Resolution problems – resampling or adding more pixels
Occasionally, you might have to deal with pictures that don't have a high enough resolution for the task you have in mind. For example, let's say you are preparing a family photo album but soon discover that some of the older photos that were scanned from the originals are too small; the images can't be enlarged past the size of a matchbox without them appearing soft and fuzzy.
Important note
Refer to Chapter 3, The Basics of Image Editing, the Understanding picture resolution section; and Chapter 9, Exporting the Finished Work, the Resolution revisited section, for more information.
Much of the free software available for producing digital book products have in-built warning symbols that appear as soon as you over-enlarge an image on a page. These warnings are there mostly to protect the company from complaints that the images being used are low-resolution. You could, of course, still complain, but...