#!/usr/bin/env python3
"""Convert extracted .bmp sprites to .png with the black background made
transparent (colorkey transparency).

The EGF bitmaps store no usable alpha channel (alpha bytes are all zero);
transparency is by colorkey, and the background is pure black RGB(0,0,0).
This loads each BMP as RGB (ignoring the junk alpha), sets every pure-black
pixel to fully transparent, and writes a PNG.

Usage:
    python3 to_png.py [dir ...]          # default: all gfx*_extracted dirs
    python3 to_png.py --key RRGGBB ...   # custom colorkey (hex), default 000000
    python3 to_png.py --keep             # keep .bmp files (default deletes them)
"""
import sys, os, glob
from PIL import Image

def convert(path, key):
    im = Image.open(path).convert('RGB')   # force RGB, drop bogus alpha
    im = im.convert('RGBA')
    px = im.getdata()
    kr, kg, kb = key
    out = [(r, g, b, 0) if (r, g, b) == (kr, kg, kb) else (r, g, b, 255)
           for (r, g, b, a) in px]
    im.putdata(out)
    dst = os.path.splitext(path)[0] + '.png'
    im.save(dst)
    return dst

def main():
    args = sys.argv[1:]
    key = (0, 0, 0)
    keep = False
    dirs = []
    i = 0
    while i < len(args):
        if args[i] == '--key':
            h = args[i+1].lstrip('#')
            key = (int(h[0:2], 16), int(h[2:4], 16), int(h[4:6], 16))
            i += 2
        elif args[i] == '--keep':
            keep = True; i += 1
        else:
            dirs.append(args[i]); i += 1
    if not dirs:
        dirs = sorted(glob.glob('gfx*_extracted'))
    total = 0
    for d in dirs:
        bmps = sorted(glob.glob(os.path.join(d, '*.bmp')))
        for b in bmps:
            try:
                convert(b, key)
                if not keep:
                    os.remove(b)
                total += 1
            except Exception as ex:
                print('  ERROR %s: %s' % (b, ex))
        print('%s -> %d png' % (d, len(bmps)))
    print('TOTAL %d png (colorkey %02x%02x%02x)' % (total, *key))

if __name__ == '__main__':
    main()