Image Drawing Alpha Blending Test

# Image Drawing Alpha Blending Test
#
# This script tests the performance and quality of the draw_image()
# method which can perform nearest neighbor, bilinear, bicubic, and
# area scaling along with color channel extraction, alpha blending,
# color palette application, and alpha palette application.

import sensor, image, time

sensor.reset()
sensor.set_pixformat(sensor.RGB565)
sensor.set_framesize(sensor.QVGA)

#hint = image.BICUBIC # image.BILINEAR image.BICUBIC

small_img = image.Image(size=(4, 4))
small_img.set_pixel(0, 0, (0,   0,   127))
small_img.set_pixel(1, 0, (47,  255, 199))
small_img.set_pixel(2, 0, (0,   188, 255))
small_img.set_pixel(3, 0, (0,   0,   127))
small_img.set_pixel(0, 1, (0,   176, 255))
small_img.set_pixel(1, 1, (222, 0,   0  ))
small_img.set_pixel(2, 1, (50,  255, 195))
small_img.set_pixel(3, 1, (86,  255, 160))
small_img.set_pixel(0, 2, (255, 211, 0  ))
small_img.set_pixel(1, 2, (83,  255, 163))
small_img.set_pixel(2, 2, (255, 211, 0))
small_img.set_pixel(3, 2, (0,   80,  255))
small_img.set_pixel(0, 3, (255, 118, 0  ))
small_img.set_pixel(1, 3, (127, 0,   0  ))
small_img.set_pixel(2, 3, (0,   144, 255))
small_img.set_pixel(3, 3, (50,  255, 195))
#small_img.to_grayscale()
#small_img.to_bitmap()

big_img = image.Image(size=(128, 128))
big_img.draw_image(small_img, 0, 0, x_scale=32, y_scale=32)
#big_img.to_grayscale()
#big_img.to_bitmap()

alpha_div = 1
alpha_value = 0
alpha_step = 2

x_bounce = sensor.width()//2
x_bounce_toggle = 1

y_bounce = sensor.height()//2
y_bounce_toggle = 1

clock = time.clock()
while(True):
    clock.tick()

    img = sensor.snapshot()
    #img.to_grayscale()
    #img.to_bitmap()
    img.draw_image(big_img, x_bounce, y_bounce,
                   rgb_channel=-1, alpha=alpha_value//alpha_div,
                   )

    x_bounce += x_bounce_toggle
    if abs(x_bounce-(img.width()//2)) >= (img.width()//2): x_bounce_toggle = -x_bounce_toggle

    y_bounce += y_bounce_toggle
    if abs(y_bounce-(img.height()//2)) >= (img.height()//2): y_bounce_toggle = -y_bounce_toggle

    alpha_value += alpha_step
    if not alpha_value or alpha_value//alpha_div == 256: alpha_step = -alpha_step

    print(clock.fps())