How to Apply Trapping in Graphic Processing Software
Trapping is a specialized prepress technique used to correct misregistration between solid CMYK color areas in printing. Even minor misalignments can create visible white gaps along color edges, which is particularly critical in professional book printing . In general, trapping should not be applied to continuous-tone images like photographs, as it may reduce detail, create color artifacts, and degrade overall image quality. Over-trapping solid colors is unnecessary and may produce visible keylines or crosshair patterns on CMYK plates, often appearing only during film output or plate making. The principle of trapping is straightforward: slightly enlarge adjacent color areas to create a very narrow overlap. This overlap compensates for minor registration errors while remaining visually undetectable in the final print. Most vector-based software, such as Adobe Illustrator and FreeHand, implements trapping using this method.