#139 Add more higher quality scaling algorithms.

[John Smith]

Add more scaling algorithms, especially upscaling. The built-in one has a lot of aliasing.

With my video player I use software called MadVR that has a large set of real time high quality image scalers for video. I'd like to be able to use these on still images too.

Jinc is the scaler I think JPEGView would benefit the most from adding since it's lightweight and has very low aliasing. The performance difference on my system(gtx 980) 1080p->1440 appears to be about 6ms for bicubic and about 6.5ms for jinc (Including other frame render operations - So the algorithms by themselves may take any amount less than 6 and 6.5ms respectively).

The scalers I personally want to use are neural net scalers. These can take 10x as long to render but when we're still talking about less than 100ms I don't see that as a problem. Especially since JPEGView allows you to zoom around with what looks like nearestneighbor while it queues up the higher quality scaler. Unfortunately MadVR's own implementation is closed source but there are other good open source ones available such as FSRCNNX.