An undesired effect from scanning a printed image which creates an overlapping herringbone, grid, or dot pattern that looks jagged, wavy, or bitmapped. This happens because a printed image has already been broken down into dots or a “screen” in order to be printed. When the printed image is scanned it creates another set of dots which don’t match the same pattern, thereby causing the strange pattern to appear.
To correct this, the scanned image must be enlarged, blurred with a filter, and then reduced to print size. This technique fuzzes and smears the edges of the dots which lessens the moire and the shrinking of the image further reduces the dot size making it appear more in focus.