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Do not modify previous frame when calculating delta in PNG #6683

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Merged
hugovk merged 1 commit into from
Oct 24, 2022
Merged

Do not modify previous frame when calculating delta in PNG #6683

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6 changes: 4 additions & 2 deletions Tests/test_file_apng.py
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Original file line number Diff line number Diff line change
Expand Up @@ -553,18 +553,20 @@ def test_apng_save_disposal(tmp_path):
def test_apng_save_disposal_previous(tmp_path):
test_file = str(tmp_path / "temp.png")
size = (128, 64)
transparent = Image.new("RGBA", size, (0, 0, 0, 0))
blue = Image.new("RGBA", size, (0, 0, 255, 255))
red = Image.new("RGBA", size, (255, 0, 0, 255))
green = Image.new("RGBA", size, (0, 255, 0, 255))

# test OP_NONE
transparent.save(
blue.save(
test_file,
save_all=True,
append_images=[red, green],
disposal=PngImagePlugin.Disposal.OP_PREVIOUS,
)
with Image.open(test_file) as im:
assert im.getpixel((0, 0)) == (0, 0, 255, 255)

im.seek(2)
assert im.getpixel((0, 0)) == (0, 255, 0, 255)
assert im.getpixel((64, 32)) == (0, 255, 0, 255)
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2 changes: 1 addition & 1 deletion src/PIL/PngImagePlugin.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1128,7 +1128,7 @@ def _write_multiple_frames(im, fp, chunk, rawmode, default_image, append_images)
prev_disposal = Disposal.OP_BACKGROUND

if prev_disposal == Disposal.OP_BACKGROUND:
base_im = previous["im"]
base_im = previous["im"].copy()
dispose = Image.core.fill("RGBA", im.size, (0, 0, 0, 0))
bbox = previous["bbox"]
if bbox:
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