Abstract: A codec that compresses video data by tiling a digital representation or frame into blocks and encoding the difference between each pixel value in an image block that is not subject to special treatment and the block minimum value using an adaptive dispersed dither. Higher output quality can be obtained by changing the dither matrix from frame to frame. Certain blocks are encoded differently to further conserve bits. Constant blocks, which are blocks in which the difference between the maximum and minimum pixel values in that block is less than a predefined threshold, are encoded differently. Blocks in which all pixels are within a predetermined distance of either the maximum or minimum block value, referred to as binary-like blocks, are encoded using a single bit. The overall coding scheme can be modified even further to accommodate a fixed bit budget for the compressed output. Other features can also be supported including contrast and brightness adjustment and accessing/decoding random blocks.

Abstract: Nozzle scheduling algorithms that provide a unified approach to designing nozzle firing algorithms that incorporate a variety of specifiable nozzle-firing constraints such as print head (nozzle) geometry, nozzle spacing, number of nozzles, head movement (number of passes), ink-media interaction, etc. Such constraints are provided as design rules for a given printer/output medium, and the result is an appropriate nozzle firing algorithm. The design algorithms may be used to generate nozzle firing sequences in a halftone-dependent or halftone-independent manner.

Abstract: A fast technique utilizes overcomplete DCT representations and performs de-blocking, de-noising and de-blurring by thresholding and transforming the transform coefficients to process images obtained from inexpensive sensors/cameras with low-quality compressed image output. A color balance algorithm is used to compensate for hue shifts. Quality differences between color channels and inter-channel correlations are exploited to significantly reduce computational requirements and yield a high-performance technique for processing such images before printing.

Abstract: Techniques for removing from scanned film regions of “missing data” which may include date regions, or may be the result of spots, scratches or folds on the film. Such techniques are particularly designed to handle larger regions of missing data, such as “thick” scratches. The techniques of the present invention segment missing data regions (which may include characters in a date field) and perform component filtering which involves determining the area/perimeter ratio of each segmented missing data region. Only those regions whose area/perimeter ratio is less than a certain threshold are kept for closest-to-radial-based-function (CRBF) filtering to estimate colors from neighboring pixels to fill in the missing data regions.

Abstract: Digital data is rapidly embedded in color/grayscale digital data by switching between a set of multi-level screens or quantizers. Each screen can be tuned to maximize the quality of the digital data product on the intended display medium, so that the quality of the displayed product does not suffer. The data embedding method/algorithm of the invention generally involves generating a set of multi-level screens, each of which is generated by selecting a set of colors that comprise the colors that can be output by that multi-level screen; screening the input digital medium with the generated multi-level screens using a dither matrix and a set of level matrices; and selecting, for each of select number of pixel locations in the input digital medium, one of the level matrices, based on a message symbol to be embedded at that pixel location, to create an output.

Abstract: An adaptive halftone scheme is applied to a compound document to smooth the rendering while preserving edge sharpness. The adaptive halftone scheme involves identifying document regions as either smooth, edge or texture. Each identified region is then processed as follows. Wherever a smooth region is adjacent to an edge region and wherever a smooth region is adjacent to a texture region, create a transition region in a portion of that smooth region bordering that other region and apply a blend of a screening halftone technique (SCN) and an error diffusion with screening halftone technique (EDSCN) to that transition region, apply SCN to the remainder of that smooth region, apply ED to that other region if it is an edge region, and apply either EDSCN or SCN if it is texture region.

Abstract: A method/algorithm enables the rapid development and tuning of multi-level and multi-frequency halftone screens to improve printer performance. The screens are primarily directed to laser printers. The method/algorithm generally involves generating a lattice of points by selecting a plurality of points along an imaginary line whose path extends along a surface of a geometric shape; assigning a dot shape to each of the lattice points; selecting a growth model for each dot shape; quantizing the lattice points and assigned dots to a specified grid of pixels; and generating multi-frequency screens from the lattice of points and associated dots.

Abstract: A differential color or luminance signal is used to embed a binary message in selected stroke segments in the text of a document and for extracting a message so embedded. The bits representing the message are embedded in the stroke segments by modifying a color or luminance value of pixels in one region of a selected stroke with respect to such a value of pixels in a second region of that stroke. To determine whether a bit is embedded in a stroke segment, a value representative of the luminance or color of pixels in the one region is compared with a value representative of the luminance or color of pixels in the second region. The presence or absence of a bit is determined by whether the difference between the two values is greater than a minimum predetermined threshold.

Abstract: The appearance of edges in an image is improved through precise placement of subpixels within pixel cells that are located on or near edges in an image. Image data is examined to identify a “target pixel” near the edge of an object that represents the object and is adjacent to a “background pixel” that represents only background. The target pixel may represent both the object and its background or it may represent the object only. A “second pixel”, adjacent to the target pixel and representing the object, is also identified. The second pixel may represent both the object and its background or it may represent the object only. The target pixel's location with respect to the second pixel is analyzed to determine the placement of a subpixel within the target pixel cell and the placement of a subpixel within the second pixel cell, such that the edge of the object is well-defined and the density of the object is preserved.

Abstract: We improve text reproduction of a scanned and printed image by identifying text-contribution colors and also image-contribution colors that are in or near the text region of the color space. When input colors are encountered that contribute both to text and image we splice together text and image color transformations of the input color to produce a color in the printer color space. We improve background reproduction, i.e. reduce bleed-through artifacts, by identifying background-contribution colors and also image-contribution colors that are in or near the background region of the color space. When input colors are encountered that contribute both to background and image we splice together background and image color transformations of the input color to produce a color in the printer color space.

Abstract: An apparatus and method for improving a color space transformation between an input device such as a scanner and an output device such as a printer. The color space transformation includes a first three-dimensional look up table that receives color information from the input device and transforms colors specified in an input device color space into colors in a device-independent color space, and a second three-dimensional look up table that receives colors from the first three-dimensional look up table and transforms colors specified in a device-independent color space into colors in an output device color space.

Abstract: A photo extraction technique is provided that scans film contained within a holder designed to accommodate that particular size and type of film and generates a low-resolution scan of the film and holder. The low-resolution scan is then processed by detecting the borders of the holder, applying a smoothen filter, detecting edge segments of the image-holding areas in the holder, identifying each of the image-holding areas, determining the orientation of the image-holding areas and correcting the orientation thereof if necessary, and locating each of the individual photos within the image-holding areas. Having identified and extracted the photos, an index page comprising thumbnail images of the photos is generated. From this page, the user can select one or more of the images to be printed or displayed in high-resolution.

Abstract: A color image reproduction system achieves higher-quality color reproduction by improving the utilization of colors within the gamut of an output device that are not in the gamut of an input device. This is accomplished by a device-dependent compensation transformation that maps a second set of colors in both the gamut of an input device and the gamut of the output device into a first set of colors in the gamut of the output device but not in the gamut of the input device. The compensation transformation may be derived in a number of ways that entail identifying the first and second sets of colors and then determining one or more scaling factors that map the second set of colors into a union of the first and second sets of colors.

Abstract: An image processor (14) in a photocopier (10) takes composite input image (20a) that includes a plurality of skewed sub-images (22a, 24a, and 26a). It revises the image so as to produce an output composite image (20b) containing aligned sub-images (22b, 24b, and 26b). To identify the input image's sub-images, the image processor (14) identifies connected groups (44, 48 and 54) of pixels that meet certain criteria, and it eliminates from consideration each group (48) whose bounding box (50) is included within the bounding box (46) of another connected group (44). Skew angles for the different sub-images are determined by finding the best-fit lines through the outline pixels of their respective connected groups, and the sub-images are de-skewed by the negatives of those lines' angles.

Abstract: A scanner (12) derives a digital image of a document that it scans optically, an image-processing circuitry (14) extracts a representation of a non-planner graph. A small-processor “smart card” derives from the first graph a second graph that is isomorphic to it and related to it in accordance with a secret permutation matrix. The image processor 14 then embeds a representation of that graph into the image and sends the results to a printer (16) to generate a copy. A second scanner (30) generates a digital image of the copy, and processing circuitry (31) extracts the two isomorphic graphs, which it conveys to a verifier circuit (36) as well as the smart card (22). By repeatedly generating and submitting to the verifier (36) test graphs that are isomorphic to the extracted graphs, the smart card (22) can demonstrate, without revealing the secret permutation matrix, that it is in possession of that permutation matrix.

Abstract: Pattern detection methods, which may be embodied in copiers or scanners/printers, examine documents to be copied or printed to determine whether the documents contain one or more targeted patterns. The pattern detection methods include algorithms that look for certain features and geometric relationships between the features in determining whether one or more of the targeted patterns are present.

Abstract: Pattern detection methods, which may be embodied in copiers or scanners/printers, examine documents to be copied or printed to determine whether the documents contain one or more targeted patterns. The pattern detection methods include algorithms that look for certain features and geometric relationships between the features in determining whether one or more of the targeted patterns are present.

Abstract: In an image reproduction system, an image processor analyzes a hierarchy of image representations of different resolutions to detect edges. In regions having edges that are detected in all hierarchical representations, little or no filtering is applied to the image. In regions having no edges or edges that are detected in only the highest-resolution representation, greater amounts of filtering are applied to the image. In regions having edges detected in two or more but not all hierarchical representations, an intermediate amount of filtering is applied to the image. In preferred embodiments, two-dimensional averaging filters of varying size are applied to the image. The size of the averaging filter is selected according to the number of hierarchical representations in which an edge is detected.

Abstract: A recalibration transformation is derived for a color image reproduction system having an input device and an output device by obtaining a medium conveying a selected color within a current gamut of the output device represented by first values in a first color space, scanning the medium with the input device to obtain second values representing the selected color in a second color space, applying a calibration transformation to map the second values to third values in the first color space, deriving an error transformation that maps from the first values to the third values, and deriving the recalibration transformation from an inverse of the error transformation that maps from the third values to the first values.

Abstract: Dither thresholds are assigned one after the other to matrix locations in the process of generating a dither matrix used for printer half-toning. The matrix location to be assigned the next threshold is chosen by locating the tightest cluster or largest void in the dot pattern that will result from the gray level with which the threshold being assigned is associated. Measures of cluster tightness for low-range and high-range thresholds are based on the areas of Voronoi partitions associated with respective candidate locations. For mid-range thresholds, a Gaussian-filter output is used as the measure. In both cases, ties between candidate locations are resolved by applying a further criterion, which depends on the candidate locations' proximities to locations assigned thresholds the same as the one being assigned or differing from it by only one.