Commercial Printing Home Page Use Spreads, Chokes, and Centerlines Following are the general internal rules Publisher uses to determine the placement, color, and size of a trap. These rules apply whether the objects being trapped are on a foreground or background page, or on the same page. Spreads trap a darker background object to a lighter foreground object. For process colors, the trap color is created by using the darkest CMYK ink values from the lighter color, which is extended into the darker color by the default trap width. For adjoining spot colors, Publisher spreads the foreground color at the default trap width.
Chokes trap a dark foreground object to a lighter background.
For process colors, the trap color is created by using the darkest CMYK ink values from the lighter color, which is extended into the darker color by the default trap width. For adjoining spot colors, Publisher extends the background color at the default trap width. Centerlines trap objects that have similar luminance values. For process colors, the trap color is created by using the darkest CMYK ink values from each object, which is extended in both directions from the centerline of the object by one-half the default trap width. For adjoining spot colors, Publisher extends both the foreground and background colors from the centerline of the object by one half the default trap width.