diff --git a/color_convert.py b/color_convert.py
index 13924da..b457c68 100644
--- a/color_convert.py
+++ b/color_convert.py
@@ -31,62 +31,64 @@ class color_format:
         b5 = (b >> 3) & 31
         return (r5 << 11) | (g5 << 5) | (b5 << 0)
 
+    def axxx4444(r, g, b, a):
+        a4 = (a >> 4) & 15
+        return (a4 << 12)
+
     def from_string(s):
         return dict([
             ("gbgr1555", color_format.gbgr1555),
             ("argb4444", color_format.argb4444),
             ("argb1555", color_format.argb1555),
             ("rgb565", color_format.rgb565),
+            ("axxx4444", color_format.axxx4444),
         ])[s]
 
-in_file = sys.argv[1]
-format = sys.argv[2]
-out_file = sys.argv[3]
-
-palette = None
-
-with Image.open(in_file) as im:
-    width, height = im.size
-    if not im.palette:
-        pixels = list(im.convert("RGBA").getdata())
-    else:
-        pixels = list(im.convert("P").getdata())
-        palette = list(im.palette.colors)
-
-has_alpha = False
-convert = color_format.from_string(format)
-
-def convert_colors(f, colors):
+def convert_colors(f, convert, colors):
     for color in colors:
         value = convert(*color)
         f.write(struct.pack("<H", value))
 
-if palette is None:
-    with open(out_file, 'wb') as f:
-        convert_colors(f, pixels)
-else:
-    with open(out_file, 'wb') as f:
-        if len(palette) <= 4:
-            for i in range(len(pixels) // 4):
-                a = pixels[i * 4 + 0]
-                b = pixels[i * 4 + 1]
-                c = pixels[i * 4 + 2]
-                d = pixels[i * 4 + 3]
-                assert a <= 3 and b <= 3 and c <= 3 and d <= 3, (a, b, c, d)
-                pixel = (d << 6) | (c << 4) | (b << 2) | (a << 0)
-                f.write(struct.pack("<B", pixel))
-        elif len(palette) <= 16:
-            for i in range(len(pixels) // 2):
-                a = pixels[i * 2 + 0]
-                b = pixels[i * 2 + 1]
-                assert a <= 15 and b <= 15, (a, b)
-                pixel = (b << 4) | (a << 0)
-                f.write(struct.pack("<B", pixel))
-        elif len(palette) <= 256:
-            for pixel in pixels:
-                assert pixel <= 255
-                f.write(struct.pack("<B", pixel))
+def convert_indices(f, palette, pixels):
+    if len(palette) <= 4:
+        for i in range(len(pixels) // 4):
+            a = pixels[i * 4 + 0]
+            b = pixels[i * 4 + 1]
+            c = pixels[i * 4 + 2]
+            d = pixels[i * 4 + 3]
+            assert a <= 3 and b <= 3 and c <= 3 and d <= 3, (a, b, c, d)
+            pixel = (d << 6) | (c << 4) | (b << 2) | (a << 0)
+            f.write(struct.pack("<B", pixel))
+    elif len(palette) <= 16:
+        for i in range(len(pixels) // 2):
+            a = pixels[i * 2 + 0]
+            b = pixels[i * 2 + 1]
+            assert a <= 15 and b <= 15, (a, b)
+            pixel = (b << 4) | (a << 0)
+            f.write(struct.pack("<B", pixel))
+    elif len(palette) <= 256:
+        for pixel in pixels:
+            assert pixel <= 255
+            f.write(struct.pack("<B", pixel))
+    else:
+        assert False, len(palette)
+
+if __name__ == "__main__":
+    in_file = sys.argv[1]
+    format = sys.argv[2]
+    out_file = sys.argv[3]
+
+    convert = color_format.from_string(format)
+
+    with Image.open(in_file) as im:
+        if not im.palette:
+            pixels = list(im.convert("RGBA").getdata())
+            with open(out_file, 'wb') as f:
+                convert_colors(f, convert, pixels)
         else:
-            assert False, len(palette)
-    with open(out_file + '.pal', 'wb') as f:
-        convert_colors(f, [(*c, 255) for c in palette])
+            pixels = list(im.convert("P").getdata())
+            palette = list(im.palette.colors)
+            with open(out_file, 'wb') as f:
+                convert_indices(f, palette, pixels)
+            with open(out_file + '.pal', 'wb') as f:
+                convert_colors(f, convert, [(*c, 255) for c in palette])