# tk_buffer_gradient_zoom.py

# tk_buffer_gradient_zoom.py

import tkinter as tk
from PIL import Image, ImageTk, ImageDraw

SQ = 600
SQ2 = SQ * 2

root = tk.Tk()
canvas = tk.Canvas(root, width=SQ, height=SQ)
canvas.pack()

source_img = Image.new('RGB', (3, 3))
pixels = source_img.load()
grid_colors = {
    (0, 0): (255, 255, 255),  # White
    (0, 1): (255, 255, 0),    # Yellow
    (0, 2): (0, 255, 0),      # Green
    (1, 0): (255, 165, 0),    # Orange
    (1, 1): (128, 128, 128),  # Gray (midpoint)
    (1, 2): (0, 0, 255),      # Blue
    (2, 0): (255, 0, 0),      # Red
    (2, 1): (128, 0, 128),    # Purple
    (2, 2): (0, 0, 0)         # Black
}
for x in range(3):
    for y in range(3):
        pixels[x, y] = grid_colors[(x, y)]
source_img = source_img.resize((SQ2, SQ2))  # never use resample

mask = Image.new('L', (SQ2, SQ2), 255)
draw = ImageDraw.Draw(mask)
for x in range(0, SQ2, 2):
    for y in range(0, SQ2, 2):
        draw.point((x, y), fill=0)

step = 20
def bystep(p):
    if p % 2 == 0:
        return p + step if p + step < 255 else p + 1
    else:
        return p - step if p - step > 0 else p - 1

def do_crop(img, zoom_size):
    return img.crop((SQ - zoom_size // 2, SQ - zoom_size // 2,
                     SQ + zoom_size // 2, SQ + zoom_size // 2))

while 1:
    zoom_size = SQ2
    cropped = do_crop(source_img, zoom_size)
    resized = cropped.resize((SQ2, SQ2))
    resized = resized.point(lambda p: bystep(p))
    masked = Image.composite(resized, source_img, mask)

    zoom_factor = 0.95
    while zoom_size > SQ:
        zoom_size = int(zoom_size * zoom_factor)

        cropped = do_crop(masked, zoom_size).resize((SQ, SQ))
        photo = ImageTk.PhotoImage(cropped)
        canvas.create_image(0, 0, image=photo, anchor='nw')
        root.update()

    source_img = cropped.resize((SQ2, SQ2))