Scale2x, Scale3x and Scale4x are real-time graphics effects
able to increase the size of small bitmaps guessing the
missing pixels without blurring the images.
They were originally developed for the AdvanceMAME project
in the year 2001 to improve the quality of old games running
at low video resolutions.
The specification of the algorithm and more details are at:
These command line tools read a .PNG file and write another
image with the effects applied.
The fast implementation of the Scale effects is used. It imposes
some limitations of the type of the image usable. Specifically :
Only the pixel sizes of 1, 2 and 4 bytes are supported. If the
image has another pixel size it's automatically converted.