Merge pull request #98 from lkoenig/master

Adding method for painting a color in transparent

wand/api.py

@@ -295,6 +295,10 @@ class MagickPixelPacket(ctypes.Structure):
                                              ctypes.c_char_p]
     library.MagickTransformImage.restype = ctypes.c_void_p
 
+    library.MagickTransparentPaintImage.argtypes = [ctypes.c_void_p, ctypes.c_void_p, 
+                                                   ctypes.c_double, ctypes.c_double, 
+                                                   ctypes.c_int]
+
     library.MagickLiquidRescaleImage.argtypes = [
         ctypes.c_void_p, ctypes.c_size_t, ctypes.c_size_t,
         ctypes.c_double, ctypes.c_double

wand/image.py

@@ -1537,6 +1537,40 @@ def transparentize(self, transparency):
                                                t)
             self.raise_exception()
 
+    def transparent_color(self, color, alpha, fuzz = 0, invert=False):
+        """Makes the color ```color`` a transparent color with a tolerance of
+        fuzz. The ``alpha``parameter specify the transparency level and the
+        parameter ``fuzz`` specify the tolerance.
+
+        :param color: The color that should be made transparent on the image,
+                      color object
+        :type color: :class:`wand.color.Color`
+        :param alpha: the level of transparency: 1.0 is fully opaque
+                      and 0.0 is fully transparent.
+        :type alpha: :class:`numbers.Real`
+        :param fuzz: By default target must match a particular pixel color
+                     exactly. However, in many cases two colors may differ
+                     by a small amount. The fuzz member of image defines how
+                     much tolerance is acceptable to consider two colors as the
+                     same. For example, set fuzz to 10 and the color red at
+                     intensities of 100 and 102 respectively are now interpreted
+                     as the same color for the color.
+        :type fuzz: :class:`numbers.Integral`
+        :param invert: Boolean to tell to paint the inverse selection.
+        :type invert: :class:`bool`
+
+        .. versionadded:: 0.2.4
+        """
+        if not isinstance(alpha, numbers.Real):
+            raise TypeError('alpha must be an float, not ' + repr(left))
+        elif not isinstance(fuzz, numbers.Integral):
+            raise TypeError('fuzz must be an integer, not ' + repr(left))
+        elif not isinstance(color, Color):
+            raise TypeError('color must be a wand.color.Color object, not ' +
+                            repr(color))
+        library.MagickTransparentPaintImage(self.wand, color.resource, alpha, fuzz, invert)
+        self.raise_exception()
+
     def composite(self, image, left, top):
         """Places the supplied ``image`` over the current image, with the top
         left corner of ``image`` at coordinates ``left``, ``top`` of the

wandtests/image.py

@@ -767,6 +767,15 @@ def rotate():
                     assert black == cloned[2, 70] == cloned[35, 37]
                     assert black == cloned[85, 88] == cloned[52, 120]
 
+@tests.test
+def transparent_color():
+    """TransparentPaint test"""
+    with Image(filename=asset('rotatetest.gif')) as img:
+        img.alpha_channel = True
+        with Color('white') as white:
+            img.transparent_color(white, 0.0, 2, 0)
+            assert img[75, 50].alpha == 0
+            assert img[0, 50].alpha == 1.0
 
 @tests.test
 def signature():