Mipmapping for canvas. Ideas and comments.

[Lukast dev]

>> Well, it seems that KisImage level really fits better.
>> Btw, doesn't OpenGL has it's own _hardware_ downsampling? Or even
>> mipmapping? I guess it's quite unreasonably to emulate mipmapping with cpu
>> when gpu can do it faster?
>
> Lukas is looking into that.
>

OpenGL uses some small textures (tiles) that are mapped on planes
(quads) and when
the image is scaled, you can decide what algorithm is used. See [1]
There are also mip-map versions. I used bi-linear interpolation for
zoom til 2.0 (200 %), and nearest neighbohour at higher zoom.

[1] http://linux.die.net/man/3/gltexparameterf