Here you can donwload Scale2x containing an example program about to apply the effect on .png image and a very fast SSE2 implementation.

FileDescription
scale2x-4.0.tar.gz The sources for GNU/Linux, Windows and any other operating system.
scale2x-4.0-windows-x86.zip Windows binary.

Other implementations can be found in the contrib/ directory of the .tar.gz archive.

Instead, you are free to use the algorithm, but please call the effect "Scale2x".

Scale4x
scale4x
Scale2x
scale2x
Original
original