Merge pull request #441 from wiredfool/lut

Image.point fixes for numpy.array and docs

PIL/Image.py

@@ -1128,14 +1128,16 @@ class Image:
         """
         Maps this image through a lookup table or function.
 
-        :param lut: A lookup table, containing 256 values per band in the
-           image. A function can be used instead, it should take a single
-           argument. The function is called once for each possible pixel
-           value, and the resulting table is applied to all bands of the
-           image.
+        :param lut: A lookup table, containing 256 (or 65336 if
+           self.mode=="I" and mode == "L") values per band in the
+           image.  A function can be used instead, it should take a
+           single argument. The function is called once for each
+           possible pixel value, and the resulting table is applied to
+           all bands of the image.
         :param mode: Output mode (default is same as input).  In the
            current version, this can only be used if the source image
-           has mode "L" or "P", and the output has mode "1".
+           has mode "L" or "P", and the output has mode "1" or the
+           source image mode is "I" and the output mode is "L".
         :returns: An :py:class:`~PIL.Image.Image` object.
         """
 
@@ -1144,10 +1146,12 @@ class Image:
         if isinstance(lut, ImagePointHandler):
             return lut.point(self)
 
-        if not isinstance(lut, collections.Sequence):
+        if callable(lut):
             # if it isn't a list, it should be a function
             if self.mode in ("I", "I;16", "F"):
                 # check if the function can be used with point_transform
+                # UNDONE wiredfool -- I think this prevents us from ever doing
+                # a gamma function point transform on > 8bit images. 
                 scale, offset = _getscaleoffset(lut)
                 return self._new(self.im.point_transform(scale, offset))
             # for other modes, convert the function to a table

Tests/test_image_point.py

@@ -17,3 +17,12 @@ def test_sanity():
     assert_no_exception(lambda: im.point(lambda x: x*1+1))
     assert_exception(TypeError, lambda: im.point(lambda x: x-1))
     assert_exception(TypeError, lambda: im.point(lambda x: x/1))
+
+
+def test_16bit_lut():
+    """ Tests for 16 bit -> 8 bit lut for converting I->L images
+        see https://github.com/python-imaging/Pillow/issues/440
+    """
+
+    im = lena("I")
+    assert_no_exception(lambda: im.point(list(range(256))*256, 'L'))

Tests/test_numpy.py

@@ -106,3 +106,15 @@ def test_to_array():
     for mode in modes:
         assert_no_exception(lambda: _to_array(*mode))
 
+
+def test_point_lut():
+    # see https://github.com/python-imaging/Pillow/issues/439
+    
+    data = list(range(256))*3
+    lut = numpy.array(data, dtype='uint8')
+
+    im = lena()
+
+    assert_no_exception(lambda: im.point(lut))
+    
+