Abstract: Methods and systems for automatic color calibration result in a cluster of printers having more uniform color output. Each printer within the cluster prints a color target. Each color target is measured, typically by sensors located in the print path. The data is sent to a central location for processing. Color look-up tables are constructed for each color and for each printer. The color look-up tables are formulated on a baseline characteristic of the printer in the cluster having the least dynamic range. That is, for each printer in the cluster, there is an input value for each color (e.g. cyan) wherein that input value results in the same output ink density as the baseline printer. Each printer in the cluster receives a color look-up table for each color, and incorporates that table in its color data flow.

Abstract: Apparatus and method establish two or more selectable colorimetrically equivalent printmasks, and—from among those—select masks for use. An image-processing stage assigns inking spatially among pixels; each mask sets temporal assignments, among print passes, of the spatially assigned inking. Selected masks are used, for successive pixels, in a randomized sequence. The image is defined as an array of input colorimetric levels, each one selectably mapped to any one of plural colorimetrically equivalent masks. Plural colorimetrically equivalent levels are defined, and then assigned (through a randomized procedure) to particular masks. The image is prepared using a pixel grid coarser than the available printer resolution; and the plural equivalent masks formed by varying allocation of printer passes among pixels of the coarser grid.

Abstract: Printhead longevity is extended by more uniformly utilizing individual printhead printing elements. A preferred algorithm moves an active zone of printing elements uniformly down the printhead on successive print passes. If insufficient printing elements are available to print the next pass, the active zone is moved to a point near the top of the printhead determined by a modulo function.

Abstract: In an error diffusion process for an inkjet printer, a look-up table is indexed by an input color tone, with entries for base output level, base level error term, threshold error term, and whatever other data may be relevant. This table may be embodied in a conventional memory or software code. The base output level corresponds to the number of ink drops to be ejected by the inkjet print for particular ink colors, the base level error term reflects the error between the input and output of the look-up table, and the threshold error term is subtracted from the total error for the pixel if the base output level is incremented by one.

Abstract: A printing technique is disclosed which takes into account the actual ink drop volumes of the print cartridges used in an inkjet printer. In one embodiment, each of the print cartridges is tested by the manufacturer, and its actual ink drop volume is determined. This actual ink drop volume, or the variance from the nominal ink drop volume, is encoded on the print cartridge itself using any number of techniques. The host computer, which converts RGB tone values to CMYK ink tone values to be printed, reads the information regarding the ink drop volume and adjusts the CMYK tone values as necessary to compensate for the variance in the ink drop volumes. Accordingly, the printer and host computer will adjust the number of CMYK ink drops printed for a particular pixel position on the medium based upon the actual ink drop volumes for the color print cartridges used in the printer.

Abstract: Optimally determined halftoning algorithms are applied to tone values by selecting among combinations of at least two algorithms that best address the tradeoff between output quality and rendering performance. Input tone values are scrutinized and matched with the algorithm combination that processes the associated tone values in a manner that increases performance (including data compressibility) without sacrificing output quality. The selection process is computationally simple and fast. Reliability is ensured because the combinations of halftoning algorithms are tabulated as a result of analysis of test samples of the printed output.

Abstract: The invented method scales a graphics image by recognizing under what resolution the image was created, identifying the resolution of the printer that will actually print the image, calculating a convenient virtual resolution, approximating, on a pixel-by-pixel basis, using the virtual resolution, how many new pixels are required to emulate each existing pixel and then storing the new pixels in memory or printing them.