utils/utils.py

import os
import pandas as pd
import numpy as np
from torch.utils.data import Dataset
from PIL import Image

class ImageData(Dataset):
    def __init__(self, img_dir, annotation_file, validation_set, transform=None):
        """
        Custom Dataset that respects the 'validation_set' column in the CSV.
        0 = Training Set
        1 = Validation Set
        """
        # Read the CSV file
        try:
            gt = pd.read_csv(annotation_file)
        except Exception as e:
            print(f"Error reading CSV {annotation_file}: {e}")
            # Return empty if failed, to prevent crash during init
            self.img_labels = pd.DataFrame()
            self.img_dir = img_dir
            self.transform = transform
            self.images = []
            self.labels = []
            return

        # Filter: 0 = Train, 1 = Validation
        if validation_set:
            self.img_labels = gt[gt["validation_set"] == 1].reset_index(drop=True)
        else:
            self.img_labels = gt[gt["validation_set"] == 0].reset_index(drop=True)
        
        self.img_dir = img_dir
        self.transform = transform
        
        # Store filenames and labels
        self.images = self.img_labels["file_name"].values
        self.labels = self.img_labels["category_id"].values
        
    def __len__(self):
        return len(self.img_labels)

    def __getitem__(self, idx):
        img_name = self.images[idx]
        img_path = os.path.join(self.img_dir, img_name)
        
        # CRITICAL: Open in RGB mode. OpenCV loads BGR by default, but PIL is safer here.
        image = Image.open(img_path).convert("RGB")
        
        label = self.labels[idx]
        
        if self.transform:
            image = self.transform(image)

        # Return image and label (as long/int for CrossEntropyLoss)
        return image, int(label)