Want to wait 7 seconds for an image to display? Then, go on. My only happiness, is that I learned Webworkers (thought it was a bigger deal) and Canvas (thought this would be easier...). If one day I will get the time, I'll go reading some lanczos stuff and improve this webworker (that, between, sucks).
May at least the appearing image of Nagi-sama bring you joy, if you're the unlucky guy who decides to test this out.
This is an experiment to bring the lanczos3 algorithm to JavaScript with some decent performance, using the code provided in the StackOverflow thread, with some changes to try improving performance - and they did improve, but not enough.
I was just checking if there's any performance gain from using webworkers, but it seems more like an attempt to heat my legs even faster than without the multithreading.