Color vector halftoning using a successive filling with improved color registration latitude

In a color printing system, a method of printing a color document with a halftone process using a single screen for a plurality of color separations wherein the screen is comprised of a plurality of pixel locations associated with successive threshold values, the method comprising steps of:

• printing a first one of the plurality of color separations in accordance with the screen, wherein a corresponding first set of screen pixel locations associated with a first set of threshold values are filled by the first one of the color separations;
• and,
• printing a next color separation in accordance with the screen, wherein a corresponding second set of screen pixel locations are filled by the next separation, the second set having threshold values successive to the first set of threshold values, and before the printing of the next color separation fills the screen, overlapping the printing of the next color separation with the first one of the separations at a portion of the first set of screen pixel locations.

A rendering apparatus for a color image represented in a halftone process by a plurality of separations, comprising:

• a halftoning screen generator for producing a screen having threshold values at pixel locations, wherein the values can be applied to contone image signals to derive a binary image signal suitable to drive the apparatus;
• and,
• a processor for rendering the color separations in accordance with the screen, wherein for constant image separation values, pixel locations are turned on for a selected separation at the pixel locations disposed in a highest available luminance region having a lowest available threshold value for a predetermined number of available threshold values less than a complete filling of the screen, and thereafter an overlap filling occurs for a portion of the turned on pixel locations.

A method of rendering a color image with a plurality of separations on an output device, with a halftone process using a single screen for said plurality of separations, wherein the screen is comprised of a plurality of pixel locations with associated threshold values and the image is comprised of a plurality of separation values, the method comprising steps of:

• rendering the colors successively in a predetermined order until the sum of the colors reaches a threshold value, and
• when the sum of the colors exceeds the threshold value, overlapping at least two of the separations.