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When saving multiple PNG frames, convert to mode rather than raw mode #8087

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merged 1 commit into from
Jun 25, 2024
Merged

When saving multiple PNG frames, convert to mode rather than raw mode #8087

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5 changes: 3 additions & 2 deletions Tests/test_file_png.py
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Original file line number Diff line number Diff line change
Expand Up @@ -655,11 +655,12 @@ def test_truncated_chunks(self, cid: bytes) -> None:
png.call(cid, 0, 0)
ImageFile.LOAD_TRUNCATED_IMAGES = False

def test_specify_bits(self, tmp_path: Path) -> None:
@pytest.mark.parametrize("save_all", (True, False))
def test_specify_bits(self, save_all: bool, tmp_path: Path) -> None:
im = hopper("P")

out = str(tmp_path / "temp.png")
im.save(out, bits=4)
im.save(out, bits=4, save_all=save_all)

with Image.open(out) as reloaded:
assert len(reloaded.png.im_palette[1]) == 48
Expand Down
17 changes: 9 additions & 8 deletions src/PIL/PngImagePlugin.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1104,7 +1104,7 @@ def write(self, data: bytes) -> None:
self.seq_num += 1


def _write_multiple_frames(im, fp, chunk, rawmode, default_image, append_images):
def _write_multiple_frames(im, fp, chunk, mode, rawmode, default_image, append_images):
duration = im.encoderinfo.get("duration", im.info.get("duration", 0))
loop = im.encoderinfo.get("loop", im.info.get("loop", 0))
disposal = im.encoderinfo.get("disposal", im.info.get("disposal", Disposal.OP_NONE))
Expand All @@ -1119,10 +1119,10 @@ def _write_multiple_frames(im, fp, chunk, rawmode, default_image, append_images)
frame_count = 0
for im_seq in chain:
for im_frame in ImageSequence.Iterator(im_seq):
if im_frame.mode == rawmode:
if im_frame.mode == mode:
im_frame = im_frame.copy()
else:
im_frame = im_frame.convert(rawmode)
im_frame = im_frame.convert(mode)
encoderinfo = im.encoderinfo.copy()
if isinstance(duration, (list, tuple)):
encoderinfo["duration"] = duration[frame_count]
Expand Down Expand Up @@ -1184,8 +1184,8 @@ def _write_multiple_frames(im, fp, chunk, rawmode, default_image, append_images)

# default image IDAT (if it exists)
if default_image:
if im.mode != rawmode:
im = im.convert(rawmode)
if im.mode != mode:
im = im.convert(mode)
ImageFile._save(im, _idat(fp, chunk), [("zip", (0, 0) + im.size, 0, rawmode)])

seq_num = 0
Expand Down Expand Up @@ -1262,6 +1262,7 @@ def _save(im, fp, filename, chunk=putchunk, save_all=False):
size = im.size
mode = im.mode

outmode = mode
if mode == "P":
#
# attempt to minimize storage requirements for palette images
Expand All @@ -1282,7 +1283,7 @@ def _save(im, fp, filename, chunk=putchunk, save_all=False):
bits = 2
else:
bits = 4
mode = f"{mode};{bits}"
outmode += f";{bits}"

# encoder options
im.encoderconfig = (
Expand All @@ -1294,7 +1295,7 @@ def _save(im, fp, filename, chunk=putchunk, save_all=False):

# get the corresponding PNG mode
try:
rawmode, bit_depth, color_type = _OUTMODES[mode]
rawmode, bit_depth, color_type = _OUTMODES[outmode]
except KeyError as e:
msg = f"cannot write mode {mode} as PNG"
raise OSError(msg) from e
Expand Down Expand Up @@ -1415,7 +1416,7 @@ def _save(im, fp, filename, chunk=putchunk, save_all=False):

if save_all:
im = _write_multiple_frames(
im, fp, chunk, rawmode, default_image, append_images
im, fp, chunk, mode, rawmode, default_image, append_images
)
if im:
ImageFile._save(im, _idat(fp, chunk), [("zip", (0, 0) + im.size, 0, rawmode)])
Expand Down
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