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Posted to dev@pdfbox.apache.org by "Tilman Hausherr (JIRA)" <ji...@apache.org> on 2018/06/23 12:25:00 UTC
[jira] [Commented] (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:comment-tabpanel&focusedCommentId=16521070#comment-16521070 ]
Tilman Hausherr commented on PDFBOX-4184:
-----------------------------------------
I'll commit the change later, after the release of 2.0.11 (yes, 2.0.11) which is planned for next week.
> [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
> Priority: Minor
> Fix For: 2.0.11, 3.0.0 PDFBox
>
> Attachments: LoadGovdocs.java, 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, 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
>
>
> 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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