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https://issues.apache.org/jira/browse/PDFBOX-5370?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17484221#comment-17484221
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Tilman Hausherr edited comment on PDFBOX-5370 at 1/29/22, 7:22 PM:
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"my" implementation used the tinttransform function. I assume that Dr. Bärfuss
did a "poor" tint transform on purpose to expose applications that don't
implement NChannels đ
I did play around a bit today, and remembered separation colors, 0 = white, 1 =
"that color". So for red, 0 would be 1 1 1 (white) and 1 would be 1 0 0 (red).
Medium red would be 1 0.5 0.5. The problem is how to combine two colors.
Combining full red and blue, 1 0 0 and 0 0 1 would bring 0 0 0 (black) if
multiplying. Adding would work here, but not for other combinations, e.g. 1 0.5
0.5 with 0.5 0.5 1.
was (Author: tilman):
"my" implementation used the tinttransform function. I assume that Dr. Bärfuss
did it is wrong on purpose to expose applications that don't implement
NChannels.
I did play around a bit today, and remembered separation colors, 0 = white, 1 =
"that color". So for red, 0 would be 1 1 1 (white) and 1 would be 1 0 0 (red).
Medium red would be 1 0.5 0.5. The problem is how to combine two colors.
Combining full red and blue, 1 0 0 and 0 0 1 would bring 0 0 0 (black) if
multiplying. Adding would work here, but not for other combinations, e.g. 1 0.5
0.5 with 0.5 0.5 1.
> 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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