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Fix #6069. Handle image masks correctly #6099

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Mar 4, 2016
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4 changes: 0 additions & 4 deletions lib/matplotlib/cm.py
Original file line number Diff line number Diff line change
Expand Up @@ -269,10 +269,6 @@ def to_rgba(self, x, alpha=None, bytes=False, norm=True):
if norm:
x = self.norm(x)
rgba = self.cmap(x, alpha=alpha, bytes=bytes)
# For floating-point greyscale images, we treat negative as
# transparent so we copy that over to the alpha channel
if x.ndim == 2 and x.dtype.kind == 'f':
rgba[:, :, 3][x < 0.0] = 0
return rgba

def set_array(self, A):
Expand Down
30 changes: 19 additions & 11 deletions lib/matplotlib/image.py
Original file line number Diff line number Diff line change
Expand Up @@ -354,20 +354,22 @@ def _make_image(self, A, in_bbox, out_bbox, clip_bbox, magnification=1.0,
out_height = int(out_height_base)

if not unsampled:
created_rgba_mask = False

if A.ndim == 2:
A = self.norm(A)
# 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)
if A.dtype.kind == 'f':
# For floating-point greyscale images, we treat negative
# numbers as transparent.

# TODO: Use np.full when we support Numpy 1.9 as a
# minimum
output = np.empty((out_height, out_width), dtype=A.dtype)
output[...] = -100.0
rgba[..., 3] = ~A.mask
else:
output = np.zeros((out_height, out_width), dtype=A.dtype)

rgba[..., 3] = np.where(A.mask, 0, np.iinfo(A.dtype).max)
A = rgba
output = np.zeros((out_height, out_width, 4), dtype=A.dtype)
alpha = 1.0
created_rgba_mask = True
elif A.ndim == 3:
# Always convert to RGBA, even if only RGB input
if A.shape[2] == 3:
Expand All @@ -388,10 +390,16 @@ def _make_image(self, A, in_bbox, out_bbox, clip_bbox, magnification=1.0,
self.get_resample(), alpha,
self.get_filternorm() or 0.0, self.get_filterrad() or 0.0)

if created_rgba_mask:
# Convert back to a masked greyscale array so
# colormapping works correctly
output = np.ma.masked_array(
output[..., 0], output[..., 3] < 0.5)

output = self.to_rgba(output, bytes=True, norm=False)

# Apply alpha *after* if the input was greyscale
if A.ndim == 2:
# Apply alpha *after* if the input was greyscale without a mask
if A.ndim == 2 or created_rgba_mask:
alpha = self.get_alpha()
if alpha is not None and alpha != 1.0:
alpha_channel = output[:, :, 3]
Expand Down
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