app.py

import gradio as gr                                                                                                                                                                                                  
import numpy as np                                                                                                                                                                                                   
from PIL import Image                                                                                                                                                                                                
                                                                                                                                                                                                                     
# Import our custom layers and activations                                                                                                                                                                           
from layers import Conv, MaxPool, Flatten, Dense                                                                                                                                                                     
from activations import GELU                                                                                                                                                                                         
                                                                                                                                                                                                                     
# 1. Initialize the network structure                                                                                                                                                                                
conv = Conv(input_shape=(1, 28, 28), kernel_size=5, num_kernels=12)                                                                                                                                                  
gelu = GELU()                                                                                                                                                                                                        
pool = MaxPool(2, 2)                                                                                                                                                                                                 
flatten = Flatten()                                                                                                                                                                                                  
dense = Dense(1728, 10)                                                                                                                                                                                              
                                                                                                                                                                                                                     
# 2. Try loading the weights safely                                                                                                                                                                                  
weights_loaded = False                                                                                                                                                                                               
try:                                                                                                                                                                                                                 
    data = np.load("model_weights.npz")                                                                                                                                                                              
    conv.kernels = data["conv_kernels"]                                                                                                                                                                              
    conv.biases = data["conv_biases"]                                                                                                                                                                                
    dense.weights = data["dense_weights"]                                                                                                                                                                            
    dense.biases = data["dense_biases"]                                                                                                                                                                              
    weights_loaded = True                                                                                                                                                                                            
    print("Weights loaded successfully!")                                                                                                                                                                            
except FileNotFoundError:                                                                                                                                                                                            
    print("Warning: model_weights.npz not found.")                                                                                                                                                                   
except Exception as e:                                                                                                                                                                                               
    print(f"Warning: error loading weights: {e}")                                                                                                                                                                    
                                                                                                                                                                                                                     
# Helper to stitch feature maps into a nice grid                                                                                                                                                                     
def make_grid(feature_maps, cols=4):                                                                                                                                                                                 
    n, h, w = feature_maps.shape                                                                                                                                                                                     
    rows = (n + cols - 1) // cols                                                                                                                                                                                    
                                                                                                                                                                                                                     
    # Pad borders between filters so they look separate                                                                                                                                                              
    padding = 2                                                                                                                                                                                                      
    grid_h = rows * h + (rows - 1) * padding                                                                                                                                                                         
    grid_w = cols * w + (cols - 1) * padding                                                                                                                                                                         
    grid = np.zeros((grid_h, grid_w), dtype=np.uint8)                                                                                                                                                                
                                                                                                                                                                                                                     
    for idx in range(n):                                                                                                                                                                                             
        r = idx // cols                                                                                                                                                                                              
        c = idx % cols                                                                                                                                                                                               
                                                                                                                                                                                                                     
        f_map = feature_maps[idx]                                                                                                                                                                                    
        f_min, f_max = f_map.min(), f_map.max()                                                                                                                                                                      
        # Normalize to [0, 255] for image display                                                                                                                                                                    
        if f_max > f_min:                                                                                                                                                                                            
            f_map = 255.0 * (f_map - f_min) / (f_max - f_min)                                                                                                                                                        
        else:                                                                                                                                                                                                        
            f_map = f_map * 0                                                                                                                                                                                        
                                                                                                                                                                                                                     
        f_map = f_map.astype(np.uint8)                                                                                                                                                                               
                                                                                                                                                                                                                     
        y_start = r * (h + padding)                                                                                                                                                                                  
        x_start = c * (w + padding)                                                                                                                                                                                  
        grid[y_start:y_start+h, x_start:x_start+w] = f_map                                                                                                                                                           
                                                                                                                                                                                                                     
    img = Image.fromarray(grid)                                                                                                                                                                                      
    # Scale up using nearest-neighbor to keep pixels clean and sharp                                                                                                                                                 
    img = img.resize((grid_w * 12, grid_h * 12), Image.Resampling.NEAREST)                                                                                                                                           
    return img                                                                                                                                                                                                       
                                                                                                                                                                                                                     
# 3. Predict function                                                                                                                                                                                                
def predict(input_image):                                                                                                                                                                                            
    if not weights_loaded:                                                                                                                                                                                           
        return {"Error: please upload 'model_weights.npz'": 1.0}, None, None                                                                                                                                         
                                                                                                                                                                                                                     
    if input_image is None:                                                                                                                                                                                          
        return "No image drawn", None, None                                                                                                                                                                          
                                                                                                                                                                                                                     
    if isinstance(input_image, dict):                                                                                                                                                                                
        img = input_image['composite']                                                                                                                                                                               
    else:                                                                                                                                                                                                            
        img = input_image                                                                                                                                                                                            
                                                                                                                                                                                                                     
    # Resize and convert to grayscale                                                                                                                                                                                
    img = img.convert('L').resize((100, 100))                                                                                                                                                                        
    arr = np.array(img)                                                                                                                                                                                              
                                                                                                                                                                                                                     
    # Invert background to match MNIST (white text on black background)                                                                                                                                              
    if arr[0, 0] > 128:                                                                                                                                                                                              
        bg_noise = max(arr[0, 0], arr[-1, -1], arr[0, -1], arr[-1, 0])                                                                                                                                               
        arr[arr > bg_noise - 10] = bg_noise                                                                                                                                                                          
        arr = bg_noise - arr                                                                                                                                                                                         
    else:                                                                                                                                                                                                            
        bg_noise = min(arr[0, 0], arr[-1, -1], arr[0, -1], arr[-1, 0])                                                                                                                                               
        arr[arr < bg_noise + 10] = bg_noise                                                                                                                                                                          
        arr = arr - bg_noise                                                                                                                                                                                         
                                                                                                                                                                                                                     
    # Center and pad the digit exactly like MNIST processing                                                                                                                                                         
    non_zero = np.argwhere(arr > 35)                                                                                                                                                                                 
    if len(non_zero) > 0:                                                                                                                                                                                            
        min_y, min_x = non_zero.min(axis=0)                                                                                                                                                                          
        max_y, max_x = non_zero.max(axis=0)                                                                                                                                                                          
        cropped = arr[min_y:max_y+1, min_x:max_x+1]                                                                                                                                                                  
        cropped[cropped < 45] = 0                                                                                                                                                                                    
                                                                                                                                                                                                                     
        h, w = cropped.shape                                                                                                                                                                                         
        cropped_img = Image.fromarray(cropped)                                                                                                                                                                       
        if h > w:                                                                                                                                                                                                    
            new_h = 20                                                                                                                                                                                               
            new_w = int(20 * w / h)                                                                                                                                                                                  
        else:                                                                                                                                                                                                        
            new_w = 20                                                                                                                                                                                               
            new_h = int(20 * h / w)                                                                                                                                                                                  
        new_w = max(1, new_w)                                                                                                                                                                                        
        new_h = max(1, new_h)                                                                                                                                                                                        
                                                                                                                                                                                                                     
        resized = cropped_img.resize((new_w, new_h), Image.Resampling.LANCZOS)                                                                                                                                       
                                                                                                                                                                                                                     
        canvas = Image.new('L', (28, 28), 0)                                                                                                                                                                         
        offset_x = (28 - new_w) // 2                                                                                                                                                                                 
        offset_y = (28 - new_h) // 2                                                                                                                                                                                 
        canvas.paste(resized, (offset_x, offset_y))                                                                                                                                                                  
        arr = np.array(canvas)                                                                                                                                                                                       
                                                                                                                                                                                                                     
    x = (arr / 255.0) - 0.5                                                                                                                                                                                          
    x = x[np.newaxis, :, :] # (1, 28, 28)                                                                                                                                                                            
                                                                                                                                                                                                                     
    # Forward pass and record intermediate activations                                                                                                                                                               
    out_conv = conv.forward(x)                                                                                                                                                                                       
    out_gelu = gelu.forward(out_conv)                                                                                                                                                                                
    out_pool = pool.forward(out_gelu)                                                                                                                                                                                
                                                                                                                                                                                                                     
    out_flat = flatten.forward(out_pool[np.newaxis, :, :, :])                                                                                                                                                        
    logits = dense.forward(out_flat)[0]                                                                                                                                                                              
                                                                                                                                                                                                                     
    # Softmax probabilities                                                                                                                                                                                          
    probs = np.exp(logits - np.max(logits))                                                                                                                                                                          
    probs /= np.sum(probs)                                                                                                                                                                                           
                                                                                                                                                                                                                     
    # Generate feature map grids for visualization                                                                                                                                                                   
    conv_grid = make_grid(out_conv)                                                                                                                                                                                  
    pool_grid = make_grid(out_pool)                                                                                                                                                                                  
                                                                                                                                                                                                                     
    # Return dictionary of classes, plus the two grids                                                                                                                                                               
    class_probs = {str(i): float(probs[i]) for i in range(10)}                                                                                                                                                       
    return class_probs, conv_grid, pool_grid                                                                                                                                                                         
                                                                                                                                                                                                                     
# Gradio Interface layout                                                                                                                                                                                            
demo = gr.Interface(                                                                                                                                                                                                 
    fn=predict,                                                                                                                                                                                                      
    inputs=gr.Sketchpad(type="pil", image_mode="L"),                                                                                                                                                                 
    outputs=[                                                                                                                                                                                                        
        gr.Label(num_top_classes=3, label="Prediction"),                                                                                                                                                             
        gr.Image(label="Layer 1: Convolutional Activations (12 Filters)", type="pil"),                                                                                                                               
        gr.Image(label="Layer 2: Max Pooling Outputs (Downsampled Features)", type="pil")                                                                                                                            
    ],                                                                                                                                                                                                               
    title="CNN from Scratch - Digit Classifier",                                                                                                                                                                     
    description="Draw a digit in the box to predict its value and see inside the model's 'brain' in real-time!"                                                                                                      
)                                                                                                                                                                                                                    
                                                                                                                                                                                                                     
if __name__ == "__main__":                                                                                                                                                                                           
    demo.launch()