Depends which way round you're drawing it. You could experiment and see which way fits what you had in mind.
If you're drawing a series of horizontal lines, say:

then MoveTo(0,i) and LineTo(image[i],i) could do the trick, or if vertical lines coming up from the bottom then you'll have to swap the parameters and do some subtraction (because (0,0) is at the top left, not at the bottom left according to the normal rules of graphing).