Abstract: A computing device receives first data indicating a first metric of a first printed test area and second data indicating a second metric of a second printed test area. The first printed test area is associated with a first plurality of Neugebauer Primaries and each Neugebauer Primary in the first plurality of Neugebauer Primaries is associated with a respective area coverage in the first printed test area. The second printed test area is associated with a second plurality of Neugebauer Primaries, wherein each Neugebauer Primary in the second plurality of Neugebauer Primaries is associated with a respective area coverage in the second printed test area and the second plurality of Neugebauer Primaries is different from the first plurality of Neugebauer Primaries. The computing device generates third data associating a color in a color space with the first plurality of Neugebauer Primaries or the second plurality of Neugebauer Primaries in dependence on the first metric and the second metric.

Abstract: In an example, a method includes acquiring data representing an article to be printed, the data comprising an element set associated with a print addressable location, the element set comprising a first element subset and a second element subset, wherein the first element subset and the second element subset comprise an element identifying a print material selection which is associated en with a probability that the print material selection is to be applied to the associated print addressable location. The method further includes determining a first set of cumulative probability values associated with the elements of the first element subset and determining a second set of cumulative probability values associated with the elements of the second element subset. The first set of cumulative probability values may span a first predetermined value range and the second set of cumulative probability values may span a second predetermined value range.

Abstract: Apparatus and methods for transforming three dimensional object data are disclosed. In some examples, data representing a three dimensional object is received, the data comprising object property data indicative of at least one attribute of at least a portion of the three dimensional object. The object property data is transformed into a plurality of device independent object property data objects having a common data structure, each object property data object comprising a value indicative of each of a predetermined set of object properties.

Abstract: A computing device receives first data indicating a first metric of a first printed test area and second data indicating a second metric of a second printed test area. The first printed test area is associated with a first plurality of Neugebauer Primaries and each Neugebauer Primary in the first plurality of Neugebauer Primaries is associated with a respective area coverage in the first printed test area. The second printed test area is associated with a second plurality of Neugebauer Primaries, wherein each Neugebauer Primary in the second plurality of Neugebauer Primaries is associated with a respective area coverage in the second printed test area and the second plurality of Neugebauer Primaries is different from the first plurality of Neugebauer Primaries. The computing device generates third data associating a color in a color space with the first plurality of Neugebauer Primaries or the second plurality of Neugebauer Primaries in dependence on the first metric and the second metric.

Abstract: Example methods and systems are described in which a color space vector is transformed into a Neugebauer primary area coverage (NPac) vector, to be used for printing. In some examples, the color space vector is transformed into a NPac vector on the basis of criteria associated to amounts or probabilities of Neugebauer primaries (NPs).

Abstract: There are disclosed techniques for error diffusion for printing. For example, there is disclosed a device comprising a pixel selector, to select a pixel from an image to be printed, wherein the pixel is associated to a group of device state probabilities, wherein each device state probability describes a probability of choosing a particular device state, wherein each device state describes the quantity of each colorant to be used in correspondence of the pixel. The device may comprise a device state determiner, to choose the device state for the selected pixel on the basis of the device state probabilities associated to the selected pixel. The device may comprise a feedback chain, to diffuse device state probability errors to pixels to be subsequently selected. The feedback chain may include a selected pixel error determiner, to determine device state probability errors for each device state probability of the selected pixel.

Abstract: Certain examples described herein relate to mapping between an input color space and an output color space. In some cases, data representing a set of candidate output color values in the output color space is obtained for a transition region between two input color values in the input color space. A sub-region of the transition region is defined, the sub-region being associated with a target colorimetry and a target value of a metric. An output color value is selected from the set of candidate output color values. The output value has an associated value of the metric and an associated colorimetry. The selecting is based on the associated colorimetry and the target colorimetry, and the value of the metric and the target value of the metric. In some cases, mapping data is generated by assigning the selected output color value to the sub-region.

Abstract: Examples analyze three-dimensional printing specifications associated with a three-dimensional printing device to determine test angles for a test object and test surfaces corresponding to the test angles for the test object. Examples generate the test object for color calibration for the three-dimensional printing device based at least in part on the test angles and test surfaces that are configured with at least one test color.

Abstract: A method is disclosed wherein data representative of a plurality of colors defined in a color space is received, the plurality of colors providing a color palette taken to be related to each other by predefined color harmony rules based on their relative positions in the color space. An irreproducible color of the color palette outside a rendering system's reproducible color gamut is determined, the reproducible color gamut having been received for a rendering system on which image data comprising colors of the color palette is to be reproduced. A suggested color for a replacement color palette also complying with the predefined color harmony rules is determined based on the reproducible color gamut to bring the color palette towards being within the rendering system's reproducible color gamut.

Abstract: Certain examples described herein relate to generating a Neugebauer Primary area coverage (NPac) vector. In certain cases, a first plurality of Neugebauer Primaries (NPs) defined by a first NPac vector is determined, the first plurality of NPs defining a set of characteristics of a printing process. A second NPac vector, defining a second plurality of NPs, is generated based on the set of characteristics and a criterion relating to the printing process.

Abstract: In an example, an image processing system may include an identification engine, a map engine, and a control engine. In that example, the identification engine may identify a color mapping resource in response to a classification identifier corresponding to image data, the map engine may map the image data with the color mapping resource having color space clause corresponding to the classification identifier, and the control engine may generate control data for operating a print apparatus to print based on the color mapping resource.

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: 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 relate to emulating a spectral measurement device in a color measurement apparatus. In these examples, a primary spectral measurement device measures a first spectral characteristic of a rendered color output. A predictive model, parametrized by parameter values, is applied to the measurement from the primary spectral measurement device to determine a predicted measurement of a second spectral characteristic of the rendered color output which would be measured by an ancillary spectral measurement device. Parameter values are generated by training the predictive model with data from the primary spectral measurement device and the ancillary spectral measurement device.

Abstract: Certain examples relate to the processing of spot colors within a printing pipeline. In these example, a palette of spot colors indicated in a print job is determined. The palette is mapped to a set of vectors in a colorant-dependent color space based on a comparison of target spectral characteristics for the spot colors and measured spectral characteristics of the printing system. The set of vectors is used to assign vectors to print-resolution areas of the print job before halftoning.

Abstract: Certain examples described herein relate to generating a color mapping between a source color gamut within a source color space and a target color gamut within a target color space. Gamuts may be set based on a color rendering device. In examples, a sequence of forward color transformations that transform the source color gamut is defined, along with a sequence of inverse color transformations that transform the target color gamut. A gamut mapping is applied between the output of the forward color transformations and the output of the inverse color transformations, wherein the color mapping is usable by a computing device to map between the source and target color spaces.

Abstract: In an example, a print system includes a redundancy engine, a separation engine, and a print engine. In that example, the redundancy engine may identify a group of nozzles based on a redundancy characteristic of a plurality of print head nozzles of a print head to be received at the print head station and the separation engine may select a color separation operation corresponding to a drop domain associated with the group of nozzles identified by the redundancy engine to operate the print head with redundancy. In that example, the print engine may generate instructions using the selected color separation operation to cause the print head to eject print fluid from a combination of nozzles corresponding to the group of nozzles based on the drop domain to operate the print head with a redundancy print mode.

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: A method of detecting printing fluid mixing is provided. A test pattern for at least one printing fluid is printed with a printing device. The test pattern for the at least one printing fluid is scanned with a scanning device. Colorimetric data of the test pattern for the at least one printing fluid are obtained. Metric values are determined from the colorimetric data. A statistical analysis is performed on the determined metric values. Based on the statistical analysis, it is determined whether printing fluid mixing has occurred and where printing fluid mixing has occurred.