Re: [ft-devel] gamma correction and FreeType

[Dave Arnold]

Hi Antti,

On 11/7/2013 12:43 PM, Antti Lankila wrote:
> Yes, I personally believe that ”optimal translation and scaling”, despite being an irritating parameter space search, would likely be the limit of the technique. More complicated strategies such as splitting the glyph box and stretching/shrinking the top/bottom halves slightly differently would still improve the alignment to pixel grid, but as previously noted, I have my dislike for solutions that imply distorting the outline. 
The CFF hinting engine splits the glyph box into a number of horizontal bands. Each split occurs at 
a declared hstem hint. You can think of the mapping along the y-axis from the original font 
"character space" to the "device space" as a piecewise linear function, where 
each piece is either a stem or the space between two stems. So, it is really an extension of your 
idea above, of splitting the glyph box.

> I guess this means that a single glyph can have both darkened and undarkened stems. 
No. I'm sorry I was not clear about this. The darkening amount is the same for all parts 
of the glyph and indeed for all glyphs. It is computed from the font dictionary entry for 
"standard stem width". (Actually, there are two values: one for horizontal 
stems and one for vertical stems.) It is not computed from actual stems.

Thanks.

-Dave