[ft-devel] Autohinting Indic text and the default script module used by FreeType2

[Rahul Bhalerao]

Hi all,

I have been trying to device a module for Indic hinting in FT2. 
The current default script module used by FT2 is latin which is not suitable for indic text and affects the display significantly.
I found out that CJK module is much suitable for Indic text and it renders quality display even at small sizes. Thus I created another module for Indic based on CJK and following are my findings:
1. CJK algorithm is suitable for Indic shapes
2. Indic text consists of major amount of ligatures(GSUB combinations of unicode chars)
3. FT2 is unable to determine script for ligature glyphs (since they don't have unicode assigned), thus uses default latin module for hinting ligature glyphs and affects the display. 
4. Above problem can be solved by changing the default fallback script to either CJK or Indic.
5. Since CJK/Indic scripts cover vast variety of shapes, they seem more suitable to be used as default modules for unidentified scripts.

To illustrate the above findings, attached is the screenshot showing three different cases of hinted Indic text:

1. hinted indic text using latin module since default script is latin
2. hinted indic text using cjk based indic module and default script as latin
3. hinted indic text using cjk based indic module and default script as cjk/indic

I seek advices from FT2 developers on this issue of changing the default script and including Indic modules.

Thanks,
Rahul Bhalerao

LatinHinted.jpg
Description: JPEG image

IndicHintedDefaultLatin.jpg
Description: JPEG image

IndicHintedDefaultCJKI.jpg
Description: JPEG image