Manga model ran through 1080 (CUDA). Really low res pictures (VGA - like DOS SCUMM games) takes less then 1 second, it`s almost instant - that`s way I was thinking of implementing this in ScummVM "on the fly". This ones took a little longer (2~3 seconds). Card is going at full blast when processing.
I've been trying some other images in CPU mode (I have a cuda card but wanted to try a the non cuda process) and it can take forever (literally minutes) on a 3.7 Ghz i7... depending on the image of course.