Image processing method to reduce marking material coverage in printing processes

A method for processing a color document image for printing, to reduce an amount of marking material used to reproduce image edge regions therein on a receiving medium, the color document image comprised of multiple separations each defined by an input image including image signals arranged in an array of scan lines, including the steps of:

• receiving electronic binary signals forming a multiple separation of the input image, in which the binary signals are suitable for driving an ink jet printer to deposit a separation colors of ink on a receiving medium, wherein a number of binary signals having a first binary state cause the ink jet printer to deposit the separation color of ink on the receiving medium and signals having a second binary state cause the ink jet printer not to deposit the separation color of ink on the receiving medium;
• processing the binary signals to form a multibit signal therefrom approximating a continuous tone image;
• processing the multibit signal to detect edges, and generating an edge detection signal indicating locations of image edges in the input image;
• processing the binary signals from the multiple separations to determine, within an image whether coverage reduction at a detected edge is required, and producing a separation correlation signal therefrom;
• logically combining the edge detection signals and the separation correlation signals, to produce a corrected edge detection signals, indicating those edges at which coverage reduction will occur;
• at locations indicated as edges in corrected edge detection signal, processing the binary signals forming the input image to reduce the number of first binary signals in the input image in regions therein adjacent to edges corresponding to the edge detection signal.

An image processing device for processing a color document image for printing with an ink jet printer, to reduce an amount of marking material used to reproduce image edge regions therein on a receiving medium, the color document image comprised of multiple separations each defined by an input image including image signals arranged in an array of scan lines, including:

• a signal input, receiving electronic binary signals forming a multiple separation of the input image, in which the binary signals are suitable for driving an ink jet printer to deposit a separation color of ink on a receiving medium, wherein a number of binary signals having a first binary state cause the ink jet printer to deposit the separation color of ink on the receiving medium and signals having a second binary state cause the ink jet printer not to deposit the separation color of ink on the receiving medium;
• a first filter, processing the received binary signals to form a multibit signal therefrom approximating a continuous tone image;
• an edge detecting circuit processing the multibit signal to detect edges, and generating an edge detection signal indicating locations of image edges in the input image;
• a separation correlation circuit processing received binary signals from the multiple separations to determine, within an image whether coverage reduction at a detected edge is required, and producing a separation correlation signal therefrom;
• a combining circuit, receiving as inputs the edge detection signal and the separation correlation circuit and combining said inputs to generate a corrected edge detection signal, indicating those edges at which coverage reduction will occur;
• an average measurement circuit, measuring coverage within a given area of the color document image and producing a value representative thereof;
• a tone reproduction curve processor, providing a lookup table in memory, and receiving as an input the binary signal value and the measured coverage value, and producing as an output a tone reproduction curve corrected signal;
• a masking arrangement, having as inputs the tone reproduction curve corrected signal and the corrected edge detection signal, and operable to mask the tone reproduction curve corrected signal with the correction edge detection signal to produce coverage reduced binary signals responsive thereto;
• a processed image output, directing the coverage reduced binary signals to an ink jet printer.