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Fix #5302: Proper alpha-blending for jpeg #5324

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Merged
merged 5 commits into from
Oct 28, 2015
Merged

Fix #5302: Proper alpha-blending for jpeg #5324

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bdea63d
Fix #5302: Proper alpha-blending for jpeg
mdboom Oct 26, 2015
3dea66d
Get background color from savefig.facecolor
mdboom Oct 27, 2015
183f246
Fix test
mdboom Oct 27, 2015
737da1e
Add prints to test
mdboom Oct 27, 2015
fb6ff8a
Adjust acceptable range
mdboom Oct 28, 2015
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Fix #5302: Proper alpha-blending for jpeg
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@mdboom
mdboom committed Oct 26, 2015
commit bdea63d1c852da5393e6844fc7edd1659e0dab70
7 changes: 5 additions & 2 deletions lib/matplotlib/backends/backend_agg.py
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Original file line number Diff line number Diff line change
Expand Up @@ -551,7 +551,6 @@ def print_to_buffer(self):
return result

if _has_pil:

# add JPEG support
def print_jpg(self, filename_or_obj, *args, **kwargs):
"""
Expand All @@ -573,14 +572,18 @@ def print_jpg(self, filename_or_obj, *args, **kwargs):
buf, size = self.print_to_buffer()
if kwargs.pop("dryrun", False):
return
# The image is "pasted" onto a white background image to safely
# handle any transparency
image = Image.frombuffer('RGBA', size, buf, 'raw', 'RGBA', 0, 1)
background = Image.new('RGB', size, (255, 255, 255))
background.paste(image, image)
options = restrict_dict(kwargs, ['quality', 'optimize',
'progressive'])

if 'quality' not in options:
options['quality'] = rcParams['savefig.jpeg_quality']

return image.save(filename_or_obj, format='jpeg', **options)
return background.save(filename_or_obj, format='jpeg', **options)
print_jpeg = print_jpg

# add TIFF support
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22 changes: 22 additions & 0 deletions lib/matplotlib/tests/test_image.py
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Expand Up @@ -453,6 +453,28 @@ def test_nonuniformimage_setnorm():
im = NonUniformImage(ax)
im.set_norm(plt.Normalize())

@knownfailureif(not HAS_PIL)
@cleanup
def test_jpeg_alpha():
plt.figure(figsize=(1, 1), dpi=300)
# Create an image that is all black, with a gradient from 0-1 in
# the alpha channel from left to right.
im = np.zeros((300, 300, 4), dtype=np.float)
im[..., 3] = np.linspace(0.0, 1.0, 300)

plt.figimage(im)

buff = io.BytesIO()
plt.savefig(buff, transparent=True, format='jpg', dpi=300)

buff.seek(0)
image = Image.open(buff)

# If this fails, there will be only one color (all black). If this
# is working, we should have all 256 shades of grey represented.
assert len(image.getcolors(256)) == 256


if __name__=='__main__':
import nose
nose.runmodule(argv=['-s','--with-doctest'], exit=False)