image_tokenizer.py

# Copyright (c) Meta Platforms, Inc. and affiliates
#
# This source code is licensed under the Chameleon License found in the
# LICENSE file in the root directory of this source tree.

import numpy as np
import PIL
import torch
import yaml
from PIL import Image

from chameleon.inference.vqgan import VQModel


class ImageTokenizer:
    def __init__(
        self,
        cfg_path: str,
        ckpt_path: str,
        device: str | torch.device | None = None,
    ):
        with open(cfg_path) as f:
            config = yaml.safe_load(f)

        params = config["model"]["params"]
        if "lossconfig" in params:
            del params["lossconfig"]
        params["ckpt_path"] = ckpt_path

        self._vq_model = VQModel(**params)
        self._vq_model.eval()

        if device is None:
            devices = {p.device for p in self._vq_model.parameters()}
            assert len(devices) == 1
            device = devices.pop()
        else:
            self._vq_model.to(device)
        self._device = device

        dtypes = {p.dtype for p in self._vq_model.parameters()}
        assert len(dtypes) == 1
        self._dtype = dtypes.pop()

    def _whiten_transparency(self, img: PIL.Image) -> PIL.Image:
        # Check if it's already in RGB format.
        if img.mode == "RGB":
            return img

        vals_rgba = np.array(img.convert("RGBA"))

        # If there is no transparency layer, simple convert and return.
        if not (vals_rgba[:, :, 3] < 255).any():
            return img.convert("RGB")

        # There is a transparency layer, blend it with a white background.

        # Calculate the alpha proportion for blending.
        alpha = vals_rgba[:, :, 3] / 255.0
        # Blend with white background.
        vals_rgb = (1 - alpha[:, :, np.newaxis]) * 255 + alpha[
            :, :, np.newaxis
        ] * vals_rgba[:, :, :3]
        return PIL.Image.fromarray(vals_rgb.astype("uint8"), "RGB")

    def _vqgan_input_from(self, img: PIL.Image, target_image_size=512) -> torch.Tensor:
        # Resize with aspect ratio preservation.
        s = min(img.size)
        scale = target_image_size / s
        new_size = (round(scale * img.size[0]), round(scale * img.size[1]))
        img = img.resize(new_size, PIL.Image.LANCZOS)

        # Center crop.
        x0 = (img.width - target_image_size) // 2
        y0 = (img.height - target_image_size) // 2
        img = img.crop((x0, y0, x0 + target_image_size, y0 + target_image_size))

        # Convert to tensor.
        np_img = np.array(img) / 255.0  # Normalize to [0, 1]
        np_img = np_img * 2 - 1  # Scale to [-1, 1]
        tensor_img = (
            torch.from_numpy(np_img).permute(2, 0, 1).float()
        )  # (Channels, Height, Width) format.

        # Add batch dimension.
        return tensor_img.unsqueeze(0)

    def img_tokens_from_pil(self, image: PIL.Image) -> list[int]:
        image = self._whiten_transparency(image)
        vqgan_input = self._vqgan_input_from(image).to(self._device).to(self._dtype)
        _, _, [_, _, img_toks] = self._vq_model.encode(vqgan_input)
        return img_toks

    def _pil_from_chw_tensor(self, chw_tensor: torch.Tensor) -> PIL.Image:
        # Ensure detachment and move tensor to CPU.
        detached_chw_tensor = chw_tensor.detach().cpu()

        # Normalize tensor to [0, 1] range from [-1, 1] range.
        normalized_chw_tensor = (
            torch.clamp(detached_chw_tensor, -1.0, 1.0) + 1.0
        ) / 2.0

        # Permute CHW tensor to HWC format and convert to NumPy array.
        hwc_array = normalized_chw_tensor.permute(1, 2, 0).numpy()

        # Convert to an 8-bit unsigned integer format.
        image_array_uint8 = (hwc_array * 255).astype(np.uint8)

        # Convert NumPy array to PIL Image.
        pil_image = Image.fromarray(image_array_uint8)

        # Convert image to RGB if it is not already.
        if pil_image.mode != "RGB":
            pil_image = pil_image.convert("RGB")

        return pil_image

    def pil_from_img_toks(self, img_tensor: torch.Tensor) -> PIL.Image:
        emb_dim = self._vq_model.quantize.embedding.weight.shape[-1]
        codebook_entry = self._vq_model.quantize.get_codebook_entry(
            img_tensor, (1, 32, 32, emb_dim)
        )
        pixels = self._vq_model.decode(codebook_entry)
        return self._pil_from_chw_tensor(pixels[0])