Simulate infrared film

[Medium]

What Bummi described first yields very close results to what you showed us. You just made the error not to limit the green channel to 0..255, which causes this "interesting" effect (caused by byte overflow). So don't just take g*2, but min(g*2, 255), and things should look quite similar to what you want.

At least color-wise. The "grain" and "flare" options simply seem to apply some noise and blur, where it could be that the blur is weighed by brightness, which gives a slight "overshot" look.

But to be honest: That doesn't really look much like an IR image, but I didn't expect that either =)