Allow nearest neighbor algorithm for scaling

- [x] Feature request.

## Feature request ##

Currently the scaling metdata is not usable for pixel art, since smoothing is enabled by default. Instead you'd want to use the "Nearest neighbor" algorithm to prevent the art from becoming blurry.

My suggestion would be a global option to choose the scaling method (I doubt pixelart would be combined with regular art).

## Workaround:

In the meanwhile for people bumping into this issue, you can use the following script to scale your images. (Requires imagemagick)

```bash
#!/bin/bash

for i in $(find -follow -iname "*.png"); do
convert $i -interpolate Nearest -filter point -resize 3000% $i
done
```