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Posted to dev@pdfbox.apache.org by "Tim Allison (JIRA)" <ji...@apache.org> on 2018/11/27 16:16:00 UTC
[jira] [Resolved] (PDFBOX-4184) [PATCH]: Support simple lossless
compression of 16 bit RGB images
[ https://issues.apache.org/jira/browse/PDFBOX-4184?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Tim Allison resolved PDFBOX-4184.
---------------------------------
Resolution: Fixed
Assignee: Tilman Hausherr (was: Tim Allison)
Re-assigning to [~tilman] who did all of the work. :)
> [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
> Assignee: Tilman Hausherr
> Priority: Minor
> Fix For: 3.0.0 PDFBox, 2.0.12
>
> Attachments: 032163.jpg, 16bit.png, LoadGovdocs.java, fix_profile_use.patch, fix_profile_use3.patch, fix_profile_use4.patch, images.zip, lossless_predictor_based_imageencoding.patch, lossless_predictor_based_imageencoding_v2.patch, lossless_predictor_based_imageencoding_v3.patch, lossless_predictor_based_imageencoding_v4.patch, lossless_predictor_based_imageencoding_v5.patch, lossless_predictor_based_imageencoding_v6.patch, pdfbox_support_16bit_image_write.patch, png16-arrow-bad-no-smask.pdf, png16-arrow-bad.pdf, png16-arrow-good-no-mask.pdf, png16-arrow-good.pdf, size_compare.txt
>
>
> 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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