Add access functions for ImagingEffectNoise with a test

PIL/Image.py

@@ -2419,3 +2419,19 @@ def _show(image, **options):
 def _showxv(image, title=None, **options):
     from PIL import ImageShow
     ImageShow.show(image, title, **options)
+
+
+# --------------------------------------------------------------------
+# Effects
+
+def effect_noise(size, sigma):
+    """
+    Generate Gaussian noise centered around 128
+
+    :param size: The requested size in pixels, as a 2-tuple:
+       (width, height).
+    :param sigma: Standard deviation of noise.
+    """
+    return Image()._new(core.effect_noise(size, sigma))
+
+# End of file

Tests/test_image.py

@@ -140,6 +140,19 @@ class TestImage(PillowTestCase):
         img_colors = sorted(img.getcolors())
         self.assertEqual(img_colors, expected_colors)
 
+    def test_noise(self):
+        # Arrange
+        size = (100, 100)
+        sigma = 128
+
+        # Act
+        im = Image.effect_noise(size, sigma)
+
+        # Assert
+        self.assertEqual(im.size, (100, 100))
+        self.assertEqual(im.getpixel((0, 0)), 60)
+        self.assertEqual(im.getpixel((0, 1)), 28)
+
 
 if __name__ == '__main__':
     unittest.main()

libImaging/Effects.c

@@ -74,7 +74,7 @@ ImagingEffectMandelbrot(int xsize, int ysize, double extent[4], int quality)
 Imaging
 ImagingEffectNoise(int xsize, int ysize, float sigma)
 {
-    /* Generate gaussian noise centered around 128 */
+    /* Generate Gaussian noise centered around 128 */
 
     Imaging imOut;
     int x, y;
@@ -95,7 +95,7 @@ ImagingEffectNoise(int xsize, int ysize, float sigma)
                 this = next;
                 nextok = 0;
             } else {
-                /* after numerical recepies */
+                /* after numerical recipes */
                 double v1, v2, radius, factor;
                 do {
                     v1 = rand()*(2.0/32767.0) - 1.0;