Abstract: In a digital halftone screen generating device for generating a digital halftone screen comprising a plurality of periodic patterns, a configuration determining section (53) determines a grid (27) indicative of a configuration of one of the periodic patterns in the digital halftone screen by using periodic constants (51). Supplied with the periodic constants (51) and a function (50) defining a procedure for obtaining threshold values in a square area, a threshold value distributing section (54) rotates the threshold values defined by the function (50) by a screen angle. The threshold value distributing section (54) expands on the grid (27) threshold values enlarged by an enlargement ratio. When the threshold values on the grid (27) have discontinuous numbers, the threshold value distributing section (54) rearranges the threshold values so as to have continuous numbers.

Abstract: A peak holding circuit includes a peak holding register for holding a current peak value, and an operation circuit for comparing the current peak value with an input signal and for performing a predetermined operation on the current peak value and the input signal when the input signal has a level greater than the current peak value, so that the current peak value is renewed and written into the peak holding register. A video processing unit which uses the above-mentioned peak holding circuit is also provided.

Abstract: A method and apparatus for reproducing half-tone images by converting continuous-tone image data into a multi-valued level density code using a predetermined threshold or thresholds includes adding an output adjusting error to a difference error between image data of a target pixel and a threshold level and diffusing the difference error to which the output adjusting error has been added into pixels surrounding the target pixel.

Abstract: High addressability image signals, each representing a pixel in an image, where the signal has one of a relatively large number of signal levels, are directed through an error diffusion quantization process, for the conversion of the signal to one of a relatively small number of levels. Each signal is modified by a correspondingly weighted error correction term signal or signals from previously processed image signals, thereby generating a modified image signal. This modified image signal is compared to a threshold to derive a preliminary output signal having a smaller number of levels. The preliminary output signal is directed to an output if it has the same level as the previous output signal. If the preliminary output signal does not have the same level as the previous output signal, the preliminary output signal is directed to the output only if the previous output signal was one of a contiguous group of a preselected number of like level signals.

Abstract: In a method for converting from a first bitmap image resolution to a second bitmap resolution, be it interpolation (an increase in resolution) or decimation (a decrease in resolution) a bitmap image defined at resolution and density I.times.J.times.a is prefiltered as a first step to ensure the preservation of original image structure and compensate for device dependence of the input image, which is necessary in order to maintain the quality and sharpness of the original image. The filter may be selected from a variety of filter choices and may also perform pixel interpolation or decimation depending on the input source. As a second step, unquantized scaling of a prefiltered image (K.times.L.times.b) is performed using an f.times.g pixel window to identify a set of neighboring input pixels surrounding a single output pixel. The window contributes input pixel density information to generate a scaled gray output pixel.

Abstract: A digital image processing system for convening continuous-tone images into halftone images to be output by a receiver with limited storage capacity. The continuous-tone image is converted into a first halftone image by threshold screening. Threshold screening involves comparing the pixel values of blocks of the continuous-tone image with cell values of a threshold array and turning on pixels of a first halftone image according to whether the pixel values of the continuous-tone block are greater than or equal to the cell values of the threshold array. The threshold array is associated with a plurality of gray patterns. A block count is determined which equals the number of pixels of each block of the first halftone image that are tuned on. A second halftone image is produced by combining gray patterns corresponding to the block counts. An error image is produced by determining differences between the first halftone image and the second halftone image. Scattered pixels in the error image are removed.

Abstract: An image processing apparatus binarizes input multi-level pixel data by changing the same either to the minimum density data corresponding to white or to a minimum reproducible density data corresponding to the minimum density level reproducible by an image forming apparatus such as a printer, when the density defined by the input multi-level pixel data is of such a low level that it cannot be reproduced by the image forming apparatus. Error incurred by the binarization is reflected in the succeeding binarizing process so that the density of the whole image is preserved, whereby an image with a highlight portion can be recorded with reduced degradation of the image quality at the highlight portion.

Abstract: A binarization method obtains an optimum threshold value for binarization which is used when converting a multi-level image data which describes an input image into a black-and-white bi-level image data. The binarization method includes the steps of counting a first number of black picture elements by varying a threshold value from a darkest tone level to a lightest tone level, counting a second number of picture elements having a tone level other than the lightest tone level, obtaining a percentage of the first number with respect to the second number for each of the varied threshold values so as to normalize a density of the input image, and determining the optimum threshold value for binarization based on the percentage which is obtained for each of the varied threshold values.

Abstract: An image processing system is provided to convert halftone images to continuous tone images. It employs an adaptive filter which processes successive pixels in an input halftone image. The adaptive filter employs a filter that is selected under feedback control from a plurality of filter sets each having a plurality of filters. The halftone image is also low-pass filtered to generate a first approximation image (FAI). A spatial gradient value is computed for each pixel in the FAI. A control operates the adaptive filter to apply one of the predetermined filters to the current pixel as a function of the associated pixel spatial gradient. An output image from the adaptive filter in a first iteration of the filtering procedure can then be applied to the input of the adaptive filter for a second adaptive filtering iteration. Pixel gradients for the second iteration are computed from the image output from the first iteration.

Abstract: An image processing system employs a scanner to generate an image having gray content from an input halftone image. The system further includes a programmed computer that determines whether each pixel is a constant area pixel or an edge area pixel. Each constant area pixel is detected to be a white pixel or a black pixel and the white or black value is set with reference to a local black or white reference point. The local reference point is then adjusted as a function of the input value of each constant area pixel. Each edge area pixel is detected to be a local-extremum pixel or a nonextremum pixel. The value of each local-extremum pixel is modified as a function of the current local reference point. The local reference point is also adjusted as a function of the value of each local-extremum or nonextremum pixel after it is detected. The modified constant and edge area pixels are stored as a modified image for output processing.

Abstract: An image processing apparatus includes a scanner for inputting image data indicative of an image with a multilevel tone, a multilevel data part for generating multilevel tone data from the input image data through a prescribed error diffusion process, the multilevel data part outputting image data having pixels to which the multilevel tone data is assigned, a storage part for temporarily storing a value of one of two successive pixels included in the image data, and a two-pixel processing part for converting the value of the one pixel stored in the storage part into a first value, and for generating second values of the two successive pixels using the first value of the one pixel, so that output image data is output to a printer, each pixel of the output image data being described by the second values of the two successive pixels.

Abstract: An estimate of a threshold value for feature extraction from image data containing noise and quantized into a plurality of quantization levels is made by filtering, such as recursively averaging n adjacent quantization levels and counting the extrema of the result. The recursive averaging is repeated with increasing values of n until only three extrema are present in the filtered data. The estimate of the threshold value is refined by comparing averages or summations of n quantization levels above and below the estimate and altering the estimated threshold value based on a comparison of the averages or summations. By basing both the estimation and refinement processes on the original data and using a value of n which is smaller in the refinement process than in the estimation process, a highly effective threshold value for the feature extraction process is obtained. Adaptive adjustment of n during the estimation process minimizes loss of data as well as computing time.

Abstract: An autonomous real-time adaptive video target detection and position locan apparatus and method. Adaptive low pass filters produce horizontal leading and trailing edge and vertical thresholds from each frame of input target and a background or clutter video signal. A user selectable input is used with the three adaptive thresholds, input video, and horizontal synchronization signal to produce a signal representing valid target detection and position information.

Abstract: A method of quantizing pixels in an image formed by a plurality of pixels, each pixel representing an optical density of the image at a location therewith, and having an original optical density value selected from one of a set of `c` original optical density values that has a number of members larger than a desired output set of `d` optical density values, through a process of error diffusion. In this process, `c` and `d` are integer values representing pixel depth. For an input image so comprised, initially, an image signal is initially modified in accordance with previously determined error. Thereafter, during the quantization step of the process, the threshold of an error diffusion process is dynamically adjusted in accordance with the original image to selectively control an amount of edge enhancement introduced into the image.

Abstract: An image treatment apparatus comprising: an input device for inputting image data; a setting circuit serving as a reference when the image data is quantized in accordance with the image data input by the input device; a quantizing circuit for quantizing the image data; and a device for outputting an image in accordance with the result of treatment performed by the quantizing circuit, wherein the quantizing circuit performs the quantization by correcting the error between the image data input by the input device and the image output by the outputting device.

Abstract: An image processing apparatus displaying an identification performance between the image of half-tone and an image of tone other than the half-tone includes a device for correcting the characteristics of the input image signal and an identifying device capable of identifying whether the input image signal is the half-tone image or not without use of the image signal whose characteristics have been corrected. In accordance with the result of the identification performed by this identifying device, an output image signal is selected.

Abstract: An image processor for processing image signals corresponding to an original image including a character image region, a halftone image region, and a continuous tone image region. The image processor includes a generator of a first kind of image signals corresponding to the character image region, and of a second kind of image signals corresponding to the halftone image region and the continuous tone image region, according to the image signals; a processor of the first image signals; and a processor of the second image signals.

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.

Abstract: A dither processing method comprising steps of:a) Defining a non-rectangle dither cell and a macro dither cell consisting of a plurality of the dither cells arranged in a predetermined form;b) Defining an order of magnitudes of threshold of pixels in the dither cell;c) Defining an order of magnitude of threshold of the dither cells in the macro dither cell;d) Defining a threshold for each the pixel of each the dither cell in the macro dither cell according to the order of magnitude of threshold of the pixels in the dither cell as well as the dither cells in the macro dither cell.

Abstract: A halftone screen with precisely controlled angles and rulings, including irrational screen angles and rulings, for screening photographic images is generated by representing a desired screen pattern in an irregular or non-grid like array of screen elements. In one embodiment, a random array of screen elements is used. In another embodiment, a Poisson-disk distribution of screen elements is used to improve quality. The error between an ideal screen point and an actual screen point in the transformed UV space is calculated and used as the basis for selecting an actual screen point as having the least error between the ideal and actual screen points in UV space. The number of error calculations may be reduced by storing pointers the nearest points to each screen point in transformed UV space, and by storing a plurality of successive screen values at a given angle and screen ruling corresponding to each point in the transformed UV space.

Abstract: A method and an arrangement for reproducing an original image that has one or more different image type regions. The arrangement has a scanner which scans and digitizes the original image into pixels, a controller coupled to the scanner to receive the digitized original image, and which produces a first signal corresponding to a gray level halftoned representation of the digitized original image, and a printer coupled to the controller to receive the first signal and which produces a gray level halftoned reproduction of the original image. The controller operates the printer in a default mode when the original image contains a text region or a halftone region, this default mode including either contour suppression applied to every pixel of the original image, or using an output screen that is a higher frequency than a screen of the original image.

Abstract: A bidirectional adaptive thresholding technique for use in an image processing system. An array of pixel sensors scans a grayscale image and generates a set of grayscale image data. A buffer storage connected to the sensors stores the grayscale image data. A forward tracker reads the image data from the buffer storage in a forward direction and provides background and peak forward tracked values. A reverse tracker reads the image data in a reverse direction and provides background and peak reverse tracked values. A threshold level generating circuit generates a threshold level that is a proportional function of either the forward or reverse tracked values based on validity criteria. Thereafter, a thresholding circuit thresholds the grayscale image data using the threshold level to provide binary image data.

Abstract: When image data having a halftone is binary-coded, each of pixel data is first read out as gradation data having multiple values, a judgement is made whether or this pixel data corresponds to a value within a predetermined range, and if this pixel data is present within this range, a halftone processing operation is carried out by way of the error diffusion method. On the other hand, if another judgement is made that the pixel data is out of this predetermined range, this pixel is simply binary-coded. Thus, a portion where characters have been written is not processed by the halftone processing operation by way of the error diffusion method, whereby a clear image may be reproduced.

Abstract: An upper limit value and a lower limit value are used to modify the correction value computed in a correction value computing circuit in such a way that the correction value ranges between the upper and lower limit values. The threshold value computed from the upper and lower limit values is compared with the modified value to compute a binary value. The upper and lower limit values are selected to become those which the correction value may take. The correction value is obtainable in conformity with the density value resulting from converting the density value of an object pixel of an original image in terms of an exponential function or the approximate function of it.

Abstract: A halftone screen pattern generation system for computing halftone screened images with rotated screens including multiple angle and ruling combinations, including irrational tangent angles, is disclosed. A screen pattern is generated by storing an oversized strip from an ideal angled screen pattern, and then assembling a sequence comprising selected scan line segments of the oversized strip. Each selected scan line segment corresponds to one of a plurality of offsets of the oversized strip. The error between the actual generated screen and ideal desired screen is computed. Each subsequent scan line segment is selected from the plurality of scan line segments corresponding to the plurality of offsets so as to minimize the accumulated error. In accordance with one aspect of the present invention, the measure of error between the actual generated screen and the ideal angled screen is the length of a vector in a transformed UV space between the actual screen sample point and the ideal screen sample point.

Abstract: This invention utilizes the fact that a maximum density difference of pixels in a window within a predetermined range including a pixel of interest is large for a character region, and is small for a photograph region. A maximum density difference of an image within the predetermined region is calculated. A quantization error of pixels around the pixel of interest is calculated, and a correction amount is then calculated by proportionally distributing the quantization error in accordance with a feature amount calculated by a feature amount calculator. The correction amount is added to an image signal of the pixel of interest to form a compensation image signal, and the compensation image signal is quantized.

Abstract: An image signal processing apparatus is provided with an image signal generation device for sequentially generating image signals representing light and shade of an original image per every picture element. The image signal processing apparatus is also provided with an extreme portion detection device for comparing the generated image signal of an observation picture element and each of the generated image signals of a plurality of peripheral picture elements which are positioned in the vicinity of the observation picture element, and judging whether the compared observation picture element is an extreme portion or not. The image signal processing apparatus is further provided with a correction device for correcting a level of the image signal of the observation picture element, which is judged to be the extreme portion by the extreme portion detection device, by use of a calculation predetermined with respect to the level of the image signal.

Abstract: A halftone screen pattern generation system for computing halftone screened images with rotated screens including multiple angle and ruling combinations, including irrational tangent angles, is disclosed. A screen pattern is generated by storing a plurality of strips from an ideal angled screen pattern, and then concatenating a sequence comprising a selected order of the plurality of strips in a sequence. The error between the actual generated screen and ideal desired screen is computed. Each subsequent strip is selected from the plurality of strips so as to reduce the accumulated error. In one embodiment, a screen pattern is generated by storing one strip of an ideal angled screen pattern, and then concatenating a selected sequence comprising the strip and substrips of the strip.

Abstract: A plurality of reference tone curves are determined in advance. An operator divides an original image into image regions and selects respective reference tone curves (f.sub.1 (x), f.sub.2 (x)) for the image regions. The operator designates weight values for the respective reference tone curves. A weighted average of the respective reference tone values is calculated with the weight values to obtain a tone curve which is then employed to convert the gradation of the original image.

Abstract: A system that converts a scanned image of a complex document into an image where text has been preserved and separated from the background. The system first subdivides the scanned image into blocks and then examines each block pixel by pixel to construct a histogram of the gray scale values of the pixels. The histogram is partitioned into a first, middle and last regions. If one or more peaks occur in the first and last regions, and a single histogram peak occurs within the middle region, the pixels are reexamined to determine the frequency of occurrence of pixels having a gray scale level of the middle peak nearby pixels which have a level of a first region peak. If this frequency is high, the middle peak is assumed to be background information. After determining the threshold, the system rescans the block applying the threshold to separate the text from background information within the block.

Abstract: An image signal processing apparatus converting an image signal representing a continuous tone image into an image signal indicating a halftone dot image. The continuous tone image signal is compared with a threshold signal. If the difference between the continuous tone image signal and the threshold signal falls within a predetermined range, then the halftone dot image signal is produced based on a probabilistically established signal. The halftone dot image thus produced is smooth without an appreciable tone jump.

Abstract: A circuit for increasing the speed of conversion of image pixels from one number of bits to another by processing a plurality of pixels in parallel. The conversion of each pixel typically results in a new value and an error term which is divided up among adjacent pixels. By using a plurality of separate conversion circuits, one for each line, and by processing the xth pixel on one line in parallel with the x-2 pixel on the next line, the plurality of pixels can be processed in parallel. All circuits are identical except that the first circuit must get the error term of the line above it from memory, and the last of the parallel circuits must store in memory the error term for the next plurality of lines.

Abstract: Gray pixel values, where the value of the pixel has one of a relatively large number of input levels, are directed through an error diffusion quantization process, for the conversion to one of a relatively small number of values. Each pixel of the gray level data is modified by a correspondingly weighted error correction term or terms from previously processed pixels, generating a modified pixel value. This modified pixel value is compared to a threshold value, the threshold value determined adaptively, based on 1) a dither pattern, having a dynamic range greater than 1, and 2) the value of the pixel to be thresholded, and optionally on its predetermined neighborhood, multiplied by a value representing an edge enhancement factor. The difference value between the modified pixel value and the output pixel value is distributed in accordance with a weighted distribution scheme to a set of neighboring unprocessed pixels, increasing or decreasing the gray values of such pixels.

Abstract: A document image signal processor of gray level for use in a facsimile. The document image signal processor establishes a local window and a broad window from document image signals scanned by a CCD image sensor. An average level and a level difference between a maximum and a minimum level of the image signals are extracted from the local window. A maximum threshold of the background of the document image is extracted from the broad window. Thus, the image signals can be binarized with an adaptive threshold. Accordingly, the inventive image signal processor provides improved image, although the document image is collected (scanned) from a material whose brightness distribution is considerably ununiform.

Abstract: An image processing apparatus comprises an image data input device and a processor for processing an image data inputted by the input device. The processor includes a binarizing circuit for binarizing the input image data, a counter for counting the binary data outputted from the binarizing circuit and a discrimination circuit for discriminating an image content in accordance with count of the counter.

Abstract: An image processing apparatus is provided with: at least one image memory for storing each picture element value of an original image; a coordinate inputting device by which a coordinate of an arbitrary point on the original image can be inputted; a device for setting a threshold according to the picture element value at the coordinate inputted by the coordinate inputting device; and a data buffer for successively storing the set threshold. The image processing apparatus is further provided with at least one look up table for converting each picture element value to either one color component data, which color indicates that the picture element value is within the region prescribed by the set threshold, or another color component data, which color indicates that the picture element value is outside the region prescribed by the set threshold, according to the set threshold, each time the threshold is set by the threshold setting device.

Abstract: An image signal correcting circuit device includes an A/D conversion unit for converting an analog image signal output from an image reading unit into a digital signal, a storage unit for storing correction data, and a correction unit for performing correction on a signal based on the correction data stored in the storage unit. The correction data stored in the storage unit is difference data between at least two pixel signals in the digital signal which is generated by a correction data generating unit. Alternatively, the correction data stored in the storage unit is obtained by amplifying an analog reference signal by an amplification factor of m (m>1) and by converting the amplified analog signal into a digital correction signal by the A/D conversion unit.

Abstract: A method and arrangement for reproducing an original image has a scanner which scans and digitizes the original image into pixels, a controller coupled to the scanner to receive the digitized original image, and a printer coupled to the controller. The controller produces a first signal corresponding to a gray level halftoned representation of the digitized original image, and stabilizes the dots at specified pixels. The printer receives the first signal and reproduces the original image with stable dots at locations corresponding to the specified pixels.

Abstract: A high quality binary valued image is reproduced from a multivalued original image by a combination of density pattern processing and error diffusion processing using density patterns prepared previously in correspondence to each density value of pixels of an image to be reproduced.

Abstract: A picture signal binarization apparatus includes two comparators for converting an analog signal into a binary signal by comparing the analog signal with two different thresholds, two counters for counting inversions of the binary signal from each comparator and supplying a count signal indicative of the number of inversions of the binary signal from each of the comparators, and a selection part for selecting a binary signal from one of the comparators in response to the count signal supplied from one of the counters so that the selected binary signal is outputted as a subsequent output binary signal, the number of inversions indicated by the count signal from the one of the counters first reaching a predetermined value.

Abstract: Gray level pixel values in an image, each pixel value represented by c levels are quantized by applying a threshold level to each pixel value in the image to produce a pixel value having d levels, and applying a weighted portion of the value of the difference (the "error") between the pixel value and the thresholded value to a predetermined set of neighboring pixels; for each neighboring pixel in the predetermined set to which the error term is to be applied, comparing the value of the neighboring pixel to each possible legal output value, and if any pixel value the predetermined set of neighboring pixels is equal to one of the legal output values, then the error term is not applied to that term, and is applied to remaining non-legal values. If all the neighboring pixels have legal values, a decision is made based on a look-ahead neighborhood (a set of pixels used to determine the fractional error allocation) as to whether the error term is discarded or preserved.

Abstract: An image processing system converts unscreened and other halftone images to continuous tone images. Value data is sequencitally generated for successive pixels of a screened or unscreened halftone image. Each image pixel is Sigma filtered with a predetermined set of filter parameters including the filter window size and a Sigma difference range that is applied to determine which pixels in the filter window are counted in determining average window pixel values. An output continuous tone image containing the Sigma filtered pixels is generated for storage and/or processing to a halftone copy or print.

Abstract: A method and arrangement for quantizing gray level pixels using a combination of halftoning and error diffusion which initially determines a best fit halftone cell, and propagates halftoning error in order to maintain gray density, while reducing halftoning and error diffusion artifacts.

Abstract: A method and apparatus for binarizing a variable density image wherein brightness of the variable density image is changed by 1/n (where n is an integer of 2 or above), and an expansion processing is carried out on the brightness changed image to generate an expanded image. A smoothing processing is performed on the expanded image to generate a smoothed image and a differential image is generated by taking a difference between the smoothed image and the variable density image. The differential image is binarized by comparing the differential image to a predetermined threshold.

Abstract: A picture processing apparatus with a texture elimination capability which is applied to a facsimile.

Abstract: A method is provided for data compression and image enhancement in a digital facsimile document transmission system. The method permits images containing gray scale content to be reproduced using conventional facsimile equipment. An irregularly shaped matrix of thresholds is employed in an adaptive approach to convert each multilevel gray scale pixel to a bilevel (black/white) pixel. The adaptive thresholding approach employed provides improved image quality in images containing both gray scale and high contrast information, e.g., identification cards. Compression performance is enhanced by an image rearrangement process in which pixels thresholded with similar threshold values are grouped together prior to run length encoding.

Abstract: An image reader utilizing a CCD line sensor (8) which involves no possibility of any stripe pattern (output irregularity) being produced with respect to dots output from the CCD line sensor (8) even if there is any characteristic error between outputs of odd n-th and even n-th elements of the CCD line sensor (8). Data of the odd n-th elements and data of the even n-th elements are supplied to an averaging circuit (52). Where the absolute value of the difference in data between odd n-th and even n-th elements is greater than a predetermined threshold value, a decision circuit outputs a select signal of H level. Where the absolute value of the difference is smaller than the threshold value, the decision circuit (56) outputs a select signal of L level. A selector (58) selects the output of each odd n-th element or even n-th element as a read output in case that the select signal is of H level. If the select signal is of L level, a mean value of the outputs of the two elements is selected as a read output.

Abstract: The dynamic range of a digitized image database is extended to permit shifting of encoded pixel values without `clipping`, and to provide limited windows of values into which specular highlights and unusually low reflectances or areas of objects in shadow light may be encoded and stored. Digital codes into which an image scanner output has been mapped by a scene balance mechanism are converted into a set of reduced-range digital codes of the same resolution but having a smaller range of basic image content values than the dynamic range of the digitized image data base.

Abstract: An image reader for reading an image of a document by an image sensor and for outputting image data after processing obtained image data includes an arrangement for binarizing image data read by the image sensor through comparison of the image data with a threshold. A system is provided for entering the threshold value from an exterior source and for giving the threshold value to the binarizing arrangement. Also, a control device is provided for controlling that system.

Abstract: A method of image conversion takes an original print ready image at a first resolution scaling and orientation, and simulates printing that image by creating a representation of a page at the particular resolution, scaling and orientation. The image is then periodically sampled through the page with an aperture that corresponds to the desired output. Because the resolution, scaling and/or orientation of the "print" and "scan" are distinct, the aperture "sees" areas which may correspond to more than a single pixel on the original image, and thereby may derive a signal that is gray, i.e., the aperture may see an area that is neither completely black or white, and the image data derived will be considered gray. The gray image data, which may be definable at several bits per pixel, is then made print-ready by reducing the number of bits defining each pixel to a valid output state.