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: A method of determining an actual phase offset of a fringe pattern in a captured image. A captured image, having a phase modulated fringe pattern, is one of a set of images captured with varying introduced phase offset and forms an intermediate demodulation image from the captured image. The intermediate demodulation image defines amplitude and complex phase parameters of the phase modulated fringe pattern. The captured image is transformed by a mask to produce a processed captured image having reduced effects of phase distortion. The mask is estimated from a function of at least one of the amplitude and complex phase parameters defined by the intermediate demodulation image. The method determines a Fourier transform of the processed captured image, and determines at least one phase offset of the fringe pattern in the processed captured image using the mask to identify interaction of peaks in the Fourier transform.

Abstract: A method forms a representative image from a crossed grating fringe pattern interferogram of an object from an interferometer. The method determines a plurality of spectral lobes from the interferogram and selects from the plurality of determined lobes, two substantially orthogonal sidelobes. The selected sidelobes represent spatial differential phase information of the interferogram. The method applies an inverse Riesz transform to the spatial differential phase information of the selected sidelobes to form a transformed differential phase image, and forms from the transformed differential phase image, a representative image emphasising high frequency detail information of the object.

Abstract: Methods, apparatuses, systems and computer program products for measuring spatial characteristics of an inkjet printer are disclosed. Group of marks of a first predetermined pattern are printed on a print medium using a first group of nozzles. Groups of marks of a second predetermined pattern are printed using a second group of nozzles. A region of overlap of the printed groups of marks is formed. At least a portion of the print medium having printed groups of marks is imaged. From the region of overlap, first and second groups of marks from the first and second printed patterns are selected. For each group of marks, a position representative of that group is determined. An offset for measuring spatial characteristics of the printer between the first and second printed patterns is determined dependent upon the representative position of each of the first and second groups of marks.

Abstract: A method determines at least one image value of a corresponding desired output position of an output image from an input image. An orientation of an edge passing through the output position is determined in a localised region of the input image. A frequency spectrum for the region of the input image is extended. A main frequency band of the edge is aligned in the extended frequency spectrum parallel to a first sampling axis of a grid based on the orientation of the edge. The grid is selected from a set of the input and output grids. The aligned main frequency band is filtered along a second sampling axis of the grid, orthogonal to the first sampling axis, the filter removing frequencies associated with replica bands and maintaining the main frequency band. The image value is determined from the filtered edge at the desired output position.

Abstract: Methods for determining a depth measurement of a scene which involve capturing at least two images of the scene with different camera parameters, and selecting corresponding image patches in each scene. A first approach calculates a plurality of complex responses for each image patch using a plurality of different quadrature filters, each complex response having a magnitude and a phase, assigns, for each quadrature filter, a weighting to the complex responses in the corresponding image patches, the weighting being determined by a relationship of the phases of the complex responses, and determines the depth measurement of the scene from a combination of the weighted complex responses.

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: 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: 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 (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: Methods (700), apparatuses, systems (500) and computer program products for measuring spatial characteristics of an inkjet printer (200, 300) are disclosed. Group of marks (810/815) of a first predetermined pattern are printed (720) on a print medium (230) using a first group of nozzles (420). Groups of marks (820/825) of a second predetermined pattern are printed (720) using a second group of nozzles (420). A region of overlap of the printed groups of marks is formed. At least a portion of the print medium (230) having printed groups of marks is imaged. From the region of overlap, first and second groups of marks from the first and second printed patterns are selected (740). For each group of marks, a position representative of that group is determined An offset for measuring spatial characteristics of the printer (200, 300) between the first and second printed patterns is determined (750) dependent upon the representative position of each of the first and second group of marks.

Abstract: Methods (200), apparatuses (700), and computer program products are disclosed for detecting the functionality of a plurality of ink ejecting nozzles of a printing device. A test chart is printed (210) using the ink ejecting nozzles of the printing device. The test chart comprises line patterns. Each line pattern is associated with an ink ejecting nozzle and varies in one-dimension. The printed test chart is imaged (220) to generate an imaged test chart. Each line pattern in the imaged test chart is distinguishable from adjacent line patterns. The imaged test chart is analyzed (240) to determine if each of the line patterns exists at an expected location in the printed test chart. If at least one line pattern does not exist at an expected location, the ink ejecting nozzle corresponding to the line pattern that is not functioning is determined.

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 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 (400) is disclosed for estimating an affine relation between a first image and a second image. The first and second images each have at least 4 non-parallel lines therein. The method (400) starts by identifying (406) sets of intersection points of the lines appearing in each of the images. The method (400) then determines (412) whether a relation between intersection points exists. If the relation exists then the first and second images are affine related and the affine distortion may be inverted (418).

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: 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: A method and system is disclosed for authenticating a physical medium (1405). The method starts by retrieving (1406) a reference digital signature (1412) previously determined (1403) based upon visual characteristics of an area (1402) of a reference physical medium (1400). A candidate digital signature (1415) is determined based upon visual characteristics of an area (1408) of the physical medium (1405), the area (1408) of the physical medium (1405) being at least partly corresponding to the area (1402) of the reference physical medium (1400). Weight values associated with different parts of at least one of the areas (1402 and 1408) are determined (201). Finally, the candidate digital signature (1415) is compared (1420) with the reference digital signature (1412), wherein the contributing of the parts in the comparison (1420) is based upon the weight values.