pride.py

from PIL import Image, ImageDraw, ImageColor
from os.path import splitext

OPACITY = 150
COLORS = [
    (*ImageColor.getrgb("red"), OPACITY),
    (*ImageColor.getrgb("orange"), OPACITY),
    (*ImageColor.getrgb("yellow"), OPACITY),
    (*ImageColor.getrgb("green"), OPACITY),
    (*ImageColor.getrgb("blue"), OPACITY),
    (*ImageColor.getrgb("purple"), OPACITY),
    
]
file = input("Filename: ")
out = splitext(file)[0] + "-pride.png"
with Image.open(file).convert("RGB") as im:
    e = int(im.height / (len(COLORS) - 1))
    draw = ImageDraw.Draw(im, "RGBA")
    for c, y in enumerate(range(0, im.height, e)):
        draw.rectangle((0, y, im.width, y+e-1), fill = COLORS[c])

    im.save(out)
    print("File saved to", out)