8. Activations

def visualize_model(model,img):
    layer_outputs = [layer.output for layer in model.layers[:12]]
    activation_model = models.Model(input=model.input, output=layer_outputs)
    activations = activation_model.predict(img)
    layer_names = []
    for layer in model.layers[:-1]:
        layer_names.append(layer.name) 
    images_per_row = 16
    for layer_name, layer_activation in zip(layer_names, activations):
        if layer_name.startswith('conv') or layer_name.startswith('max') or layer_name.startswith('drop'):
            n_features = layer_activation.shape[-1]
            size = layer_activation.shape[1]
            n_cols = n_features // images_per_row
            display_grid = np.zeros((size * n_cols, images_per_row * size))
            for col in range(n_cols):
                for row in range(images_per_row):
                    channel_image  = layer_activation[0,:, :, col * images_per_row + row]
                    channel_image -= channel_image.mean()
                    channel_image /= channel_image.std()
                    channel_image *= 64
                    channel_image += 128
                    channel_image = np.clip(channel_image, 0, 255).astype('uint8')
                    display_grid[col * size : (col + 1) * size,
                                 row * size : (row + 1) * size] = channel_image
            scale = 1. / size
            plt.figure(figsize=(scale * display_grid.shape[1],
                                scale * display_grid.shape[0]))
            plt.title(layer_name)
            plt.grid(False)
            plt.imshow(display_grid, aspect='auto', cmap='viridis')

visualize_model(model,X_test[1,:].reshape([1,28,28,1]))