Abstract: Certain examples described herein relate to printer calibration. In some cases, adjustment data is received, indicating an adjustment to be applied to a given colorant. A Neugebauer Primary area coverage (NPac) vector defining an operating set of Neugebauer Primaries (NPs) is obtained. Configuration data is determined, dependent on the operating set of NPs. The configuration data maps colorant adjustments to relationships between NPs in the operating set, for both an increase and a decrease in the given colorant. In some cases, the configuration data and the adjustment parameters are used to identify first and second subsets of the operating set of NPs. The NPac vector is adjusted by decreasing an area coverage of an NP in the first subset and complementarily increasing an area coverage of an NP in the second subset.

Abstract: In an example a method includes deriving a print agent coverage vector specifying an area coverage for each of a plurality of elements, wherein each element is associated with a print agent, a print agent combination or an absence of print agent. Deriving the print agent coverage vector comprises, for a first element of the print agent coverage vector, applying a first weighting function which varies based on an intended area color value.

Abstract: Certain examples described herein relate to updating a lookup table for an imaging system. An initial lookup table for an imaging system is obtained, the initial lookup table mapping between a first color space and a second color space. A smoothed version of the initial lookup table is also obtained. Further obtained are color property values corresponding to nodes of the lookup tables that map from a vertex-to-vertex axis of the first color space. The color property values are derived from measurements of test areas rendered by the imaging system. For a target node of the smoothed version of the initial lookup table that maps from the vertex-to-vertex axis, a pair of nodes in the initial lookup table are selected based on the obtained color property values. A mapped value in the second color space for the target node is updated, based on an interpolation of mapped values for the pair of nodes in the initial lookup table.

Abstract: Certain examples described herein relate to printer calibration. In certain cases, measurement data is received, the measurement data indicative of an adjustment to be applied to a given colorant in a set of colorants printable by a printing system. In certain examples, a Neugebauer primary area coverage (NPac) vector comprising an area coverage of a first Neugebauer primary (NP) is obtained. Based on the received measurement data, the NPac vector is adjusted by decreasing the area coverage in the NPac vector of the first NP and increasing an area coverage in the NPac vector of a second NP. The first NP and the second NP correspond to colorant combinations that differ by a predetermined amount of the given colorant.

Abstract: From a statistical distribution of different color states in an image subdivided in pixels, pixel color states are selected by performing comparisons between predetermined values and values associated to per-pixel state probabilities. Errors (based on drifts between selected color states and per-pixel state probabilities) are diffused to per-pixel state probabilities of subsequent pixels.

Abstract: Methods for printer color calibration are disclosed. A nominal Neugebauer Primary area coverage (NPac) vector from an NPac space is then determined from a color mapping, the nominal NPac vector corresponding to a given color value in a color space. One or more colorant calibration factors each associated with a color of colorant are received; the calibration factors representing operational characteristics of the printer. One or more optimization metrics for constraining desired properties of an objective calibrated NPac vector to be generated are also received. The calibrated NPac vector is generated based on the nominal NPac vector such that: the generated calibrated NPac vector is convex; and for each given color of colorant the usage of colorant associated with the generated calibrated NPac vector is equal to the product of usage of colorant associated with the nominal NPac vector; and the calibration factor for the given color of colorant.

Abstract: Certain examples described herein relate to printer calibration. In certain cases, measurement data is received, the measurement data indicative of an adjustment to be applied to a given colorant in a set of colorants printable by a printing system. In certain examples, a Neugebauer primary area coverage (NPac) vector comprising an area coverage of a first Neugebauer primary (NP) is obtained. Based on the received measurement data, the NPac vector is adjusted by decreasing the area coverage in the NPac vector of the first NP and increasing an area coverage in the NPac vector of a second NP. The first NP and the second NP correspond to colorant combinations that differ by a predetermined amount of the given colorant.

Abstract: Methods for printer color calibration are disclosed. A nominal Neugebauer Primary area coverage (NPac) vector from an NPac space is then determined from a color mapping, the nominal NPac vector corresponding to a given color value in a color space. One or more colorant calibration factors each associated with a color of colorant are received; the calibration factors representing operational characteristics of the printer. One or more optimization metrics for constraining desired properties of an objective calibrated NPac vector to be generated are also received. The calibrated NPac vector is generated based on the nominal NPac vector such that: the generated calibrated NPac vector is convex; and for each given color of colorant the usage of colorant associated with the generated calibrated NPac vector is equal to the product of usage of colorant associated with the nominal NPac vector; and the calibration factor for the given color of colorant.

Abstract: A method of generating a set of halftone parameters. The method comprises assigning a first set of halftone parameters to a first location in a color space, the first location in the color space corresponding to a first color, and assigning a second set of halftone parameters to a second location in the color space, the second location in the color space corresponding to a second color. An interpolating between the first set of halftone parameters and the second set of halftone parameters is performed, based on the first location and the second location, to determine a third set of halftone parameters corresponding to a third location in the color space. The result of the interpolation is output data associating the third set of halftone parameters with a third color corresponding to the third location in the color space.

Abstract: A method of generating a set of halftone parameters. The method comprises assigning a first set of halftone parameters to a first location in a color space, the first location in the color space corresponding to a first color, and assigning a second set of halftone parameters to a second location in the color space, the second location in the color space corresponding to a second color. An interpolating between the first set of halftone parameters and the second set of halftone parameters is performed, based on the first location and the second location, to determine a third set of halftone parameters corresponding to a third location in the color space. The result of the interpolation is output data associating the third set of halftone parameters with a third color corresponding to the third location in the color space.

Abstract: A method of obtaining a calibration factor for color calibration of a printing system. The method includes printing, using the printing system, a plurality of Neugebauer primaries (NPs) each defined by a respective Neugebauer primary area coverage (NPac) vector. For each of the NPs, an area coverage change of the NP is determined from a measurement of a visual property for the NP and a measurement of the visual property for a corresponding reference NP corresponding to the respective NPac vector. The calibration N factor for the printing system is obtained based on the area coverage change for respective NPs of the plurality of NPs.

Abstract: From a statistical distribution of different color states in an image subdivided in pixels, pixel color states are selected by performing comparisons between predetermined values and values associated to per-pixel state probabilities. Errors (based on drifts between selected color states and per-pixel state probabilities) are diffused to per-pixel state probabilities of subsequent pixels.