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to_png.py

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+#!/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 keeps 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)
+    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
+        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)
+                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()