def process(self, img):
matte = False
self.save_kwargs = {}
if img.mode == 'RGBA':
if self.format in RGBA_TRANSPARENCY_FORMATS:
pass
elif self.format in PALETTE_TRANSPARENCY_FORMATS:
# If you're going from a format with alpha transparency to one
# with palette transparency, transparency values will be
# snapped: pixels that are more opaque than not will become
# fully opaque; pixels that are more transparent than not will
# become fully transparent. This will not produce a good-looking
# result if your image contains varying levels of opacity; in
# that case, you'll probably want to use a processor to matte
# the image on a solid color. The reason we don't matte by
# default is because not doing so allows processors to treat
# RGBA-format images as a super-type of P-format images: if you
# have an RGBA-format image with only a single transparent
# color, and save it as a GIF, it will retain its transparency.
# In other words, a P-format image converted to an
# RGBA-formatted image by a processor and then saved as a
# P-format image will give the expected results.
alpha = img.split()[-1]
mask = Image.eval(alpha, lambda a: 255 if a <= 128 else 0)
img = img.convert('RGB').convert('P',
palette=Image.ADAPTIVE,
colors=255)
img.paste(255, mask)
self.save_kwargs['transparency'] = 255
else:
# Simply converting an RGBA-format image to an RGB one creates a
# gross result, so we matte the image on a white background. If
# that's not what you want, that's fine: use a processor to deal
# with the transparency however you want. This is simply a
# sensible default that will always produce something that looks
# good. Or at least, it will look better than just a straight
# conversion.
matte = True
elif img.mode == 'P':
if self.format in PALETTE_TRANSPARENCY_FORMATS:
try:
self.save_kwargs['transparency'] = img.info['transparency']
except KeyError:
pass
elif self.format in RGBA_TRANSPARENCY_FORMATS:
# Currently PIL doesn't support any RGBA-mode formats that
# aren't also P-mode formats, so this will never happen.
img = img.convert('RGBA')
else:
matte = True
else:
img = img.convert('RGB')
# GIFs are always going to be in palette mode, so we can do a little
# optimization. Note that the RGBA sources also use adaptive
# quantization (above). Images that are already in P mode don't need
# any quantization because their colors are already limited.
if self.format == 'GIF':
img = img.convert('P', palette=Image.ADAPTIVE)
if matte:
img = img.convert('RGBA')
bg = Image.new('RGBA', img.size, (255, 255, 255))
bg.paste(img, img)
img = bg.convert('RGB')
if self.format == 'JPEG':
self.save_kwargs['optimize'] = True
return img
def process(self, img):
matte = False
self.save_kwargs = {}
self.rgba_ = img.mode == 'RGBA'
if self.rgba_:
if self.format in RGBA_TRANSPARENCY_FORMATS:
pass
elif self.format in PALETTE_TRANSPARENCY_FORMATS:
# If you're going from a format with alpha transparency to one
# with palette transparency, transparency values will be
# snapped: pixels that are more opaque than not will become
# fully opaque; pixels that are more transparent than not will
# become fully transparent. This will not produce a good-looking
# result if your image contains varying levels of opacity; in
# that case, you'll probably want to use a processor to matte
# the image on a solid color. The reason we don't matte by
# default is because not doing so allows processors to treat
# RGBA-format images as a super-type of P-format images: if you
# have an RGBA-format image with only a single transparent
# color, and save it as a GIF, it will retain its transparency.
# In other words, a P-format image converted to an
# RGBA-formatted image by a processor and then saved as a
# P-format image will give the expected results.
alpha = img.split()[-1]
mask = Image.eval(alpha, lambda a: 255 if a <= 128 else 0)
img = img.convert('RGB').convert('P', palette=Image.ADAPTIVE,
colors=255)
img.paste(255, mask)
self.save_kwargs['transparency'] = 255
else:
# Simply converting an RGBA-format image to an RGB one creates a
# gross result, so we matte the image on a white background. If
# that's not what you want, that's fine: use a processor to deal
# with the transparency however you want. This is simply a
# sensible default that will always produce something that looks
# good. Or at least, it will look better than just a straight
# conversion.
matte = True
elif img.mode == 'P':
if self.format in PALETTE_TRANSPARENCY_FORMATS:
try:
self.save_kwargs['transparency'] = img.info['transparency']
except KeyError:
pass
elif self.format in RGBA_TRANSPARENCY_FORMATS:
# Currently PIL doesn't support any RGBA-mode formats that
# aren't also P-mode formats, so this will never happen.
img = img.convert('RGBA')
else:
matte = True
else:
img = img.convert('RGB')
# GIFs are always going to be in palette mode, so we can do a little
# optimization. Note that the RGBA sources also use adaptive
# quantization (above). Images that are already in P mode don't need
# any quantization because their colors are already limited.
if self.format == 'GIF':
img = img.convert('P', palette=Image.ADAPTIVE)
if matte:
img = img.convert('RGBA')
bg = Image.new('RGBA', img.size, (255, 255, 255))
bg.paste(img, img)
img = bg.convert('RGB')
if self.format == 'JPEG':
self.save_kwargs['optimize'] = True
return img
