Merge pull request #2058 from matthew-brett/fix-numpy-bit-conversion

BF: fix conversion of bit images to numpy arrays

PIL/Image.py

@@ -246,7 +246,7 @@ else:
 
 _MODE_CONV = {
     # official modes
-    "1": ('|b1', None),  # broken
+    "1": ('|b1', None),  # Bits need to be extended to bytes
     "L": ('|u1', None),
     "LA": ('|u1', 2),
     "I": (_ENDIAN + 'i4', None),
@@ -615,17 +615,21 @@ class Image(object):
         self.save(b, 'PNG')
         return b.getvalue()
 
-    def __getattr__(self, name):
-        if name == "__array_interface__":
-            # numpy array interface support
-            new = {}
-            shape, typestr = _conv_type_shape(self)
-            new['shape'] = shape
-            new['typestr'] = typestr
+    @property
+    def __array_interface__(self):
+        # numpy array interface support
+        new = {}
+        shape, typestr = _conv_type_shape(self)
+        new['shape'] = shape
+        new['typestr'] = typestr
+        new['version'] = 3
+        if self.mode == '1':
+            # Binary images need to be extended from bits to bytes
+            # See: https://github.com/python-pillow/Pillow/issues/350
+            new['data'] = self.tobytes('raw', 'L')
+        else:
             new['data'] = self.tobytes()
-            new['version'] = 3
-            return new
-        raise AttributeError(name)
+        return new
 
     def __getstate__(self):
         return [

Tests/test_image_array.py

@@ -25,13 +25,26 @@ class TestImageArray(PillowTestCase):
         self.assertEqual(test("RGBX"), (3, (100, 128, 4), '|u1', 51200))
 
     def test_fromarray(self):
+
+        class Wrapper(object):
+            """ Class with API matching Image.fromarray """
+
+            def __init__(self, img, arr_params):
+                self.img = img
+                self.__array_interface__ = arr_params
+
+            def tobytes(self):
+                return self.img.tobytes()
+
         def test(mode):
             i = im.convert(mode)
             a = i.__array_interface__
-            a["strides"] = 1  # pretend it's non-contiguous
-            i.__array_interface__ = a  # patch in new version of attribute
-            out = Image.fromarray(i)
+            a["strides"] = 1  # pretend it's non-contigous
+            # Make wrapper instance for image, new array interface
+            wrapped = Wrapper(i, a)
+            out = Image.fromarray(wrapped)
             return out.mode, out.size, list(i.getdata()) == list(out.getdata())
+
         # self.assertEqual(test("1"), ("1", (128, 100), True))
         self.assertEqual(test("L"), ("L", (128, 100), True))
         self.assertEqual(test("I"), ("I", (128, 100), True))

Tests/test_numpy.py

@@ -117,6 +117,15 @@ class TestNumpy(PillowTestCase):
         self._test_img_equals_nparray(img, np_img)
         self.assertEqual(np_img.dtype, numpy.dtype('<u2'))
 
+    def test_1bit(self):
+        # Test that 1-bit arrays convert to numpy and back
+        # See: https://github.com/python-pillow/Pillow/issues/350
+        arr = numpy.array([[1, 0, 0, 1, 0], [0, 1, 0, 0, 0]], 'u1')
+        img = Image.fromarray(arr * 255).convert('1')
+        self.assertEqual(img.mode, '1')
+        arr_back = numpy.array(img)
+        numpy.testing.assert_array_equal(arr, arr_back)
+
     def test_save_tiff_uint16(self):
         '''
         Open a single-channel uint16 greyscale image and verify that it can be saved without