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https://issues.apache.org/jira/browse/PDFBOX-5370?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17484214#comment-17484214
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Andreas Lehmkühler edited comment on PDFBOX-5370 at 1/29/22, 6:53 PM:
----------------------------------------------------------------------
Looks like your implementation uses the opposite order of the adobe
implementation, the lightest colour is on the right (yours) vs. left (adobe)
side.
I'm not sure if I understood the spec correct, but maybe inverting the colour
values is the way to go:
{quote}
For DeviceN colour spaces that do not have a subtype of NChannel, 0.0 shall
represent the minimum
amount of colorant; 1.0 shall represent the maximum. Tints shall always be
treated as subtractive colours,
even if the device produces output for the designated component by an additive
method. Thus, a tint value
of 0.0 shall denote the lightest colour that can be achieved with the given
colorant, and 1.0 the darkest.
{quote}
was (Author: lehmi):
Looks like your implementation uses the opposite order of the adobe
implementation, the lightest colour is on the right (your) vs. left (adobe)
side.
I'm not sure if I understood the spec correct, but maybe inverting the colur
values is the way to go:
{quote}
For DeviceN colour spaces that do not have a subtype of NChannel, 0.0 shall
represent the minimum
amount of colorant; 1.0 shall represent the maximum. Tints shall always be
treated as subtractive colours,
even if the device produces output for the designated component by an additive
method. Thus, a tint value
of 0.0 shall denote the lightest colour that can be achieved with the given
colorant, and 1.0 the darkest.
{quote}
> DeviceN/NChannel Seperation fails for rgb
> -----------------------------------------
>
> Key: PDFBOX-5370
> URL: https://issues.apache.org/jira/browse/PDFBOX-5370
> Project: PDFBox
> Issue Type: Bug
> Components: Rendering
> Affects Versions: 2.0.25, 2.0.26, 3.0.0 PDFBox
> Reporter: Maruan Sahyoun
> Priority: Major
> Attachments: NChannel-Pantone-1.BMP, NChannel-Pantone-1.PNG,
> NChannel-Pantone.bmp, NChannel-Pantone.pdf, NChannel-cmyk-1.BMP,
> NChannel-cmyk-1.PNG, NChannel-cmyk.bmp, NChannel-cmyk.pdf,
> NChannel-rgb-1.BMP, NChannel-rgb-1.PNG, NChannel-rgb.bmp, NChannel-rgb.pdf,
> image-2022-01-29-10-51-18-421.png, image-2022-01-29-10-51-44-286.png
>
>
> The files NChannel-xx.pdf use different color modes for separation which is
> described in chapter 10.8.3 of the PDF spec. The matching .bmp files show
> the expected results. The -1.BMP and -1.PNG files show the results generated
> by PDFBox trunk (2.0 is the same result).
> As can be seen the results for cmyk and Pantone are fine/close with the rgb
> rendering failing.
> The PDFs and expected results have been provided by Hans Bärfuss, PDF Tools
> AG. Thank you for contributing the samples.
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