for y in range(height):
r = int(start_color[0] + (end_color[0] start_color[0]) * y / height)
g = int(start_color[1] + (end_color[1] start_color[1]) * y / height)
b = int(start_color[2] + (end_color[2] start_color[2]) * y / height)
draw.line((0, y, width, y), fill=(r, g, b))