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workaround for Pillow >= 8.3.0 which limits CCITT Group4 strip size to 64 KB (closes: #122)

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Johannes Schauer Marin Rodrigues 2021-10-03 13:24:41 +02:00
parent f483638b17
commit 6eec05c11c
Signed by untrusted user: josch
GPG key ID: F2CBA5C78FBD83E1
1 changed files with 31 additions and 3 deletions
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src/img2pdf.py
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@ -1357,14 +1357,15 @@ def ccitt_payload_location_from_pil(img):
# Read the TIFF tags to find the offset(s) of the compressed data strips.
strip_offsets = img.tag_v2[TiffImagePlugin.STRIPOFFSETS]
strip_bytes = img.tag_v2[TiffImagePlugin.STRIPBYTECOUNTS]
rows_per_strip = img.tag_v2.get(TiffImagePlugin.ROWSPERSTRIP, 2 ** 32 - 1)
# PIL always seems to create a single strip even for very large TIFFs when
# it saves images, so assume we only have to read a single strip.
# A test ~10 GPixel image was still encoded as a single strip. Just to be
# safe check throw an error if there is more than one offset.
if len(strip_offsets) != 1 or len(strip_bytes) != 1:
raise NotImplementedError("Transcoding multiple strips not supported")
raise NotImplementedError(
"Transcoding multiple strips not supported by the PDF format"
)
(offset,), (length,) = strip_offsets, strip_bytes
@ -1388,7 +1389,33 @@ def transcode_monochrome(imgdata):
# killed by a SIGABRT:
# https://gitlab.mister-muffin.de/josch/img2pdf/issues/46
im = Image.frombytes(imgdata.mode, imgdata.size, imgdata.tobytes())
im.save(newimgio, format="TIFF", compression="group4")
# Since version 8.3.0 Pillow limits strips to 64 KB. Since PDF only
# supports single strip CCITT Group4 payloads, we have to coerce it back
# into putting everything into a single strip. Thanks to Andrew Murray for
# the hack.
#
# This can be dropped once this gets merged:
# https://github.com/python-pillow/Pillow/pull/5744
pillow__getitem__ = TiffImagePlugin.ImageFileDirectory_v2.__getitem__
def __getitem__(self, tag):
overrides = {
TiffImagePlugin.ROWSPERSTRIP: imgdata.size[1],
TiffImagePlugin.STRIPBYTECOUNTS: [
(imgdata.size[0] + 7) // 8 * imgdata.size[1]
],
TiffImagePlugin.STRIPOFFSETS: [0],
}
return overrides.get(tag, pillow__getitem__(self, tag))
# use try/finally to make sure that __getitem__ is reset even if save()
# raises an exception
try:
TiffImagePlugin.ImageFileDirectory_v2.__getitem__ = __getitem__
im.save(newimgio, format="TIFF", compression="group4")
finally:
TiffImagePlugin.ImageFileDirectory_v2.__getitem__ = pillow__getitem__
# Open new image in memory
newimgio.seek(0)
@ -1633,6 +1660,7 @@ def read_images(rawdata, colorspace, first_frame_only=False, rot=None):
imgformat == ImageFormat.TIFF
and imgdata.info["compression"] == "group4"
and len(imgdata.tag_v2[TiffImagePlugin.STRIPOFFSETS]) == 1
and len(imgdata.tag_v2[TiffImagePlugin.STRIPBYTECOUNTS]) == 1
):
photo = imgdata.tag_v2[TiffImagePlugin.PHOTOMETRIC_INTERPRETATION]
inverted = False