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From "ASF subversion and git services (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (PDFBOX-4184) [PATCH]: Support simple lossless compression of 16 bit RGB images
Date Sun, 27 May 2018 11:46:00 GMT

    [ https://issues.apache.org/jira/browse/PDFBOX-4184?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16491992#comment-16491992

ASF subversion and git services commented on PDFBOX-4184:

Commit 1832328 from [~tilman] in branch 'pdfbox/branches/2.0'
[ https://svn.apache.org/r1832328 ]

PDFBOX-4184: remote loading of test file 032163.jpg / http://www.crh.noaa.gov/Image/gjt/images/ImageGallery/Uncompahgre_small.jpg

> [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: 2.0.10, 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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