Re: [ft-devel] ttfautohint: How to install

[vernon adams]

Should also show that applying 'double links' rather than 'single links' to the 
y-axis-stems of the 'O' is a better solution, but exactly same principle of 
snapping to bottom pixel at alignment zone.

(above) original ttfautohint 'O'

(above) single links at y-axis stems)

(above) double links at y-axis stems






On 30 Jun 2011, at 08:09, vernon adams wrote:

> Sorry, i'm allways wary of posting images to a list.
> 
> This should illustrate my observation;
> 
> <PastedGraphic-2.tiff>
> 
> (above) Upper case 'O', ttfautohint version, opened in Fontlab 'Truetype 
> hinting' mode, showing alignment zones & pixels arranged by ttfautohints 
> instructions. 27 ppem. Note the egging at top curve, as snapping is to pixel 
> at TOP of alignment zone.
> 
> (below) Same font & glyph but with a single link applied from at top edge 
> (and one at baseline). note the top stem now snaps to pixel at bottom of 
> alignment zone. All is now well with the glyph imo :)
> 
> <PastedGraphic-3.tiff>
> 
> 
> hope that helps
> ps - this also reduces the 'vertical stretching' at certain ppems too!
> 
> -vern
> 
> 
> 
> 
> On 30 Jun 2011, at 07:32, Werner LEMBERG wrote:
> 
>> 
>>>> If you limit hinting-range-max to a value where the blue zones are
>>>> still handled, the generated bytecode uses this hinting set for all
>>>> larger sizes also.  Finding a good value for hinting-range-max has
>>>> to be done with trial and error, but a waterfall already indicates
>>>> bad sizes, so hinting-range-max must be less than that).
>>> 
>>> hmm i have tested varying min-range & max-range - by shifting ranges
>>> i can get the 'egging issue' to move up/down a ppem size, so the
>>> issue persists but just at different ppem's.
>> 
>> OK.
>> 
>>> It seems to me that the egging issue is caused by the top curves of
>>> the 'o' snapping to the top edge of the pixel that corresponds to
>>> that alignment zone, if i force these curves to snap to the bottom
>>> edge of the alignment zone pixel then the egging is fixed!  Of
>>> course then i need all pixels in the alignment zone to snap to the
>>> bottom of the pixel to get uniform x-height throughout all glyphs.
>>> 
>>> Could there be a way to force pixel snapping to the bottom of pixel
>>> in some alignment zones like this with ttfautohint?
>> 
>> While I basically understand what you write, I have some difficulties
>> to imagine it visually.  Could you provide FontLab snapshots of an
>> `egged o', together with your proposed fix?
>> 
>> 
>>   Werner
>