Images and overlays need to be resized when the source rectangle is a different size to the destination rectangle. This resizing can be accomplished by several means.
Arbitary stretching and/or shrinking means that resizing by any amount is possible.
Arithmetic stretching along the Y axis is available, but arithmetic stretching along the X axis or arithmetic shrinking is not unless the driver performs them as a default.
Binary shrinking is dividing the data by a binary value such as 2, 8, 32, etc.
Integer stretching and/or shrinking means the size must reduce or increase by an integer multiple.
Stretching or shrinking using pixel doubling is the most basic of the stretching techniques, involving the simple addition or sampling of pixels to accomplish the action.