Emmeran Seehuber created PDFBOX-4184:
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Summary: [PATCH]: Support simple lossless compression of 16 bit
RGB images
Key: PDFBOX-4184
URL: https://issues.apache.org/jira/browse/PDFBOX-4184
Project: PDFBox
Issue Type: Improvement
Components: Writing
Affects Versions: 2.0.9
Reporter: Emmeran Seehuber
Attachments: pdfbox_support_16bit_image_write.patch
The attached patch add support to write 16 bit per component images correctly.
I've integrated a test for this here:
[https://github.com/rototor/pdfbox-graphics2d/commit/8bf089cb74945bd4f0f15054754f51dd5b361fe9]
It only supports 16-Bit TYPE_CUSTOM with DataType == USHORT images - but this
is what you usually get when you read a 16 bit PNG file.
This would also fix [https://github.com/danfickle/openhtmltopdf/issues/173].
The patch is against 2.0.9, but should apply to 3.0.0 too.
There is still some room for improvements when writing lossless images, as the
images are currently not efficiently encoded. I.e. you could use PNG encodings
to get a better compression. (By adding a COSName.DECODE_PARMS with a
COSName.PREDICTOR == 15 and encoding the images as PNG). But this is something
for a later patch. It would also need another API, as there is a tradeoff speed
vs compression ratio.
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