Re: [ft-devel] [Patch] Compensate blue zone rounding after scale

[Just Fill Bugs]

On 05/13/2011 09:32 PM, Werner LEMBERG wrote:
> > In af_cjk_metrics_scale_dim(), when we scale the blue zone to the
> > font size, the blue zone is also rounded to pixel grid. The offset
> > introduced in the rounding at both the bottom and top could have
> > undesirable effect on the glyph height at certain font size. [...]
>
> Again, it would be great if you can provide images which demonstrate
> the usefulness of your change.  It seems that such a fix must be
> applied to the latin hinter also for consistency...

The result is a mix. Attached a comparison for wqy-zenhei.ttc at 11.5pt. 
I actually have to patch ftstring to make it increase font size by half 
a point to reach 11.5pt.

The lines are:
1. without height compensation.
2. with height compensation.

As can be seem, some chars does benefit from a height glyph size, like 
置,道,裡.

However, the whole line looked worse with the compensation in height. 
It's because of chars which are outside the bottom blue zone displayed a 
bigger gap toward the chars adjusted with blue zone.

The 主,些,它,生,里 are not adjusted by the blue zone because their 
bottom line were too high in the original design. With compensation, the 
distance between blue zone to the un-adjust bottom line increased by 1px.

To conclude, if we cannot catch the bottom line of ALL the glyphs into 
the blue zones, adding extra 1px to the bottom might not be a good idea 
in practice.

blue-compensate-comp.png
Description: PNG image