Fix a bug where _fit_global_palette would crash if there were fewer

than 16 global colours computed.

convert.py

@@ -83,17 +83,22 @@ class ClusterPalette:
 
         clusters = cluster.MiniBatchKMeans(n_clusters=16, max_iter=10000)
         clusters.fit_predict(self._colours_cam)
+        num_colours = clusters.n_clusters
 
         labels = clusters.labels_
+
+        # Dict of {palette idx : frequency count}
+        palette_freq = {idx: 0 for idx in range(16)}
+        for idx, freq in zip(*np.unique(labels, return_counts=True)):
+            palette_freq[idx] = freq
         frequency_order = [
             k for k, v in sorted(
-                # List of (palette idx, frequency count)
-                list(zip(*np.unique(labels, return_counts=True))),
-                key=lambda kv: kv[1], reverse=True)]
+                list(palette_freq.items()), key=lambda kv: kv[1], reverse=True)]
 
-        return dither_pyx.convert_cam16ucs_to_rgb12_iigs(
-            clusters.cluster_centers_[frequency_order].astype(
-                np.float32))
+        self._global_palette = (
+            dither_pyx.convert_cam16ucs_to_rgb12_iigs(
+                clusters.cluster_centers_[frequency_order].astype(
+                    np.float32)))
 
     def _palette_splits(self, palette_height=35):
         # The 16 palettes are striped across consecutive (overlapping) line
@@ -126,7 +131,7 @@ class ClusterPalette:
 
         new_lower = np.clip(new_lower, 0, np.clip(new_upper, 1, 200) - 1)
         new_upper = np.clip(new_upper, new_lower + 1, 200)
-        assert new_lower >= 0, new_upper-1
+        assert new_lower >= 0, new_upper - 1
 
         self._palette_splits[palette_to_mutate] = (new_lower, new_upper)
         self._palette_mutate_idx = palette_to_mutate
@@ -185,7 +190,7 @@ class ClusterPalette:
         # Compute a new 16-colour global palette for the entire image,
         # used as the starting center positions for k-means clustering of the
         # individual palettes
-        self._global_palette = self._fit_global_palette()
+        self._fit_global_palette()
 
         dynamic_colours = 16 - self._reserved_colours
 
@@ -338,8 +343,8 @@ def main():
         palettes_used = [False] * 16
         for palette in new_line_to_palette:
             palettes_used[palette] = True
-        for palette_idx, palette in enumerate(palettes_used):
-            if palette:
+        for palette_idx, palette_used in enumerate(palettes_used):
+            if palette_used:
                 continue
             print("Reassigning palette %d" % palette_idx)
             max_width = 0
@@ -354,7 +359,8 @@ def main():
             lower, upper = last_good_splits[split_palette_idx]
             if upper - lower > 20:
                 mid = (lower + upper) // 2
-                cluster_palette._palette_splits[split_palette_idx] = (lower, mid)
+                cluster_palette._palette_splits[split_palette_idx] = (
+                    lower, mid - 1)
                 cluster_palette._palette_splits[palette_idx] = (mid, upper)
             else:
                 lower = np.random.randint(0, 199)