Create dot pattern image using Python3 and PIL

dotpatternimage.py

from PIL import Image, ImageDraw

img = Image.open("beach.jpg")
pixels = img.load()

# Choose the pixelization length
pixelization_length = 6

# Define the pixelize and mask image
pixelize_image = Image.new('RGBA', img.size)
mask_image = Image.new('RGBA', img.size, 'black')

x_units = int(img.size[0] / pixelization_length)
y_units = int(img.size[1] / pixelization_length)

draw = ImageDraw.Draw(pixelize_image)
mask_draw = ImageDraw.Draw(mask_image)

for i in range(0, x_units):
    for j in range(0, y_units):
        mask_draw.ellipse((i * pixelization_length, j * pixelization_length,
                  i * pixelization_length + pixelization_length - 1,
                  j * pixelization_length + pixelization_length - 1),
                 (255,255,255,0))

        total_red_intensity = total_green_intensity = total_blue_intensity = 0
        averaging_pixel_number = pixelization_length * pixelization_length

        for k in range(0, pixelization_length):
            for l in range(0, pixelization_length):
                total_red_intensity += pixels[i * pixelization_length + k, j * pixelization_length + l][0]
                total_green_intensity += pixels[i * pixelization_length + k, j * pixelization_length + l][1]
                total_blue_intensity += pixels[i * pixelization_length + k, j * pixelization_length + l][2]

        average_red_intensity = int(total_red_intensity / averaging_pixel_number)
        average_green_intensity = int(total_green_intensity / averaging_pixel_number)
        average_blue_intensity = int(total_blue_intensity / averaging_pixel_number)

        draw.rectangle((i * pixelization_length, j * pixelization_length,
                        i * pixelization_length + pixelization_length - 1,
                        j * pixelization_length + pixelization_length - 1),
                       (average_red_intensity, average_green_intensity, average_blue_intensity))

# Save the intermediate images for demo purpose
mask_image.save("mask.png")
pixelize_image.save("pixelize_beach.jpg")

pixelize_image.paste(mask_image, mask=mask_image)
pixelize_image.save("result.png")