FIX: carry through the over/under in resampling

tacaswell · tacaswell · commit 0a1667295f07 · 2016-06-28T23:25:22.000-04:00
Use the same trick for carrying through the masked points to use the
green and blue channels to carry the under/over markers.
diff --git a/lib/matplotlib/image.py b/lib/matplotlib/image.py
@@ -361,7 +361,10 @@ def _make_image(self, A, in_bbox, out_bbox, clip_bbox, magnification=1.0,
                 # If the image is greyscale, convert to RGBA with the
                 # correct alpha channel for resizing
                 rgba = np.empty((A.shape[0], A.shape[1], 4), dtype=A.dtype)
-                rgba[..., 0:3] = np.expand_dims(A, 2)
+                rgba[..., 0] = A  # normalized data
+                rgba[..., 1] = A < 0  # under data
+                # TODO, ask the norm or colormap what this threshold should be
+                rgba[..., 2] = A > 1  # over data
                 if A.dtype.kind == 'f':
                     rgba[..., 3] = ~A.mask
                 else:
@@ -393,8 +396,13 @@ def _make_image(self, A, in_bbox, out_bbox, clip_bbox, magnification=1.0,
             if created_rgba_mask:
                 # Convert back to a masked greyscale array so
                 # colormapping works correctly
+                hid_output = output
                 output = np.ma.masked_array(
-                    output[..., 0], output[..., 3] < 0.5)
+                    hid_output[..., 0], hid_output[..., 3] < 0.5)
+                # relabel under data
+                output[hid_output[..., 1] > .5] = -1
+                # relabel over data
+                output[hid_output[..., 2] > .5] = 2
 
             output = self.to_rgba(output, bytes=True, norm=False)
 
