Fix image2image for SDXL (#563)

---------

Co-authored-by: Angelos Katharopoulos <katharas@gmail.com>

stable_diffusion/image2image.py

@@ -7,7 +7,7 @@ import numpy as np
 from PIL import Image
 from tqdm import tqdm
 
-from stable_diffusion import StableDiffusion
+from stable_diffusion import StableDiffusion, StableDiffusionXL
 
 if __name__ == "__main__":
     parser = argparse.ArgumentParser(
@@ -15,10 +15,11 @@ if __name__ == "__main__":
     )
     parser.add_argument("image")
     parser.add_argument("prompt")
+    parser.add_argument("--model", choices=["sd", "sdxl"], default="sdxl")
     parser.add_argument("--strength", type=float, default=0.9)
     parser.add_argument("--n_images", type=int, default=4)
-    parser.add_argument("--steps", type=int, default=50)
+    parser.add_argument("--steps", type=int)
-    parser.add_argument("--cfg", type=float, default=7.5)
+    parser.add_argument("--cfg", type=float)
     parser.add_argument("--negative_prompt", default="")
     parser.add_argument("--n_rows", type=int, default=1)
     parser.add_argument("--decoding_batch_size", type=int, default=1)
@@ -29,10 +30,23 @@ if __name__ == "__main__":
     parser.add_argument("--verbose", "-v", action="store_true")
     args = parser.parse_args()
 
-    sd = StableDiffusion("stabilityai/stable-diffusion-2-1-base", float16=args.float16)
+    if args.model == "sdxl":
+        sd = StableDiffusionXL("stabilityai/sdxl-turbo", float16=args.float16)
+        if args.quantize:
+            QuantizedLinear.quantize_module(sd.text_encoder_1)
+            QuantizedLinear.quantize_module(sd.text_encoder_2)
+            QuantizedLinear.quantize_module(sd.unet, group_size=32, bits=8)
+        args.cfg = args.cfg or 0.0
+        args.steps = args.steps or 2
+    else:
+        sd = StableDiffusion(
+            "stabilityai/stable-diffusion-2-1-base", float16=args.float16
+        )
         if args.quantize:
             QuantizedLinear.quantize_module(sd.text_encoder)
             QuantizedLinear.quantize_module(sd.unet, group_size=32, bits=8)
+        args.cfg = args.cfg or 7.5
+        args.steps = args.steps or 50
     if args.preload_models:
         sd.ensure_models_are_loaded()
 
@@ -64,6 +78,10 @@ if __name__ == "__main__":
     # The following is not necessary but it may help in memory
     # constrained systems by reusing the memory kept by the unet and the text
     # encoders.
+    if args.model == "sdxl":
+        del sd.text_encoder_1
+        del sd.text_encoder_2
+    else:
         del sd.text_encoder
     del sd.unet
     del sd.sampler

stable_diffusion/stable_diffusion/__init__.py

@@ -264,3 +264,42 @@ class StableDiffusionXL(StableDiffusion):
             cfg_weight,
             text_time=text_time,
         )
+
+    def generate_latents_from_image(
+        self,
+        image,
+        text: str,
+        n_images: int = 1,
+        strength: float = 0.8,
+        num_steps: int = 2,
+        cfg_weight: float = 0.0,
+        negative_text: str = "",
+        seed=None,
+    ):
+        # Set the PRNG state
+        seed = seed or int(time.time())
+        mx.random.seed(seed)
+
+        # Define the num steps and start step
+        start_step = self.sampler.max_time * strength
+        num_steps = int(num_steps * strength)
+
+        # Get the text conditioning
+        conditioning, pooled_conditioning = self._get_text_conditioning(
+            text, n_images, cfg_weight, negative_text
+        )
+        text_time = (
+            pooled_conditioning,
+            mx.array([[512, 512, 0, 0, 512, 512.0]] * len(pooled_conditioning)),
+        )
+
+        # Get the latents from the input image and add noise according to the
+        # start time.
+        x_0, _ = self.autoencoder.encode(image[None])
+        x_0 = mx.broadcast_to(x_0, (n_images,) + x_0.shape[1:])
+        x_T = self.sampler.add_noise(x_0, mx.array(start_step))
+
+        # Perform the denoising loop
+        yield from self._denoising_loop(
+            x_T, start_step, conditioning, num_steps, cfg_weight, text_time=text_time
+        )