Hp Indigo B.v.

Hewlett-packard Indigo B.v.

Hewlett-packard Development Company, L.P.

Oded Perry

Oren Haik

Avi Malki

Liron Itan

Smadar Shiffman

Noam Shaham

Ram Dagan

Gregory Braverman

Tal Frank

Mirta Perlman

Eli Chen

Omri Shacham

Alexander Spivakovsky

Tal Framk

Liron Iton

A first separation distance is determined between a first pair of defects in a scanned image of a first printed sheet, and a second separation distance is determined between a second pair of defects in a scanned image of a second printed sheet. The defects are determined as having a separation distance in that the first and second separation distances are each within a first threshold of a specified separation distance and/or a difference between the first and second separation distances is below a second threshold. A source of the defects can be determined based on the characteristic separation distance.

Determining defects having a characteristic separation distance

Examples of the present disclosure relate to a method for skew detection in a printing system. The method comprises printing a document from an original digital image, scanning the document to produce a digital representation using an in line scanner of the printing system, and detecting skew in the digital representation independently from the original digital image.

Digital representation

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 an intermediate transfer member. 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 dent defect on the ITM is identified utilizing the integrated defect map.

ITM dent identification utilizing integrated defect maps

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.

Adjusting a colour in an image

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.

Identifying linear defects

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.

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.

Gray component replacement in a digital image to generate a color transformed image

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.

Scratch identification utilizing integrated defect maps

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.

Image defect detection

A method includes obtaining an image of a document against a background. A bounding box that bounds a region of the image that is distinguishable from the background is found. Coordinates of a plurality of points of the distinguishable region are found, each point being a point of the distinguishable region that is closest to each corner of the bounding box. The document is identified within the image as a region of the image whose corners are defined by the found coordinates.

Automatic detection of corners of an imaged document

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.

Velocity estimation methods, and imaging devices and printing devices using the methods

A method to generate an image in which a plurality of offset vectors for portions of a first image are determined by comparing the similarity of the portions to portion of a second image.

To generate an image

A method to generate a histogram matched image in which a portion of a first reference image is partitioned into a plurality of regions. Histogram matching is performed separately on the plurality of regions of the first reference image and corresponding regions in a second image to generate a plurality of first histogram matched reference images. Histogram matching is also performed on the portion of the first reference image and a corresponding portion in the second image to generate a second histogram matched reference image. An area from one of at least a first histogram matched reference image and the second histogram matched reference image is selected to generate a finalized histogram matched reference image.

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Ness Ziona, Israel

Oded Perry