Re: Text anti-aliasing on the Mac

On Tue, Oct 2, 2012 at 6:38 PM, John Hudson <> wrote:
> On 02/10/12 4:49 PM, Andrew Fedoniouk wrote:
>> But I agree that in some cases some configuration is needed.
>> For example I was forced to introduce property
>>    font-rendering-mode: snap-pixel | sub-pixel;
>> for my engine running Direct2D backend on Windows.
>> font-rendering-mode:snap-pixel; is what Windows GDI uses for rendering
>> fonts in desktop UI - glyphs snap to pixel grid. That is good for e.g.
>> input elements especially edit elements.
>> and text having relatively small font-sizes (but not always).
>> font-rendering-mode: sub-pixel; is when glyph allowed to start
>> anywhere inside single pixel.
> Your terminology may be confusing for some people. It sounds like you are
> describing what Microsoft's rendering folk call full- vs sub-pixel
> *positioning*. Sub-pixel positioning is a particular kind of (usually*)
> sub-pixel rendering in which, as you say, glyphs outlines may begin anywhere
> inside the pixel (this is DirectWrite's default rendering). GDI ClearType
> does sub-pixel rendering but positioned on a full pixel grid, so your term
> 'font-rendering-mode: sub-pixel' sounds ambiguous even though you seem to
> mean specifically sub-pixel positioning.

Thanks for the clarification.
Yes, I know that these names are technically not that perfect.
But they are short  :)

> * This all got more complicated in the Windows 8 Metro environment, in which
> greyscale 8x4 asymmetric antialiasing is applied with sub-pixel positioning.
> And if that's a surprise to you imagine how I felt when told of this change
> two weeks before code lockdown on the new UI fonts we were delivering. :0

I can imagine. If window manager supports device rotation then I think some
isotropic AA algorithm is needed so no surprise.

Andrew Fedoniouk.

Received on Wednesday, 3 October 2012 03:10:48 UTC