Look in this chapter to find answers to questions on:
Q What’s the difference between the Canvas Size and Image Size commands?
A Canvas Size (Image>Canvas Size) adds extra canvas without altering the image itself. For example, if you added 1 inch to the Width and Height (with the Relative option checked), you’d get a half-inch border around the image. The Image Size command alters the image itself, so if you open an image that is 3x4″ at 72 ppi and change any of the dimension settings, the actual image will physically be bigger or smaller.
Q Is it possible to change the gray background around an image? Sometimes when I look at an image, I’d like the area outside ...