Update and add more tool scripts

tools/rgb555.py

@@ -0,0 +1,38 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+
+"""
+Usage: python rgb555.py image.png
+
+Round all colors of the input image to RGB555.
+"""
+
+import sys
+
+import png
+
+def rgb8_to_rgb5(c):
+	return (c & 0b11111000) | (c >> 5)
+
+def round_pal(filename):
+	with open(filename, 'rb') as file:
+		width, height, rows = png.Reader(file).asRGBA8()[:3]
+		rows = list(rows)
+	for row in rows:
+		del row[3::4]
+	rows = [[rgb8_to_rgb5(c) for c in row] for row in rows]
+	writer = png.Writer(width, height, greyscale=False, bitdepth=8, compression=9)
+	with open(filename, 'wb') as file:
+		writer.write(file, rows)
+
+def main():
+	if len(sys.argv) < 2:
+		print(f'Usage: {sys.argv[0]} pic.png', file=sys.stderr)
+		sys.exit(1)
+	for filename in sys.argv[1:]:
+		if not filename.lower().endswith('.png'):
+			print(f'{filename} is not a .png file!', file=sys.stderr)
+		round_pal(filename)
+
+if __name__ == '__main__':
+	main()