The amazing #waifu2x algorithm http://waifu2x.udp.jp/ can largely reduce pixel artifacts due to discretisation. It can also reduce the typical JPEG compression artifacts when the strong compression uses only the low coefficients with poor discretisation of the discrete cosine transform. What's more, this algorithm is #opensource and can be obtained via #github .
The quality improvement really amazes me. In the accompanying example I started with a very low quality image (left) on purpose, on the right is the waifu2x result.
What this means to me in practice is that I will have much less work manually cleaning up poor quality example images for my presentations.