Optimize memory a bit

precompute_conversion.py

@@ -1,5 +1,6 @@
 """Precompute CIE2000 perceptual colour distance matrices.
 
+XXX
 The matrix of delta-E values is computed for all pairs of 24-bit RGB values,
 and Apple II target palette values.  This is written out as a file that is
 mmapped at runtime for efficient access.  For a 16-colour target palette this
@@ -14,16 +15,18 @@ def main():
     print("Precomputing conversion matrix from RGB to CAM16UCS colour space")
 
     # Compute matrix of all 24-bit RGB values, normalized to 0..1 range
-    bits24 = np.arange(2 ** 24).reshape(-1, 1)
-    all_rgb = (np.concatenate(
+    bits24 = np.arange(2 ** 24, dtype=np.uint32).reshape(-1, 1)
+    all_rgb = np.concatenate(
         [bits24 >> 16 & 0xff, bits24 >> 8 & 0xff, bits24 & 0xff],
-        axis=1) / 255).astype(np.float32)
+        axis=1).astype(np.float32) / 255
+    del bits24
 
     with colour.utilities.suppress_warnings(colour_usage_warnings=True):
         # Compute matrix of corresponding CAM16UCS colour values, indexed
         # by 24-bit RGB value
         all_cam16 = colour.convert(all_rgb, "RGB", "CAM16UCS").astype(
             np.float32)
+    del all_rgb
     np.save("data/rgb_to_cam16ucs.npy", all_cam16)