timhoffm
diff --git a/‎lib/matplotlib/image.py‎
Lines changed: 7 additions & 5 deletions b/‎lib/matplotlib/image.py‎
Lines changed: 7 additions & 5 deletions
diff --git a/‎lib/matplotlib/tests/baseline_images/test_image/image_composite_alpha.pdf‎
-22.6 KB b/‎lib/matplotlib/tests/baseline_images/test_image/image_composite_alpha.pdf‎
-22.6 KB
diff --git a/‎lib/matplotlib/tests/baseline_images/test_image/image_composite_alpha.png‎
-3.72 KB b/‎lib/matplotlib/tests/baseline_images/test_image/image_composite_alpha.png‎
-3.72 KB
diff --git a/‎lib/matplotlib/tests/baseline_images/test_image/image_composite_alpha.svg‎
Lines changed: 34 additions & 39 deletions b/‎lib/matplotlib/tests/baseline_images/test_image/image_composite_alpha.svg‎
Lines changed: 34 additions & 39 deletions
diff --git a/‎lib/matplotlib/tests/baseline_images/test_image/interp_alpha.png‎
14.6 KB b/‎lib/matplotlib/tests/baseline_images/test_image/interp_alpha.png‎
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diff --git a/‎lib/matplotlib/tests/baseline_images/test_png/pngsuite.png‎
5.48 KB b/‎lib/matplotlib/tests/baseline_images/test_png/pngsuite.png‎
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diff --git a/‎lib/matplotlib/tests/test_image.py‎
Lines changed: 14 additions & 0 deletions b/‎lib/matplotlib/tests/test_image.py‎
Lines changed: 14 additions & 0 deletions
@@ -493,21 +493,23 @@ def _make_image(self, A, in_bbox, out_bbox, clip_bbox, magnification=1.0,
                     alpha = 1
 
                 #resample alpha channel
-                alpha_channel = A[...,3]
+                alpha_channel = A[..., 3]
                 _image.resample(
-                    alpha_channel, output_a, t, _interpd_[self.get_interpolation()],
+                    alpha_channel, output_a, t,
+                    _interpd_[self.get_interpolation()],
                     self.get_resample(), alpha,
                     self.get_filternorm(), self.get_filterrad())
 
                 #resample rgb channels
-                A = _rgb_to_rgba(A[...,:3])
+                A = _rgb_to_rgba(A[..., :3])
                 _image.resample(
-                    A, output, t, _interpd_[self.get_interpolation()],
+                    A, output, t,
+                    _interpd_[self.get_interpolation()],
                     self.get_resample(), alpha,
                     self.get_filternorm(), self.get_filterrad())
 
                 #recombine rgb and alpha channels
-                output[...,3] = output_a
+                output[..., 3] = output_a
 
             # at this point output is either a 2D array of normed data
             # (of int or float)
 
@@ -43,6 +43,20 @@ def test_image_interps():
     ax3.set_ylabel('bicubic')
 
 
+@image_comparison(baseline_images=['interp_alpha'],
+                  extensions=['png'], remove_text=True)
+def test_alpha_interp():
+    'Test the interpolation of the alpha channel on RGBA images'
+    fig, (axl, axr) = plt.subplots(1, 2)
+    # full green image
+    img = np.zeros((5, 5, 4))
+    img[..., 1] = np.ones((5, 5))
+    # transparent under main diagonal
+    img[..., 3] = np.tril(np.ones((5, 5), dtype=np.uint8))
+    axl.imshow(img, interpolation="none")
+    axr.imshow(img, interpolation="bilinear")
+
+
 @image_comparison(baseline_images=['interp_nearest_vs_none'],
                   extensions=['pdf', 'svg'], remove_text=True)
 def test_interp_nearest_vs_none():