# chroma-key a generated image on its corner colour, despeckle, crop to the content bbox,
# and (optionally) downscale to a target width. For standalone art (logo, popup panels) —
# unlike assets/_slice.py this does NOT split frames or force a sprite height.
import sys
from PIL import Image

KEY_D2 = 60 * 60

def main(src, dst, target_w=None):
    im = Image.open(src).convert('RGBA')
    w, h = im.size
    px = im.load()
    bg = px[0, 0][:3]
    for x in range(w):
        for y in range(h):
            r, g, b, a = px[x, y]
            if (r - bg[0]) ** 2 + (g - bg[1]) ** 2 + (b - bg[2]) ** 2 < KEY_D2 or (min(r, b) > g + 40):
                px[x, y] = (0, 0, 0, 0)
    im = im.crop(im.getbbox())
    if target_w and im.width > target_w:
        im = im.resize((target_w, max(1, round(im.height * target_w / im.width))), Image.LANCZOS)
    im.save(dst)
    print(dst, im.size)

if __name__ == '__main__':
    main(sys.argv[1], sys.argv[2], int(sys.argv[3]) if len(sys.argv) > 3 else None)