If it's too slow, why not use the original MMX-optimized code: http://www.hiend3d.com/bin/hq2x_src_asm.zip

... it needs to be fast, so I optimized it "a bit". The plain C code is done so far... ...Currently I am working on an MMX version... Why reinvent the wheel? Go to http://www.hiend3d.com/hq2x.html page, and scroll all the way down. You'll see the link to "Optimized Source code (100% asm)". It's …