# Tk_4x2_Color_Gradient.py

# Tk_4x2_Color_Gradient.py

from tkinter import *
from PIL import Image, ImageTk
import math

root = Tk()
root.title("# Tk_4x2_Color_Gradient")
ww = 1200
hh = 600
root.geometry("%dx%d+-10+0"%(ww,hh))
canvas = Canvas(root, width=ww, height=hh)
canvas.pack()

colors = [(0, 0, 0), (255, 0, 0), (255, 165, 0), (255, 255, 0),
(75, 0, 130), (0, 0, 255), (0, 128, 0), (255, 255, 255)]

rx = 4 / ww
ry = 2 / hh

def bicubic(c00, c10, c01, c11, x, y):
    w00 = (1 - x) * (1 - y)
    w10 = x * (1 - y)
    w01 = (1 - x) * y
    w11 = x * y

    r = int(w00 * c00[0] + w10 * c10[0] + w01 * c01[0] + w11 * c11[0])
    g = int(w00 * c00[1] + w10 * c10[1] + w01 * c01[1] + w11 * c11[1])
    b = int(w00 * c00[2] + w10 * c10[2] + w01 * c01[2] + w11 * c11[2])

    return (r, g, b)

def transition_color():
    x_index = int(x // (ww // 4))
    y_index = int(y // (hh // 2)) * 4
    c00 = colors[x_index + y_index]

    if mode == "bicubic":
        c10 = colors[(x_index + 1) + y_index]
        c01 = colors[x_index + (y_index + 4)]
        c11 = colors[(x_index + 1) + (y_index + 4)]
        x_ratio = x * rx
        y_ratio = y * ry
        x_fraction = x_ratio - x_index
        y_fraction = y_ratio - y_index

        return bicubic(c00, c10, c01, c11, x_fraction, y_fraction)
    return c00

def toggle_mode(event):
    global toggle, mode
    mode = "solid" if mode == "bicubic" else "bicubic"
    toggle = 1
root.bind("<space>", toggle_mode)

rgb = [(128, 128, 128)] * (ww * hh)
mode = "bicubic"
toggle = 1
img = Image.new('RGB', (ww, hh))

while 1:
    if toggle:
        if mode == "bicubic":
            for y in range(hh // 2):
                for x in range(int(ww * 0.75)):
                    rgb[x + y * ww] = transition_color()
        else:
            for y in range(hh):
                for x in range(ww):
                    rgb[x + y * ww] = transition_color()
        img.putdata(rgb)
        if mode == "bicubic":
            img.putdata(rgb)
            img = img.crop((0, 0, int(ww * 0.75), int(hh * 0.5)))
            img = img.resize((ww, hh))
        imgTk = ImageTk.PhotoImage(img)
        canvas.create_image(0, 0, anchor=NW, image=imgTk)
        toggle = 0
    root.update()

root.mainloop()