I'm taking programming class and instructor loves to work with images so most of our assignments involve manipulating raw RGB image data. One of our assignments is to implement a standard image converter that converts SD images to HD images and vice versa. I always take advantage of these types of assignments to go a little beyond what we were asked to do, so I added a basic anti-aliasing process that uses the average pixel color of the 3x3 surrounding pixels to improve the converted image. While it helps a bit, the resulting image still doesn't look good, which is ok because it's not expected to for the assignment. I've learned that converting an SD to HD images has shown to be much harder than down sampling to SD from HD just because SD to HD effectively involves increasing resolution when it is not there. Obviously, it is hard to create pixels from nothing, but I'd like enhance my anti-aliasing to something that provides better results when upscaling an image. Most of the techniques I find and read on the internet are far beyond my level of image processing and programming.

Can anybody suggest any better methods or processes to create good HD content from SD content that may be within my programming skill level? I know that's a difficult thing to gauge since you don't know me, but perhaps knowing that I can write c++ code to read in raw RGB data and upscale/downscale it with simple average-anti-aliasing will give you an idea.

Thanks in advance for all your help!