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https://issues.apache.org/jira/browse/PDFBOX-4184?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16620827#comment-16620827
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Tilman Hausherr edited comment on PDFBOX-4184 at 9/19/18 4:39 PM:
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The cmyk test fails, there are many 1-differences like this if I modify the
test so that it reports differences without failing:
expected: <FF070606> but was: <FF070505>;
expected: <FF070607> but was: <FF070507>;
expected: <FF808181> but was: <FF808081>;
expected: <FF070606> but was: <FF070505>;
expected: <FF808181> but was: <FF808081>;
This is not much but I wonder why it works for you. What OS and what Java are
you using? I tested this on W10 with jdk8 latest.
was (Author: tilman):
The cmyk test fails, there are many 1-differences like this:
expected: <FF070606> but was: <FF070505>;
expected: <FF070607> but was: <FF070507>;
expected: <FF808181> but was: <FF808081>;
expected: <FF070606> but was: <FF070505>;
expected: <FF808181> but was: <FF808081>;
This is not much but I wonder why it works for you. What OS and what Java are
you using? I tested this on W10 with jdk8 latest.
> [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: 2.0.12, 3.0.0 PDFBox
>
> Attachments: 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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