app.py

#!/usr/bin/env python3
"""
HuggingFace Spaces App for ImageNet ResNet50 Classifier
Trained from scratch to 78%+ Top-1 accuracy
"""

import gradio as gr
import torch
import torch.nn as nn
import torch.nn.functional as F
from torchvision import transforms
from PIL import Image
import json

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

class Bottleneck(nn.Module):
    expansion = 4
    
    def __init__(self, in_planes, planes, stride=1):
        super().__init__()
        self.conv1 = nn.Conv2d(in_planes, planes, kernel_size=1, bias=False)
        self.bn1 = nn.BatchNorm2d(planes)
        self.conv2 = nn.Conv2d(planes, planes, kernel_size=3, stride=stride, padding=1, bias=False)
        self.bn2 = nn.BatchNorm2d(planes)
        self.conv3 = nn.Conv2d(planes, self.expansion * planes, kernel_size=1, bias=False)
        self.bn3 = nn.BatchNorm2d(self.expansion * planes)
        
        self.shortcut = nn.Sequential()
        if stride != 1 or in_planes != self.expansion * planes:
            self.shortcut = nn.Sequential(
                nn.Conv2d(in_planes, self.expansion * planes, kernel_size=1, stride=stride, bias=False),
                nn.BatchNorm2d(self.expansion * planes)
            )
    
    def forward(self, x):
        out = F.relu(self.bn1(self.conv1(x)))
        out = F.relu(self.bn2(self.conv2(out)))
        out = self.bn3(self.conv3(out))
        out += self.shortcut(x)
        out = F.relu(out)
        return out


class ResNet50(nn.Module):
    def __init__(self, num_classes=1000):
        super().__init__()
        self.in_planes = 64
        
        self.conv1 = nn.Conv2d(3, 64, kernel_size=7, stride=2, padding=3, bias=False)
        self.bn1 = nn.BatchNorm2d(64)
        self.maxpool = nn.MaxPool2d(kernel_size=3, stride=2, padding=1)
        
        self.layer1 = self._make_layer(Bottleneck, 64, 3, stride=1)
        self.layer2 = self._make_layer(Bottleneck, 128, 4, stride=2)
        self.layer3 = self._make_layer(Bottleneck, 256, 6, stride=2)
        self.layer4 = self._make_layer(Bottleneck, 512, 3, stride=2)
        
        self.avgpool = nn.AdaptiveAvgPool2d((1, 1))
        self.fc = nn.Linear(512 * 4, num_classes)
    
    def _make_layer(self, block, planes, num_blocks, stride):
        strides = [stride] + [1] * (num_blocks - 1)
        layers = []
        for stride in strides:
            layers.append(block(self.in_planes, planes, stride))
            self.in_planes = planes * block.expansion
        return nn.Sequential(*layers)
    
    def forward(self, x):
        out = F.relu(self.bn1(self.conv1(x)))
        out = self.maxpool(out)
        out = self.layer1(out)
        out = self.layer2(out)
        out = self.layer3(out)
        out = self.layer4(out)
        out = self.avgpool(out)
        out = torch.flatten(out, 1)
        out = self.fc(out)
        return out


# ============================================================================
# MODEL LOADING
# ============================================================================

def load_model():
    """Load the trained model (CPU-optimized for HuggingFace)"""
    model = ResNet50(num_classes=1000)
    
    try:
        # Try to load checkpoint
        checkpoint_path = "best_model_final.pth"  # Will be uploaded separately
        checkpoint = torch.load(checkpoint_path, map_location='cpu')
        
        # Handle different checkpoint formats
        if isinstance(checkpoint, dict):
            if 'model' in checkpoint:
                state_dict = checkpoint['model']
            elif 'state_dict' in checkpoint:
                state_dict = checkpoint['state_dict']
            else:
                state_dict = checkpoint
        else:
            state_dict = checkpoint
        
        # Remove 'module.' prefix if present (from DataParallel)
        new_state_dict = {}
        for k, v in state_dict.items():
            name = k.replace('module.', '') if k.startswith('module.') else k
            new_state_dict[name] = v
        
        model.load_state_dict(new_state_dict)
        print(f"✅ Model loaded successfully from {checkpoint_path}")
        
    except Exception as e:
        print(f"⚠️ Could not load checkpoint: {e}")
        print("Using randomly initialized model for demo purposes")
    
    model.eval()
    return model


# ============================================================================
# IMAGE PREPROCESSING
# ============================================================================

transform = 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])
])


# ============================================================================
# IMAGENET CLASS LABELS
# ============================================================================

# Top 20 most common ImageNet classes for demo
IMAGENET_CLASSES = {
    0: "tench", 1: "goldfish", 2: "great white shark", 3: "tiger shark",
    4: "hammerhead", 5: "electric ray", 6: "stingray", 7: "cock",
    8: "hen", 9: "ostrich", 10: "brambling", 11: "goldfinch",
    12: "house finch", 13: "junco", 14: "indigo bunting", 15: "robin",
    151: "Chihuahua", 207: "golden retriever", 281: "tabby cat",
    282: "tiger cat", 283: "Persian cat", 285: "Egyptian cat",
    291: "lion", 292: "tiger", 293: "jaguar", 294: "leopard",
    404: "airliner", 407: "container ship", 468: "cab",
    511: "convertible", 609: "jeep", 627: "limousine",
    817: "sports car", 751: "racer", 779: "school bus",
    555: "fire engine", 569: "garbage truck", 717: "pickup",
    # Add more as needed
}

# Load full class names - MUST use the corrected mapping!
# This model was trained with folders named 0-999 (lexicographically sorted)
# NOT with standard ImageNet WordNet IDs
try:
    with open('imagenet_classes_corrected.json', 'r') as f:
        loaded_classes = json.load(f)
        # Ensure it's a dict with string keys
        if isinstance(loaded_classes, list):
            IMAGENET_CLASSES = {str(i): name for i, name in enumerate(loaded_classes)}
        else:
            IMAGENET_CLASSES = loaded_classes
    print(f"✅ Loaded corrected ImageNet class mapping with {len(IMAGENET_CLASSES)} classes")
except FileNotFoundError:
    print("⚠️  WARNING: imagenet_classes_corrected.json not found! Using fallback mapping.")
    print("   Model predictions will be INCORRECT without the corrected mapping!")
except Exception as e:
    print(f"⚠️  WARNING: Failed to load class mapping: {e}")


# ============================================================================
# INFERENCE FUNCTION
# ============================================================================

def predict(image):
    """
    Predict ImageNet class for input image
    
    Args:
        image: PIL Image
        
    Returns:
        dict: Top-5 predictions with confidence scores
    """
    if image is None:
        return {"Error": 0.0, "Please upload an image": 0.0}
    
    try:
        # Preprocess
        img_tensor = transform(image).unsqueeze(0)  # Add batch dimension
        
        # Inference
        with torch.no_grad():
            outputs = model(img_tensor)
            probabilities = torch.nn.functional.softmax(outputs[0], dim=0)
        
        # Get top 5 predictions
        top5_prob, top5_indices = torch.topk(probabilities, 5)
        
        # Format results - MUST be dict with string keys and float values
        results = {}
        for i in range(5):
            idx = top5_indices[i].item()
            prob = top5_prob[i].item()
            class_name = IMAGENET_CLASSES.get(str(idx), f"Class {idx}")
            results[class_name] = float(prob)
        
        return results
        
    except Exception as e:
        # Return valid format even for errors
        return {"Prediction Error": 0.0, f"Details: {str(e)[:50]}": 0.0}


# ============================================================================
# GRADIO INTERFACE
# ============================================================================

# Load model globally
print("Loading model...")
model = load_model()
print("Model loaded successfully!")

# Create Gradio interface
with gr.Blocks(theme=gr.themes.Soft()) as demo:
    gr.Markdown("""
    # 🔥 ImageNet ResNet50 Classifier
    
    **Trained from scratch to 77%+ Top-1 accuracy on ImageNet!**
    
    Upload any image and get top-5 predictions with confidence scores.
    """)
    
    with gr.Row():
        with gr.Column():
            image_input = gr.Image(type="pil", label="Upload Image")
            predict_btn = gr.Button("Classify Image", variant="primary")
            
            gr.Markdown("""
            ### 📝 Tips:
            - Works best with **clear, centered objects**
            - Supports **1000 ImageNet classes** (animals, vehicles, objects, etc.)
            - Try images from different categories!
            """)
        
        with gr.Column():
            output = gr.Label(num_top_classes=5, label="Top-5 Predictions")
            
            gr.Markdown("""
            ### 🎯 Model Info:
            - **Architecture:** ResNet50 (25.5M params)
            - **Training:** From scratch (no pretrained weights)
            - **Dataset:** ImageNet (1.2M images, 1000 classes)
            - **Accuracy:** 77.09% Top-1 validation
            
            ### 🔗 Links:
            - [GitHub Repository](https://github.com/Shwethaamrutha/TSAI-S9)
            """)
    
    # Example images
    gr.Markdown("### 🖼️ Try These Examples:")
    gr.Examples(
        examples=[
            ["GermanShephard.jpg"],
            ["Goldfish.jpg"],
            ["Tiger.jpg"],
            ["SilkyTerrier.avif"],
        ],
        inputs=image_input,
        outputs=output,
        fn=predict,
        cache_examples=False,
    )
    
    # Connect button
    predict_btn.click(fn=predict, inputs=image_input, outputs=output)
    


# Launch
if __name__ == "__main__":
    demo.launch()