Abstract: A halftone method and apparatus provides a line screen frequency of N/2 for a printer resolution of N without negative print effects. A 300 lines per inch halftone screen for a 600 dpi printer may thus be created by alternating white and saturated colored lines when half of a given color component's pels are on. Empirical rules are used to create the screens based on how that printer creates consistent and reliable levels for each color component. These rules allow intermediate intensity values between white and full-on at each pel. Since the halftoning is done in the hardware just before printing, the print direction relative to the threshold matrix is known. No rotation capability is needed in the hardware. If an image needs to be rotated, it can be done previously to being sent to the hardware. Furthermore, because a pair of pels are turned on for the lightest values (or possibly with a one level difference between the first and second dots in the pair), the electronics are stressed less.

Abstract: An image processing method and apparatus for enhancing the quality of a printed image without degrading overall printer performance or throughput by simulating 2 bit pel printing on a bi-level printer using intelligent double dotting. The present invention allows a bi-level printer to print an 2N dpi 1 bit-per-pel image through intelligent double dotting, thus enhancing the half resolution rendered image to approach the print quality as if the image were rendered at full resolution. In one embodiment, an enhanced resolution mode which uses a bi-level printer's 1200 dpi mode to print 600 dpi, 2 bit-per-pel images, results in an image having higher resolution quality than rendering the image using traditional halftone methods at either 600 dpi or 1200 dpi. Image enhancement through higher order resolution multiplication is also disclosed.

Abstract: A digital halftoning technique for controlling a spot function is disclosed. A method for generating a spot for use in halftoning according to the present invention includes defining a spot function that combines two functions selected to provide a predetermined spot shape for use in a halftone cell and scaling the spot function using a scaling function that varies according to a value of a first and second spot function ordinate. Asymmetric modulation of spot functions is used to control the touching of adjacent spots, and to change the shape of the spots with the gray region.

Abstract: An image processing method and apparatus for enhancing the quality of a printed image without degrading overall printer performance or throughput by simulating 2 bit pel printing on a bi-level printer using intelligent double dotting. The present invention allows a bi-level printer to print an 2N dpi 1 bit-per-pel image through intelligent double dotting, thus enhancing the half resolution rendered image to approach the print quality as if the image were rendered at full resolution. In one embodiment, an enhanced resolution mode which uses a bi-level printer's 1200 dpi mode to print 600 dpi, 2 bit-per-pel images, results in an image having higher resolution quality than rendering the image using traditional halftone methods at either 600 dpi or 1200 dpi. Image enhancement through higher order resolution multiplication is also disclosed.

Abstract: A digital halftoning technique for controlling a spot function to address gear noise, printer stress, and general print quality is disclosed. A method for generating a spot for use in halftoning according to the present invention includes defining a spot function that combines two functions selected to provide a predetermined spot shape for use in a halftone cell and scaling the spot function using a scaling function that varies according to a value of a first and second spot function ordinate. Asymmetric modulation of spot functions is used to control the touching of adjacent spots, and to change the shape of the spots with the gray region. The resulting non-separable shape-changing spot function can reduce printer stress and improve print quality.