example_usage.py

#!/usr/bin/env python3
"""
Example: Using SDXL Detector from HuggingFace
==============================================

Simple example showing how to use the SDXL detector
to classify images as real or SDXL-generated.
"""

import torch
from torchvision import transforms
from PIL import Image
from huggingface_hub import hf_hub_download
import torch.nn as nn
import torchvision.models as models

# ============================================================================
# MODEL DEFINITION
# ============================================================================

class SDXLDetector(nn.Module):
    """ResNet-50 based SDXL detector"""
    
    def __init__(self):
        super().__init__()
        self.backbone = models.resnet50(pretrained=False)
        num_features = self.backbone.fc.in_features
        
        self.backbone.fc = nn.Sequential(
            nn.Dropout(p=0.3),
            nn.Linear(num_features, 512),
            nn.BatchNorm1d(512),
            nn.ReLU(inplace=True),
            nn.Dropout(p=0.15),
            nn.Linear(512, 2)
        )
    
    def forward(self, x):
        return self.backbone(x)

# ============================================================================
# LOAD MODEL
# ============================================================================

def load_model(device='cpu'):
    """Load model from HuggingFace Hub"""
    
    # Download checkpoint
    model_path = hf_hub_download(
        repo_id="ash12321/sdxl-detector-resnet50",
        filename="best.pth"
    )
    
    # Load checkpoint
    checkpoint = torch.load(model_path, map_location=device)
    
    # Create model and load weights
    model = SDXLDetector()
    model.load_state_dict(checkpoint['model_state_dict'])
    model.to(device)
    model.eval()
    
    print(f"✅ Model loaded from {model_path}")
    print(f"   Trained for {checkpoint['epoch'] + 1} epochs")
    print(f"   Best validation accuracy: {checkpoint['best_val_acc']:.2f}%")
    
    return model

# ============================================================================
# PREPROCESSING
# ============================================================================

def get_transform():
    """Get image preprocessing transform"""
    return transforms.Compose([
        transforms.Resize(256),
        transforms.CenterCrop(224),
        transforms.ToTensor(),
        transforms.Normalize(
            mean=[0.485, 0.456, 0.406],
            std=[0.229, 0.224, 0.225]
        )
    ])

# ============================================================================
# PREDICTION
# ============================================================================

def predict_image(model, image_path, device='cpu'):
    """
    Predict if an image is real or SDXL-generated
    
    Args:
        model: Loaded SDXLDetector model
        image_path: Path to image file
        device: Device to run inference on
    
    Returns:
        dict with prediction, confidence, and probabilities
    """
    
    # Load and preprocess image
    image = Image.open(image_path).convert('RGB')
    transform = get_transform()
    input_tensor = transform(image).unsqueeze(0).to(device)
    
    # Predict
    with torch.no_grad():
        outputs = model(input_tensor)
        probs = torch.softmax(outputs, dim=1)
        prediction = torch.argmax(probs, dim=1).item()
        confidence = probs[0][prediction].item()
    
    # Format results
    labels = ['Real', 'SDXL-generated']
    
    return {
        'prediction': labels[prediction],
        'confidence': confidence,
        'probabilities': {
            'real': probs[0][0].item(),
            'sdxl': probs[0][1].item()
        }
    }

# ============================================================================
# MAIN
# ============================================================================

def main():
    """Example usage"""
    
    # Setup
    device = 'cuda' if torch.cuda.is_available() else 'cpu'
    print(f"Using device: {device}")
    
    # Load model
    model = load_model(device)
    
    # Example prediction
    image_path = "test_image.jpg"  # Replace with your image
    
    result = predict_image(model, image_path, device)
    
    print(f"\n📊 Results for {image_path}:")
    print(f"   Prediction: {result['prediction']}")
    print(f"   Confidence: {result['confidence']*100:.2f}%")
    print(f"   \nProbabilities:")
    print(f"      Real: {result['probabilities']['real']*100:.2f}%")
    print(f"      SDXL: {result['probabilities']['sdxl']*100:.2f}%")

if __name__ == "__main__":
    main()