Abstract: This invention relates to an image processing method of quantizing a multivalued image to perform image processing. The luminance frequency of the multivalued image is calculated, a quantization threshold for quantization is specified on the basis of the calculated luminance frequency, a representative value used for quantization of the multivalued image is calculated on the basis of the specified quantization threshold and the luminance frequency, and the multivalued image is quantized using the calculated representative value. The quantization threshold is an average luminance value obtained when the histogram distribution converges to make the skew of the histogram distribution of the luminance frequency fall within a predetermined range. The representative value is an average luminance value in each distribution region of the histogram distribution of the luminance frequency that is divided by the quantization threshold.

Abstract: A multi-level input image is divided into blocks, each of which is quantized to a bi-level output block. A single quantization error value is calculated for each block, and distributed over neighboring blocks that have not yet been processed. Blocks containing abrupt changes in image content are preferably converted by comparing each picture element individually with a threshold value. Blocks not containing abrupt changes are preferably quantized by comparing the average value of the block with multiple threshold values to determine a multi-level block output value, from which a predetermined pattern of bi-level picture elements is generated.

Abstract: An image processing apparatus includes a first detection unit for detecting an edge of an input image on the basis of an input image signal, a second detection unit for detecting a screen portion of the input image on the basis of the input image signal, a processing unit for executing processing of the input image signal according to detection results of the first and second detection units, and a setting unit for setting detection modes of the first and second detection units.

Abstract: Periodic inking artifacts are reduced by randomness introduced into an image-processing stage. This goes beyond providing a fixed pattern earlier derived through random processing; rather the system literally introduces randomness or at least pseudorandomness into the image-processing stage. Preferably a superpixel is selected, essentially at random, from a plurality of superpixels—at least for points with an intermediate tonal level, which is the part of the tonal range where dot-placement error is most conspicuous. If image scaling or some other reason for using superpixels (and starting with a coarse grid) is not present, the randomness-introduction approach preferably includes preparing the image using a pixel grid that is coarser than the available printer resolution. The selected superpixel is applied at the coarser grid to define a set of individual pixels at printer resolution.

Abstract: An image processing apparatus including an input unit for inputting multi-valued input image data, a quantization unit for quantizing the input image data input by the input unit into output image data having a number of levels which is smaller than that of the input image data, and a correction unit for correcting a quantization error which occurs during a quantization process of the quantization unit, the correction unit correcting the quantization error by diffusing an error amount into input image data which have not yet been quantized by the quantization unit, wherein the correction unit periodically varies the error amount to be diffused into the input image data within a range of values up to and including the quantization error.

Abstract: A method and apparatus are provided to allow threshold values needed for the desired number of gradations to be set through a simple process when converting image data with numerous values into a low number of gradations. The desired number of gradations is achieved without shading being noticeable even for images having shading. The cumulative frequency distribution of the pixels for each brightness is determined from image data having a brightness range with designated gradations. The average brightness and standard deviation of the portion that is primarily background is determined from this cumulative frequency distribution. The first threshold value is determined on the basis of this average brightness and standard deviation, the second through n-1st threshold values corresponding to the meaningful information are determined on the basis of this first threshold value. An n value conversion process is accomplished using these threshold values.

Abstract: A dithering device converts a multi-gradation image into a binary image by comparing, in sequence, values of pixels forming the multi-gradation image with threshold values of corresponding elements forming a dither matrix. For determining the element corresponding to the pixel, the dithering device uses an array representing a relationship between a first group of positions of the elements to be used currently and a second group of positions of the elements to be used next. By referring to the array, the dithering device determines the position of the element from the second group based on the position of the element in the first group so as to compare the next pixel with the threshold value of the determined element.

Abstract: There is provided an image processing apparatus such as facsimile apparatus or digital copying machine for digitizing image data into two values or multi-values. The apparatus comprises: an input device to input data of a target pixel to be digitized; a calculating circuit to obtain an average density value of a predetermined region; a digitizing circuit such as a binarizing circuit for digitizing or binarizing the target pixel data on the basis of the average density value obtained by the calculating circuit; and a correction circuit to correct a difference which occurs upon digitization by the digitizing circuit. The calculating circuit calculates the average density value m.sub.1 of the pre-determined region when the target pixel data was binarized to 1 and the average density value m.sub.2 of the predetermined region when the target pixel data was binarized to 0 by using a predetermined weighting mask. The digitizing circuit binarizes the target pixel data by using (m.sub.1 +m.sub.

Abstract: Digital image data read in by an image scanner is added with a binary error calculated by a peripheral error weighting filter in an error adder to correct binary error. The corrected data is compared with a predetermined threshold value T.sub.0 by a comparator provide output as binary data. A binary error calculation unit calculates a binary error according to the output binary data and error correction data, which is fed back to the digital image data. A variable base value calculation unit for providing to the binary error calculation unit a base value to calculate calculation error and a maximum value/minimum value detection unit are provided outside the feedback loop.

Abstract: There is disclosed an image processing apparatus such that after completion of one scan of a scanner unit, a controller obtains a background value in a range to be read by one scan from an image processing IC and compares the background value with a binarization threshold value used in the present scan, and when it is equal to or less than a predetermined value, the background value is used in the next scan, and when it is equal to or larger than the predetermined value, by correcting the threshold value, an image can be read at a high quality.

Abstract: Input image data is stored in a register matrix of 7.times.7 in a successive manner. A pattern detecting section detects a black- or white-pixel connective pattern of the reference pixels of a marked pixel. When the reference pixel pattern is a black-pixel connective pattern of 1:n (n=1, 2, 3, . . . ), an enlarging/smoothing processor section interpolates a part of the enlarged marked pixel with black pixels. When it is a white-pixel connective pattern of 1:n (n=1, 2, 3, . . . ), the enlarging/smoothing processor erases a part of the enlarged marked pixel. As a result, the oblique line can be smoothed. The line that is made thick by the smoothing process can be shaped into a thin line. Thus, a high-quality image can be produced.

Abstract: An image processing method for automatically executing operation steps of repairing a defect of an image of a document which is read by a scanner and changing a background image in a short time and a recording medium for storing them. An image processing method comprising a step of separating background image data from said image data by processing by a maximum filter for comparing the brightness of each pixel constituting said image data with the brightness of peripheral pixels and replacing it with the maximum brightness; and a step of separating character and figure image data by subtracting the background image data obtained by the above step in (a) from the above image data.

Abstract: Document image thresholding using foreground and background is disclosed. A document (16) is scanned and a region (30) and a sub-region (32) of the document is selected. The intensity value of a pixel in the region is compared to an average intensity value of pixels in a foreground cluster and to an average intensity value of pixels in a background cluster (50). The pixel is assigned to the foreground cluster (53) if the intensity value of the pixel is closer to the average intensity of the foreground cluster, or to the background cluster (54) if the pixel intensity is closer to the average intensity value of the background cluster. A new average intensity value is calculated for the foreground cluster (55) and the background cluster (56). A new pixel is compared to the new average intensity values for the foreground and background clusters and the process is repeated until all pixels in the region have been compared (57).

Abstract: A dither method converts multi-bit grey level pixel values into an image array of binary level pixel values, wherein the image array is arranged as a raster of scan lines.

Abstract: A technique which combines the advantages of blue noise and clustering obtains more pleasant "blueish" effects in the rendering of the grey levels for which the original multicell mask generates unwanted periodic representations. Such original multicell clustered dither array patterns which are undesirable are replaced by less periodic ones while preserving all benefits of the classical methods, and in particular, leaving the nicest patterns unchanged. An automated process redistributes the locations of the threshold values corresponding to undesirable grey levels to obtain more pleasant "blueish" effects in the rendering of the grey levels.

Abstract: A dispersed-dot stochastic dither array is provided for rendering halftone images having excellent visual quality and are created by a minimum density variance method. By minimizing the variance in the number of dots within each local region of the image, a smooth and dispersed distribution of dots may be obtained. For color printing, a separate threshold array is generated for each of the color planes, however, the stochastic screens are interlocked so that the threshold arrays are generated while considering the other color threshold arrays. In this manner, a blue noise distribution may be produced by the individual arrays as well as by any combination of the individual arrays. When generating a single threshold array for a color plane, a particular criterion is used to determine where the next threshold value should be located, and the selection of a threshold location in each array considers the criterion for all the threshold arrays being generated.

Abstract: In case of subjecting input graduation image data of 8 bits per pixel to multilevel dither processing, to convert them into image data having gradients of 3 bits per pixel on the basis of dither threshold planes, in a combination of threshold arrays extending over the plural dither threshold planes, dither thresholds for raising spatial fre0 quency, as shown in FIG. 8A, are arranged in low density areas of the input graduation image data, and dither thresholds for making spatial frequency lower than that in the low density areas, as shown in FIG. 8C, are arranged in half tone areas and high density areas of the input graduation image data.

Abstract: According to the invention there is provided a method for transforming a gray-level image, divided into pixels, into a black-and-white image, comprising the steps of: dividing the gray-level image into a number of generally square sub images which comprise more than one pixel; calculating and storing, for each sub image, at least one measurement value representing the gray-level of the sub image; calculating, for each sub image, a threshold value based on the measurement values of the sub image, and a number of sub images that are adjacent the sub image; and transforming, for each sub image, each pixel in the sub image to either a white or a black pixel depending upon whether the gray-level of the pixel exceeds the threshold value of the sub image or not. Preferably, parts of the gray-level image, the measurement value or values that is/are calculated, for each sub image, and the threshold value that is calculated, for each sub image, are temporarily stored in one or more memory buffers.

Abstract: In this proposal a method of multilevel halftoning is described that allows the definition of halftone patterns using more than two gray levels at a time. This feature can be employed to eliminate the texture contours produced when shades formed by a pattern of two levels blends into a shade formed by a single gray level. The method also gives control over the degree to which a given output gray level is used. This can be employed to limit ink coverage when certain levels require more ink to produce than do others. According to the method: initial pixel intensity ranges are obtained; the initial pixel intensity ranges are compared to at least two overlapping threshold arrays; and selection of enhanced pixel intensity levels are determined for halftone cells according to the comparison results of the initial pixel intensity ranges to at least two overlapping threshold arrays wherein the enhanced pixel intensity levels are a function of results from the comparison.

Abstract: What is disclosed is a mapping circuit configured to map a range of captured intensity values to a companded intensity level based upon the density of captured intensity values present in the captured image. Also provided is a companding circuit coupled to the mapping circuit, the companding circuit configured to replace each pixel of the captured image with a corresponding mapped intensity value pixel. The companding circuit and mapping circuit are configured to preserve image characteristics.

Abstract: An image processing apparatus includes a window setting unit which sets a window for input low-resolution information, including a target pixel and pixels surrounding the target pixel. A detection unit detects MAX and MIN values from among the pixels within the window, and a quantization unit quantizes information relating to each pixel, having n values within the window, into a value smaller than n. A LUT (look-up table) determines a distribution ratio of the MAX and MIN values based on quantized values provided by the quantization unit within the window. A transformation unit synthesizes the MAX and MIN values based on the distribution ratio, and a forming unit forms high-resolution output information from the synthesized values. Thus, input low-resolution information is converted into high-resolution output information, at a high speed, to produce a high quality image.

Abstract: A dither matrix is produced by creating an array of dots and dividing the array into a mutiplicity of regions, each of the regions having a multiplicity of dots. Borders of the regions are altered to have substantially continuous randomly irregular boundaries, and dither values are assigned to each of the regions.

Abstract: A multible value image filtering device selectively filters segments making up an image signal. The selection is made according to the segments' characteristics, such as the optical density or amount of change of optical density between adjacent segments. The characteristics are compared to a threshold which can be changed according to various conditions, such as the type of document being scanned.

Abstract: A method for determining whether a pixel of a digitized image is a background or object pixel includes the steps of determining whether the pixel is in a static state or a transient state according to the variation in its gray-level compared with the gray-level of an adjacent pixel located in a first direction, setting a static threshold if the pixel is in the static state or a dynamic threshold if the pixel is in the transient state, comparing the gray-level of the pixel and the applicable threshold to determine whether the pixel is a background or object pixel, and repeating the determination with respect to static or dynamic thresholds, as applicable, in a second direction.

Abstract: A method of processing a matrix of gray scale picture elements derived from lifting an image of a document to extract strokes from the image of the document comprises the steps of (a) calculating a global average value of the gray scale picture elements, (b) placing a window over a portion of the matrix of gray scale picture elements, (c) calculating a local average value of the gray scale picture elements contained in the window of step (b), (d) comparing the global average value of step (a) with the local average value of step (c), (e) calculating a relative figure of importance (RFI) value for each gray scale picture element contained in the window of step (b) when the local average value calculated in step (c) is less than the global average value calculated in step (a), (f) increasing the size of the window of step (b) and replacing the window of step (b) with this increased sized window when the local average value calculated in step (c) is greater than the global average value calculated in step (a), a

Abstract: Image data scanned by a scanner in a digital scanner, a digital copying machine or a facsimile machine is processed to detect an edge despite low contrast. A first MTF compensation portion enhances an edge area of the image data. An edge detector detects edge data from the first PTF co pensation portion. A second MTF compensation portion enhances the edge data from the equalization filter. An equalization filter calculates a binary cut-off level for input data. Another edge detector functions as a device for detecting edge data from the equalization filter by a Laplacian filter. Clamp circuits clamp a highest limit and a lowest limit of the binary cut-off level of signals from the equalization filter. A first comparator compares an output signal from the MTF compensation portion to an output signal from one of the clamp circuits. A second comparator compares an output signal from the first equalization filter to an output signal from the other clamp circuit.

Abstract: A plurality of uniform density pixel matrices Di are prepared so that each matrix Di will have all pixels of a uniform density i. First, in S110, the pixels of one uniform density pixel matrix Di are converted into binary values (0 or 1) while performing an error diffusion operation. Thus obtained binary value pixel matrix Fi is stored in the working memory 14. Then, while the uniform density value i is repeatedly incremented, the above-described converting-and-storing processes are repeated. Afterward, binary values throughout all the binary value pixel matrices are summed at each pixel position. Thus, in S150, an accumulated value matrix M1 is produced to have a corresponding element constructed from the total value. Next, threshold values of a dither matrix DM are determined based on the elements of the matrix M1. That is, the threshold values are determined one by one using the elements of the matrix M1 from its element having the lowest value.

Abstract: A binarization processing apparatus for converting multi-value image data into binary image data is constructed by pixel groups in which pixels to be binarized are divided into a plurality of groups, a plurality of memories which correspond to the pixel groups and hold data in a binarization processing step, a control unit which performs the reading operation for one of the plurality of memories and simultaneously performs the writing operation for the other memory, and a unit for performing the converting process on the basis of an error diffusing method. The plurality of memories have a single common input/output port.

Abstract: Density data produced by an image reading unit is input to a surface density detection unit, which detects a surface density by averaging density data of pixels within a predetermined density range. A period setting unit sets a period of sampling density data of pixels to be used for calculation of the surface density. A surface reference density generation unit generates a surface reference density by adding an offset to the detected surface density. A surface color elimination unit corrects density data of a pixel lower than the surface reference density to the white level to eliminate a surface color.

Abstract: A method and apparatus of preparing the reproduction of a document based on scanning the original including generating a signal representing grey tone values for points along lines across the scanned original and providing a set of threshold values for said points. The set of threshold values being determined so that grey tone values in a uniform area on the original are converted into a uniform black or white representation in a first one-bit representation. The method and apparatus provides parameter values for said points in a dither circuit, and converts the grey tone signal received from the line scanning unit into a signal comprising a second one-bit representation. The conversion into a one-bit representation is performed by depending on the individual grey tone values compared with the present threshold values and the dither circuit output for the points in question.

Abstract: A first aspect of the present invention provides a white level setting system for an image scanner. The system compares an analog image signal obtained by scanning an original or a white reference with a predetermined analog white level signal, to provide a digital image signal corresponding to an image on the original, calculates a white level for the next scan line according to the digital image signal, and employs the white level for the next scan line. A second aspect of the present invention provides a binarization system for an image scanner. The system divides read image data into predetermined unit blocks, finds rates of changes in gray levels in each of the blocks, detects edges of the image data according to the rates of changes, determines a slice level for each of the blocks according to the gray levels of the edges, and converts the image data of each of the blocks into binary data according to the slice level.

Abstract: Disclosed herein is a binarizing circuit comprising a setting circuit for responding to changes in density of inputted image data based on a unique algorithm and for setting an optimal binarizing density level, a delay circuit for delaying the inputted image data for a predetermined time period and for outputting delayed image data, and a comparator for comparing the delayed image data supplied from the delay circuit with the binarizing density level set by the setting circuit and for generating optimal binarized image data in accordance with the changes in density of the inputted image data. When an image of a low contrast is read from an original, character portions of a low contrast can be reproduced, with background noise being eliminated to achieve excellent binarizing.

Abstract: A method for transforming grayscale image data in accordance with preselected transformation factors may be accomplished by first reducing the number of gray image pixels by "punching to black" gray image pixels having intensity values less than a black punch value and by "punching to white" gray image pixels having intensity values greater than a white punch value. The resulting "punched" image data are then transformed in accordance with preselected transformation factors to create transformed image data. The transformed image data are then converted to binary image data, which may be reproduced in a conventional manner.

Abstract: A method of halftoning a sample value from an intensity range including the steps of providing threshold arrays having threshold values from distinct ranges, one of which is the same as the intensity range, selecting the one with the same range as the intensity range and using the selected threshold array to halftone the sample value. Embodiments may include the following features. The threshold arrays are a first one having a first threshold value range and a second one having a second threshold value range that has more levels than does the first threshold value range. The first threshold array is built by scaling each value in the second threshold array down to the range of the first threshold array. The scaling is done by dividing by 257 and rounding up to the next whole number. The first threshold array has a threshold value range of zero to 255 and the second threshold array has a threshold value range of zero to 65535 or zero to 4095.

Abstract: A process and apparatus is described to improve error diffusion halftone imaging by reducing the amount of time necessary to perform the halftoning process. This processing time reduction is produced without sacrificing the quality of the output binary images by achieving parallelism of error diffusion within an image row. The method works by cutting each image row into a number of segments and error diffusing these segments in parallel. It utilizes two different error diffusion filters: the cut filter for the pixel just before the cuts and the normal filter for the rest of the pixels. Dependencies among the segments is eliminated by ensuring that the cut filter has zero weight for the right neighboring pixel. The normal filter can be any filters that can show excellent quality of the output binary images. Banding artifacts along the cuts are minimized through careful design of the cut filter.

Abstract: In acquiring and reproducing an image, my method and apparatus correct for spurious gray background. Image brightness is sensed in multiple regions of an original image, to provide a corresponding multiplicity of signals for use in reproducing the image. In response to the multiple signals, a corresponding multiplicity of corrected signals is provided by adjusting each signal. The amount of adjustment depends on the size of the signal, and preferably includes jitter--i. e., a random component. Preferably the random component is partially smoothed. The multiple corrected signals are used in reproduction of the image. Preferably the dependence of adjustment on signal size is a multivalued monotonic function. Preferably the function increases the brightness of image regions that are already relatively more bright, in comparison with image regions that are relatively less bright.

Abstract: A dithered image reconstruction system and method that compensates for inter-detector errors in a manner that does not adversely affect detection of small-amplitude images in the presence of a very bright large-amplitude background. An overlapping dither pattern is employed in a detector array (103), and outputs generated by individual detectors (302) are adjusted in an iterative fashion to hold all outputs for a particular detector substantially constant, while allowing each set of outputs for each image section to converge on a solution. The system and method do not substantially distort the received signal, nor do they fail when the image characteristics have little spatial variation, such as when a large target area is being detected.

Abstract: A method and apparatus are described for employing non-uniform quantization to avoid marking dots within a region where there is inadequate control of marking density or color. The techniques are typically applied to dye transfer media used in thermal printers where the dye transfer media has a potential variance among lots. Dithering modifications are described for use with non-uniform quantization to provide control of color marking in areas where the energy input into a dye transfer medium results in an output that can vary between different lots of the transfer medium. Error diffusion may also be used with such non-uniform quantization.

Abstract: An overhead scanning system records pages from bound documents in an upright and open condition. A light stripe is projected onto each page of the bound document to measure the non-planar deformations of each page. The scanning system records a first image with the light stripe and a second image without the light stripe. After identifying a set of pixels representing the light stripe in the first image, the set of pixels is smoothed to minimize large transitions between scan lines. Subsequently, a crease is identified in the set of pixels that represents the spine of the bound document. The pixels forming the crease are replaced with pixels that are defined using a parametric model that approximates the spine region of a bound document. This substitution insures that the spine region of a bound document is accurately depicted before determining a page shape transform with the identified set of pixels representing defining the projected light stripe.

Abstract: Method and device for binary segmentation of a digital image with a threshold obtained using a histogram to obtain a binary segmented digital image. The digital image is thresholded a number of grey levels, and the number of objects which appear when the digital image is thresholded at each of the grey levels is counted. A histogram of the number of objects per grey level is constructed, and a segmentation threshold is determined automatically on the basis of the histogram. The digital image is then thresholded at the segmentation threshold to obtain the binary segmented digital image.

Abstract: An error-diffusion quantization process is conducted on all the pixels of a continuous tone image, pixel by pixel. In the error-diffusion quantization process to an object pixel, a threshold value T is randomly set for the object pixel. Input density data I.sub.x,y of the object pixel is modified by a sum of quantization errors E distributed to the object pixel during error-diffusion quantization processes previously performed for preceding nearby pixels. The modified input density I'.sub.x,y of the object pixel is compared with the threshold value T set for the object pixel, whereby the input density data of the object pixel is converted into a quantized output data Ie. A quantization error "e" between the modified input density I'.sub.x,y and the quantized output data Ie is determined. The quantization error "e" is distributed to subsequent nearby pixels, which have not yet been quantized, with the use of the weight coefficient matrix .alpha..

Abstract: A method and apparatus for selectively depositing ink on a recording medium is described. The method and apparatus implement a technique in which portions of a clustered-dot dither matrix are identified and no ink is deposited under any circumstances in the so-identified portions. The portions are organized into a relatively large dispersed distribution matrix within the clustered-dot dither matrix.

Abstract: A method for thresholding a gray scale matrix representative of an image to generate binary matrix representative of the image. Elemental features of the image are determined and characterized, and a plurality of thresholding algorithms is selected. For each algorithm a sequence of binary matrices is generated as scaling factor applied to the algorithm is varied. Features of each binary matrix are determined and characterized and compared to elemental features of the image. For each determined feature which matches a an elemental feature of the image a score is incremented; and for each determined feature which does not match the score is decremented. The binary matrix having the highest score is selected.

Abstract: A binarization circuit compares the density value of the target pixel with the density value of surrounding pixels in the vicinity. A judging unit judges whether or not the target pixel is isolated from the surrounding pixels. A detection unit detects the density values of the target pixels which make the target pixels isolated by a binarization process. A calculation unit calculates the accumulated isolated pixel frequencies of each density value detected by the detecting function when the judging unit and the detecting unit have finished processing all of the original image. A determination unit determines a threshold value on the basis of the accumulated isolated pixels frequencies.

Abstract: A method for processing an input image including a plurality of input pixels each having a first number of possible input levels of optical density to form an output image including a plurality of separations each including a plurality of output pixels each having a second number of possible output levels of optical density.

Abstract: An error diffusion process adds an error value to an input grey image value to produce a modified input grey image value before comparing the modified input grey image value with a predetermined threshold value. A rendering value and error is generated based on the comparison. An error equal to the modified input grey value is generated when the modified input grey value is less than the predetermined threshold value, and an error equal to the modified input grey value minus a black reference value is generated when the modified input grey value is equal to or greater than the predetermined threshold value. This error value is further compensation for pixel growth when the output of the previously processed pixel is not equal to the output of the presently processed pixel.

Abstract: An image processing method and an image processing apparatus for determining the best digitizing threshold value, thereby enabling best-case digitizing across the entire input image, even when determination of a subject image within an image block is mistaken. The input image is separated into plural blocks; a temporary digitization threshold value is calculated for each of the separated blocks; the presence of text characters or other predetermined subject images is evaluated in each of the separated blocks; and block information for each of the separated blocks, including the temporary digitization threshold value, subject presence information, and the final digitization threshold value of each block for which said threshold value has been determined, is referenced to determine the final digitization threshold value for each block. Each block is then digitized using these best-case threshold values to achieve consistent, best-case digitization across the entire input image.

Abstract: An apparatus and method for suppressing noise and an input image having a plurality of pixels, each of the pixels in the plurality of pixels having a range of possible values between at least two extremities. A first group of pixels is determined, each pixel of the first group having a value that is less than a predetermined amount from the value of at least one of the extremities. The values of pixels adjacent to each pixel in the first group are examined to determine if the adjacent pixels are also members of the first group and, when a predetermined number of the pixels adjacent to a pixel in the first group are also members of the first group, reassigning the pixel value of that pixel in the first group and each of its adjacent pixels to have the value of at least one of the extremities.

Abstract: A system for generating a binary representation signal, which is suitable for outputting on an output device, from a continuous toned image signal that is adapted insure local correspondence between the average value of the input signal and the output being representation signal for local spatial areas comprises a processor, an input device, an image adaptor, a summer, a dither signal generator, and a pixel activator. The image adaptor receives a reference image signal, determines the number of pixels in local areas that are to be activated and generates an adaptive signal. The summer sums a dither signal from the dither signal generator and a continuous toned image signal to generate a ditherized signal. The pixel activator receives the adaptive signal and the ditherized signal. The pixel activator generates a signal to activate the pixels in each local area that have the highest sum according to the adaptive signal.

Abstract: A method for processing an input image including a plurality of input pixels each having a first number of possible input levels of optical density to form an output image including a plurality of separations each including a plurality of output pixels each having a second number of possible output levels of optical density.