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

[vernon adams]

Sorry, i'm allways wary of posting images to a list.

This should illustrate my observation;

(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 :)

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