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Do not use background or transparency index for new color

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This commit is contained in:
Andrew Murray 2021-06-30 00:05:25 +10:00
parent 4b4e5f0e2c
commit eab2b17d64
2 changed files with 28 additions and 1 deletions
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19
Tests/test_imagepalette.py
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@ -49,6 +49,25 @@ def test_getcolor():
palette.getcolor("unknown")
def test_getcolor_not_special():
im = Image.new("P", (1, 1))
for index, palette in {
# Test when the palette is not full
0: ImagePalette.ImagePalette(),
# Test when the palette is full
255: ImagePalette.ImagePalette("RGB", list(range(256)) * 3),
}.items():
# Do not use transparency index as a new color
im.info["transparency"] = index
index1 = palette.getcolor((0, 0, 0), im)
assert index1 != index
# Do not use background index as a new color
im.info["background"] = index1
index2 = palette.getcolor((0, 0, 1), im)
assert index2 not in (index, index1)
def test_file(tmp_path):
palette = ImagePalette.ImagePalette("RGB", list(range(256)) * 3)

10
src/PIL/ImagePalette.py
View File

@ -118,11 +118,19 @@ class ImagePalette:
if not isinstance(self.palette, bytearray):
self._palette = bytearray(self.palette)
index = len(self.palette) // 3
special_colors = ()
if image:
special_colors = (
image.info.get("background"),
image.info.get("transparency"),
)
while index in special_colors:
index += 1
if index >= 256:
if image:
# Search for an unused index
for i, count in reversed(list(enumerate(image.histogram()))):
if count == 0:
if count == 0 and i not in special_colors:
index = i
break
if index >= 256: