[cairo] The problem of seams, again

[Owen Taylor]

On Mon, 2006-01-02 at 11:58 +0100, Elia Cogodi wrote:
> Mail monster ate my Dec 30 post, so here it is again...

> I suck at ASCII art, but the idea is simple: here's a pixel
> 
>     0    .08       .25
> 1.0 +----+---------+
>     |     \########|
>     |      \#######| 
>     |       \######|              R,G,B,A, P=(.08,.55)      
>     |        \#####|
>     |         \####|
>     |          \###|
>     +-----------+--+
>     .75        .55 .50
>     
> Parametrize the edge of the pixel with a float, for example clockwise, 
> in the range of a semi-closed interval [0,1.0[. Define the P channel of a 
> pixel with an ordered couple of numbers in this range. The idea is that
> the couple of numbers defines the intersecting segment of a coloured 
> semiplan over the pixel. The ordering guarantees we know the
> orientation,
> for example defining it so that the covered part is on the left when 
> going from P1 to P2.

Remember, you also need to handle cases like a pixel evenly divided
between red and blue polygons, and then someone draws a green polygon
on top replacing the red part and leaving the blue part untouched.
Or the pixel could be divided into three color segments...

Regards,
						Owen

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