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If all 256 colors are in use, then there is no need for an additional color for background or transparency

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This commit is contained in:
Andrew Murray 2021-06-23 19:28:46 +10:00
parent fa559277fb
commit 8210645e4b
3 changed files with 39 additions and 15 deletions
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3
Tests/test_imagepalette.py
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@ -31,8 +31,11 @@ def test_getcolor():
assert palette.getcolor((0, 0, 0)) == palette.getcolor((0, 0, 0, 255)) assert palette.getcolor((0, 0, 0)) == palette.getcolor((0, 0, 0, 255))
# An error is raised when the palette is full
with pytest.raises(ValueError): with pytest.raises(ValueError):
palette.getcolor((1, 2, 3)) palette.getcolor((1, 2, 3))
# But not if the image is not using one of the palette entries
palette.getcolor((1, 2, 3), image=Image.new("P", (1, 1)))
# Test unknown color specifier # Test unknown color specifier
with pytest.raises(ValueError): with pytest.raises(ValueError):

10
src/PIL/GifImagePlugin.py
View File

@ -760,7 +760,15 @@ def _get_background(im, infoBackground):
# WebPImagePlugin stores an RGBA value in info["background"] # WebPImagePlugin stores an RGBA value in info["background"]
# So it must be converted to the same format as GifImagePlugin's # So it must be converted to the same format as GifImagePlugin's
# info["background"] - a global color table index # info["background"] - a global color table index
background = im.palette.getcolor(background, im) try:
background = im.palette.getcolor(background, im)
except ValueError as e:
if str(e) == "cannot allocate more than 256 colors":
# If all 256 colors are in use,
# then there is no need for the background color
return 0
else:
raise
return background return background

41
src/PIL/Image.py
View File

@ -979,19 +979,27 @@ class Image:
if isinstance(t, tuple): if isinstance(t, tuple):
try: try:
t = trns_im.palette.getcolor(t, self) t = trns_im.palette.getcolor(t, self)
except Exception as e: except ValueError as e:
raise ValueError( if str(e) == "cannot allocate more than 256 colors":
"Couldn't allocate a palette color for transparency" # If all 256 colors are in use,
) from e # then there is no need for transparency
trns_im.putpixel((0, 0), t) t = None
else:
if mode in ("L", "RGB"): raise ValueError(
trns_im = trns_im.convert(mode) "Couldn't allocate a palette color for transparency"
) from e
if t is None:
trns = None
else: else:
# can't just retrieve the palette number, got to do it trns_im.putpixel((0, 0), t)
# after quantization.
trns_im = trns_im.convert("RGB") if mode in ("L", "RGB"):
trns = trns_im.getpixel((0, 0)) trns_im = trns_im.convert(mode)
else:
# can't just retrieve the palette number, got to do it
# after quantization.
trns_im = trns_im.convert("RGB")
trns = trns_im.getpixel((0, 0))
elif self.mode == "P" and mode == "RGBA": elif self.mode == "P" and mode == "RGBA":
t = self.info["transparency"] t = self.info["transparency"]
@ -1050,9 +1058,14 @@ class Image:
if new_im.mode == "P": if new_im.mode == "P":
try: try:
new_im.info["transparency"] = new_im.palette.getcolor(trns, new_im) new_im.info["transparency"] = new_im.palette.getcolor(trns, new_im)
except Exception: except ValueError as e:
del new_im.info["transparency"] del new_im.info["transparency"]
warnings.warn("Couldn't allocate palette entry for transparency") if str(e) != "cannot allocate more than 256 colors":
# If all 256 colors are in use,
# then there is no need for transparency
warnings.warn(
"Couldn't allocate palette entry for transparency"
)
else: else:
new_im.info["transparency"] = trns new_im.info["transparency"] = trns
return new_im return new_im