Could be the screen, could be the video card or it could be the cable running between the two.
If your picture is a screen capture via software or a image that is taken external from the computer and cropped?
I would say you should take make an appointment at your local apple store and let them look at it, they will be able to tell you what it is much easer because they are not diagnosing it via a web forum. they will also be able to give you a price on the repair.
There are no "technical solutions" to your "artistic problems".
Don't let technology get in the way of your creativity!