[jira] [Commented] (PDFBOX-3293) Chinese font glyphs with overlapping paths not rendered correctly

["Tilman Hausherr (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/PDFBOX-3293?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16042806#comment-16042806 ] 

Tilman Hausherr commented on PDFBOX-3293:
-----------------------------------------

Somebody at fontforge pointed me to the FAQ:
{quote}
I looked at kaiu.ttf or mingliu.ttf and the outlines looked nothing like the correct glyphs. What’s wrong?

Some truetype fonts (kaiu and mingliu are examples) do not store the correct outline. Instead they rely on using the instructions to move points around to generate the outline. The outline does not appear to be grid-fit at all, just positioned. FontForge will not process the instructions as it reads the font. In most fonts this would be the wrong thing to do, and I don’t know how I could tell when it needs to be done…
{quote}
So this means that if we would implement hinting and switch it on, we may have other problems.

At least one of our competitors (Ic*PDF) has implemented hinting, but they offer fine-tuning on when to use it and when not to use it.



> Chinese font glyphs with overlapping paths not rendered correctly
> -----------------------------------------------------------------
>
>                 Key: PDFBOX-3293
>                 URL: https://issues.apache.org/jira/browse/PDFBOX-3293
>             Project: PDFBox
>          Issue Type: Bug
>          Components: FontBox, Rendering
>    Affects Versions: 2.0.0
>            Reporter: Pei-Tang Huang
>         Attachments: fontforge.png, glyf.png, hinted.png, PDFBOX-3293_reduced.pdf, PDFBOX-3293.ttf, sample.pdf, sample_rendered.tif, unhinted.png
>
>
> Font glyphs with overlapping paths may be rendered in correctly, especially when the font size is small.
> Sadly, the Traditional Chinese edition of Windows bundled fonts 細明體&新細明體 (MingLiU & PMingLiU) and 標楷體 (DFKai-SB) all suffer from this problem.
> See attached sample.pdf and the rendered sample_rendered.tif.



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