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From "Tilman Hausherr (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (PDFBOX-4468) Incorrect tiling pattern rendering when step smaller than bbox
Date Tue, 19 Feb 2019 19:32:00 GMT

    [ https://issues.apache.org/jira/browse/PDFBOX-4468?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16772265#comment-16772265
] 

Tilman Hausherr commented on PDFBOX-4468:
-----------------------------------------

Insert this code in TilingPaint.java just before the {{graphics.dispose()}} call:
{code:java}
        float xStep = Math.abs(pattern.getXStep());
        float pos = xStep;
        AffineTransform savedTransform = graphics.getTransform();
        while (pos < pattern.getBBox().getWidth())
        {
            graphics.translate(-xStep, 0);
            drawer.drawTilingPattern(graphics, pattern, colorSpace, color, newPatternMatrix);
            pos += xStep;
        }
        graphics.setTransform(savedTransform);
        float yStep = Math.abs(pattern.getYStep());
        pos = yStep;
        while (pos < pattern.getBBox().getHeight())
        {
            graphics.translate(0, -yStep);
            drawer.drawTilingPattern(graphics, pattern, colorSpace, color, newPatternMatrix);
            pos += yStep;
        }{code}
Sadly this brings a regression on PDFJS-9770-slow.pdf so I won't commit for now. Only 2 of
1082 test files show a difference in rendering. The code may have a flaw with negative steps,
or with bounding boxes that have negative edges.

> Incorrect tiling pattern rendering when step smaller than bbox
> --------------------------------------------------------------
>
>                 Key: PDFBOX-4468
>                 URL: https://issues.apache.org/jira/browse/PDFBOX-4468
>             Project: PDFBox
>          Issue Type: Bug
>          Components: Rendering
>    Affects Versions: 2.0.13
>            Reporter: Tilman Hausherr
>            Priority: Major
>              Labels: Pattern
>         Attachments: PDFJS-9770-slow.pdf, gs-bugzilla690487.pdf, gs-bugzilla690487.pdf-1-NEW-GOOD.png,
gs-bugzilla690487.pdf-1.png, patterns-Xstep-7.pdf, patterns-Xstep10.pdf, patterns-Xstep5.pdf,
patterns-Xstep7.pdf
>
>
> From a remark by Rob Wu in a PDF.js project PR, I noticed that we're not doing tiling
patterns correctly when the XStep or YStep is smaller than bounding box width / height. We're
doing exactly what he told not to do.
> {quote}Base pattern:
>  \/
> Expected rendering of repeated pattern (recall xstep = half of width):
>  \XXXX
> Actual rendering if truncating pattern width to xstep:
>  \\\\\
> {quote}
>  



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