Add dupeframes.py tool to find duplicate animated Pokémon frames

Fixes #1067

tools/dupeframes.py

@@ -0,0 +1,34 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+
+"""
+Usage: python dupeframes.py
+
+Check for duplicate frames in Pokemon sprites (gfx/pokemon/*/front.png).
+"""
+
+import sys
+import glob
+
+import png
+
+def check_duplicate_frames(filename):
+	with open(filename, 'rb') as file:
+		width, height, rows = png.Reader(file).asRGBA8()[:3]
+		rows = list(rows)
+	if height % width:
+		print(f'{filename} is not a vertical strip of square frames!', file=sys.stderr)
+		return
+	num_frames = height // width
+	frames = [rows[i*width:(i+1)*width] for i in range(num_frames)]
+	for i in range(num_frames):
+		for j in range(i + 1, num_frames):
+			if frames[i] == frames[j]:
+				print(f'{filename}: frame {j} is a duplicate of frame {i}', file=sys.stderr)
+
+def main():
+	for filename in sorted(glob.glob('gfx/pokemon/*/front.png')):
+		check_duplicate_frames(filename)
+
+if __name__ == '__main__':
+	main()