data = []
for c, category in enumerate(categories):
    images = [os.path.join(dp, f) for dp, dn, filenames
              in os.walk(category) for f in filenames
              if os.path.splitext(f)[1].lower() in ['.jpg','.png','.jpeg']]
    for img_path in images:
        img, x = get_image(img_path)
        data.append({'x':np.array(x[0]), 'y':c})

# count the number of classes
num_classes = len(categories)