[
https://issues.apache.org/jira/browse/PDFBOX-4847?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17184675#comment-17184675
]
Emmeran Seehuber commented on PDFBOX-4847:
------------------------------------------
While preparing the patch I found a somewhat unrelated change in the
PNGConverter laying around... [^png-compress-icc-profile.patch]
This patch will ensure that an embedded sRGB color profile is also compressed.
(Without this patch the sRGB color profile is embedded uncompressed)
> [PATCH] Allow to access raw image data and fix ICC profile embedding in
> PNGConverter
> ------------------------------------------------------------------------------------
>
> Key: PDFBOX-4847
> URL: https://issues.apache.org/jira/browse/PDFBOX-4847
> Project: PDFBox
> Issue Type: New Feature
> Components: PDModel, Writing
> Affects Versions: 2.0.19
> Reporter: Emmeran Seehuber
> Priority: Minor
> Labels: feature, patch
> Fix For: 3.0.0 PDFBox, 2.0.22
>
> Attachments: 2.0-raw-raster-v2.patch, 2.0-raw-raster.patch,
> color_difference.png, pdfbox-image-compare.patch, pdfbox-rawimages.patch,
> png-compress-icc-profile.patch
>
>
> This patch was primary thought to add access to raw image data (i.e. without
> any kind of color conversion/reduction). While implementing and testing it I
> also found a bug with ICC profile embedding in the PNGConverter.
> This patch does those things:
> - add a method getRawRaster() to PDImage. This allows to read the original
> raster data in 8 or 16 bit without any kind of color interpretation. The user
> must know what he wants to do with this himself (E.g. to access the raw data
> of DeviceN images).
> - add a method getRawImage(). Tries to return the raster obtained by
> getRawRaster() as a BufferedImage. This is only successful if there is a
> matching java ColorSpace for the colorspace of the image. I.e. only for
> ICCBased images. In theory this also should work for PDIndexed sRGB images.
> But I have to find a PDF with such an image first to test it.
> - add a -noColorConversion switch to the ExtractImage utility to extract
> images in their original colorspace. For CMYK images this only works when a
> TIFF encoder (e.g. from TwelveMonkeys) is in the class path.
> - add support to export PNGs with ICC profile data in ImageIOUtil.
> - fix a bug in PNGConverter which does not correctly embed the ICC profile
> from the png file.
> - the PNGConverterTest tests the raw images; While reading PNG files to
> compare it also ensures that the embedded ICC profile is correctly respected.
> The default PNG reader at least till JDK11 does *not* respect the embedded
> ICC profile. I.e. the colors are wrong. But there is a workaround for this in
> the PNGConverterTest (which I have in production for years now). See the
> screenshot for the correct color display of the png_rgb_romm_16.png testfile
> (left side; macOS Preview app) and the wrong display (right side; Java;
> inside IDEA).
>
> Access to the raw image allows beside finding bugs like in the PNGConverter
> it also to do all kind of funny color things. E.g. a future patch could be to
> allow using the raw images to print PDFs. If the PDF you want to print has
> images with a gamut > sRGB (i.e. all modern cameras) and the target printer
> has also a gamut > sRGB (i.e. some ink photo printer) you will for sure see a
> difference in the resulting print. Such a mode would be rather slow, as the
> current sRGB image handling is optimized for speed and using the original raw
> images would need on demand color conversions in the printer driver. But you
> get „high quality“ out of it (at least in respect to colors).
> I don’t think this is in time for the 2.0.20 release.
--
This message was sent by Atlassian Jira
(v8.3.4#803005)
---------------------------------------------------------------------
To unsubscribe, e-mail: dev-unsubscr...@pdfbox.apache.org
For additional commands, e-mail: dev-h...@pdfbox.apache.org
