finish morph

and add erode/dilate convenience functions to Vips.py

TODO

@@ -1,3 +1,15 @@
+- add imageize from 2D arrays, eg. we should be able to write
+
+        im = im.erode([[128, 255, 128], 
+		       [255, 255, 255], 
+		       [128, 255, 128]])
+
+  see test_morphology.py
+
+- add median convenience function, see test_morphology.py
+
+
+
 - use vips_resize() in vipsthumbnail?
 
   should the sharpening filter be selectable?

python/Vips.py

@@ -866,6 +866,14 @@ class Image(Vips.Image):
         """Return 10 ** pixel."""
         return self.math(Vips.OperationMath.EXP10)
 
+    def erode(self, mask):
+        """Erode with a structuring element."""
+        return self.morph(mask, Vips.OperationMorphology.ERODE)
+
+    def dilate(self, mask):
+        """Dilate with a structuring element."""
+        return self.morph(mask, Vips.OperationMorphology.DILATE)
+
     # we need different imageize rules for this operator ... we need to 
     # imageize th and el to match each other first
     @add_doc(generate_docstring("ifthenelse"))

test/test_morphology.py

@@ -33,6 +33,11 @@ class TestMorphology(unittest.TestCase):
         for x, y in zip_expand(a, b):
             self.assertAlmostEqual(x, y, places = places, msg = msg)
 
+    def setUp(self):
+        self.mask = Vips.Image.new_from_array([[128, 255, 128], 
+                                               [255, 255, 255], 
+                                               [128, 255, 128]])
+
     def test_countlines(self):
         im = Vips.Image.black(100, 100)
         im = im.draw_line(255, 0, 50, 100, 50)
@@ -47,5 +52,32 @@ class TestMorphology(unittest.TestCase):
         self.assertEqual(opts['segments'], 3)
         self.assertEqual(mask.max(), 2)
 
+    def test_erode(self):
+        im = Vips.Image.black(100, 100)
+        im = im.draw_circle(255, 50, 50, 25, fill = True)
+        im2 = im.erode(self.mask)
+        self.assertEqual(im.width, im2.width)
+        self.assertEqual(im.height, im2.height)
+        self.assertEqual(im.bands, im2.bands)
+        self.assertTrue(im.avg() > im2.avg())
+
+    def test_dilate(self):
+        im = Vips.Image.black(100, 100)
+        im = im.draw_circle(255, 50, 50, 25, fill = True)
+        im2 = im.dilate(self.mask)
+        self.assertEqual(im.width, im2.width)
+        self.assertEqual(im.height, im2.height)
+        self.assertEqual(im.bands, im2.bands)
+        self.assertTrue(im2.avg() > im.avg())
+
+    def test_rank(self):
+        im = Vips.Image.black(100, 100)
+        im = im.draw_circle(255, 50, 50, 25, fill = True)
+        im2 = im.rank(3, 3, 8)
+        self.assertEqual(im.width, im2.width)
+        self.assertEqual(im.height, im2.height)
+        self.assertEqual(im.bands, im2.bands)
+        self.assertTrue(im2.avg() > im.avg())
+
 if __name__ == '__main__':
     unittest.main()