Method and apparatus for underprinting pixels

摘要

Methods and apparatus for trapping to prevent a polychromatic printing artifact are described. One method includes the step of selecting a region of a source image comprising a plurality of concentric rings of pixels centered about a selected pixel. Each pixel has a plurality of toner values. Each of the toner values considered for trapping is associated with a non-black color plane. A trapped value is generated for each color plane of the selected pixel. The trapped value for a selected color plane corresponds to the maximum toner value for that color plane within the smallest ring having at least one non-black pixel. A trapped flag for each color plane of the selected pixel is generated. The trapped flag for a selected color plane is enabled only if the selected pixel is black and at least one ring not comprising the selected pixel includes a pixel having a nonzero toner value for the selected color plane. The trapped value is substituted for the corresponding toner value of a given color plane of the selected pixel, if the trapped flag for the given color plane is enabled.