Abstract: Methods and apparatus associated with three-dimensional objects are described. In an example, a method comprises receiving data representing a three-dimensional model object, the data comprising object model data and object property data. For at least one object property, a sub-region of the object in which the object property is non-variable is identified and, for at least one location within the object, all sub-regions in which the location is situated are identified. Based on the combination of identified sub-regions for a location, print material data is determined for the location. Control data for the production of a three-dimensional object is generated according to the print material data.

Abstract: In an example, a method for generating control data for production of a three-dimensional object is described. A model of the three-dimensional object is obtained as a array of voxels, and it is determined for each voxel whether that voxel comprises part of a first or a second sub-object of the three-dimensional object. Each first sub-object voxel is mapped to a volume coverage representation defining print material data for that voxel. The second sub-object voxels are mapped to a volume coverage representation defining common print material data for the voxels of second sub-object. Control data for printing the first sub-object is generated from the print material data for that voxel common print material data for the Control data for printing the second sub-object is generated according to the volume coverage representation for the second sub-object.

Abstract: Cells of an n-dimensional object are indexed. A plurality of indexing digits are grouped for each axis of the n dimensions of the n-dimensional object. A first indexing digit of a given group is allocated to each of at least two cells resulting from at least one subdivision of the dimension of the object along the axis of the given group; and an mth subsequent indexing digit of the given group is allocated to any subsequent at least two cells resulting from any subsequent at least one subdivision of at least one cell of the at least two cells resulting from the m?1th subdivision of the dimension of the object along the axis of the given group.

Abstract: Certain examples described herein relate to a three-dimensional threshold matrix. The three-dimensional threshold matrix may be used for three-dimensional halftoning. In one example, values for a predefined two-dimensional threshold matrix are shifted with respect to a third dimension to provide the three-dimensional threshold matrix. In one example, the three-dimensional threshold matrix may then be processed in association with a digital representation of a three-dimensional object to output discrete material arrangement instructions for at least one production material. The instructions may be used to control an additive manufacturing system to produce the three-dimensional object.

Abstract: The present disclosure relates particularly but not exclusive to a method for printing in a multipass print mode using a first printhead (PT1) and a second printhead (PT2), the method including printing in a first pass a first image in a first area of a print medium using a first set (ST21) of nozzles (N5-N24) from the first printhead (PT1), printing in a second pass a coating layer over the first image using a second set (ST22) of nozzles (P4-P22) from the second printhead (PT2), and printing in a third pass a second image over the coating layer using a third set (ST23) of nozzles (N1-20) from the first printhead (PT1).

Abstract: A calibration target is disclosed. The calibration target is created such that a color patch is sensitive to drop weight changes based on drop weight variations that show greater changes in color for a given change in drop weight.

Abstract: A method of defining color separation for printing an image via NPacs, the method comprising: selecting a plurality of NPacs corresponding to a plurality of points within an RGB cube to provide a tessellation in RGB space translated to a valid tessellation in an NPac-related space; and defining color separation from the selected NPacs.

Abstract: The present disclosure relates to a computer implemented method for color separation for a printer, systems, and methods for printing using a printer. In some examples, the method for color separation for a printer comprises forming a color gamut for the printer in the form of a hull in a color space, the hull having vertices corresponding to Neugebauer Primaries, predicting the colorimetry in the color space of at least one Neugebauer Primary lying outside of an ink limit for the printer, determining the Neugebauer Primary area coverages that can produce a desired color in the color space using at least one Neugebauer Primary lying outside of the ink limit.

Abstract: A method of color halftone processing is disclosed. A plurality of color mappings each provide a mapping from a color value in a color space to a set of Neugebauer Primary area coverage (NPac) values in an NPac space. An imaging metric is obtained for each NPac value in the set. An NPac value in the set is selected based on the imaging metric. The selected NPac value is used as an output NPac value in a combined color mapping for the color value.

Abstract: A printing system and method to process image data is disclosed. The printing system includes an identification module and image pipeline module include a linear threshold array algorithm and a halftoning algorithm to process the image data. An image pipeline module applies a linear threshold array algorithm to line regions and a halftoning algorithm to the non-line regions.

Abstract: In a method to generate a print specification color separation look-up table, a device color space is sampled to provide at least one sampled value. The sampled value is transformed to a device independent color space. The transformed sampled value is gamut mapped using a source color gamut and a color separation color gamut to provide a color separation value. The gamut mapping is performed in an expansion mode and a compression mode.

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: A processing apparatus is provided. The processing apparatus includes a controller to process information as part of a Halftone Area Neugebauer Separation printing process to use at least one opaque ink as a process colorant in combination with at least one further process colorant.

Abstract: A calibration target is disclosed. The calibration target is created such that a color patch is sensitive to drop weight changes based on drop weight variations that show greater changes in color for a given change in drop weight.

Abstract: Certain methods and systems are described to provide color modelling. This color modelling applies to halftone images. In one example, a correction parameter for a color model is determined by minimizing a distance metric between a set of estimated spectral reflectance values and a set of measured spectral reflectance values to generate a multi-dimensional correction parameter. This enables a color model to be used to map at least one Neugebauer Primary area coverage value to at least one spectral reflectance value.

Abstract: A calibration target is disclosed. The calibration target is created such that a color patch is sensitive to drop weight changes.

Abstract: A color image is processed into a renderable image. The color image comprises a plurality of pixels. Each pixel has colorimetry defined in a first color space. The renderable image comprises a plurality of renderable pixels defined by a device-vector in a second color space. For each pixel: a device-vector defined in the second color space is selected (301) based on the colorimetry defined in a first color space of the pixel. The device-vector comprises a plurality of elements. Each element includes an identifier and an accumulated weighting. An element of the selected device-vector is reselected (303) until the accumulated weighting (a) is greater than a threshold value (t) associated with the pixel (305). The levels for each color of the second color space (or mappings) for the currently selected (307) element of the selected device-vector is determined (309) to convert the pixel into a renderable pixel.

Abstract: A calibration target is disclosed. The calibration target is created such that a color patch is sensitive to drop weight changes.

Abstract: A method of defining color separation for printing an image via NPacs, the method comprising: selecting a plurality of NPacs corresponding to a plurality of points within an RGB cube to provide a tessellation in RGB space translated to a valid tessellation in an NPac-related space; and defining color separation from the selected NPacs.

Abstract: In a method to generate a print specification color separation look-up table, a device color space is sampled to provide at least one sampled value. The sampled value is transformed to a device independent color space. The transformed sampled value is gamut mapped using a source color gamut and a color separation color gamut to provide a color separation value. The gamut mapping is performed in an expansion mode and a compression mode.