Divide resolution and stretch to screen/window/canvas

For free-supported platforms (mobile&pc), is there a way to divide the player resolution by 2, 3 or 4, and stretch rendered frame to the screen/window/canvas? This would take less pixels to process (alpha, pixel shaders…), and by the way make pixel-art games easier than scaling everything.

Note : choose a fixed resolution or ratio is not my goal at all, and I use the free version of Unity3D.

I’m sure you’ve tried “Screen.width / 2” and “Screen.hight / 2”

I use ScaleToFit the strech my images to the full size of the screen.

GUI.DrawTexture(Rect(0,0,Screen.width,Screen.hight), aTexture, ScaleMode.ScaleToFit);