Abstract: Techniques for estimating an average background value and an average foreground value of an image data formed by a plurality of pixels by selecting a first plurality of pixels forming a first calculation window from the plurality of pixels, determining at least first, second and third statistical moments for the first plurality of pixels, and determining at least one of average background value and average foreground value using the at least first, second and third statistical moments determined for the first plurality of pixels.

Abstract: Apparatus and methods that adjust image data for show-through image information of an image on a front side of an image bearing substrate having image data on a back side and on an adjacent side of a backing substrate, e.g., the pages of a bound volume. Image data for a front side image, a back side image and an adjacent side image is obtained from an optical sensor that senses light reflected from the image bearing substrate. The image data is stored in a memory and is used to determine scanned density data and approximate absorbency data for the respective sides of the substrates. Show-through compensated density data for the front side image is computed by filtering the absorbency data for the back and adjacent side with a filter characteristic of the show-through characteristics of the image bearing substrate and subtracting this filtered absorbency data from the front side scanned density data.

Abstract: In an imaging apparatus such as a scanner or digital camera, a photosensitive device includes multiple linear arrays of photosensors. One of the arrays has a higher spatial resolution than other arrays. The high-resolution array is filtered to detect different portions of the color spectrum than the low-resolution arrays.

Abstract: A method and apparatus are described for detecting photocopier tracking signatures placed on documents produced by color photocopiers. The apparatus includes an input terminal that supplies digital image data representing an input document produced by a color photocopier. The digital image data includes a plurality of pixel values grouped together to form a plurality of color separations that represent the input document. The apparatus also includes an image processing unit that generates an output image based on the digital image data. The image processing unit generates the output image based on differences between corresponding pixel values of at least two of the plurality of color separations. The apparatus further includes an ouput terminal for displaying the output image to view the photocopier tracking signature. Color differences can be detected by combining two or more of the color separations into a resulting monochromatic image and then enhancing the resulting color differences.

Abstract: Techniques for estimating an average background value and an average foreground value of an image data formed by a plurality of pixels by selecting a first plurality of pixels forming a first calculation window from the plurality of pixels, determining at least first, second and third statistical moments for the first plurality of pixels, and determining at least one of average background value and average foreground value using the at least first, second and third statistical moments determined for the first plurality of pixels.

Abstract: A method and apparatus are provided for enhancing JPEG compressed digital image data wherein only the DC components of the compressed image data are required to obtain a statistical subsampling of the corresponding uncompressed image data. JPEG compressed image data are received that represent an input digital image, and the JPEG compressed image data include a plurality of DC components. DC components are extracted from the JPEG compressed image data, and the extracted plurality of said DC components represent a subsampling of the input digital image. At least some of the plurality of extracted DC components are input to an automated image enhancement system. The DC components input to the automated image enhancement system are used to derive at least one of a final correction tone reproduction curve and a sharpness filter for enhancement of the input digital image represented by the JPEG compressed data.

Abstract: A method and apparatus are described for detecting photocopier tracking signatures placed on documents produced by color photocopiers. The apparatus includes an input terminal that supplies digital image data representing an input document produced by a color photocopier. The digital image data includes a plurality of pixel values grouped together to form a plurality of color separations that represent the input document. The apparatus also includes an image processing unit that generates an output image based on the digital image data. The image processing unit generates the output image based on differences between corresponding pixel values of at least two of the plurality of color separations. The apparatus further includes an ouput terminal for displaying the output image to view the photocopier tracking signature. Color differences can be detected by combining two or more of the color separations into a resulting monochromatic image and then enhancing the resulting color differences.

Abstract: Visible digital watermarks enable a robust tracking method to be associated with one or more input images. Specifically, by modifying a halftone screen within a certain area by setting a gray-scale range within that area to a threshold, and halftoning an input image based on this modified halftone screen, visible watermarks can be embedded into an input image.

Abstract: A method and apparatus are described for detecting photocopier tracking signatures placed on documents produced by color photocopiers. The apparatus includes an input terminal that supplies digital image data representing an input document produced by a color photocopier. The digital image data includes a plurality of pixel values grouped together to form a plurality of color separations that represent the input document. The apparatus also includes an image processing unit that generates an output image based on the digital image data. The image processing unit generates the output image based on differences between corresponding pixel values of at least two of the plurality of color separations. The apparatus further includes an output terminal for displaying the output image to view the photocopier tracking signature. Color differences can be detected by combining two or more of the color separations into a resulting monochromatic image and then enhancing the resulting color differences.

Abstract: In an imaging apparatus such as a scanner or digital camera, a photosensitive device includes multiple linear arrays of photosensors. One of the arrays has a higher spatial resolution than other arrays. The high-resolution array is filtered to detect different portions of the color spectrum than the low-resolution arrays.

Abstract: An oversize document, one that is larger than the platen of the scanner, can be scanned in several segments then stitched together electronically. A method is described to analyze the scan segments to determine the orientation, magnification and translation of the different scanned segments to be stitched together. Operator assistance is required to identify salient features in the different segments to be analyzed. The location of these features is determined by calculating the centroid from a rough crop of each feature. The orientation, magnification, and translation of the scanned segment can all be determined from a comparison of the locations of the identified features. The segments are blended together with standard blending techniques.

Abstract: A method is described to combine together at least two continuous tone digital images into a combined digital image. When viewed in the standard manner, the combined image appears to be the first of the two images. The second image cannot be seen. When the bits within each pixel of the combined image are reversed, i.e. the least significant bit (LAB) is exchanged with the most significant bit (MB), and the resultant image is viewed, then the second image is seen. In this way, one image can be hidden inside the noise bits of another image. The method is applied to color images by treating each color separation independently. The encoding of one image into the other, while maintaining good image quality is accomplished using two simultaneous error diffusion calculations to determine the single output value for each pixel.

Abstract: An image processing method and system for mitigating the effects of show-through in scanning multiple two-sided documents during book scanning applications in a scanning system. With the disclosed system and method: a scanned first side image P is derived from a first side image A of a duplexed document and a scanned second side image Q is derived from a second side image B of the duplexed document, where at least first side image P includes a component attributable to show-through from said second side of said document, and storing images P and Q; a scanned first side image R is then derived from a first side image C of a subsequent duplexed document and a scanned second side image S is derived from a second side image D of said subsequent duplexed document, and at least the first side image R included a component attributable to show-through from the second side of the subsequent document.

Abstract: An image processing method for mitigating the effects of show-through in scanning a duplexed document in a duplex scanning system, including: deriving a scanned first side image P from a first side image A of a duplexed document and a scanned second side image Q from a second side image B of the duplexed document, at least the first side image P including a component thereof attributable to show-through from the second side of the document, and storing images P and Q; from second side image Q, generating a representation thereof corresponding to the show-through contribution to first side image P; processing image P to remove show-through as a function of the representation Q, thereby deriving correct image A.

Abstract: This invention discloses a method of correcting the measurement of the amount of light reflected by a document that is being processed by a digital image acquisition apparatus. A typical image acquisition apparatus measures the amount of light reflected from the surface of the original document and sets a corresponding set of electrical signals to a printing or storage module. Image acquisition usually requires illuminating the original document with a reflecting cavity, which causes the measurement of the amount of light present on the surface of the document to become distorted. The method disclosed by the present invention corrects this phenomenon by calculating the amount of light that reaches the surface of the original document by being reflected from the illumination system and the surrounding cavity. This allows the measured reflectance to be corrected, and the true reflectance to be used for subsequent output or storage.

Abstract: A method for generating watermarks in a digitally reproducible document which are substantially invisible when viewed including the steps of: (1) producing a first stochastic screen pattern suitable for reproducing a gray image on a document; (2) deriving at least one stochastic screen description that is related to said first pattern; (3) producing a document containing the first stochastic screen; (4) producing a second document containing one or more of the stochastic screens in combination, whereby upon placing the first and second document in superposition relationship to allow viewing of both documents together, correlation between the first stochastic pattern on each document occurs everywhere within the documents where the first screen is used, and correlation does not occur where the area where the derived stochastic screens occur and the image placed therein using the derived stochastic screens becomes visible.

Abstract: A processing system for processing electronic images defined in terms of image signals, each image signal representing density at a discrete position within the electronic image, and quantizing image signals defined at "c" gray levels for use in a device requiring image signals defined at "d" levels, where "d" may be less than or equal to "c", the system including an image input receiving at least a portion of the electronic image as input signals; an error adding circuit, adding error signals determined from any previous thresholding processing to the input signals to generate corrected input signals; a thresholding processor, receiving corrected image signals defined at "c" levels, and quantizing the corrected image signals to "d" levels, by comparison to at least one threshold signal and outputting the corrected image signals at "d" levels as output signals; an image output, outputting output signals defined at "d" levels; a differencing circuit, generating a difference signal representative of the differe

Abstract: A calibration system, for calibrating a printer response to halftone images directed thereto, includes a test pattern, stored in a memory, providing a plurality of samples of combinations of printed spots, printable on a media by the printer; a gray measuring device, to derive a gray measurement of the samples of printed spots; a calibration processor correlating gray measurements with a particular combination of spots, and deriving parameters describing the printer response to the particular combination; generating at least one gray image correction, including a set of correction values selected in accordance with said the described printer response, and a calibration memory, storing the generated halftone patterns.

Abstract: An image processing method for mitigating the effects of show-through in scanning a duplexed document in a duplex scanning system, including: deriving a scanned first side image P from a first side image A of a duplexed document and a scanned second side image Q from a second side image B of the duplexed document, at least the first side image P including a component thereof attributable to show-through from the second side of the document, and storing images P and Q; from second side image Q, generating a representation thereof corresponding to the show-through contribution to first side image P; processing image P to remove show-through as a function of the representation Q, thereby deriving correct image A.

Abstract: A method and arrangement for the application of under compensated error diffusion to a pixel quantizing method in the conversion of image data from a number of input levels that is relatively large with respect to a number of desired output levels.