Re: [matplotlib-devel] Cairo Backend and Subpixel Rendering

Hi all,

On 11 May 2009, at 12:43, Michael Droettboom wrote:
> I'm with Eric on this -- let's try to do the right thing without
> requiring any user intervention.  I actually can't think of a use case
> that would require a subpixel argument on text... am I missing  
> something?

Cairo has an image backend, which is usually used for both on-screen  
rendering and which also supports saving to a file. When displaying on- 
screen the default is most probably fine -- Cairo gets its subpixel  
rendering settings from the OS (fontconfig on Linux) so all is well.

However, when saving to a file, depending on its intended use one may  
either want to enable/disable subpixel antialiasing/rendering. If it  
is intended for print you probably want to disable it, however, for  
web graphics subpixel rendering is extremely common.

Furthermore Cairo also has provisions for subpixel antialiasing for  
line art. (So the same techniques which are applied to text are also  
applied to polygons, curves &c.) While none of the backends currently  
make use of it, it is quite likely that in the future the image  
backend will support it. Therefore a general subpixel antialiasing  
setting might be a better bet.

I would therefore suggest having two options: one for when printing  
and another for displaying on screen. The default for printing/saving  
should probably be off, while the displaying should be got from the  
system.

Regards, Freddie.