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https://issues.apache.org/jira/browse/PDFBOX-2681?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14317528#comment-14317528
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John Hewson edited comment on PDFBOX-2681 at 2/12/15 3:45 AM:
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{quote}
Color hue is wrong. Is this a CMYK to RGB issue?
{quote}
I know it's not expected, but it's actually the intended behaviour. The PDFs
you've attached use the DeviceCMYK color space, which is device-dependent (i.e.
it represents the physical inks available in a specific printing process and
not any sort of standard, convertible color space). If you want reproducible
color then you'll need to use one of the CIE-based color spaces which are
available in PDF, which even allow for embedding ICC profiles.
In case you're wondering, internally PDFBox uses "ISO Coated v2 300%" as its
DeviceCMYK profile while Acrobat uses "US Web Coated (SWOP) v2". Unfortunately
we're not allowed to redistribute the Adobe profile, so we can't provide
exactly the same DeviceCMYK as Acrobat.
If you do have a copy of the Adobe profile, you can use it with PDFBox by
creating your own subclass of PDDeviceCMYK which overrides getICCProfile and
then calling PDDeviceCMYK.INSTANCE = foo, where foo is an instance of your
subclass. You'll need to check the terms of the profile license first, to see
what usage is permitted.
{quote}
Opacity of gradient is wrong and much different. The jpg from Illustrator shows
much more of the photo without a gradient over it.
{quote}
Yes, though I don't think it's an opacity issue, it looks more like the
gradient's function is somehow wrong, as if its been stretched out across the
entire width of the image rather than filling only half of it. It's y-position
is also off by quite a few pixels. [~tilman] might have some thoughts on this.
was (Author: jahewson):
{quote}
Color hue is wrong. Is this a CMYK to RGB issue?
{quote}
I know it's not expected, but it's actually the intended behaviour. The PDFs
you've attached use the DeviceCMYK color space, which is device-dependent (i.e.
it represents the physical inks available in a specific printing process and
not any sort of standard, convertible color space). If you want reproducible
color then you'll need to use one of the CIE-based color spaces which are
available in PDF, which even allow for embedding ICC profiles.
In case you're wondering, internally PDFBox uses "ISO Coated v2 300%" as its
DeviceCMYK profile while Acrobat uses "US Web Coated (SWOP) v2". Unfortunately
we're not allowed to redistribute the Adobe profile, so we can't provide
exactly the same DeviceCMYK as Acrobat.
If you do have a copy of the Adobe profile, you can use it with PDFBox by
creating your own subclass of PDDeviceCMYK which overrides getICCProfile and
then calling PDDeviceCMYK.INSTANCE = foo, where foo is an instance of your
subclass. You'll need to check the terms of the profile license first, to see
what usage is permitted.
{quote}
Opacity of gradient is wrong and much different. The jpg from Illustrator shows
much more of the photo without a gradient over it.
{quote}
Yes, though I don't think it's an opacity issue, it looks more like the
gradient's function is somehow wrong, as if its been stretched out across the
entire width of the image rather than filling only half of it. It's x-position
is also off by quite a few pixels. [~tilman] might have some thoughts on this.
> Colors inaccurate rastered CMYK source w/ gradient + photo
> ----------------------------------------------------------
>
> Key: PDFBOX-2681
> URL: https://issues.apache.org/jira/browse/PDFBOX-2681
> Project: PDFBox
> Issue Type: Bug
> Components: Rendering
> Affects Versions: 2.0.0
> Environment: Tested on OS X 10.10, Java 1.6 / 1.8
> Reporter: Jon Wu
> Attachments: gradient-test-illustrator.jpg, gradient-test-pdfbox.jpg,
> gradient-test-photo-illustrator.jpg, gradient-test-photo-pdfbox.jpg,
> gradient-test-photo.pdf, gradient-test.pdf
>
>
> In the attached gradient-test-photo.pdf, there's a photo with a gradient on
> top of it. The colors in the gradient are CMYK. When rasterizing this test
> file with PDFBox 2.0.0 SNAPSHOT 20150209, the resulting image's gradient is
> different from the original and the colors of the photo under the gradient
> look significantly different vs the display in Adobe tools like Illustrator
> or other compliant PDF readers.
> Issues:
> - Color hue is wrong. Is this a CMYK to RGB issue?
> - Opacity of gradient is wrong and much different. The jpg from Illustrator
> shows much more of the photo without a gradient over it.
> Without a photo, there's still a difference, but it's much harder to see.
> Example in gradient-test.pdf where the same gradient is drawn over a grey
> rectangle.
> If I convert the PDF to RGB in Illustrator first and rasterize the RGB PDF
> with PDFBox, the result is nearly identical between Illustrator and PDFBox so
> this seems like a CMYK conversion issue in both the general color conversion
> and maybe how the gradient is calculated.
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