Add vae_roundtrip.py example (#7104)

* Add vae_roundtrip.py example

* Add cuda support to vae_roundtrip

* Move vae_roundtrip.py into research_projects/vae

* Fix channel scaling in vae roundrip and also support taesd.

* Apply ruff --fix for CI gatekeep check

---------
Co-authored-by: Álvaro Somoza <asomoza@users.noreply.github.com>

examples/research_projects/vae/README.md

+# VAE
+
+`vae_roundtrip.py` Demonstrates the use of a VAE by roundtripping an image through the encoder and decoder. Original and reconstructed images are displayed side by side.
+
+```
+cd examples/research_projects/vae
+python vae_roundtrip.py \
+    --pretrained_model_name_or_path="runwayml/stable-diffusion-v1-5" \
+    --subfolder="vae" \
+    --input_image="/path/to/your/input.png"
+```

examples/research_projects/vae/vae_roundtrip.py

+#!/usr/bin/env python
+# coding=utf-8
+# Copyright 2024 The HuggingFace Inc. team. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+
+import argparse
+import typing
+from typing import Optional, Union
+
+import torch
+from PIL import Image
+from torchvision import transforms  # type: ignore
+
+from diffusers.image_processor import VaeImageProcessor
+from diffusers.models.autoencoders.autoencoder_kl import (
+    AutoencoderKL,
+    AutoencoderKLOutput,
+)
+from diffusers.models.autoencoders.autoencoder_tiny import (
+    AutoencoderTiny,
+    AutoencoderTinyOutput,
+)
+from diffusers.models.autoencoders.vae import DecoderOutput
+
+
+SupportedAutoencoder = Union[AutoencoderKL, AutoencoderTiny]
+
+
+def load_vae_model(
+    *,
+    device: torch.device,
+    model_name_or_path: str,
+    revision: Optional[str],
+    variant: Optional[str],
+    # NOTE: use subfolder="vae" if the pointed model is for stable diffusion as a whole instead of just the VAE
+    subfolder: Optional[str],
+    use_tiny_nn: bool,
+) -> SupportedAutoencoder:
+    if use_tiny_nn:
+        # NOTE: These scaling factors don't have to be the same as each other.
+        down_scale = 2
+        up_scale = 2
+        vae = AutoencoderTiny.from_pretrained(  # type: ignore
+            model_name_or_path,
+            subfolder=subfolder,
+            revision=revision,
+            variant=variant,
+            downscaling_scaling_factor=down_scale,
+            upsampling_scaling_factor=up_scale,
+        )
+        assert isinstance(vae, AutoencoderTiny)
+    else:
+        vae = AutoencoderKL.from_pretrained(  # type: ignore
+            model_name_or_path,
+            subfolder=subfolder,
+            revision=revision,
+            variant=variant,
+        )
+        assert isinstance(vae, AutoencoderKL)
+    vae = vae.to(device)
+    vae.eval()  # Set the model to inference mode
+    return vae
+
+
+def pil_to_nhwc(
+    *,
+    device: torch.device,
+    image: Image.Image,
+) -> torch.Tensor:
+    assert image.mode == "RGB"
+    transform = transforms.ToTensor()
+    nhwc = transform(image).unsqueeze(0).to(device)  # type: ignore
+    assert isinstance(nhwc, torch.Tensor)
+    return nhwc
+
+
+def nhwc_to_pil(
+    *,
+    nhwc: torch.Tensor,
+) -> Image.Image:
+    assert nhwc.shape[0] == 1
+    hwc = nhwc.squeeze(0).cpu()
+    return transforms.ToPILImage()(hwc)  # type: ignore
+
+
+def concatenate_images(
+    *,
+    left: Image.Image,
+    right: Image.Image,
+    vertical: bool = False,
+) -> Image.Image:
+    width1, height1 = left.size
+    width2, height2 = right.size
+    if vertical:
+        total_height = height1 + height2
+        max_width = max(width1, width2)
+        new_image = Image.new("RGB", (max_width, total_height))
+        new_image.paste(left, (0, 0))
+        new_image.paste(right, (0, height1))
+    else:
+        total_width = width1 + width2
+        max_height = max(height1, height2)
+        new_image = Image.new("RGB", (total_width, max_height))
+        new_image.paste(left, (0, 0))
+        new_image.paste(right, (width1, 0))
+    return new_image
+
+
+def to_latent(
+    *,
+    rgb_nchw: torch.Tensor,
+    vae: SupportedAutoencoder,
+) -> torch.Tensor:
+    rgb_nchw = VaeImageProcessor.normalize(rgb_nchw)  # type: ignore
+    encoding_nchw = vae.encode(typing.cast(torch.FloatTensor, rgb_nchw))
+    if isinstance(encoding_nchw, AutoencoderKLOutput):
+        latent = encoding_nchw.latent_dist.sample()  # type: ignore
+        assert isinstance(latent, torch.Tensor)
+    elif isinstance(encoding_nchw, AutoencoderTinyOutput):
+        latent = encoding_nchw.latents
+        do_internal_vae_scaling = False  # Is this needed?
+        if do_internal_vae_scaling:
+            latent = vae.scale_latents(latent).mul(255).round().byte()  # type: ignore
+            latent = vae.unscale_latents(latent / 255.0)  # type: ignore
+            assert isinstance(latent, torch.Tensor)
+    else:
+        assert False, f"Unknown encoding type: {type(encoding_nchw)}"
+    return latent
+
+
+def from_latent(
+    *,
+    latent_nchw: torch.Tensor,
+    vae: SupportedAutoencoder,
+) -> torch.Tensor:
+    decoding_nchw = vae.decode(latent_nchw)  # type: ignore
+    assert isinstance(decoding_nchw, DecoderOutput)
+    rgb_nchw = VaeImageProcessor.denormalize(decoding_nchw.sample)  # type: ignore
+    assert isinstance(rgb_nchw, torch.Tensor)
+    return rgb_nchw
+
+
+def main_kwargs(
+    *,
+    device: torch.device,
+    input_image_path: str,
+    pretrained_model_name_or_path: str,
+    revision: Optional[str],
+    variant: Optional[str],
+    subfolder: Optional[str],
+    use_tiny_nn: bool,
+) -> None:
+    vae = load_vae_model(
+        device=device,
+        model_name_or_path=pretrained_model_name_or_path,
+        revision=revision,
+        variant=variant,
+        subfolder=subfolder,
+        use_tiny_nn=use_tiny_nn,
+    )
+    original_pil = Image.open(input_image_path).convert("RGB")
+    original_image = pil_to_nhwc(
+        device=device,
+        image=original_pil,
+    )
+    print(f"Original image shape: {original_image.shape}")
+    reconstructed_image: Optional[torch.Tensor] = None
+
+    with torch.no_grad():
+        latent_image = to_latent(rgb_nchw=original_image, vae=vae)
+        print(f"Latent shape: {latent_image.shape}")
+        reconstructed_image = from_latent(latent_nchw=latent_image, vae=vae)
+        reconstructed_pil = nhwc_to_pil(nhwc=reconstructed_image)
+    combined_image = concatenate_images(
+        left=original_pil,
+        right=reconstructed_pil,
+        vertical=False,
+    )
+    combined_image.show("Original | Reconstruction")
+    print(f"Reconstructed image shape: {reconstructed_image.shape}")
+
+
+def parse_args() -> argparse.Namespace:
+    parser = argparse.ArgumentParser(description="Inference with VAE")
+    parser.add_argument(
+        "--input_image",
+        type=str,
+        required=True,
+        help="Path to the input image for inference.",
+    )
+    parser.add_argument(
+        "--pretrained_model_name_or_path",
+        type=str,
+        required=True,
+        help="Path to pretrained VAE model.",
+    )
+    parser.add_argument(
+        "--revision",
+        type=str,
+        default=None,
+        help="Model version.",
+    )
+    parser.add_argument(
+        "--variant",
+        type=str,
+        default=None,
+        help="Model file variant, e.g., 'fp16'.",
+    )
+    parser.add_argument(
+        "--subfolder",
+        type=str,
+        default=None,
+        help="Subfolder in the model file.",
+    )
+    parser.add_argument(
+        "--use_cuda",
+        action="store_true",
+        help="Use CUDA if available.",
+    )
+    parser.add_argument(
+        "--use_tiny_nn",
+        action="store_true",
+        help="Use tiny neural network.",
+    )
+    return parser.parse_args()
+
+
+# EXAMPLE USAGE:
+#
+# python vae_roundtrip.py --use_cuda --pretrained_model_name_or_path "runwayml/stable-diffusion-v1-5" --subfolder "vae" --input_image "foo.png"
+#
+# python vae_roundtrip.py --use_cuda --pretrained_model_name_or_path "madebyollin/taesd" --use_tiny_nn --input_image "foo.png"
+#
+def main_cli() -> None:
+    args = parse_args()
+
+    input_image_path = args.input_image
+    assert isinstance(input_image_path, str)
+
+    pretrained_model_name_or_path = args.pretrained_model_name_or_path
+    assert isinstance(pretrained_model_name_or_path, str)
+
+    revision = args.revision
+    assert isinstance(revision, (str, type(None)))
+
+    variant = args.variant
+    assert isinstance(variant, (str, type(None)))
+
+    subfolder = args.subfolder
+    assert isinstance(subfolder, (str, type(None)))
+
+    use_cuda = args.use_cuda
+    assert isinstance(use_cuda, bool)
+
+    use_tiny_nn = args.use_tiny_nn
+    assert isinstance(use_tiny_nn, bool)
+
+    device = torch.device("cuda" if use_cuda else "cpu")
+
+    main_kwargs(
+        device=device,
+        input_image_path=input_image_path,
+        pretrained_model_name_or_path=pretrained_model_name_or_path,
+        revision=revision,
+        variant=variant,
+        subfolder=subfolder,
+        use_tiny_nn=use_tiny_nn,
+    )
+
+
+if __name__ == "__main__":
+    main_cli()