Abstract: A method for processing an image is disclosed. The method may include obtaining a target image to be printed using print agent in a printable area of a substrate of a particular colour. The method may include obtaining a scanned image of a substrate on which the target image has been printed, the substrate being of the particular colour. The method may include determining, from the scanned image, the particular colour of the substrate. The method may include using the target image as a reference image against which the scanned image is to be compared. The method may include adjusting a colour in the reference image according to the determined particular colour of the substrate. An apparatus and a machine-readable medium are also disclosed.

Abstract: A monitoring device includes circuitry to compare a printed output with a reference representing a target output and to determine potential defects in the printed output based on the comparison. The monitoring device further includes and circuitry to implement a convolutional neural network to classify each potential defect as a true defect or a false alarm.

Abstract: In one example of the disclosure, a set of scanned images is accessed. The scanned images are scans of distinct printouts of subject images produced utilizing a photo imaging plate. A set of defect maps is created by comparing the scanned images to reference data for the subject images. The set of defect maps are combined into an integrated defect map. A scratch defect on the PIP is identified utilizing the integrated defect map.

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: 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: In one example of the disclosure, a set of scanned images is accessed. The scanned images are scans of distinct printouts of subject images produced utilizing a photo imaging plate. A set of defect maps is created by comparing the scanned images to reference data for the subject images. The set of defect maps are combined into an integrated defect map. A scratch defect on the PIP is identified utilizing the integrated defect map.

Abstract: In an example, a method includes determining, by a processor, a cumulative indication of defects present in linear sub-portions located in a common position of each of a plurality of substrate sheets bearing a printed image. The method may further comprise identifying, by the processor, a linear defect based on the cumulative indication of defects.

Abstract: A method and apparatus for generating print data are described herein. An apparatus comprising an image processor (110) is configured to select a region of an image spanning an intersection between at least two adjacent sub-images that partition the image. The spanning region is divided based on a non-linear path that is determined on the basis of a user input, resulting in at least two modified adjacent sub-images. Print data operable to cause a printing device (150) to print the respective modified adjacent sub-images are generated on the basis of the dividing.

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: In an example, a method includes determining, by a processor, at least one separation distance between defects in a scanned image of a printed substrate sheet bearing a printed image, wherein the separation distance determined in a predetermined direction. The method may further comprise determining, by the processor, if the defects have a characteristic separation distance.

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: Apparatus to detect a defect in a printed image and methods of detecting detects in a printed image are described. In some examples, a printing operation is initiated using image data to generate a printed image. The printed image is then scanned to generate a scanned image. A resolution of the scanned image is estimated, calculated or determined on the basis of a characteristic of the printing operation, and a reference image, having a resolution corresponding to the estimated, calculated or determined resolution, is generated from the image data. Whether defects are present in the printed image may be determined on the basis of a comparison of the reference image with the scanned image.

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: Streaks in images are detected by determining a rotation angle of an image and calculating a rotated image based on a rotation of the image by the rotation angle. A cross-sectional pixel profile of the rotated image is determined and a peak in the cross-sectional pixel profile of the rotated image is determined. A streak in the image is identified based on the determined peak.

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: 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: An example system includes a histogram engine. The histogram engine is to generate a target histogram based on a target image. The example system also includes a dispersion engine to calculate a dispersion of the target histogram. The example system also includes a spreading engine to diffuse a reference histogram for a reference image based on the dispersion of the target histogram. The histogram engine also is to generate a mapping between the reference histogram with diffusion and the target histogram.

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.