prompt_embeddings=sparse_embeddings,
dense_prompt_embeddings=dense_embeddings,
multimask_output=multimask_output,
)
# Upscale the masks to the original image resolution
masks = self.model.postprocess_masks(
low_res_masks, self.input_size, self.original_size
)
if not return_logits:
masks = masks > self.model.mask_threshold
return masks, iou_predictions, low_res_masks
def get_image_embedding(self) -> mx.array:
"""
Returns the image embeddings for the currently set image, with
shape 1xCxHxW, where C is the embedding dimension and (H,W) are
the embedding spatial dimension of SAM (typically C=256, H=W=64).
"""
if not self.is_image_set:
raise RuntimeError(
"An image must be set with .set_image(...) to generate an embedding."
)
assert (
self.features is not None
), "Features must exist if an image has been set."
return self.features
def reset_image(self) -> None:
"""Resets the currently set image."""
self.is_image_set = False
self.features = None
self.orig_h = None
self.orig_w = None
self.input_h = None
self.input_w = None

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from typing import Optional, Tuple, Type
import mlx.core as mx
import mlx.nn as nn
from .common import LayerNorm2d
class PromptEncoder(nn.Module):
def __init__(
self,
embed_dim: int,
image_embedding_size: Tuple[int, int],
input_image_size: Tuple[int, int],
mask_in_chans: int,
activation: Type[nn.Module] = nn.GELU,
) -> None:
"""
Encodes prompts for input to SAM's mask decoder.
Args:
embed_dim (int): The prompts' embedding dimension
image_embedding_size (tuple(int, int)): The spatial size of the
image embedding, as (H, W).
input_image_size (int): The padded size of the image as input
to the image encoder, as (H, W).
mask_in_chans (int): The number of hidden channels used for
encoding input masks.
activation (nn.Module): The activation to use when encoding
input masks.
"""
super().__init__()
self.embed_dim = embed_dim
self.input_image_size = input_image_size
self.image_embedding_size = image_embedding_size
self.num_point_embeddings: int = 4 # pos/neg point + 2 box corners
self.point_embed = [
nn.Embedding(1, embed_dim) for i in range(self.num_point_embeddings)
]
self.not_a_point_embed = nn.Embedding(1, embed_dim)
self.mask_input_size = (
4 * image_embedding_size[0],
4 * image_embedding_size[1],
)
self.mask_embed = MaskEmbed(embed_dim, mask_in_chans, activation)
self.no_mask_embed = nn.Embedding(1, embed_dim)
def _embed_points(
self,
points: mx.array,
labels: mx.array,
pad: bool,
pe_layer: nn.Module,
) -> mx.array:
"""Embeds point prompts."""
points = points + 0.5 # Shift to center of pixel
if pad:
padding_point = mx.zeros((points.shape[0], 1, 2))
padding_label = -mx.ones((labels.shape[0], 1))
points = mx.concatenate([points, padding_point], axis=1)
labels = mx.concatenate([labels, padding_label], axis=1)
point_embedding = pe_layer.forward_with_coords(points, self.input_image_size)
point_embedding = mx.where(
labels[..., None] == -1,
self.not_a_point_embed.weight[:, None],
point_embedding,
)
point_embedding = mx.where(
labels[..., None] == 0,
point_embedding + self.point_embed[0].weight[:, None],
point_embedding,
)
point_embedding = mx.where(
labels[..., None] == 1,
point_embedding + self.point_embed[1].weight[:, None],
point_embedding,
)
return point_embedding
def _embed_boxes(self, boxes: mx.array, pe_layer: nn.Module) -> mx.array:
"""Embeds box prompts."""
boxes = boxes + 0.5 # Shift to center of pixel
coords = boxes.reshape(-1, 2, 2)
corner_embedding = pe_layer.forward_with_coords(coords, self.input_image_size)
corner_embedding[:, 0, :] += self.point_embed[2].weight
corner_embedding[:, 1, :] += self.point_embed[3].weight
return corner_embedding
def _embed_masks(self, masks: mx.array) -> mx.array:
"""Embeds mask inputs."""
mask_embedding = self.mask_embed(masks)
return mask_embedding
def _get_batch_size(
self,
points: Optional[Tuple[mx.array, mx.array]],
boxes: Optional[mx.array],
masks: Optional[mx.array],
) -> int:
"""
Gets the batch size of the output given the batch size of the input prompts.
"""
if points is not None:
return points[0].shape[0]
elif boxes is not None:
return boxes.shape[0]
elif masks is not None:
return masks.shape[0]
else:
return 1
def __call__(
self,
points: Optional[Tuple[mx.array, mx.array]],
boxes: Optional[mx.array],
masks: Optional[mx.array],
pe_layer: nn.Module,
) -> Tuple[mx.array, mx.array]:
"""
Embeds different types of prompts, returning both sparse and dense
embeddings.
Args:
points (tuple(mx.array, mx.array) or none): point coordinates
and labels to embed
boxes (mx.array or none): boxes to embed
masks (mx.array or none): masks to embed
pe_layer (PositionEmbeddingRandom): shared position embedding
layer
Returns:
mx.array: sparse embeddings for the points and boxes, with shape
BxNx(embed_dim), where N is determined by the number of input points
and boxes.
mx.array: dense embeddings for the masks, in the shape
Bx(embed_H)x(embed_W)x(embed_dim)
"""
bs = self._get_batch_size(points, boxes, masks)
sparse_embeddings = mx.zeros((bs, 0, self.embed_dim))
if points is not None:
coords, labels = points
point_embeddings = self._embed_points(
coords, labels, pad=(boxes is None), pe_layer=pe_layer
)
sparse_embeddings = mx.concatenate(
[sparse_embeddings, point_embeddings], axis=1
)
if boxes is not None:
box_embeddings = self._embed_boxes(boxes, pe_layer=pe_layer)
sparse_embeddings = mx.concatenate(
[sparse_embeddings, box_embeddings], axis=1
)
if masks is not None:
dense_embeddings = self._embed_masks(masks)
else:
dense_embeddings = mx.broadcast_to(
self.no_mask_embed.weight,
shape=(
bs,
self.image_embedding_size[0],
self.image_embedding_size[1],
self.embed_dim,
),
)
return sparse_embeddings, dense_embeddings
class MaskEmbed(nn.Module):
def __init__(self, embed_dim, mask_in_chans, activation):
super().__init__()
self.conv1 = nn.Conv2d(1, mask_in_chans // 4, kernel_size=2, stride=2)
self.layer_norm1 = LayerNorm2d(mask_in_chans // 4)
self.conv2 = nn.Conv2d(
mask_in_chans // 4, mask_in_chans, kernel_size=2, stride=2
)
self.layer_norm2 = LayerNorm2d(mask_in_chans)
self.conv3 = nn.Conv2d(mask_in_chans, embed_dim, kernel_size=1)
self.activation = activation()
def __call__(self, x):
x = self.activation(self.layer_norm1(self.conv1(x)))
x = self.activation(self.layer_norm2(self.conv2(x)))
return self.conv3(x)
class PositionEmbeddingRandom(nn.Module):
"""
Positional encoding using random spatial frequencies.
"""
def __init__(self, num_pos_feats: int = 64, scale: Optional[float] = None) -> None:
super().__init__()
if scale is None or scale <= 0.0:
scale = 1.0
self.positional_embedding = scale * mx.random.normal((2, num_pos_feats))
def _pe_encoding(self, coords: mx.array) -> mx.array:
"""Positionally encode points that are normalized to [0,1]."""
# assuming coords are in [0, 1]^2 square and have d_1 x ... x d_n x 2 shape
coords = 2 * coords - 1
coords = coords @ self.positional_embedding
coords = 2 * mx.pi * coords
# outputs d_1 x ... x d_n x C shape
return mx.concatenate([mx.sin(coords), mx.cos(coords)], axis=-1)
def __call__(self, size: Tuple[int, int]) -> mx.array:
"""Generate positional encoding for a grid of the specified size."""
h, w = size
grid = mx.ones((h, w), dtype=mx.float32)
y_embed = grid.cumsum(axis=0) - 0.5
x_embed = grid.cumsum(axis=1) - 0.5
y_embed = y_embed / h
x_embed = x_embed / w
pe = self._pe_encoding(mx.stack([x_embed, y_embed], axis=-1))
return pe # HWC
def forward_with_coords(
self, coords_input: mx.array, image_size: Tuple[int, int]
) -> mx.array:
"""Positionally encode points that are not normalized to [0,1]."""
coords = coords_input * 1
coords[:, :, 0] = coords[:, :, 0] / image_size[1]
coords[:, :, 1] = coords[:, :, 1] / image_size[0]
return self._pe_encoding(coords.astype(mx.float32)) # B x N x C

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import json
from functools import partial
from pathlib import Path
from typing import Any, Dict, List, Tuple
import mlx.core as mx
import mlx.nn as nn
from .image_encoder import ImageEncoderViT
from .mask_decoder import MaskDecoder
from .prompt_encoder import PositionEmbeddingRandom, PromptEncoder
from .transformer import TwoWayTransformer
class Sam(nn.Module):
mask_threshold: float = 0.0
image_format: str = "RGB"
def __init__(
self,
vision_encoder: ImageEncoderViT,
prompt_encoder: PromptEncoder,
mask_decoder: MaskDecoder,
pixel_mean: List[float] = [123.675, 116.28, 103.53],
pixel_std: List[float] = [58.395, 57.12, 57.375],
) -> None:
"""
SAM predicts object masks from an image and input prompts.
Args:
vision_encoder (ImageEncoderViT): The backbone used to encode the
image into image embeddings that allow for efficient mask prediction.
prompt_encoder (PromptEncoder): Encodes various types of input prompts.
mask_decoder (MaskDecoder): Predicts masks from the image embeddings
and encoded prompts.
pixel_mean (list(float)): Mean values for normalizing pixels in the input image.
pixel_std (list(float)): Std values for normalizing pixels in the input image.
"""
super().__init__()
self.vision_encoder = vision_encoder
self.prompt_encoder = prompt_encoder
self.mask_decoder = mask_decoder
self._pixel_mean = mx.array(pixel_mean).reshape(1, 1, -1)
self._pixel_std = mx.array(pixel_std).reshape(1, 1, -1)
self.shared_image_embedding = PositionEmbeddingRandom(
prompt_encoder.embed_dim // 2
)
def __call__(
self,
batched_input: List[Dict[str, Any]],
multimask_output: bool,
) -> List[Dict[str, mx.array]]:
"""
Predicts masks end-to-end from provided images and prompts.
If prompts are not known in advance, using SamPredictor is
recommended over calling the model directly.
Args:
batched_input (list(dict)): A list over input images, each a
dictionary with the following keys. A prompt key can be
excluded if it is not present.
'image': The image as a mlx tensor in HxWx3 format,
already transformed for input to the model.
'original_size': (tuple(int, int)) The original size of
the image before transformation, as (H, W).
'point_coords': (mx.array) Batched point prompts for
this image, with shape BxNx2. Already transformed to the
input frame of the model.
'point_labels': (mx.array) Batched labels for point prompts,
with shape BxN.
'boxes': (mx.array) Batched box inputs, with shape Bx4.
Already transformed to the input frame of the model.
'mask_inputs': (mx.array) Batched mask inputs to the model,
in the form BxHxWx1.
multimask_output (bool): Whether the model should predict multiple
disambiguating masks, or return a single mask.
Returns:
(list(dict)): A list over input images, where each element is
as dictionary with the following keys.
'masks': (mx.array) Batched binary mask predictions,
with shape BxCxHxW, where B is the number of input prompts,
C is determined by multimask_output, and (H, W) is the
original size of the image.
'iou_predictions': (mx.array) The model's predictions
of mask quality, in shape BxC.
'low_res_logits': (mx.array) Low resolution logits with
shape BxCxHxW, where H=W=256. Can be passed as mask input
to subsequent iterations of prediction.
"""
input_images = mx.stack(
[self.preprocess(x["image"]) for x in batched_input], axis=0
)
image_embeddings = self.vision_encoder(input_images)
outputs = []
for image_record, curr_embedding in zip(batched_input, image_embeddings):
if "point_coords" in image_record:
points = (image_record["point_coords"], image_record["point_labels"])
else:
points = None
sparse_embeddings, dense_embeddings = self.prompt_encoder(
points=points,
boxes=image_record.get("boxes", None),
masks=image_record.get("mask_inputs", None),
pe_layer=self.shared_image_embedding,
)
low_res_masks, iou_predictions = self.mask_decoder(
image_embeddings=curr_embedding[None],
image_pe=self.shared_image_embedding(
self.prompt_encoder.image_embedding_size
),
sparse_prompt_embeddings=sparse_embeddings,
dense_prompt_embeddings=dense_embeddings,
multimask_output=multimask_output,
)
masks = self.postprocess_masks(
low_res_masks,
input_size=image_record["image"].shape[-3:-1],
original_size=image_record["original_size"],
)
masks = masks > self.mask_threshold
outputs.append(
{
"masks": masks,
"iou_predictions": iou_predictions,
"low_res_logits": low_res_masks,
}
)
return outputs
def postprocess_masks(
self,
masks: mx.array,
input_size: Tuple[int, ...],
original_size: Tuple[int, ...],
) -> mx.array:
"""
Remove padding and upscale masks to the original image size.
Args:
masks (mx.array): Batched masks from the mask_decoder,
in BxHxWxC format.
input_size (tuple(int, int)): The size of the image input to the
model, in (H, W) format. Used to remove padding.
original_size (tuple(int, int)): The original size of the image
before resizing for input to the model, in (H, W) format.
Returns:
(mx.array): Batched masks in BxCxHxW format, where (H, W)
is given by original_size.
"""
scale_factor = (
self.vision_encoder.img_size / masks.shape[1],
self.vision_encoder.img_size / masks.shape[2],
)
masks = nn.Upsample(
scale_factor=scale_factor, mode="linear", align_corners=False
)(masks)
masks = masks[:, : input_size[0], : input_size[1]]
scale_factor = (
original_size[0] / masks.shape[1],
original_size[1] / masks.shape[2],
)
masks = nn.Upsample(
scale_factor=scale_factor, mode="linear", align_corners=False
)(masks)
return masks
def preprocess(self, x: mx.array) -> mx.array:
"""Normalize pixel values and pad to a square input."""
# Normalize colors
x = (x - self._pixel_mean) / self._pixel_std
# Pad
h, w = x.shape[-3:-1]
padh = self.vision_encoder.img_size - h
padw = self.vision_encoder.img_size - w
if x.ndim == 3:
pad_width = [(0, padh), (0, padw), (0, 0)]
elif x.ndim == 4:
pad_width = [(0, 0), (0, padh), (0, padw), (0, 0)]
else:
raise Exception("x.ndim can only be 3 or 4.")
x = mx.pad(x, pad_width)
return x
def load(model_path):
model_path = Path(model_path)
with open(model_path / "config.json", "r") as fid:
config = json.load(fid)
encoder_embed_dim = config["vision_config"]["hidden_size"]
encoder_depth = config["vision_config"]["num_hidden_layers"]
encoder_num_heads = config["vision_config"]["num_attention_heads"]
encoder_global_attn_indexes = config["vision_config"]["global_attn_indexes"]
prompt_embed_dim = 256
image_size = 1024
vit_patch_size = 16
image_embedding_size = image_size // vit_patch_size
sam = Sam(
vision_encoder=ImageEncoderViT(
depth=encoder_depth,
embed_dim=encoder_embed_dim,
img_size=image_size,
mlp_ratio=4,
norm_layer=partial(nn.LayerNorm, eps=1e-6),
num_heads=encoder_num_heads,
patch_size=vit_patch_size,
qkv_bias=True,
use_rel_pos=True,
global_attn_indexes=encoder_global_attn_indexes,
window_size=14,
out_chans=prompt_embed_dim,
),
prompt_encoder=PromptEncoder(
embed_dim=prompt_embed_dim,
image_embedding_size=(image_embedding_size, image_embedding_size),
input_image_size=(image_size, image_size),
mask_in_chans=16,
),
mask_decoder=MaskDecoder(
num_multimask_outputs=3,
transformer=TwoWayTransformer(
depth=2,
embedding_dim=prompt_embed_dim,
mlp_dim=2048,
num_heads=8,
),
transformer_dim=prompt_embed_dim,
iou_head_depth=3,
iou_head_hidden_dim=256,
),
)
sam.load_weights(str(model_path / "model.safetensors"), strict=True)
return sam

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import math
from typing import Tuple, Type
import mlx.core as mx
import mlx.nn as nn
from .common import MLPBlock
class TwoWayTransformer(nn.Module):
def __init__(
self,
depth: int,
embedding_dim: int,
num_heads: int,
mlp_dim: int,
activation: Type[nn.Module] = nn.ReLU,
attention_downsample_rate: int = 2,
) -> None:
"""
A transformer decoder that attends to an input image using
queries whose positional embedding is supplied.
Args:
depth (int): number of layers in the transformer
embedding_dim (int): the channel dimension for the input embeddings
num_heads (int): the number of heads for multihead attention. Must
divide embedding_dim
mlp_dim (int): the channel dimension internal to the MLP block
activation (nn.Module): the activation to use in the MLP block
"""
super().__init__()
self.depth = depth
self.embedding_dim = embedding_dim
self.num_heads = num_heads
self.mlp_dim = mlp_dim
self.layers = []
for i in range(depth):
self.layers.append(
TwoWayAttentionBlock(
embedding_dim=embedding_dim,
num_heads=num_heads,
mlp_dim=mlp_dim,
activation=activation,
attention_downsample_rate=attention_downsample_rate,
skip_first_layer_pe=(i == 0),
)
)
self.final_attn_token_to_image = Attention(
embedding_dim, num_heads, downsample_rate=attention_downsample_rate
)
self.layer_norm_final_attn = nn.LayerNorm(embedding_dim)
def __call__(
self,
image_embedding: mx.array,
image_pe: mx.array,
point_embedding: mx.array,
) -> Tuple[mx.array, mx.array]:
"""
Args:
image_embedding (mx.array): image to attend to. Should be shape
B x h x w x embedding_dim for any h and w.
image_pe (mx.array): the positional encoding to add to the image. Must
have the same shape as image_embedding.
point_embedding (mx.array): the embedding to add to the query points.
Must have shape B x N_points x embedding_dim for any N_points.
Returns:
mx.array: the processed point_embedding
mx.array: the processed image_embedding
"""
# BxHxWxC -> BxHWxC == B x N_image_tokens x C
bs, h, w, c = image_embedding.shape
image_embedding = image_embedding.reshape(bs, h * w, c)
image_pe = image_pe.reshape(h * w, c)
# Prepare queries
queries = point_embedding
keys = image_embedding
# Apply transformer blocks and final layernorm
for layer in self.layers:
queries, keys = layer(
queries=queries,
keys=keys,
query_pe=point_embedding,
key_pe=image_pe,
)
# Apply the final attention layer from the points to the image
q = queries + point_embedding
k = keys + image_pe
attn_out = self.final_attn_token_to_image(q=q, k=k, v=keys)
queries = queries + attn_out
queries = self.layer_norm_final_attn(queries)
return queries, keys
class TwoWayAttentionBlock(nn.Module):
def __init__(
self,
embedding_dim: int,
num_heads: int,
mlp_dim: int = 2048,
activation: Type[nn.Module] = nn.ReLU,
attention_downsample_rate: int = 2,
skip_first_layer_pe: bool = False,
) -> None:
"""
A transformer block with four layers: (1) self-attention of sparse
inputs, (2) cross attention of sparse inputs to dense inputs, (3) mlp
block on sparse inputs, and (4) cross attention of dense inputs to sparse
inputs.
Args:
embedding_dim (int): the channel dimension of the embeddings
num_heads (int): the number of heads in the attention layers
mlp_dim (int): the hidden dimension of the mlp block
activation (nn.Module): the activation of the mlp block
skip_first_layer_pe (bool): skip the PE on the first layer
"""
super().__init__()
self.self_attn = Attention(embedding_dim, num_heads)
self.layer_norm1 = nn.LayerNorm(embedding_dim)
self.cross_attn_token_to_image = Attention(
embedding_dim, num_heads, downsample_rate=attention_downsample_rate
)
self.layer_norm2 = nn.LayerNorm(embedding_dim)
self.mlp = MLPBlock(embedding_dim, mlp_dim, activation)
self.layer_norm3 = nn.LayerNorm(embedding_dim)
self.layer_norm4 = nn.LayerNorm(embedding_dim)
self.cross_attn_image_to_token = Attention(
embedding_dim, num_heads, downsample_rate=attention_downsample_rate
)
self.skip_first_layer_pe = skip_first_layer_pe
def __call__(
self, queries: mx.array, keys: mx.array, query_pe: mx.array, key_pe: mx.array
) -> Tuple[mx.array, mx.array]:
# Self attention block
if self.skip_first_layer_pe:
queries = self.self_attn(q=queries, k=queries, v=queries)
else:
q = queries + query_pe
attn_out = self.self_attn(q=q, k=q, v=queries)
queries = queries + attn_out
queries = self.layer_norm1(queries)
# Cross attention block, tokens attending to image embedding
q = queries + query_pe
k = keys + key_pe
attn_out = self.cross_attn_token_to_image(q=q, k=k, v=keys)
queries = queries + attn_out
queries = self.layer_norm2(queries)
# MLP block
mlp_out = self.mlp(queries)
queries = queries + mlp_out
queries = self.layer_norm3(queries)
# Cross attention block, image embedding attending to tokens
q = queries + query_pe
k = keys + key_pe
attn_out = self.cross_attn_image_to_token(q=k, k=q, v=queries)
keys = keys + attn_out
keys = self.layer_norm4(keys)
return queries, keys
class Attention(nn.Module):
"""
An attention layer that allows for downscaling the size of the embedding
after projection to queries, keys, and values.
"""
def __init__(
self,
embedding_dim: int,
num_heads: int,
downsample_rate: int = 1,
) -> None:
super().__init__()
self.embedding_dim = embedding_dim
self.internal_dim = embedding_dim // downsample_rate
self.num_heads = num_heads
assert (
self.internal_dim % num_heads == 0
), "num_heads must divide embedding_dim."
self.q_proj = nn.Linear(embedding_dim, self.internal_dim)
self.k_proj = nn.Linear(embedding_dim, self.internal_dim)
self.v_proj = nn.Linear(embedding_dim, self.internal_dim)
self.out_proj = nn.Linear(self.internal_dim, embedding_dim)
def _separate_heads(self, x: mx.array, num_heads: int) -> mx.array:
b, n, c = x.shape
x = x.reshape(b, n, num_heads, c // num_heads)
return x.transpose(0, 2, 1, 3) # B x N_heads x N_tokens x C_per_head
def _recombine_heads(self, x: mx.array) -> mx.array:
b, n_heads, n_tokens, c_per_head = x.shape
x = x.transpose(0, 2, 1, 3)
return x.reshape(b, n_tokens, n_heads * c_per_head) # B x N_tokens x C
def __call__(self, q: mx.array, k: mx.array, v: mx.array) -> mx.array:
# Input projections
q = self.q_proj(q)
k = self.k_proj(k)
v = self.v_proj(v)
# Separate into heads
q = self._separate_heads(q, self.num_heads)
k = self._separate_heads(k, self.num_heads)
v = self._separate_heads(v, self.num_heads)
# Attention
_, _, _, c_per_head = q.shape
attn = q @ k.transpose(0, 1, 3, 2) # B x N_heads x N_tokens x N_tokens
attn = attn / math.sqrt(c_per_head)
attn = mx.softmax(attn, axis=-1)
# Get output
out = attn @ v
out = self._recombine_heads(out)
out = self.out_proj(out)
return out

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import math
from copy import deepcopy
from itertools import product
from typing import Any, Dict, Generator, ItemsView, List, Tuple
import mlx.core as mx
import numpy as np
class MaskData:
"""
A structure for storing masks and their related data in batched format.
Implements basic filtering and concatenation.
"""
def __init__(self, **kwargs) -> None:
for v in kwargs.values():
assert isinstance(
v, (list, np.ndarray, mx.array)
), "MaskData only supports list, numpy arrays, and mlx arrays."
self._stats = dict(**kwargs)
def __setitem__(self, key: str, item: Any) -> None:
assert isinstance(
item, (list, np.ndarray, mx.array)
), "MaskData only supports list, numpy arrays, and mlx arrays."
self._stats[key] = item
def __delitem__(self, key: str) -> None:
del self._stats[key]
def __getitem__(self, key: str) -> Any:
return self._stats[key]
def items(self) -> ItemsView[str, Any]:
return self._stats.items()
def filter(self, keep: mx.array) -> None:
if keep.dtype == mx.bool_:
keep = mx.array(np.where(keep)[0])
for k, v in self._stats.items():
if v is None:
self._stats[k] = None
elif isinstance(v, mx.array):
self._stats[k] = v[keep]
elif isinstance(v, np.ndarray):
self._stats[k] = v[keep]
elif isinstance(v, list):
self._stats[k] = [v[i] for i in keep.tolist()]
else:
raise TypeError(f"MaskData key {k} has an unsupported type {type(v)}.")
def cat(self, new_stats: "MaskData") -> None:
for k, v in new_stats.items():
if k not in self._stats or self._stats[k] is None:
self._stats[k] = deepcopy(v)
elif isinstance(v, mx.array):
self._stats[k] = mx.concatenate([self._stats[k], v], axis=0)
elif isinstance(v, np.ndarray):
self._stats[k] = np.concatenate([self._stats[k], v], axis=0)
elif isinstance(v, list):
self._stats[k] = self._stats[k] + deepcopy(v)
else:
raise TypeError(f"MaskData key {k} has an unsupported type {type(v)}.")
def to_numpy(self) -> None:
for k, v in self._stats.items():
if isinstance(v, mx.array):
self._stats[k] = np.array(v)
def is_box_near_crop_edge(
boxes: mx.array, crop_box: List[int], orig_box: List[int], atol: float = 20.0
) -> mx.array:
"""Filter masks at the edge of a crop, but not at the edge of the original image."""
crop_box_mlx = mx.array(crop_box, dtype=mx.float32)
orig_box_mlx = mx.array(orig_box, dtype=mx.float32)
boxes = uncrop_boxes_xyxy(boxes, crop_box).astype(mx.float32)
near_crop_edge = mx.isclose(boxes, crop_box_mlx[None, :], atol=atol, rtol=0)
near_image_edge = mx.isclose(boxes, orig_box_mlx[None, :], atol=atol, rtol=0)
near_crop_edge = mx.logical_and(near_crop_edge, ~near_image_edge)
return mx.any(near_crop_edge, axis=1)
def box_xyxy_to_xywh(box_xyxy: mx.array) -> mx.array:
box_xywh = deepcopy(box_xyxy)
box_xywh[2] = box_xywh[2] - box_xywh[0]
box_xywh[3] = box_xywh[3] - box_xywh[1]
return box_xywh
def batch_iterator(batch_size: int, *args) -> Generator[List[Any], None, None]:
assert len(args) > 0 and all(
len(a) == len(args[0]) for a in args
), "Batched iteration must have inputs of all the same size."
n_batches = len(args[0]) // batch_size + int(len(args[0]) % batch_size != 0)
for b in range(n_batches):
yield [arg[b * batch_size : (b + 1) * batch_size] for arg in args]
def mask_to_rle_mlx(tensor: mx.array) -> List[Dict[str, Any]]:
"""
Encodes masks to an uncompressed RLE, in the format expected by
pycoco tools.
"""
# Put in fortran order and flatten h,w
b, h, w = tensor.shape
tensor = mx.transpose(tensor, axes=(0, 2, 1)).flatten(1)
# Compute change indices
diff = mx.bitwise_xor(tensor[:, 1:], tensor[:, :-1])
# TODO: fix this with mlx
change_indices = np.stack(np.array(diff).nonzero(), axis=1)
# Encode run length
out = []
for i in range(b):
cur_idxs = change_indices[change_indices[:, 0] == i, 1]
cur_idxs = mx.array(cur_idxs)
cur_idxs = mx.concatenate(
[
mx.array([0], dtype=cur_idxs.dtype),
cur_idxs + 1,
mx.array([h * w], dtype=cur_idxs.dtype),
]
)
btw_idxs = cur_idxs[1:] - cur_idxs[:-1]
counts = [] if tensor[i, 0] == 0 else [0]
counts.extend(btw_idxs.tolist())
out.append({"size": [h, w], "counts": counts})
return out
def rle_to_mask(rle: Dict[str, Any]) -> np.ndarray:
"""Compute a binary mask from an uncompressed RLE."""
h, w = rle["size"]
mask = np.empty(h * w, dtype=bool)
idx = 0
parity = False
for count in rle["counts"]:
mask[idx : idx + count] = parity
idx += count
parity ^= True
mask = mask.reshape(w, h)
return mask.transpose() # Put in C order
def area_from_rle(rle: Dict[str, Any]) -> int:
return sum(rle["counts"][1::2])
def calculate_stability_score(
masks: mx.array, mask_threshold: float, threshold_offset: float
) -> mx.array:
"""
Computes the stability score for a batch of masks. The stability
score is the IoU between the binary masks obtained by thresholding
the predicted mask logits at high and low values.
"""
# One mask is always contained inside the other.
# Save memory by preventing unnecessary cast to mx.int64
# COMMENT OUT DTYPE CASTING FOR COREML
intersections = (
(masks > (mask_threshold + threshold_offset))
.astype(mx.int16)
.sum(-1)
.astype(mx.int32)
.sum(-1)
)
unions = (
(masks > (mask_threshold - threshold_offset))
.astype(mx.int16)
.sum(-1)
.astype(mx.int32)
.sum(-1)
)
return intersections / unions
def build_point_grid(n_per_side: int) -> np.ndarray:
"""Generates a 2D grid of points evenly spaced in [0,1]x[0,1]."""
offset = 1 / (2 * n_per_side)
points_one_side = np.linspace(offset, 1 - offset, n_per_side)
points_x = np.tile(points_one_side[None, :], (n_per_side, 1))
points_y = np.tile(points_one_side[:, None], (1, n_per_side))
points = np.stack([points_x, points_y], axis=-1).reshape(-1, 2)
return points
def build_all_layer_point_grids(
n_per_side: int, n_layers: int, scale_per_layer: int
) -> List[mx.array]:
"""Generates point grids for all crop layers."""
points_by_layer = []
for i in range(n_layers + 1):
n_points = int(n_per_side / (scale_per_layer**i))
points_by_layer.append(mx.array(build_point_grid(n_points)))
return points_by_layer
def generate_crop_boxes(
im_size: Tuple[int, ...], n_layers: int, overlap_ratio: float
) -> Tuple[List[List[int]], List[int]]:
"""
Generates a list of crop boxes of different sizes. Each layer
has (2**i)**2 boxes for the ith layer.
"""
crop_boxes, layer_idxs = [], []
im_h, im_w = im_size
short_side = min(im_h, im_w)
# Original image
crop_boxes.append([0, 0, im_w, im_h])
layer_idxs.append(0)
def crop_len(orig_len, n_crops, overlap):
return int(math.ceil((overlap * (n_crops - 1) + orig_len) / n_crops))
for i_layer in range(n_layers):
n_crops_per_side = 2 ** (i_layer + 1)
overlap = int(overlap_ratio * short_side * (2 / n_crops_per_side))
crop_w = crop_len(im_w, n_crops_per_side, overlap)
crop_h = crop_len(im_h, n_crops_per_side, overlap)
crop_box_x0 = [int((crop_w - overlap) * i) for i in range(n_crops_per_side)]
crop_box_y0 = [int((crop_h - overlap) * i) for i in range(n_crops_per_side)]
# Crops in XYWH format
for x0, y0 in product(crop_box_x0, crop_box_y0):
box = [x0, y0, min(x0 + crop_w, im_w), min(y0 + crop_h, im_h)]
crop_boxes.append(box)
layer_idxs.append(i_layer + 1)
return crop_boxes, layer_idxs
def uncrop_boxes_xyxy(boxes: mx.array, crop_box: List[int]) -> mx.array:
x0, y0, _, _ = crop_box
offset = mx.array([[x0, y0, x0, y0]])
# Check if boxes has a channel dimension
if len(boxes.shape) == 3:
offset = offset.unsqueeze(1)
return boxes + offset
def uncrop_points(points: mx.array, crop_box: List[int]) -> mx.array:
x0, y0, _, _ = crop_box
offset = mx.array([[x0, y0]])
# Check if points has a channel dimension
if len(points.shape) == 3:
offset = offset.unsqueeze(1)
return points + offset
def uncrop_masks(
masks: mx.array, crop_box: List[int], orig_h: int, orig_w: int
) -> mx.array:
x0, y0, x1, y1 = crop_box
if x0 == 0 and y0 == 0 and x1 == orig_w and y1 == orig_h:
return masks
# Coordinate transform masks
pad_x, pad_y = orig_w - (x1 - x0), orig_h - (y1 - y0)
pad = [(0, 0), (y0, pad_y - y0), (x0, pad_x - x0)]
return mx.pad(masks, pad, 0)
def remove_small_regions(
mask: np.ndarray, area_thresh: float, mode: str
) -> Tuple[np.ndarray, bool]:
"""
Removes small disconnected regions and holes in a mask. Returns the
mask and an indicator of if the mask has been modified.
"""
import cv2 # type: ignore
assert mode in ["holes", "islands"]
correct_holes = mode == "holes"
working_mask = (correct_holes ^ mask).astype(np.uint8)
n_labels, regions, stats, _ = cv2.connectedComponentsWithStats(working_mask, 8)
sizes = stats[:, -1][1:] # Row 0 is background label
small_regions = [i + 1 for i, s in enumerate(sizes) if s < area_thresh]
if len(small_regions) == 0:
return mask, False
fill_labels = [0] + small_regions
if not correct_holes:
fill_labels = [i for i in range(n_labels) if i not in fill_labels]
# If every region is below threshold, keep largest
if len(fill_labels) == 0:
fill_labels = [int(np.argmax(sizes)) + 1]
mask = np.isin(regions, fill_labels)
return mask, True
def coco_encode_rle(uncompressed_rle: Dict[str, Any]) -> Dict[str, Any]:
from pycocotools import mask as mask_utils # type: ignore
h, w = uncompressed_rle["size"]
rle = mask_utils.frPyObjects(uncompressed_rle, h, w)
rle["counts"] = rle["counts"].decode("utf-8") # Necessary to serialize with json
return rle
def batched_mask_to_box(masks: mx.array) -> mx.array:
"""
Calculates boxes in XYXY format around masks. Return [0,0,0,0] for
an empty mask. For input shape C1xC2x...xHxW, the output shape is C1xC2x...x4.
"""
# mx.max below raises an error on empty inputs, just skip in this case
if np.prod(masks.shape) == 0:
return mx.zeros(*masks.shape[:-2], 4)
# Normalize shape to CxHxW
shape = masks.shape
h, w = shape[-2:]
if len(shape) > 2:
masks = masks.flatten(0, -3)
else:
masks = masks.unsqueeze(0)
# Get top and bottom edges
in_height = mx.max(masks, axis=-1)
in_height_coords = in_height * mx.arange(h)[None, :]
bottom_edges = mx.max(in_height_coords, axis=-1)
in_height_coords = in_height_coords + h * (~in_height)
top_edges = mx.min(in_height_coords, axis=-1)
# Get left and right edges
in_width = mx.max(masks, axis=-2)
in_width_coords = in_width * mx.arange(w)[None, :]
right_edges = mx.max(in_width_coords, axis=-1)
in_width_coords = in_width_coords + w * (~in_width)
left_edges = mx.min(in_width_coords, axis=-1)
# If the mask is empty the right edge will be to the left of the left edge.
# Replace these boxes with [0, 0, 0, 0]
empty_filter = (right_edges < left_edges) | (bottom_edges < top_edges)
out = mx.stack([left_edges, top_edges, right_edges, bottom_edges], axis=-1)
out = out * (~empty_filter)[..., None]
# Return to original shape
if len(shape) > 2:
out = out.reshape(*shape[:-2], 4)
else:
out = out[0]
return out

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from copy import deepcopy
from typing import Tuple
import mlx.core as mx
import mlx.nn as nn
import numpy as np
from PIL import Image
class ResizeLongestSide:
"""
Resizes images to the longest side 'target_length', as well as provides
methods for resizing coordinates and boxes. Provides methods for
transforming both numpy array and batched mlx tensors.
"""
def __init__(self, target_length: int) -> None:
self.target_length = target_length
def apply_image(self, image: np.ndarray) -> np.ndarray:
"""
Expects a numpy array with shape HxWxC in uint8 format.
"""
target_size = self.get_preprocess_shape(
image.shape[0], image.shape[1], self.target_length
)
return np.array(
Image.fromarray(image).resize(
target_size[::-1], resample=Image.Resampling.BILINEAR
)
)
def apply_coords(
self, coords: mx.array, original_size: Tuple[int, ...]
) -> mx.array:
"""
Expects a mlx tensor with length 2 in the last dimension. Requires the
original image size in (H, W) format.
"""
old_h, old_w = original_size
new_h, new_w = self.get_preprocess_shape(
original_size[0], original_size[1], self.target_length
)
return coords * mx.array([new_w / old_w, new_h / old_h])
def apply_boxes(self, boxes: mx.array, original_size: Tuple[int, ...]) -> mx.array:
"""
Expects a mlx tensor with shape ...x4. Requires the original image
size in (H, W) format.
"""
boxes = self.apply_coords(boxes.reshape(-1, 2, 2), original_size)
return boxes.reshape(-1, 4)
@staticmethod
def get_preprocess_shape(
oldh: int, oldw: int, long_side_length: int
) -> Tuple[int, int]:
"""
Compute the output size given input size and target long side length.
"""
scale = long_side_length * 1.0 / max(oldh, oldw)
newh, neww = oldh * scale, oldw * scale
neww = int(neww + 0.5)
newh = int(newh + 0.5)
return (newh, neww)