Re: [ft-devel] new CFF engine

[Vernon Adams]

:) ah thanks. it was under my nose all the time.
very interesting. 


On 12 May 2013, at 07:34, octoploid <address@hidden> wrote:

> 
> 
> 12.05.2013, 15:52, "Vernon Adams" <address@hidden>:
>> I have been testing the new adobe-Freetype CFF engine, and was wondering if 
>> the default 'darkness' of stem darkening is a little too high?
>> How does the width of stems in a font effect the amount of darkness 
>> rendered? I think someone mentioned that thinner stems will render with 
>> relatively more darkness than thicker stems? Is that correct? Or is the 
>> amount of darkness a uniform value across all rendered fonts?
> 
> You should read src/cff/cf2font.c:
> 95       /*
> 96        * Total darkening amount is computed in 1000 unit character space
> 97        * using the modified 5 part curve as Avalon rasterizer.
> 98        * The darkening amount is smaller for thicker stems.
> 99        * It becomes zero when the stem is thicker than 2.333 pixels.
> 100        *
> 101        * In Avalon rasterizer,
> 102        *
> 103        *   darkenAmount = 0.5 pixels   if scaledStem <= 0.5 pixels,
> 104        *   darkenAmount = 0.333 pixels if 1 <= scaledStem <= 1.667 pixels,
> 105        *   darkenAmount = 0 pixel      if scaledStem >= 2.333 pixels,
> 106        *
> 107        * and piecewise linear in-between.
> 108        *
> 109        */
> 110       if ( scaledStem < cf2_intToFixed( 500 ) )
> 111         *darkenAmount = FT_DivFix( cf2_intToFixed( 400 ), ppem );
> 112
> 113       else if ( scaledStem < cf2_intToFixed( 1000 ) )
> 114         *darkenAmount = FT_DivFix( cf2_intToFixed( 525 ), ppem ) -
> 115                           FT_MulFix( stemWidthPer1000,
> 116                                      cf2_floatToFixed( .25 ) );
> 117
> 118       else if ( scaledStem < cf2_intToFixed( 1667 ) )
> 119         *darkenAmount = FT_DivFix( cf2_intToFixed( 275 ), ppem );
> 120
> 121       else if ( scaledStem < cf2_intToFixed( 2333 ) )
> 122         *darkenAmount = FT_DivFix( cf2_intToFixed( 963 ), ppem ) -
> 123                           FT_MulFix( stemWidthPer1000,
> 124                                      cf2_floatToFixed( .413 ) );