Abstract: A method (300) is described of determining characteristic of an ink jet printer (15). A chart containing multiple regions or patches is printed (320) on a print medium (115) using the ink jet print (15). The chart includes at least a first region printed using a first set of nozzles, and at least a second region printed using a second set of nozzles. The first and second sets of nozzles are a predetermined distance apart in the printer head of the printer (15). The printing of the first and second regions is also separated by a print medium advance operation equal to the predetermined distance. This causes the first and second regions to be aligned in the direction of the print medium advance operation. The chart is then imaged using scanner (16) chart to form a chart image. The positions of the regions appearing in the chart image are next determined (340).

Abstract: Disclosed is a method of determining at least one three-dimensional (3D) geometric parameter of an imaging device. A two-dimensional (2D) target image is provided having a plurality of alignment patterns. The target image is imaged with an imaging device to form a captured image. At least one pattern of the captured image is compared with a corresponding pattern of the target image. From the comparison, the geometric parameter of the imaging device is then determined. The alignment patterns include at least one of (i) one or more patterns comprising a 2D scale and rotation invariant basis function, (ii) one or more patterns comprising a 1D scale invariant basis function, and (iii) one or more patterns having a plurality of grey levels and comprising a plurality of superimposed sinusoidal patterns, the plurality of sinusoidal patterns having a plurality of predetermined discrete orientations.

Abstract: A method of identifying a printed page from a scan of the printed page is disclosed. The method comprises the steps of generating a page key of the printed page on the basis of the scan (710), searching a database (199) for a similar page key (730). For each found similar page key (740), the method further comprises; retrieving from the database an instance key location (750), generating an instance key for the printed page (530), based on the retrieved instance key location of the referenced page instance; and comparing the generated instance key for the printed page with the retrieved instance key of the referenced page instance (770). A match between the instance keys indicates that the printed page is the referenced page instance.

Abstract: A method determines displacements between pixels in a captured image of a reference pattern and corresponding pixels in the reference pattern including the steps of capturing the image of the reference pattern having a source pattern modulated by a plurality of carrier frequencies in a corresponding plurality of directions in the source pattern, demodulating at least three of the carrier frequencies in the captured image to form an amplitude image and a wrapped phase image for each of the carrier frequencies, and combining the wrapped phase images weighted by the amplitude images to determine the displacements between pixels in the captured image and corresponding pixels in the reference pattern.

Abstract: Disclosed herein is a method of estimating a geometrical relationship between a first image (101) and a second image (102), wherein the second image (102) includes a noise component. The method determines a location and size of each one of a plurality of image patches (201), based on the noise component included in the second image (102) and correlation information derived from the first image (101). The method then identifies a plurality of first image areas in the first image and a corresponding plurality of second image areas in the second image, based on the location and size of each one of the plurality of image patches. Each first image area of the first image (101) corresponds to a related second image area of the second image (102).

Abstract: A method (1000) of measuring performance parameters of an imaging device (120, 160) is disclosed. The method (1000) maintains a test pattern image (1005), the test pattern image (1005) comprising alignment features and image analysis features. A test chart (110, 170) containing a representation of the test pattern image is next imaged using the imaging device (120, 160) to form a second image (1010). The test pattern image (1005) and the second image (1010) are then registered using region based matching (1035) operating on the alignment features. Finally, the performance parameters are measured by analysing (1060) the image analysis features.

Abstract: Methods (300, 1000) of determining a light scattering property of a medium (152), are disclosed. The medium (152) is illuminated through a test pattern (e.g., 155, 510), the test pattern (155, 510) comprising at least one region containing a first pattern with substantial variation in two orthogonal directions at one scale. The test pattern (300, 1000) further comprises at least one other region containing the first pattern at a different scale. The light reflected from the illuminated medium (152) through the test pattern is measured to capture an image of the illuminated medium. A light scattering property of the medium (152) is determined based on the measured light.

Abstract: Disclosed is a method (100) for detecting print errors, the method comprising printing (130) a source input document (166) to form an output print (163), imaging (140) the output print (163) to form a scan image (164), determining a set of parameters modelling characteristics of the printer used to perform the printing step, determining values for the set of parameters dependent upon operating condition data for the printer, rendering (120) the source document (166), dependent upon the parameter values, to form an expected digital representation (227), and comparing (270) the expected digital representation to the scan image to detect the print errors

Abstract: A system (100) and a method (500) are described for determining a two-dimensional position of a location in an image. The method (500) starts by imaging (510) a two-dimensional pattern (440). The two-dimensional pattern comprises a plurality of at least partially overlapping two-dimensional sub-patterns (410, 420, 430). The sub-patterns (410, 420, 430) repeat with different spatial periods to form the two-dimensional pattern, and the spatial period of the sub-patterns are anharmonic. A two-dimensional offset for each of the sub-patterns is then determined (540) at the location in the image formed by the imaging. The two-dimensional position is determined from said two-dimensional offsets.

Abstract: A method (200) of determining at least rotation and scale parameters of a transformation relating two images is disclosed. The method (200) starts by forming a spatial domain representation of each of the images that is invariant to translation of the images. A correlation in the log-polar domain is next performed between the representations. After detecting a magnitude peak in the correlation, the method (200) determines the rotation and scale parameters from the position of the magnitude peak.

Abstract: Disclosed is a method (700) for determining displacements between pixels in a captured image (601) of a reference pattern (501) and corresponding pixels in the reference pattern (501), said method comprising the steps of capturing the image (601) of the reference pattern (501) comprising a source pattern modulated by a plurality of carrier frequencies in a corresponding plurality of directions in the source pattern, demodulating (930) at least three of the carriers in the captured image (601) to form an amplitude image (1041) and a wrapped phase image (1100) for each of the carrier frequencies, and combining (1220) the wrapped phase images (1100) weighted by the amplitude images (1041) to determine said displacements between pixels in the captured image (601) and corresponding pixels in the reference pattern (501).

Abstract: A method of identifying a printed page from a scan of the printed page is disclosed. The method comprises the steps of generating a page key of the printed page on the basis of the scan (710), searching a database (199) for a similar page key (730). For each found similar page key (740), the method further comprises; retrieving from the database an instance key location (750), generating an instance key for the printed page (530), based on the retrieved instance key location of the referenced page instance; and comparing the generated instance key for the printed page with the retrieved instance key of the referenced page instance (770). A match between the instance keys indicates that the printed page is the referenced page instance.

Abstract: An anti-tampering method for processing documents is disclosed. The method comprises, in regard to an encoding step, the steps of resolving (in a step 2303) in regard to an N-level image to be recorded, a pixel of the image into a major component having N possible values, selecting (in the step 2303) a pattern element depending upon the major component and the position of the pixel in the image, and recording the selected pattern element (in a step 2308) onto a transfer medium. In regard to a corresponding decoding step the method comprises extracting (in a step 2405) from the recorded document, a retrieved pattern element for said pixel, determining a pattern element (in a step 2407) depending upon a major component extracted from the retrieved pattern element and the position of the pixel on the recorded document, and comparing (in a step 2409) the retrieved pattern element and the said determined pattern element.

Abstract: A method (300) is disclosed of performing chromatic adaptation. The method (300) predicts final colour data viewed under a final illuminant from initial colour data viewed under a initial illuminant. The method (300) receives (310) the initial and final illuminant spectra and spectral sensitivity functions of the colors between which chromatic adaptation is to be performed. A linear chromatic adaptation transform is then determined (320) for transforming the initial color data to the final color data. The linear chromatic adaptation transform is determined (320) by minimising the residual error between color data predicted using the chromatic adaptation transform and the final color data. Different spectral bands of the illuminant spectra and the spectral sensitivity functions are weighted based on the contribution made by each spectral band to a predefined function. The method (300) then applies (330) the linear chromatic adaptation transform to the initial color data.

Abstract: Disclosed is a method of determining at least one three-dimensional (3D) geometric parameter of an imaging device. A two-dimensional (2D) target image is provided having a plurality of alignment patterns. The target image is imaged with an imaging device to form a captured image. At least one pattern of the captured image is compared with a corresponding pattern of the target image. From the comparison, the geometric parameter of the imaging device is then determined. The alignment patterns include at least one of (i) one or more patterns comprising a 2D scale and rotation invariant basis function, (ii) one or more patterns comprising a 1D scale invariant basis function, and (iii) one or more patterns having a plurality of grey levels and comprising a plurality of superimposed sinusoidal patterns, the plurality of sinusoidal patterns having a plurality of predetermined discrete orientations.

Abstract: Disclosed herein is a method of estimating a geometrical relationship between a first image (101) and a second image (102), wherein the second image (102) includes a noise component. The method determines a location and size of each one of a plurality of image patches (201), based on the noise component included in the second image (102) and correlation information derived from the first image (101). The method then identifies a plurality of first image areas in the first image and a corresponding plurality of second image areas in the second image, based on the location and size of each one of the plurality of image patches. Each first image area of the first image (101) corresponds to a related second image area of the second image (102).

Abstract: Methods (300, 1000) of determining a light scattering property of a medium (152), are disclosed. The medium (152) is illuminated through a test pattern (e.g., 155, 510), the test pattern (155, 510) comprising at least one region containing a first pattern with substantial variation in two orthogonal directions at one scale. The test pattern (300, 1000) further comprises at least one other region containing the first pattern at a different scale. The light reflected from the illuminated medium (152) through the test pattern is measured to capture an image of the illuminated medium. A light scattering property of the medium (152) is determined based on the measured light.

Abstract: A method of generating a matching key for an image is disclosed. The matching key is substantially invariant to rotation, scale and translation. The method starts by forming a spatial domain representation of the image that is substantially invariant to translation of the image. Rotation and/or scaling in the spatial domain representation is next transformed into translation to form a transformed image. A representation of the transformed image is then formed that is substantially invariant to translation of the transformed image. The representation of the transformed image is the matching key for the image.

Abstract: A method (300) is disclosed of calibrating a printing device (110). The method (300) starts by printing (310) a calibration chart (800) comprising a plurality of machine readable marks (920 and 925) and at least one calibration area (820). The machine readable marks (920 and 925) are disposed on different sides of the calibration area (820). Each machine readable mark (920 and 925) independently identifies a type of the calibration area (820). The printed calibration chart is next imaged (330). Finally, the calibration area (820) is utilized to calibrate the printing device (110) in accordance with the identity of the type of calibration area (820).

Abstract: A method (300) is described of determining characteristic of an ink jet printer (15). A chart containing multiple regions or patches is printed (320) on a print medium (115) using the ink jet print (15). The chart includes at least a first region printed using a first set of nozzles, and at least a second region printed using a second set of nozzles. The first and second sets of nozzles are a predetermined distance apart in the printer head of the printer (15). The printing of the first and second regions is also separated by a print medium advance operation equal to the predetermined distance. This causes the first and second regions to be aligned in the direction of the print medium advance operation. The chart is then imaged using scanner (16) chart to form a chart image. The positions of the regions appearing in the chart image are next determined (340).