US Patent 7738136 Creating traps with asymmetric widths

Methods and apparatus, including computer program apparatus, implementing techniques for preparing a region of an electronic document for printing on a printing device having asymmetric misregistration behavior. The techniques include trapping the region asymmetrically to compensate for asymmetric misregistration behavior of a printing device. The region can be an entire page or a portion of a page represented in a page description language or a raster representation. The techniques can include defining an asymmetric transformation; applying the asymmetric transformation to the region to generate a transformed region; processing the transformed region to generate transformed traps; and applying an inverse transformation to the transformed traps to generate traps for the region, the inverse transformation being an inverse of the asymmetric transformation. Defining the asymmetric transformation can be done by obtaining a first trap width magnitude and direction, the first trap width being a minimum trap width for the device; obtaining a second trap width magnitude and direction, the second trap width being a maximum trap width for the device; defining a rotational component of the asymmetric transformation by determining an angle by which a first axis of a device space has to be rotated to be aligned with the first trap width direction; and defining a scaling component of the asymmetric transformation according to a ratio of the first trap width magnitude and the second trap width magnitude.