Abstract: An image signal processing apparatus and a method thereof are disclosed. The image signal processing apparatus includes a random producing unit which produces seed values to a plurality of frames input for a predetermined period by using a linear feedback shift register (LFSR), and a dithering processing unit which carries out a dithering to input image signals by using the seed values produced by the random producing unit. With this construction, the apparatus can carry out the dithering without using a frame buffer, thereby allowing a high-definition image to be realized.

Abstract: In a halftone module, it is judged whether or not the value “rate” for each pixel is greater than zero (0). In other words, it is judged whether or not the eight-bit input data Iin of each pixel is around a half of the relative density value for a small dot of a corresponding color. If the eight-bit input data Iin of the subject pixel is near to a half of the relative density value for a small dot, noise is added to the threshold values Ta, Tb, and Tc. The noise-added threshold values Ta?, Tb?, and Tc? are used in the comparing process.

Abstract: A method of building threshold matrices for stochastic screening by using the actual size and shape of imaged pixel and/or pixel agglomerate instead of the nominal one, in the stage of calculating appropriate threshold matrices. For each relevant combination of imager and imaged media, a matrix with desirable blue-noise-like characteristics is created from actual imaged pixels and/or pixel agglomerates, taking into account their overlap when placed in close proximity.

Abstract: A display system provides temporal stochastic dithering to image data for storage in a frame buffer for display. Stochastic dithering is used to reduce the size of the frame buffer and the complexity of the drive circuitry that is used to display an image in accordance with the image data. The bit depth of the frame buffer is reduced by spatially dithering image data for the image data before the image data is written into the frame buffer. Additionally, the displayed image is temporally dithered by using a different dither pattern for successive frames. Uncorrelated stochastic dither patterns are used to minimize detection of the dither patterns within the displayed image.

Abstract: Artifact reduction is achieved by altering the growth of sub-cells for each super-cell in either a pre-determined or random manner. The means of alteration is selected such that the sum of all the groups equals a halftone value. In another embodiment, the random group is selected by using predetermined patterns which are different among sub-cells, such as different means of constructing a dot. Preferably a different pattern is used in adjacent super-cells. In yet another embodiment, the method selects sub-cells patterns that are not aligned on the super-cell boundaries.

Abstract: The image-processing device comprises a quantization threshold produce unit producing quantization threshold values corresponding to each pixel of multivalued image data according to a dither threshold matrix, a random dither quantize unit quantizing the multivalued image data in multivalues by a random dither process using the quantization threshold values so as to output quantized data, and a resolution convert binarize unit converting the quantized data into binary image data having a resolution higher than that of the multivalued image data. The resolution convert binarize unit determines the number of dot-on pixels to be output in a plural-pixel field of the binary image data according to the quantized data value of a pixel being processed of the multivalued image data. The plural-pixel field corresponds to the pixel.

Abstract: The present invention relates to the manipulation of differential gloss as may be inherent in halftoned images by utilization of tags. By selectively applying halftones with anisotropic structure characteristics, which are significantly different in orientation while remaining identical in density, as directed by tag settings, a gloss image may be superimposed within an image without the need for special toners or paper. Conventional copier systems will not typically be able to copy such a superimposed gloss image.

Abstract: The present invention relates to the segmentation of an image into a main area and a image segment for variable glossmark data. By selectively applying halftones with anisotropic structure characteristics which are significantly different in orientation while remaining identical in density to the image segment, a variable glossmark may be superimposed within an image with reduced processing and storage requirements.

Abstract: A system and method for the halftoning of gray scale images by utilizing a pixel-by-pixel comparison of the image against an anisotropic stochastic screen is disclosed. The anisotropic stochastic screen comprises a non-deterministic, non-white noise function which, when thresholded, is designed to produce anisotropic dot patterns having a power spectrum characterized as having negligible low frequency components and a high-frequency region which has an absence of stronger dominant spikes.

Abstract: An image processing circuit compares a pixel value to a threshold value and modifies the pixel value if the pixel value has a predetermined relationship to the threshold value. Alternatively, the image processing circuit generates a random number and combines the random number with a pixel value. Such image processing circuits can be used to remove artifacts such as contour artifacts from a decoded electronic image or a sequence of decoded video frames.

Abstract: A method is provided for rendering a color image with a plurality of separations with a halftone process using a single screen. The screen is comprised of a plurality of pixel locations with associated threshold values and the image is comprised of a plurality of separation values. The method includes the steps of rendering a first one of the plurality of separations in accordance with the screen, wherein the plurality of pixel locations are turned on or off at a given pixel location based on a comparison of the image separation value at that pixel with the screen threshold value. The rendering of the next color separation is made in accordance with the rendering of the first separation and the screen, wherein for constant image separation values, pixel locations are turned on for the separation at pixel locations disposed in a highest available luminance region having a lowest available threshold value.

Abstract: The present invention relates to providing a designer with the tools for the manipulation of differential gloss in halftoned images. A special mask layer is provided for the rendering of desired glossmark image data. The desired glossmark image data is used to select between two halftones with anisotropic structure characteristics which are significantly different in orientation while remaining identical in density. This selection is made for each corresponding portion of primary image data. In this way, a halftone image of the primary image is generated with glossmarks imbedded therein which will display differential gloss without the need for special toners or paper.

Abstract: A display system provides stochastic dithering to image data for storage in a frame buffer for display. Dithering is used to reduce the size of the frame buffer and to reduce the complexity of the drive circuitry that is used to display an image. The bit depth of the frame buffer is reduced by spatially dithering image data before it is written into the frame buffer. Stochastic dither patterns (which are uncorrelated) are used to minimize adverse effects of the dither patterns within the displayed image.

Abstract: A method and system are disclosed for displaying Y-bit coded RGB image data that is received as X-bit coded RGB or YCbCr image data, where X>Y. The method includes receiving X-bit coded image data, where each color channel comprises m-bits; arithmetically processing the image data to include dithering noise values that result in maintaining the luminance of the image data substantially constant; converting the YCbCr image data to RGB image data, and quantizing the image data to Y-bit coded RGB image data where each color channel comprises n-bits. For example, X=24 and Y=12. The step of arithmetically processing includes, for the RGB case and for each pixel, generating an integer random number lying in the range of [?Q/2 . . . Q/2], where Q is a quantization step size; adding the random number to each of the Red and Blue color channels, and subtracting the random number from the Green color channel; and truncating and clipping the result in each color channel. Preferably, Q=2(m?n).

Abstract: A printhead controller controls printing of a page by at least one printhead. The printhead controller, in use, receives data, in a compressed format relating to the page to be printed, the data including a page description comprising a bi-level black layer and a contone color layer. The printhead controller extracts from the compressed data relating to the bi-level black layer the contone color layer. Memory is provided for temporary storage of the expanded data. A dithering/compositing unit produces a ditherer page from the data temporally stored in the memory and feeds its out put to the printhead.

Abstract: An image processing apparatus capable of providing an output image which is close to an actual image observed with human eyes is structured in the following way. An image data from an input unit is supplied from an output unit with a reduced number of gray levels. Based on an input value, an occurrence probability determining unit outputs dot occurrence probabilities d1-d3 for reproducing respective gray levels. Initial thresholds t1-t3 from an initial threshold generating unit are corrected based on a processed pixel in the vicinity of a pixel to be processed, and thus correction thresholds t?1-t?3 are derived. A selecting unit selects which dot is to be output based on the correction thresholds and occurrence probabilities.

Abstract: Halftone generating methods and systems convert continuous tone anti-aliased image data to halftone image data using halftoning techniques that efficiently use memory resources. One of a plurality of Holladay counters is selected and the address bits from the selected Holladay counter are output to a look-up table that efficiently stores various halftone screens. Halftone image data is then output. If necessary, the halftone image data is unpacked and replicated as required depending on the resolution requirements of the halftone screen.

Abstract: In a method for converting the coordinates of image data, the positions of new picture elements in a new coordinate system are calculated by means of coordinate transformation equations from the positions of initial picture elements in an initial coordinate system. The positions of the new picture elements are randomly modified in a variation range around the positions calculated by way of the coordinate transformation. For this purpose, random values are added to the calculated coordinates of the new picture elements. The method can be used in case of scale conversions, image rotation, etc. to improve the quality of the converted image. The method avoids both the corruption of the image structures caused by coordinate conversion and the formation of disruptive moire patterns. The method can be combined with known methods for calculating the color values of the new picture elements, such as the nearest-neighbor method or the interpolation method.

Abstract: An image processor unit minimizes image-quality degradation that can be caused by the addition of predetermined information to an image and that enables the predetermined information to be added to the image so that embedded information can be accurately extracted. The image processor unit includes an input unit for inputting the image; a plurality of quantization-threshold setting unit, of which occurrence probability distributions are different from one another, for setting quantization thresholds in terms of probability; a control unit for controlling a regularity for selection of the plurality of quantization-threshold setting unit in units of a predetermined image region according to the predetermined information; and a quantizing unit that uses quantization thresholds set by the quantization-threshold setting unit and thereby quantizes the image according to an error diffusion method.

Abstract: This invention relates to a color image dithering method and apparatus for producing an output point in an output color space corresponding to a selected vertex in a tetrahedron of a three-dimensional cubic subinterval of a pixel point in a source color space.

Abstract: A system and method for gray-scale or color printing is disclosed. One embodiment of the present invention transposes multiple pairs of pixels at the same time. During this process a record of the values of the cost function is kept. After a good statistical sample of multiple pairs of pixel replacements has occurred, the top five combinations are then selected for further refinement. During this next round of calculations the multiple of pairs of pixels transposed is reduced by a factor of two. In another embodiment of the present invention, the selection of the groups of pixels to transpose is controlled. During the initial iteration stages, a minimal radial offset of separation is imposed upon the pixel selection. Typically this minimum radial offset starts at one quarter of the array height. This selection process ensures that transpositions have the largest mixture around the array.

Abstract: A method for performing a digital multistage screening of a continuous-tone image with a screen having any desired screen resolution and any desired screen angle, in which the screening is carried out by reading out threshold values and comparing the threshold values read out with the color values of the continuous-tone image. Threshold value matrices are used in which the threshold values represent one or more screen dots of a given screen, with which the desired screen resolution and the desired angle are approximated. While the threshold values are being read out, an error between the coordinates of the desired screen and of the given screen is determined, and the error is compensated for by correcting the read address for the threshold value matrix, as soon as the error exceeds a predefined limiting value. Instead of the threshold value matrices, printing-value matrices can also be used.

Abstract: A method is provided for rendering a color image with a plurality of separations with a halftone process using a single screen for a plurality of separations. The screen is comprised of a plurality of pixel locations with associated threshold values and the image is comprised of a plurality of separation values. The method includes the steps of rendering a first one of the plurality of separations in accordance with the screen, wherein the plurality of pixel locations are turned on or off at a given pixel location based on a comparison of the image separation value at that pixel with the screen threshold value. The rendering of the next color separation is made in accordance with the rendering of the first separation and the screen, wherein for constant image separation values, pixel locations are turned on for the separation at pixel locations disposed in a highest available luminance region having a lowest available threshold value.

Abstract: A method of generating a stochastic screen for use in printing a halftone containing image on a surface, where the generated stochastic screen comprises an array of threshold values each of which represents a halftone threshold at which pixels are printed at the corresponding location. The method comprises a) entering a first threshold value into the array and b) for a first halftone level, defining a number of threshold values to be entered into the array and, for each threshold value to be placed, for each of a number of candidate locations in the array, computing a distance function between the candidate location and the locations of threshold values already placed into the array, and placing the threshold value into the array at a location for which the distance function is substantially minimized. The process of step b) is then repeated for each subsequent halftone level.

Abstract: A stochastic halftone pattern has been invented which has a narrow band power spectrum due to the incorporation of a dot growth process. The narrow band power spectrum may be matched to the resolution characteristics of specific printers, resulting in smoother printed halftone textures. The spectrum of a halftone pattern may be made anisotropic (angularly dependent), helping to de-couple sets of patterns for color printing with reduced color noise or mottle.

Abstract: A method and system for halftoning images that uses error diffusion with partial dots is provided. First, an input picture element (input pixel) that has a picture level (e.g., gray level) is received. Next, a reproducible gray level is generated based on the gray level of an input pixel. Then, a corrected gray level is generated based on the gray level of an input pixel and an error amount (e.g., error propagated or diffused from adjacent areas or pixels). A determination is made whether the corrected gray level is in a predetermined relationship with a threshold. When the corrected gray level is in a predetermined relationship with the threshold, the reproducible gray level (i.e., partial dot size) is provided as output. When the corrected gray level is not in a predetermined relationship with the threshold, a zero value is provided as output.

Abstract: The present invention relates to providing a designer with the tools for the manipulation of differential gloss in halftoned images. A special mask layer is provided for the rendering of desired glossmark image data. The desired glossmark image data is used to select between two halftones with anisotropic structure characteristics which are significantly different in orientation while remaining identical in density. This selection is made for each corresponding portion of primary image data. In this way, a halftone image of the primary image is generated with glossmarks imbedded therein which will display differential gloss without the need for special toners or paper.

Abstract: A technique is described to greatly reduce or avoid the quantization errors that occur when mapping a relatively linear RGB color space into a greatly non-linear printer CMY color space of equal precision, avoiding the contouring or banding that occurs when printing color gradients in a non-linear printing system. The technique performs a dither-like process on the original RGB continuous tone data. The RGB values are dithered to create a range of values that, when mapped to the non-linear printer continuous tone CMY values, creates a range of CMY values that, on average, represent the correct average tone of the input RGB values. The generated CMY continuous tone values are then halftoned and printed.

Abstract: A system and method for the halftoning of gray scale images by utilizing a pixel-by-pixel comparison of the image against an anisotropic stochastic screen is disclosed. The anisotropic stochastic screen comprises a non-deterministic, non-white noise function which, when thresholded, is designed to produce anisotropic dot patterns having a power spectrum characterized as having negligible low frequency components and a high-frequency region which has an absence of stronger dominant spikes.

Abstract: There is provided a pseudo-halftone image expression method capable of processing vector data with an excellent image quality and small computational complexity. Gray levels of n×n/m are expressed by varying the number of formed dots within a matrix of n×n dots on an m-dot basis (where n denotes an integer of 8 or more and m denotes an integer of 4 or more). A dot formation rule corresponding to each gray level within a matrix is divided into at least two stages, form a low gray level to a high gray level. In a first stage, dots are arranged at random and in dispersion so as to separate a dot from each other. In a second stage, dots are extended in random directions in turn so as to prevent an island of successive dots from coupling with each other using the dots arranged at the first stage as a nucleus.

Abstract: Halftone processing section carries out a halftone processing using a dither threshold plane on which thresholds in a predetermined threshold range corresponding to the tone range of input image data are arranged, and provides halftone-processed image data. Image output section has intrinsic, basic tone characteristics and outputs an image corresponding to the halftone-processed image data provided from the halftone processing section. The dither threshold plane consists of a plurality of same unit threshold matrixes and each of the unit threshold matrix consists of a plurality of sub-matrixes. An array of relatively low thresholds in the predetermined threshold range is equal among the plural sub-matrixes, and relatively medium thresholds and high thresholds in the predetermined threshold range are arranged periodically to extend over series of sub-matrixes.

Abstract: Selective edge softening and selective edge dithering is introduced into an image representation to improve local control where halo problems are expected. Selective areas of dilation are isolated and separately dithered or halftoned, the result of which is then swapped back into or substituted for the stored original image. In this manner misregistration and color plane-to-plane interactions can be compensated for in plural image forming station architecture systems. The same technique is also valuable in monochrome systems as an aid to overcoming edge displacement and slow toner problems when the selective edge softening is selectively applied to edges which are in particular perpendicular to the fast scan direction.

Abstract: A computerized method for controlling the density of pixels deposited by a print engine includes the steps of: (a) obtaining a two-dimensional pixel map of an image to be printed; (b) comparing a value of a first pixel element in the pixel map with values of pixel elements adjacent to the first pixel element in the pixel map; (c) changing the value of the first pixel element responsive to a determination, in the comparing step, that a predetermined number of pixel elements adjacent to the first pixel element have the same value as the first pixel element; and (d) dispatching the pixel map to a print engine. The comparing step (b) includes the steps of assigning like-value pixel elements immediately adjacent to the first pixel element a first weight, assigning like-value pixel elements diagonally adjacent to the first pixel element a second weight, different than the first weight, adding the assigned weights together to produce a total weight, and testing the weight against a predetermined threshold.

Abstract: This invention has as its object to realize multi-pass print control which requires a short processing time by a simple arrangement. To this end, a printer according to this invention attains multi-grayscale print control by changing the number of dots to be printed on each pixel to overlap each other in multi-pass print control that prints the pixel in a plurality of scans. In this case, index patterns, each of which designates which of scans is to be used to print in accordance with the density level of a pixel, are prepared for respective pixel values. If a plurality of patterns are prepared for each pixel value, a pattern is randomly selected from them. An image is printed in accordance with a print pattern defined by the selected pattern.

Abstract: A circuit for generating a threshold bias signal for processing n color separations representing a color image includes a threshold bias register which holds and outputs the current threshold bias signal.

Abstract: The present invention relates to the manipulation of differential gloss as may be inherent in halftoned images. By selectively applying halftones with anisotropic structure characteristics which are significantly different in orientation while remaining identical in density, a gloss image may be superimposed within an image without the need for special toners or paper. Conventional copier systems will not typically be able to copy such a superimposed gloss image.

Abstract: A stochastic halftone pattern has been invented which has a narrow band power spectrum due to the incorporation of a dot growth process. The narrow band power spectrum may be matched to the resolution characteristics of specific printers, resulting in smoother printed halftone textures. The spectrum of a halftone pattern may be made anisotropic (angularly dependent), helping to de-couple sets of patterns for color printing with reduced color noise or mottle.

Abstract: When clustered-dot dithering is employed in laser printers a banding effect sometimes results from the interaction of the dither matrix with non-uniform line spacing in the printer. We have found that we can lessen the effect of this interaction if we change the dither matrix as it moves over the image. We do this by modulating the dither matrix (halftone cell) as a function of the spatial position of the sub-area in the image. Halftone cells can be formed in a variety of patterns (e.g. vertical, horizontal, etc.) but generally their threshold values grow from a minimum value to a maximum value. Our process is to modulate the halftone cell according to a function: f (s, h) where s is the spatial position of the sub-area of the image and h is the halftone cell. We modulate the cell by altering the relative positions of the threshold values in the cell as we move the cell over the image.

Abstract: A stochastic halftone pattern has been invented which has a narrow band power spectrum due to the incorporation of a dot growth process. The narrow band power spectrum may be matched to the resolution characteristics of specific printers, resulting in smoother printed halftone textures. The spectrum of a halftone pattern may be made anisotropic (angularly dependent), helping to de-couple sets of patterns for color printing with reduced color noise or mottle.

Abstract: A technique combines most of the advantages of both blue noise and clustering in generating a partially clustered aperiodic mask and using it in a dither array algorithm for halftoning, such that the amount of clustering can be modulated. A method to create an enlarged partially clustered aperiodic dither mask, appearing as a modulated version of a periodic enlargement of original mask, is used when the original mask generates patterns that are not visually pleasing or the original mask doesn't generate enough distinct grey levels. The method of halftoning of grey scale images utilizes a pixel-by-pixel comparison of the image against a partially clustered aperiodic mask in which the clustered aperiodic mask is comprised of a partly random and partly deterministic single valued function which is designed to produce visually pleasing dot configurations when thresholded at any level of grey.

Abstract: A computer implemented method to include microscopic perforations (perforations) in an printing plate is revealed. The particles improve the properties of the plate towards printability of an image on different kinds of offset presses. The perforations are formed by perforations which are added in a fully digital way. Aspects of the invention include of three alternative embodiments for include the repelling particles, and these alternative embodiments may be uses alone or in combination depending on the user's preferred workflow. The third alternative embodiment adds the perforations through an additional layer in the page description, this layer comprising a pattern which erases small particles in the original design elements. The first alternative embodiment adds the perforations through a modified screening method. The second alternative embodiment includes perforations into existing bitmaps.

Abstract: A stochastic screening mask is provided for rendering halftone images. A filter controlled force masking method is used to vary the mask patterns from regularity to randomness. Dot size (amplitude), dot number (frequency), and dot shape are modulated integrally at each gray level during the generation of the mask. The single pixel limit for blue noise masking is broken down by this approach. The halftone patterns generated with this method can have visually pleasing blue noise attribute. This new screening method would provide flexible solutions for different types of printing processes.

Abstract: A frequency-modulation halftone screen and method for making same, utilizing local randomization of a deterministic screen. The deterministic screen optimizes uniformity of the halftone dot distribution, while the local randomization suppresses artifacts due to subject moiré.

Abstract: A method and system for designing a plurality of correlated stochastic screens or conjugate screen portions intended for use in color halftoning of a corresponding plurality of color separations. A merit function is associated with each screen or screen portion. The merit function represents a measure of the desirability of the screen, particularly with regard to maximizing ink dispersion and optimizing spatial frequency response. An additional merit function value is associated with a combination of the screens and screen portions. Additional merit function represents a measure of desirability of the screen combination with regard to ink dispersion and combined spatial frequency response. The merit functions are iteratively applied to possible screens until an optimized merit value is calculated. The screens are selected that correspond to the optimized merit value. The image is generated using the selected screens in a conventional color halftoning process with a plurality of color separations.

Abstract: A method for halftoning a gray scale image to generate a halftoned image uses a stochastic screen is designed to provide visually pleasing, blue noise dot profiles when thresholded at any gray level and wherein substantially all the threshold values corresponding to gray levels between gs1 and gs2 coincide with black positions in a constraining checkerboard pattern and substantially all the threshold values corresponding to gray levels between gs2 and gs3 coincide with white positions in the constraining checkerboard pattern.

Abstract: A method and apparatus for producing halftone images which utilizes the advantageous stochastic patterning of dots found in frequency-modulated, blue-noise masks, and avoids the problem of dot gain provided in amplitude-modulated masks. Here a green-noise spectrum is used to generate a dither mask and the halftone patterns for each gray-level are subjected to the stacking constraint. The filters used in building the green-noise masks comprise filters using the conventional blue-noise mask for a coarseness parameter M′(g)=1 and filters having a principle frequency fg less than the principle frequency of blue-noise fb when coarseness parameter M′(g)>1. Unlike blue-noise dither patterns, green-noise dither patterns comprise pixel clusters, making them less susceptible to image degradation from dot gain, generating dot-profiles that are visually pleasing to the human eye.

Abstract: A method for compensating for dot gain in printing with stochastic screens comprises obtaining continuous tone CMYK files and screening the files at a resolution that is lower than the resolution of an output device that will be used to print the files. The lower resolution stochastically screened files are then expanded to the resolution of the output device, thereby effectively increasing the size of the dots by creating a number of subdots for each dot in the lower resolution stochastically screened files. Subdots within the expanded stochastically screened files can then be selectively removed to compensate for dot gain. In addition, overlapping dots in the screened CMYK files are removed and additional stochastically screened files are created that print a dot of a color of the previously overlapping dots and at the location of the previously overlapping dots to prevent colors from running together when printing on certain media.