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Derive PCX plane count from the image, not the line width #9798

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Derive PCX plane count from the image, not the line width #9798

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Derive PCX plane count from the image, not the line width
chuenchen309 Jul 19, 2026
2f3f7ff
Simplified code
radarhere Jul 28, 2026
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5 changes: 3 additions & 2 deletions Tests/test_file_pcx.py
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Original file line number Diff line number Diff line change
Expand Up @@ -80,13 +80,14 @@ def test_invalid_file() -> None:


@pytest.mark.parametrize("mode", ("1", "L", "P", "RGB"))
def test_odd(tmp_path: Path, mode: str) -> None:
@pytest.mark.parametrize("size", (3, 511))
def test_odd(tmp_path: Path, mode: str, size: int) -> None:
# See issue #523, odd sized images should have a stride that's even.
# Not that ImageMagick or GIMP write PCX that way.
# We were not handling properly.
# larger, odd sized images are better here to ensure that
# we handle interrupted scan lines properly.
_roundtrip(tmp_path, hopper(mode).resize((511, 511)))
_roundtrip(tmp_path, hopper(mode).resize((size, size)))


def test_odd_read() -> None:
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8 changes: 2 additions & 6 deletions src/libImaging/PcxDecode.c
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Expand Up @@ -62,18 +62,14 @@ ImagingPcxDecode(Imaging im, ImagingCodecState state, UINT8 *buf, Py_ssize_t byt
if (state->x >= state->bytes) {
int bands;
int xsize = 0;
int stride = 0;
if (state->bits == 2 || state->bits == 4) {
xsize = (state->xsize + 7) / 8;
bands = state->bits;
stride = state->bytes / state->bits;
} else {
xsize = state->xsize;
bands = state->bytes / state->xsize;
if (bands != 0) {
stride = state->bytes / bands;
}
bands = im->bands;
}
int stride = state->bytes / bands;
if (stride > xsize) {
int i;
for (i = 1; i < bands; i++) { // note -- skipping first band
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