diff --git a/contrib/gallery.py b/contrib/gallery.py
index b4db318..abfacbf 100644
--- a/contrib/gallery.py
+++ b/contrib/gallery.py
@@ -2,39 +2,47 @@
 Outputs a huge image with all currently-supported block textures.
 """
 
-from overviewer_core import textures
+import argparse
+
+from PIL import Image
 import sys
-import Image
+import os
 
-if len(sys.argv) != 2:
-    print "usage: %s [output.png]" % (sys.argv[0],)
-    sys.exit(1)
+# incantation to be able to import overviewer_core
+if not hasattr(sys, "frozen"):
+    sys.path.insert(0, os.path.abspath(os.path.join(os.path.split(__file__)[0], '..')))
 
-t = textures.Textures()
-t.generate()
 
-blocks = {}
+def main(outfile):
+    from overviewer_core import textures
+    t = textures.Textures()
+    t.generate()
 
-for blockid in xrange(textures.max_blockid):
-    for data in xrange(textures.max_data):
-        tex = t.blockmap[blockid * textures.max_data + data]
-        if tex:
-            if not blockid in blocks:
-                blocks[blockid] = {}
-            blocks[blockid][data] = tex
+    blocks = {}
 
-columns = max(map(len, blocks.values()))
-rows = len(blocks)
-texsize = t.texture_size
+    for blockid in range(textures.max_blockid):
+        for data in range(textures.max_data):
+            tex = t.blockmap[blockid * textures.max_data + data]
+            if tex:
+                if blockid not in blocks:
+                    blocks[blockid] = {}
+                blocks[blockid][data] = tex
 
-gallery = Image.new("RGBA", (columns * texsize, rows * texsize), t.bgcolor)
+    columns = max(len(v) for v in blocks.values())
+    rows = len(blocks)
+    texsize = t.texture_size
 
-row = 0
-for blockid, textures in blocks.iteritems():
-    column = 0
-    for data, tex in textures.iteritems():
-        gallery.paste(tex[0], (column * texsize, row * texsize))
-        column += 1
-    row += 1
+    gallery = Image.new("RGBA", (columns * texsize, rows * texsize), t.bgcolor)
 
-gallery.save(sys.argv[1])
+    for row, (blockid, textures) in enumerate(blocks.items()):
+        for column, (data, tex) in enumerate(textures.items()):
+            gallery.paste(tex[0], (column * texsize, row * texsize))
+
+    gallery.save(outfile)
+
+
+if __name__ == '__main__':
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument('file', metavar='output.png')
+    args = parser.parse_args()
+    main(args.file)