I had mentioned on the VSC project description page that I am looking at various methods for scaling my digital amiga video output from 320×200 to 640×400. My initial plan was just to do pixel doubling, or quadrupling where I would copy a pixel horizontally, so making two pixels from one, and then copying the line.
Steve from BMOW had suggested that doing this would be most faithful to the original, and I was happy about that because it is by far the most simplest of ways.
I played around yesterday a little bit with scaling some images, especially those containing diagonal lines (like text for example), using multiple methods in both GIMP2 and Photoshop. The results were pretty clear, doing no interpolation resulted in the worst image. There was some very noticeable aliasing.(stair-stepping, the jaggies) The best result seemed to be Lanczos3 in GIMP2, actually. The result was nice and sharp!
There is a method called Scale2x which looks promising. It’s relatively straight-forward, but like most of these algorithms, it needs to have the surrounding data available, like at least the line before and the line after the current one. I might be able to increase the size of my line buffer, but I have to look to see what the best way to address it is.
I could always do pixel doubling and then have a switch or something that will turn on the filter.