Abstract: In an example, a method includes obtaining, by at least one processor, a first halftone screen tile having a first halftone pattern. In some examples, the method further comprises obtaining a second halftone screen tile having a second halftone pattern. The method may include determining a halftone screen having a predetermined spatial arrangement of the first and second halftone screen tiles wherein the relative placement of the first and second halftone screen tiles in the predetermined spatial arrangement provides a signature for the halftone screen which when applied to image data provides a printed output in which the signature is discernible.

Abstract: In an example, a method includes determining, using a processor, a first halftone screen comprising a plurality of cells. Each of the cells may contain a predetermined pixel cluster pattern, and a centre position of a cluster pattern within a first cell may be different to a centre position of a cluster pattern within a second cell.

Abstract: In an example, a method includes determining, using a processor, a first halftone screen comprising a plurality of cells. Each of the cells may contain a predetermined pixel cluster pattern, and a centre position of a cluster pattern within a first cell may be different to a centre position of a cluster pattern within a second cell.

Abstract: In an example, a method includes determining an indication of pixel separation for an image region to be printed to a substrate. A power level of a laser light source to address a pixel on a region of a photoconductive surface corresponding to the image region may be adjusted based on the indication of pixel separation to compensate for print spot size variation associated with pixel separation.

Abstract: Certain examples described herein relate to a method in which a model for predicting a characteristic of a printed halftone image is generated. The method may include receiving sets of image data, each representing a respective image. The sets of image data may include input image data representing the respective image using a halftone pattern, and corresponding printed image data representing a printed version of the respective image printed on the basis of the halftone pattern. A training process may be iteratively performed to train a neural network to generate a mapping between input image data and printed image data. The model may be generated on the basis of the mapping. An apparatus, a system and a non-transitory computer-readable storage medium are also described.

Abstract: In an example, a method includes determining an indication of pixel separation for an image region to be printed to a substrate. A power level of a laser light source to address a pixel on a region of a photoconductive surface corresponding to the image region may be adjusted based on the indication of pixel separation to compensate for print spot size variation associated with pixel separation.

Abstract: A method comprises forming a halftone screen set comprising first, second and third halftone screens. A first regular halftone screen for the screen set is selected. A second regular halftone screen is determined, using a processor, by performing a regularity invariant transformation on the first regular halftone screen. A third halftone screen is determined based on at least one predetermined condition being satisfied between the first, second and third halftone screens.

Abstract: Examples analyze a digital image to determine an amount of high-frequencies corresponding to each pixel of the digital image based at least in part on gradients corresponding to a pixel neighborhood of each pixel. Examples analyze the digital image to determine a degree of randomness for each pixel based at least in part on the corresponding gradients. Examples generate an activity mask for the digital image based at least in part on the amount of high-frequencies and the degree of randomness corresponding to each pixel. Examples process the pixels of the digital image by performing gray component replacement to generate a color transformed image based at least in part on the activity mask.

Abstract: Measures for use in calibrating a printing device. Historical dot gain linearization lookup table data for the printing device is processed. On the basis of the processed historical dot gain linearization lookup table data, a plurality of input points for a current dot gain linearization lookup table are dynamically determined. The printing device is calibrated according to the dynamically determined current dot gain linearization lookup table.

Abstract: An example system includes a color engine to separate an image into a plurality of color components. The system also includes a halftone engine to generate a plurality of halftone images based on the plurality of color components and a plurality of halftone screens. For each halftone screen, the halftone cell centers for that halftone screen occur at regular or semi-regular distances relative to a dot pitch. The plurality of halftone screens forms a high frequency moire pattern when the halftone screens are overlaid on each other. Each of the halftone screens have a granularity metric less than a threshold.

Abstract: Certain examples described herein relate to the halftoning of a color image. In one example, a set of clusters are determined based on the color image. A set of edges are also detected in the color images. Clusters within these edges are then merged. A set of screens for halftoning are assigned to the set of clusters. This assignment is based on color property metrics for the set of clusters. The color image is halftoned using the set of screens assigned to the merged clusters.

Abstract: In an example, a method includes determining, using a processor, a set of halftone screens each comprising tiles spanning a plurality of cells, wherein at least one screen is a non-orthogonal screen and the cells comprise parallelograms being defined by a first vector having a first length and second vector having a second length. A first and a second fundamental frequency may be determined for each of the screens using a projection of the first and of the second vector into each axis of a print apparatus reference frame, the first length and the second length. Using the first and second fundamental frequencies, it may be determined which screens are associated with moiré effects below a threshold.

Abstract: Examples analyze a digital image to determine an amount of high-frequencies corresponding to each pixel of the digital image based at least in part on gradients corresponding to a pixel neighborhood of each pixel. Examples analyze the digital image to determine a degree of randomness for each pixel based at least in part on the corresponding gradients. Examples generate an activity mask for the digital image based at least in part on the amount of high-frequencies and the degree of randomness corresponding to each pixel. Examples process the pixels of the digital image by performing gray component replacement to generate a color transformed image based at least in part on the activity mask.

Abstract: A halftone comprises a first halftone screen and a second halftone screen. The first halftone screen comprises a first plurality of amplitude modulated dots arranged according to a first plurality of rows, the first plurality of rows being orientated according to a first direction and comprising a first dot spacing. The second halftone screen comprises a second plurality of amplitude modulated dots arranged according to a second plurality of rows, the second plurality of row being orientated in a second direction and comprising a second dot spacing. The first direction and the second direction define an angle of 45 degrees or less and a ratio of the second dot spacing to the first dot spacing is less than one.

Abstract: Measures for use in calibrating a printing device. Historical dot gain linearization lookup table data for the printing device is processed. On the basis of the processed historical dot gain linearization lookup table data, a plurality of input points for a current dot gain linearization lookup table are dynamically determined. The printing device is calibrated according to the dynamically determined current dot gain linearization lookup table.

Abstract: A halftone comprises a first halftone screen and a second halftone screen. The first halftone screen comprises a first plurality of amplitude modulated dots arranged according to a first plurality of rows, the first plurality of rows being orientated according to a first direction and comprising a first dot spacing. The second halftone screen comprises a second plurality of amplitude modulated dots arranged according to a second plurality of rows, the second plurality of row being orientated in a second direction and comprising a second dot spacing. The first direction and the second direction define an angle of 45 degrees or less and a ratio of the second dot spacing to the first dot spacing is less than one.

Abstract: An example system includes a color engine to separate an image into a plurality of color components. The system also includes a halftone engine to generate a plurality of halftone images based on the plurality of color components and a plurality of halftone screens. For each halftone screen, the halftone cell centers for that halftone screen occur at regular or semi-regular distances relative to a dot pitch. The plurality of halftone screens forms a high frequency moire pattern when the halftone screens are overlaid on each other. Each of the halftone screens have a granularity metric less than a threshold.

Abstract: A halftone comprises a first halftone screen and a second halftone screen. The first halftone screen comprises a first plurality of amplitude modulated dots arranged according to a first plurality of rows, the first plurality of rows being orientated according to a first direction and comprising a first dot spacing. The second halftone screen comprises a second plurality of amplitude modulated dots arranged according to a second plurality of rows, the second plurality of row being orientated in a second direction and comprising a second dot spacing. The first direction and the second direction define an angle of 45 degrees or less and a ratio of the second dot spacing to the first dot spacing is less than one.

Abstract: A halftone comprises a first halftone screen and a second halftone screen. The first halftone screen comprises a first plurality of amplitude modulated dots arranged according to a first plurality of rows, the first plurality of rows being orientated according to a first direction and comprising a first dot spacing. The second halftone screen comprises a second plurality of amplitude modulated dots arranged according to a second plurality of rows, the second plurality of row being orientated in a second direction and comprising a second dot spacing. The first direction and the second direction define an angle of 45 degrees or less and a ratio of the second dot spacing to the first dot spacing is less than one.

Abstract: A method of determining the velocity of relative displacement between a substrate and an image sensor, for example the velocity of displacement of a page relative to a scanner, involves imaging a reference pattern on the substrate, using the image sensor, while the relative displacement occurs between the substrate and the image sensor. The reference pattern includes plural crossing points marked at predetermined locations on the substrate, each crossing point formed of a first line portion crossing a second line portion. Locations in the image that correspond to the crossing points are compared to the predetermined locations on the substrate and the velocity of the relative displacement between the image sensor and the substrate is determined using relationships between the predetermined locations and the detected locations in the generated image.