diff --git a/color_convert.py b/color_convert.py
index 07a6756..4a8a369 100644
--- a/color_convert.py
+++ b/color_convert.py
@@ -84,32 +84,33 @@ def pack_indices(f, indices):
         f.write(struct.pack("<B", value))
 
 def mip_levels(n):
-    while True:
-        n = n >> 1
+    while n > 0:
         yield n
-        if n == 1:
-            break
+        n = n >> 1
+
+def resize(im, l):
+    new = im.resize(
+        size=(l, l),
+        resample=Image.Resampling.LANCZOS,
+    )
+    new.save(f"{l:03}.png")
+    return new
 
 def generate_mips(im):
     w, h = im.size
     assert w == h and npot(w) == w, (w, h)
     assert w >= 8, (w, h)
 
-    images = [im] + [
-        im.resize(
-            size=(l, l),
-            resample=Image.Resampling.LANCZOS,
-        )
-        for l in mip_levels(w)
-    ]
+    images = [im] + [resize(im, l) for l in mip_levels(w >> 1)]
 
     return list(reversed(images))
 
 def write_mip(f, mip: Image, is_twiddled: bool, convert):
     width, height = mip.size
-    print("mip", width, "offset", f"{f.tell():06x}")
-    pixels = list(im.convert("RGBA").getdata())
+    #print("mip", width, "offset", f"{f.tell():06x}")
+    pixels = list(mip.convert("RGBA").getdata())
     colors = list(convert_colors(convert, pixels))
+    assert len(colors) == width * height, len(colors)
     if is_twiddled:
         new_colors = [0] * width * height
         max_twiddle_ix = twiddle_texture(new_colors, colors, width, height)
@@ -121,7 +122,7 @@ def write_mips(f, im: Image, is_twiddled: bool, convert):
     for mip in generate_mips(im):
         write_mip(f, mip, is_twiddled, convert)
 
-if __name__ == "__main__":
+def main():
     in_file = sys.argv[1]
     format = sys.argv[2]
     assert sys.argv[3] in {"twiddled", "non_twiddled"}
@@ -145,6 +146,7 @@ if __name__ == "__main__":
                 else:
                     write_mip(f, im, is_twiddled, convert)
         else:
+            assert False
             pixels = list(im.convert("P").getdata())
             palette = list(im.palette.colors)
             indices = list(convert_indices(palette, pixels))
@@ -160,3 +162,6 @@ if __name__ == "__main__":
 
             with open(out_file, 'wb') as f:
                 pack_indices(f, indices)
+
+if __name__ == "__main__":
+    main()