Let's say I'm making a 2D game and I want to implement a zoom in/out feature. Normally this is as simple as modifying the projection matrix to get more or less of the world to show. However, this results in quite blurry resizing, and I suspect the culprit is the GL_LINEAR parameter you supply to glTexParameteri as explained here.
I've done my fair share of video resizing and I know much better algorithms exist such as bicubic filtering, lanczos, spline, etc, however the only one OpenGL offers is (tri?)linear. What would be the best way of improving 2d scaling? I suppose this would involve shaders but I'm not familiar with the approach. Any reference to working code would be a nice plus.