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Correct saving more than two MPO frames #10326

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Merged
radarhere merged 3 commits into from
Oct 27, 2026
Merged

Correct saving more than two MPO frames #10326

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495a8db
Fix MPO frame sizes and offsets when saving multiple images
umtong Oct 26, 2026
be0c4c6
Merge branch 'main' into fix-mpo-frame-offsets
radarhere Oct 27, 2026
287c21d
Simplify code
radarhere Oct 27, 2026
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2 changes: 1 addition & 1 deletion Tests/test_file_mpo.py
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Original file line number Diff line number Diff line change
Expand Up @@ -356,7 +356,7 @@ def test_save_all() -> None:
assert_image_similar(im, im_reloaded, 30)

im_rgb = Image.new("RGB", (1, 1))
for colors in (("#f00",), ("#f00", "#0f0")):
for colors in (("#f00",), ("#f00", "#0f0"), ("#f00", "#0f0", "#00f")):
append_images = [Image.new("RGB", (1, 1), color) for color in colors]
im_reloaded = roundtrip(im_rgb, save_all=True, append_images=append_images)

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6 changes: 4 additions & 2 deletions src/PIL/MpoImagePlugin.py
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Expand Up @@ -51,6 +51,7 @@ def _save_all(im: Image.Image, fp: IO[bytes], filename: str | bytes) -> None:
return

mpf_offset = 28
prev_offset = 0
offsets: list[int] = []
im_sequences = [im, *append_images]
total = sum(getattr(seq, "n_frames", 1) for seq in im_sequences)
Expand All @@ -72,12 +73,13 @@ def _save_all(im: Image.Image, fp: IO[bytes], filename: str | bytes) -> None:
mpf_offset += 4 + len(exif)

JpegImagePlugin._save(im_frame, fp, filename)
offsets.append(fp.tell())
else:
encoderinfo = im_frame._attach_default_encoderinfo(im)
im_frame.save(fp, "JPEG")
im_frame.encoderinfo = encoderinfo
offsets.append(fp.tell() - offsets[-1])
offset = fp.tell()
offsets.append(offset - prev_offset)
prev_offset = offset

ifd = TiffImagePlugin.ImageFileDirectory_v2()
ifd[0xB000] = b"0100"
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