Automatic kerning

#26258

Hi

To what extend does PD4ML support (automatic) kerning and if it does, what factors do affect it.

My problem, I’m using a custom font folder with an Arial Narrow font (right now I use the ttf File from OS X, but this might change) and in some rare letter combinations (especially with Te) it appears like PD4ML doesn’t do any automatic kerning.

You can see the (small) difference in these two pictures:

The second one was rendered by PD4ML.

Thanks for your help!
Cheers,
Reto

#27498

For the time being PD4ML does not support the feature.

There is a technical problem: for HTML layouting PD4ML needs to have a possibility to measure PDF string widths from Java. In regular mode it is easy to do – it is just a sum of string character widths. The character widths can be taken from TTF fonts metrics or from Acroread built-in fonts metrics (The acroread font metrics are hardcoded to PD4ML lib).

If we rely to the autokerning feature of PDF format – we cannot get anymore the exact width of a particular string, until we re-implemented kerning algorithms of Acroread, for example. We did not address the issue yet.

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