Interpolate upscaled imageries

[BathoryPeter]

Currently JOSM doesn't use pixel interpolation for upscaled imagery tiles. Satellit imageries usually has lower resolution than what would be required for the scale used for mapping, so we often work from upscaled images. It means, most of the time we see pixelated background.

I recommend using pixel interpolation if the tiles are displayed in a larger size than the original. A simple linear interpolation would be enough I think.