Add color quantization

CHANGELOG.md

@@ -125,7 +125,7 @@
 * [rarely breaking] Added a `pad_mode` argument to `imgaug.pool()`,
   `imgaug.avg_pool()`, `imgaug.max_pool()`, `imgaug.min_pool()` and
   `imgaug.median_pool()`. This breaks code relying on the order of the
-  functions arguments.
+  functions arguments.s
   * Changed the default `pad_mode` of `avg_pool` from `constant` (`cval=128`)
     to `reflect`.
   * Changed the default `pad_mode` of `max_pool` from `constant` (`cval=0`)
@@ -137,6 +137,18 @@
 * Renamed argument `cval` to `pad_cval` in `imgaug.pool()`,
   `imgaug.avg_pool()` and `imgaug.max_pool()`. The old name `cval` is now
   deprecated.
+* Added `augmenters.color._AbstractColorQuantization`. #347
+* Added `augmenters.color.KMeansColorQuantization` and corresponding
+  `augmenters.color.quantize_colors_kmeans()`. Both deal with quantizing
+  similar colors using k-Means clustering. #347
+    * Added a check script for `KMeansColorQuantization` under
+      `checks/check_kmeans_color_quantization.py`. #347
+* Added `augmenters.color.UniformColorQuantization` and corresponding
+  `augmenters.color.quantize_colors_uniform()`. Both deal with quantizing
+  similar colors using k-Means clustering. #347
+    * Added a check script for `UniformColorQuantization` under
+      `checks/check_uniform_color_quantization.py`. #347
+
 
 ## Fixes
 

checks/check_kmeans_color_quantization.py

@@ -0,0 +1,31 @@
+from __future__ import print_function, division
+import numpy as np
+import imgaug as ia
+import imgaug.augmenters as iaa
+
+
+def main():
+    image = ia.quokka_square((256, 256))
+    image_q2 = iaa.quantize_colors_kmeans(image, 2)
+    image_q16 = iaa.quantize_colors_kmeans(image, 16)
+    ia.imshow(np.hstack([image_q2, image_q16]))
+
+    from_cs = "RGB"
+    to_cs = ["RGB", "Lab"]
+    kwargs = {"from_colorspace": from_cs, "to_colorspace": to_cs}
+    augs = [
+        iaa.KMeansColorQuantization(2, **kwargs),
+        iaa.KMeansColorQuantization(4, **kwargs),
+        iaa.KMeansColorQuantization(8, **kwargs),
+        iaa.KMeansColorQuantization((2, 16), **kwargs),
+    ]
+
+    images_aug = []
+    for aug in augs:
+        images_aug.extend(aug(images=[image]*8))
+
+    ia.imshow(ia.draw_grid(images_aug, cols=8))
+
+
+if __name__ == "__main__":
+    main()

checks/check_uniform_color_quantization.py

@@ -0,0 +1,25 @@
+from __future__ import print_function, division
+import numpy as np
+import imgaug as ia
+import imgaug.augmenters as iaa
+
+
+def main():
+    image = ia.quokka_square((256, 256))
+    ia.imshow(
+        ia.draw_grid([
+            iaa.quantize_colors_uniform(image, 2),
+            iaa.quantize_colors_uniform(image, 4),
+            iaa.quantize_colors_uniform(image, 8),
+            iaa.quantize_colors_uniform(image, 16),
+            iaa.quantize_colors_uniform(image, 32),
+            iaa.quantize_colors_uniform(image, 64)
+        ], cols=6)
+    )
+
+    aug = iaa.UniformColorQuantization((2, 16))
+    ia.imshow(ia.draw_grid(aug(images=[image] * 16)))
+
+
+if __name__ == "__main__":
+    main()