code/src/data/dataset/kvasir_seg.py

# Kvasir-SEG Dataset for PixelGen Medical Image Generation
# Polyp segmentation dataset: 1000 RGB colonoscopy images with binary masks

import os
import torch
import random
import numpy as np
from torch.utils.data import Dataset
from PIL import Image
import torchvision.transforms as transforms
import torchvision.transforms.functional as TF
from torchvision.transforms import Normalize


class KvasirSEGDataset(Dataset):
    """
    Kvasir-SEG dataset for mask-conditional image generation.

    Data format:
    - Images: ~620x530 RGB colonoscopy images (varying sizes)
    - Masks: Binary polyp segmentation (near 0/255, grayscale)
    - 1000 image pairs total

    Returns format compatible with PixelGen:
    - normalized_image: [3, H, W] in range [-1, 1]
    - label: class label (0 for all)
    - metadata: dict with 'raw_image', 'mask', 'class'
    """

    def __init__(self, data_root, resolution=256, split='train', train_ratio=0.9,
                 augment=True, seed=42, max_samples=None, random_flip=True):
        super().__init__()
        self.data_root = data_root
        self.resolution = resolution
        self.split = split
        self.augment = augment and (split == 'train')
        self.random_flip = random_flip and (split == 'train')

        self.img_dir = os.path.join(data_root, 'images')
        self.mask_dir = os.path.join(data_root, 'masks')

        # Get all image files
        all_files = sorted([f for f in os.listdir(self.img_dir)
                           if f.endswith(('.jpg', '.png', '.jpeg'))])

        # Split by index
        random.seed(seed)
        indices = list(range(len(all_files)))
        random.shuffle(indices)
        split_idx = int(len(indices) * train_ratio)

        if split == 'train':
            selected_indices = indices[:split_idx]
        else:
            selected_indices = indices[split_idx:]

        self.images = [all_files[i] for i in sorted(selected_indices)]

        # Limit samples if specified
        if max_samples is not None and max_samples < len(self.images):
            random.seed(seed)
            self.images = random.sample(self.images, max_samples)

        # Normalization for images ([-1, 1] range)
        self.normalize = Normalize(mean=[0.5, 0.5, 0.5], std=[0.5, 0.5, 0.5])

        print(f"[KvasirSEGDataset] {split} set: {len(self.images)} images")

    def __len__(self):
        return len(self.images)

    def _load_and_process(self, idx):
        """Load and process a single sample."""
        img_name = self.images[idx]
        img_path = os.path.join(self.img_dir, img_name)
        mask_path = os.path.join(self.mask_dir, img_name)

        # Load images - RGB colonoscopy
        image = Image.open(img_path).convert('RGB')
        mask = Image.open(mask_path).convert('L')

        # Resize to target size (square)
        image = TF.resize(image, (self.resolution, self.resolution),
                         interpolation=transforms.InterpolationMode.BILINEAR)
        mask = TF.resize(mask, (self.resolution, self.resolution),
                        interpolation=transforms.InterpolationMode.NEAREST)

        # Data augmentation
        if self.augment:
            # Random horizontal flip
            if self.random_flip and random.random() > 0.5:
                image = TF.hflip(image)
                mask = TF.hflip(mask)

            # Random vertical flip
            if self.random_flip and random.random() > 0.5:
                image = TF.vflip(image)
                mask = TF.vflip(mask)

            # Random color jitter for image only
            if random.random() > 0.5:
                brightness_factor = random.uniform(0.85, 1.15)
                image = TF.adjust_brightness(image, brightness_factor)
                contrast_factor = random.uniform(0.85, 1.15)
                image = TF.adjust_contrast(image, contrast_factor)
                saturation_factor = random.uniform(0.85, 1.15)
                image = TF.adjust_saturation(image, saturation_factor)

        return image, mask

    def __getitem__(self, idx):
        max_retries = 10
        for retry in range(max_retries):
            try:
                actual_idx = (idx + retry) % len(self.images)
                image, mask = self._load_and_process(actual_idx)
                break
            except Exception as e:
                if retry == max_retries - 1:
                    raise RuntimeError(f"Failed to load image after {max_retries} retries: {e}")
                continue

        raw_image = TF.to_tensor(image)  # [3, H, W], range [0, 1]
        normalized_image = self.normalize(raw_image)
        mask_tensor = TF.to_tensor(mask)  # [1, H, W], range [0, 1]

        label = 0
        metadata = {
            "raw_image": raw_image,
            "mask": mask_tensor,
            "class": label,
        }

        return normalized_image, label, metadata


class KvasirSEGRandnDataset(Dataset):
    """
    Random noise dataset for evaluation/prediction.
    Samples random masks from the dataset.
    """

    def __init__(self, data_root, resolution=256, max_num_instances=1000,
                 noise_scale=1.0, seed=42):
        super().__init__()
        self.resolution = resolution
        self.noise_scale = noise_scale

        mask_dir = os.path.join(data_root, 'masks')
        all_files = sorted([f for f in os.listdir(mask_dir)
                           if f.endswith(('.jpg', '.png', '.jpeg'))])

        random.seed(seed)
        if max_num_instances <= len(all_files):
            self.mask_files = random.sample(all_files, max_num_instances)
        else:
            self.mask_files = all_files * (max_num_instances // len(all_files) + 1)
            self.mask_files = self.mask_files[:max_num_instances]

        self.mask_dir = mask_dir
        print(f"[KvasirSEGRandnDataset] {len(self.mask_files)} samples for generation")

    def __len__(self):
        return len(self.mask_files)

    def __getitem__(self, idx):
        xT = self.noise_scale * torch.randn(3, self.resolution, self.resolution)

        mask_path = os.path.join(self.mask_dir, self.mask_files[idx])
        mask = Image.open(mask_path).convert('L')
        mask = TF.resize(mask, (self.resolution, self.resolution),
                        interpolation=transforms.InterpolationMode.NEAREST)
        mask_tensor = TF.to_tensor(mask)

        label = 0
        metadata = {
            "mask": mask_tensor,
            "class": label,
        }

        return xT, label, metadata