[
https://issues.apache.org/jira/browse/PDFBOX-4267?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16580066#comment-16580066
]
Jani Pehkonen commented on PDFBOX-4267:
---------------------------------------
When decoding an image, you must reverse the operation by solving for c. You
get: c = (c' - m) / alpha + m. The variable c' is the color stored in the PDF
file. If alpha == 0, avoid division by zero and just set the alpha of the pixel
to zero. Note that the equations assume all color components are in range
0.0-1.0. The code of PDF.js has colors in range 0-255.
> Incorrect rendering when /Matte entry
> -------------------------------------
>
> Key: PDFBOX-4267
> URL: https://issues.apache.org/jira/browse/PDFBOX-4267
> Project: PDFBox
> Issue Type: Bug
> Components: Rendering
> Affects Versions: 2.0.11, 3.0.0 PDFBox
> Reporter: Tilman Hausherr
> Priority: Major
> Attachments: bugzilla888437.pdf, gs-bugzilla688797-reduced.pdf,
> gs-bugzilla688797.pdf
>
>
> The image softmask in the attached file has a {{/Matte 0 0 0}} entry. PDFBox
> displays the PDF differently than Adobe Reader, the reflection shown by
> PDFBox is barely visible. When the /Matte entry is deleted, then it is barely
> visible in Adobe Reader too. So the /Matte entry does make some difference,
> although I don't understand how.
> In the PDF specification, the formula shown is c' = m + α x (c - m). So 0
> should have no effect?!
> I looked at the code of PDF.js, they have a special handling when alpha is 0,
> don't know why.
--
This message was sent by Atlassian JIRA
(v7.6.3#76005)
---------------------------------------------------------------------
To unsubscribe, e-mail: dev-unsubscr...@pdfbox.apache.org
For additional commands, e-mail: dev-h...@pdfbox.apache.org
