Merge pull request #1 from radarhere/autocontrast

Updated documentation; Simplified code

Tests/test_imageops.py

@@ -305,11 +305,9 @@ def check(orientation_im):
 def test_autocontrast_cutoff():
     # Test the cutoff argument of autocontrast
     with Image.open("Tests/images/bw_gradient.png") as img:
-        assert (
-            ImageOps.autocontrast(img, cutoff=10).histogram()
-            == ImageOps.autocontrast(img, cutoff=(10, 10)).histogram()
-        )
-        assert (
-            ImageOps.autocontrast(img, cutoff=10).histogram()
-            != ImageOps.autocontrast(img, cutoff=(1, 10)).histogram()
-        )
+
+        def autocontrast(cutoff):
+            return ImageOps.autocontrast(img, cutoff).histogram()
+
+        assert autocontrast(10) == autocontrast((10, 10))
+        assert autocontrast(10) != autocontrast((1, 10))

src/PIL/ImageOps.py

@@ -70,7 +70,9 @@ def autocontrast(image, cutoff=0, ignore=None):
     becomes white (255).
 
     :param image: The image to process.
-    :param cutoff: How many percent to cut off from the histogram.
+    :param cutoff: The percent to cut off from the histogram on the low and
+                   high ends. Either a tuple of (low, high), or a single
+                   number for both.
     :param ignore: The background pixel value (use None for no background).
     :return: An image.
     """
@@ -105,7 +107,7 @@ def autocontrast(image, cutoff=0, ignore=None):
                     cut = 0
                 if cut <= 0:
                     break
-            # remove cutoff% samples from the hi end
+            # remove cutoff% samples from the high end
             cut = n * cutoff[1] // 100
             for hi in range(255, -1, -1):
                 if cut > h[hi]: