[cairo] cairo anti aliasing

[DANIELLLANO]

Tim Janik wrote:
> there is one major essential feature i currently see cairo
> lacking for that though.
> adjusting the amount of anti-aliasing:
>   currently, i can render rectangles with varying amounts of smoothness at
>   the edges, similar to the "Feather Edge" feature of the gimp "rectangle
>   select" command. this is essentially adjusting the radius of a 2D gaussian
>   curve in pixels, used to smooth the figure edges.
>   as an example, i have attached an image, containing 4 times the same
>   rectangle, rendered with feather edges of 0, 1, 2 and 3 from left to 
>   right.
> 
> to address this issues, I'd like to know:
> where in cairo or pixman is the current anti-aliasing amount encoded
> (approximately 1.5 pixels feather edge if compared to my example picture)
> and what is required to make that configurable?

It seems you don't get what antialias is. (I'm not an expert either)
The thing is that ideally you want to get, when rendering a pixel, all
the energy in there (being that the integral or mean of the color
(energy) of that pixel).

So there's nothing like amount of antialiasing, just better or worse
algorithms to calculate the pixel energy fast (because (I don't know
here) it seems that integral is not always analytic and can't be easily
calculated using todays computers)

Am I right in my explanation?
Do you know any pointers to more explained sources about what I'm
talking for better reference?

Anyway, you can't use pixels in the vector drawing units if you want the
image rendered to be scalable.