Abstract: A method for color mapping is disclosed based on obtaining a measurement of one or more characteristics of an imaging system. A set of color mappings are provided and the color mapping is selected based on the measurement. Each of the color mappings enables a mapping from a first color space to Neugebauer Primary area coverage vector space. A method for generating a color mapping is disclosed.

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 and apparatus relating to substructures for three-dimensional objects are described. In an example, a processing apparatus includes: an interface to receive data representing a three-dimensional model object, the data including object model data and object property data; a mapping module to map received data to a print material coverage representation; a halftone module to provide halftone threshold data; and a substructure module to define a substructure for a three-dimensional object to be generated, the substructure specifying in at least a region thereof a consistent lattice structure and a variable material distribution. The apparatus is to apply a substructure and a halftoning to the print material coverage representation to generate control data for the production of a three-dimensional object having the substructure.

Abstract: A method of calibrating a printing system. Data defining a color mapping that maps a first set of n-dimensional color Input points to a corresponding second set of n-dimensional color output points, the color mapping representing a measured behavior of the printing system, is obtained. A smoothed mapping function of color input points that satisfies a predetermined optimization condition based on a mapping error between the smoothed mapping function and the color mapping is determined. The mapping error is a function of individual errors between outputs of the smoothed mapping function as applied to respective color input points in the first set of color input points and corresponding color output points from the second set of color output points as mapped from the respective color input points by the color mapping. The smoothed mapping function is used to calibrate the printing system.

Abstract: A method is described in which printing instructions representing printing content to be printed by a printing system are received, the printing system comprising a dispenser to dispense printing material. Whether to perform a first mapping process or a second mapping process is then selected. The first mapping process comprises mapping an indicator to a first dispensing process to dispense printing material from the dispenser to produce content according to a content characteristic of the printing content at a given location, and the second mapping process comprises mapping the indicator to a second dispensing process to dispense printing material to produce content according to the content characteristic at the given location. The first dispensing process is different than the second dispensing process. The indicator represents the content characteristic. The method also comprises performing the selected mapping process.

Abstract: In some examples, octree serialization can include non-transitory machine-readable medium storing instructions, the instructions executable by a processing resource to evaluate two or more nodes sequentially in an octree structure until a leaf node is reached, wherein the two or more nodes include at least one non-leaf node, and generate a serialized octree document based on a respective node identifier in a header associated with each node of the two or more nodes.

Abstract: A method is described in which data representing a three-dimensional object to be printed is obtained. The data comprises sub-volumes representing the three-dimensional object. A characteristic for the three-dimensional object to be printed is identified. Based on the identified characteristic, property data is set for individual sub-volumes to be used in printing the three-dimensional object. The identified characteristic is a function of the property data. The property data comprises material property data, structural property data and printing property data.

Abstract: A method is described. The method comprises determining a lightness coordinate value corresponding to a first color value along a black-white axis in an input device color space. A set of color values corresponding to the lightness coordinate value, in the input device color space is determined. A subset of the set, based on the respective angular positions of the color values in the set and an angular position of the first color value is determined. The method comprises deriving a set of print color space values of a target printing system comprising print color space values corresponding to the subset and a color value corresponding to the position of the lightness coordinate value, based on a predetermined association between input device color space values and print color space values. The method comprises determining a given print color space value corresponding to the first color value based on the derived set of print color space values.

Abstract: A method is described in which data representing a three-dimensional object to be printed is obtained. The data comprises sub-volumes representing the three-dimensional object. A characteristic for the three-dimensional object to be printed is identified. Based on the identified characteristic, property data is set for individual sub-volumes to be used in printing the three-dimensional object. The identified characteristic is a function of the property data. The property data comprises material property data, structural property data and printing property data.

Abstract: A method is disclosed in which a lookup table (LUT) that maps chromatic and achromatic device color space vectors into Neugebauer primary area coverages (NPacs) is obtained. According to the method, a LUT that maps chromatic device color space vectors into NPacs is combined with a LUT that maps achromatic device color space vectors into NPacs.

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: In an example, processing apparatus includes a substructure module to define a substructure for a three dimensional object. The substructure module includes a weighting module to apply relative weights to data relating to each of the plurality of substructures and a blending module to blend data relating to the substructures. The substructure module is to generate data defining an intermediate substructure from a weighted blend of the data relating to the plurality of substructures.

Abstract: The application refers to a method for generating three-dimensional object models for an additive manufacturing process in a layer-by-layer manner, e.g. 3D-printing, and to generating control data for use by the print apparatus. The object models are generated from a geometric description and from object generation data, which comprise the print apparatus and attributes such as a halftone scheme, a print apparatus setting, an object structure and a print material coverage representation. The method is implemented in the form of a computer software product and generates data specific for each identifies printing device.

Abstract: A method is described in which colorant-space calibration data for a colorant-space image processing pipeline are determined. The colorant-space calibration data are converted into probability-space calibration data for a probability-space image processing pipeline. The probability-space calibration data are applied to image data processed in the probability-space image processing pipeline.

Abstract: In an example, a method includes acquiring data representing an article to be printed. The data may include at least one element set associated with print addressable location(s) and comprising a first and second element. The elements each identify a print material or print material combination and is each associated with a probability that the print material or print material combination identified thereby is to be applied to the associated print addressable location. A halftone matrix may be acquired comprising threshold values of a first and second value range. The threshold values of the first and second value range are distributed according to a first and second distribution pattern respectively. The halftone matrix may be applied to the data to determine print instructions to distribute the print material or print material combination identified by the first and second element according to the first and second distribution patterns respectively.

Abstract: A printer apparatus comprises one or more ports (2011 to 201M) for receiving one or more colorant units (INK1 to INKN), and a processing unit. The processing unit is adapted to determine which one or more colorant units (INK1 to INKN) have been loaded into the printer apparatus. The processing unit is adapted to retrieve colorant information from each loaded colorant unit (INK1 to INKN), and determine an ink-set configuration using the colorant information retrieved from each loaded colorant unit (INK1 to INKN). Operation of the printer apparatus is configured according to the determined colorant-set configuration.

Abstract: An example method of setting ink limits for a printing system is described. The method involves printing a first set of color ramps. Each color ramp has test areas which are printed based different Neugebauer Primary Area Coverage (NPac) vectors. A test area for each color ramp is indicated that meets an image quality metric and Neugebauer Primary ink use limits are set based on these test areas. A second set of color ramps, for combinations of the set of available Neugebauer Primaries, is then printed, The test areas for each ramp are defined by monotonically-varying vector element values for one Neugebauer Primary in a combination and the second set of ramps are defined by monotonically-varying vector element values across said ramps for another Neugebauer Primary in the combination. Test areas are then indicated again for the second set of color ramps to set ink use limits for the printing system.

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 smoothing a lookup table for an imaging system. The lookup table comprises entries to map elements in a first color space to corresponding elements in a second color space. In certain cases, the entries of the lookup table are classified into a plurality of classes, each of the plurality of classes being based on a color space characteristic in the first color space or the second color space. Each of the plurality of classes of entries is sequentially smoothed.

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.