# tk_540x540_Gradient.py

# tk_540x540_Gradient.py

from tkinter import *
from PIL import Image, ImageTk

root = Tk()
root.title("540x540 Gradient")
ww = 540
hh = 540
root.geometry("%dx%d+-10+0"%(ww,hh))
canvas = Canvas(root, width=ww, height=hh)
canvas.pack()

D = 20
t = [z for z in range(256)]
a = {}
for z in t:
    v = min(z,256-D)
    a[z] = range(v,v+D)
p = {}
def gen(w,h):
    w2 = w/255.0
    h2 = h/255.0
    for y in range(h):
        cy = int(y/h2)
        for x in range(w):
            cx = int(x/w2)
            r = 255-cx
            g = 255-cy
            b = int((cx+cy)/2)
            for bbb in a[b]:
                z = (r,g,bbb)
                try:
                    p[z]
                except:
                    break
            rgb.append(z)
            p[z] = 1

rgb = []
gen(ww,hh)
img = Image.new('RGB', (ww,hh))
img.putdata(rgb)
imgTk = ImageTk.PhotoImage(img)
canvas.create_image(0, 0, anchor=NW, image=imgTk)
root.update()