Hi Piotr, On Thu, Sep 9, 2021 at 2:34 PM piotrunio-2...@wp.pl <piotrunio-2...@wp.pl> wrote:
> In > https://www.freetype.org/freetype2/docs/reference/ft2-gasp_table.html#ft_gasp_xxx > , > For better (but still insufficient) explanations, https://docs.microsoft.com/en-us/typography/opentype/spec/gasp but, to be honest, I do not know what symmetric smoothing even means. FT_GASP_SYMMETRIC_SMOOTHING > > If set, smoothing along multiple axes must be used with ClearType. > This is entirely incorrect. > > From the observed behaviour of Microsoft ClearType renderers, the > behaviour is as following: > > If set, 6×5 or 6×1 oversampling may be used. If unset, 6×1 oversampling is > always used. > They do say that the flag is used in combination with FT_GASP_SYMMETRIC_GRIDFIT and might interact. Perhaps you're onto something and smoothing really means LCD filtering, which is not necessary if GRIDFITing. Unfortunately, OpenType specifications do not explain it. > > This in turn roughly translates to FreeType language to the following: > > If set, smoothing along multiple axes may or may not be used with > ClearType. > If unset, smoothing along multiple axes should not be used with ClearType. > > The sentence "If set, smoothing along multiple axes must be used with > ClearType." is therefore incorrect and should be changed. > We do not use or apply gasp directly but we might have that functionality at user's discretion. We need more clarity on what they actually mean by CleatType smoothing. Alexei
