[willis936]

You can remove the guesswork. You can start with a high resolution (or even raster export of a vector image for an extreme example), downsample it (various methods and downsampling factors for completeness), then attempt to upscale it.

[OJFord]

That's exactly what GP is talking about, the 'guesswork' comes in when you upscale as a function of only the downsampled version.