Abstract: This system and method error-diffuse image data to generate printing decisions; scan and print stages are preferably included. Multiple image-data rows are held in longterm memory, usually external to an integrated circuit that does the processing; preferably data from plural rows at a time are received from that memory. Error from earlier-processed data is also held in longterm memory and fed to the circuit. Longterm-memory access is shared with many other functions; the invention keeps error diffusion from dominating that access. Processing preferably proceeds generally transverse (preferably skewed, ideally at 45.degree.) to data rows, with final error distribution into each pixel when it is the "left pixel" (or when it is the "next pixel" if it is at the top of a row group).

Abstract: Decoder reconstruction error is estimated so as to provide compensation at the encoder which equalizes the errors over different frames, since the errors created by some frames are lower than those created by other frames. The compensation is provided by means of temporal weighting applied in the form of temporal bands each associated with specific numbered frames within a frame group. The technique can be applied to a logarithmic temporal decimation frame structure in which one frame within a group of 2.sup.n frames is an `I` frame and the remaining frames are `B` frames.

Abstract: A half-tone processing method includes the steps of generating a half-tone processed pixel value h(u,v) determined by comparing a pixel value f'(u,v) with the dither matrix g(u,v) having the corresponding threshold values, computing an error value e(u,v) between a half-tone processed pixel value h(u,v) and an original pixel value f(u,v), and recomputing a pixel value f'(u+m,v+n) by diffusing the error value e (u,v) to the adjacent pixel f(u+m,v+n) of the original pixel value f(u,v) corresponding to f'(u,v).

Abstract: The detection method and apparatus detects abnormalities having a first signal propagation property within a host medium having a second signal propagation property based upon signals which have been reflected, scattered and/or absorbed by the host medium and any abnormalities therein. The detection apparatus includes a signal source for introducing a signal into the host medium which varies with respect to a predetermined signal parameter, such as time, frequency or source location. The detection apparatus also includes a plurality of detectors disposed along some or all of the boundary of the host medium for detecting the signal following propagation through the host medium and any abnormalities within the host medium. The detection apparatus further includes a signal processor for constructing at least one partial differential equation to describe the propagation of a regularized signal through a medium having the same shape as the host medium.

Abstract: In an image processing apparatus and method, such a problem that the user must wait for a long time until region separation processing is completed is solved. A binary-coding unit performs binary coding of a luminance component of input color-image data. An encoding unit performs arithmetic encoding of the binary image data, and another encoding unit performs block encoding of the color-image data, and codes obtained from the two encoding units are stored in different storage units. A predetermined pair of codes read from the storage unit are decoded by decoding units. A region discrimination unit discriminates image regions of decoded binary image data, and outputs data of character-line-drawing regions. A color-gradation-image extraction unit extracts data of color-gradation-image regions from decoded color-image data.

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: The present invention performs error diffusion halftoning while taking into account multiple color planes, such as cyan and magenta, when determining the placement of a dot in any of the color planes. Using this technique, printed dots of two or more colors are dispersed so as to avoid noticeable clumping of dots of two or more colors. This technique can be used to augment any existing error diffusion method.

Abstract: A printing method and apparatus takes into account the errors in the amount of black due to dot shape and size at the pixel where these errors occur, propagates corrections of these errors in order to preserve the logics of error diffusion, and permits a trade-off between completeness of the correction and computational time. The method and apparatus corrects for the actual shape of the printer dots in most error diffusion methods usable in digital halftoning.

Abstract: The present invention provides a method and apparatus for error diffusing a series of images, each of said images being made up of component pixels. The method comprises, for each of said pixels determining a current error diffused value for said pixel; adding an error margin to each current error diffused value to produce a marginalised error diffused value, said marginalised error diffused value being a translation of said current error diffused value in a direction towards that of a previous output value for said pixel; utilising said marginalised error diffused value to determine a closest possible output value to said marginalised error diffused value; and error diffusing the difference between said closest possible output value and said error diffused value to adjacent pixels.

Abstract: A method and system accumulates an error from an error diffusion process used for rendering continuous images. A scan from an original document generates a plurality of original pixel values which are adjusted by an accumulated error value corresponding to the total effect of neighboring pixels. The adjusted pixel error value is determined between the adjusted pixel value and an output. The adjusted pixel error value is weighted by a predetermined weighting technique and diffused among a plurality of neighboring pixel locations to generate a plurality of intermediate pixel error values. Intermediate pixel errors are accumulated and stored in an error buffer before being combined with an original pixel value. Repetitive access to a memory location associated with the adjusted pixel value is obviated by accumulation of the intermediate pixel values in intermediate registers. A compressor compresses the diffused error values before storage in a buffer as accumulated error values.

Abstract: A printing system for rendering marks on a recording medium receives a multi-level grey scale pixel value representing a pixel having a first resolution. A screening circuit generates a screened multi-level grey scale pixel value equal to (G.sub.L -V.sub.i)+(S.sub.i -Th)*Dmp.sub.Vi *Mod.sub.Eff wherein G.sub.L is the maximum grey level value of the pixel, V.sub.i is equal to the multi-level grey scale pixel value of the first resolution, S.sub.i is equal to a screen value corresponding to a position of the pixel, Th is the threshold value, Dmp.sub.Vi is a video dependent dampening factor, and Mod.sub.Eff is a modulation multiplication factor. An interpolator converts the screened multi-level grey scale pixel value to a second resolution, the second resolution being higher than the first resolution, and a binarization circuit binarizes the converted multi-level grey scale pixel value so as to output a binary signal and an error value, the error value having a resolution equal to the first resolution.

Abstract: An image processing system and method for varying the resolution of multi-gradated image data to output image data having a different resolution. In the system and method, the resolution of the multi-gradated image data is converted to prepare image data having alternating dots arranged in lines and rows such that those of said dots present in odd-numbered lines and those of said dots present in even-numbered lines are positioned in alternate rows. The image data having alternating dots is transformed into binarization data. The binarization data is converted into binary gradated image data by using an error diffusion method or an average error minimization method. The dot arrangement of the binary gradated image data is then transformed into a dot arrangement equal to that of the image data having alternating dots. The system and method thus obtains a high quality reproduced image at a speed as high as possible.

Abstract: Error data .SIGMA.e.sub.P accumulated for a target pixel of binary coding or pixel of interest P is read from an error memory (20) and inputted into an adder (22). The adder (22) adds the error data to multi-valued image data regarding the pixel of interest P, so as to correct the multi-valued image data. A comparator (24) compares the corrected multi-valued image data outputted from the adder (22) with a predetermined reference value and outputs binary image data based on a result of the comparison. A bit converter (28) converts the one-bit binary image data to 8-bit data. A subtracter (26) subtracts the binary-coded image data from the image data prior to binary coding to obtain an error `e`. An error distribution circuit (30) distributes the error `e` into pixels A, C, D, and E, where the pixels A, C, and D are respectively located on the immediate right of, immediately below, and on the lower left of the pixel of interest P and the pixel E is located on the immediate left of the pixel D.

Abstract: A multi-valued image signal I(x,y) is compared with a threshold signal TH by a comparator to produce a binary image signal P(x,y), and an error signal E(x,y) is determined from the binary image signal P(x,y) and the multi-valued image signal I(x,y). Error diffusion coefficients W1(k,l), W2(k,l), W3(k,l) are prepared in advance which correspond respectively to the filter characteristics of a "Jarvis-type filter", an "elongate rectangular filter", and a "Floyd-type filter". A mixing ratio setting circuit determines mixing ratios t1(I.sub.0), t2(I.sub.0), t3(I.sub.0) depending on the multi-valued image signal. The mixing ratios t1(I.sub.0), t2(I.sub.0), t3(I.sub.0) are accumulated and added to the error diffusion coefficients W1(k,l), W2(k,l), W3(k,l), and an error signal E(x-k,y-l) and an error diffusion coefficient W(k,l,I.sub.0) are accumulated and added, producing a diffusion error signal .DELTA.E(x,y). The diffusion error signal .DELTA.E(x,y) is added to the multi-valued image signal I.sub.

Abstract: A method and system assigns an image classification to a multi-level grey scale pixel value. The multi-level grey scale pixel value is modified based on an error generated by previously processed pixels and the image classification of the multi-level grey scale pixel and processed based on the assigned image classification to reduce the number of grey levels in the multi-level grey scale pixel value. An error is generated based on the processing of the modified multi-level grey scale pixel value and a portion of the error is diffused to a next pixel in a fastscan direction and a remaining portion of the error is diffused to pixels in a slowscan direction. The modified multi-level grey scale pixel value referred above includes an error from the previously processed neighboring pixels if the current pixel is classified as being processed as an error diffused pixel.

Abstract: An input signal represented by values of many levels obtained by reading out an original image is applied to a pixel characteristic extracting unit for extraction of a characteristic of a pixel. Based on the extracted pixel characteristic, a gain calculating process is effected based on the pixel characteristic in a first gain calculating unit. An attribute flag showing an image characteristic extracted by the pixel characteristic extracting unit is added to the gain calculated error data which is stored. An area characteristic is determined in an area characteristic extracting unit based on the flag. Based on the determination result, error correction with high precision is carried out in a second gain calculating unit.

Abstract: In an image processing apparatus of this invention, an error diffusion processing means having a multi level signal conversion means changes the conversion characteristics of the multi level signal conversion means, e.g., corrects the output value of error diffusion processing, on the basis of an output from a means for detecting a variation in toner attachment amount or image forming condition. That is, this invention executes error diffusion processing as follows when an input dimension is different from an output dimension (e.g., input dimension=reflection factor or density, output dimension=number of gradation levels) with respect to a multi-value conversion means because error diffusion processing cannot be simply performed.

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: An image processing device is provided with a scanning means which performs subscanning by a pitch corresponding to a width covering a number of pixels less than the number of detectable pixels by a one dimensional image sensor by two or more pixels so as to overlap two or more line pixels. An edge emphasizing means performs an edge emphasis processing for the pixels from the second pixel to the second last pixel according to the image data obtained in response to the scanning by the scanning means.

Abstract: An 8-bit input image data value has its range adjusted by an image range conversion lookup table and is converted into a 4-bit dither image data value f2 with a multi-value dither circuit. The converted 4-bit dither image data value f2 is error-corrected by an error correction unit, and then binarized with a predetermined binarization threshold value of Th=8. An error between binarized data value g and error-correction image data value f2' is calculated by the error calculation unit to be stored in an error storage line memory. Error data e' is provided with respect to a pixel of interest by a peripheral error weighting filter, whereby error is propagated to peripheral pixels of the pixel of interest. As a result, an image processing apparatus of high picture quality, high speed, and low cost is provided.

Abstract: A printing system and method performs lossy compression on a bitonal image when the printing system runs out of available memory for processing a page. The lossy compression is performed by dividing the image into subregions and by then determining a contone value for each subregion. Next, each contone value is converted to a bitonal value (i.e. either a "1" or a "0") to achieve lossy compression. In converting the contone values to bitonal values, the system determines the error associated with each conversion and diffuses the error to adjacent subregions using a random perturbation technique to determine the proportion of the error to diffuse to each subregion. When compressing color images, contone values are determined for each color plane. A relative color ordering of each contone value is also stored and used in converting the contone values to bitonal values in order to solve phasing and color alignment problems which would otherwise arise.

Abstract: The invention is an image transmitting method and system including receiving encoded images, decoding those images and post-processing the decoded images. The post-processing reduces visual artifacts, such as blocking artifacts and mosquito noise, through separate detection, mapping and smoothing operations while avoiding many of the complexities associated with existing techniques. In detecting blocking artifacts, the inventive method employs DCT-domain detection rather than edge detection in the pixel domain. Also, the interior of a detected block is updated based on the surrounding blocks without disturbing the surrounding blocks. In reducing mosquito noise, the inventive method smooths the non-edge pixels within blocks containing edge pixels rather than smoothing the edge pixels. Also, distortion-induced false edge pixels are distinguished from true edge pixels and heavily smoothed.

Abstract: A method and apparatus for converting an input image including a plurality of input pixels each having a number of possible input levels of optical density to an output image including a plurality of output pixels each having a number of possible output levels of optical density using phantom output levels in an error diffusion technique, an automatic image enhancement technique, or other printing methods and apparatus where errors are fed back to alter an input image. The method includes generating a modified optical density value by adding an error value, if any, to the input level of one of the input pixels, generating a phantom output level as a function of the modified optical density level, determining the error value as a function of the selected phantom output level; and generating an output pixel having one of the output levels determined as a function of the modified optical density value.

Abstract: There is provided by the present invention an image processing apparatus for outputting a multiple gradation color image with a printer which can express colors fewer than those specified in input image data comprising an output color predicting section for predicting colors, which will be reproduced by a printer, from color control signals given to the printer, an error computing/error adding section for computing an error between colors specified in input image data and those predicted by the output color predicting section, diffusing the error to peripheral pixels and adding the diffused error to a value of each of the pixels, and an output color selecting section for selecting colors to be reproduced by the printer, which are closest to colors specified in the input image data, according to an output from the error computing/error adding section.

Abstract: A printing system for rendering marks on a recording medium receives a multi-level grey scale pixel value representing a pixel having a first resolution. A screening circuit generates a screened multi-level grey scale pixel value equal to (G.sub.L -V.sub.i)+(S.sub.i -Th)*Dmp.sub.vi *Mod.sub.Eff wherein G.sub.L is the maximum grey level value of the pixel, V.sub.i is equal to the multi-level grey scale pixel value of the first resolution, S.sub.i is equal to a screen value corresponding to a position of the pixel, Th is the threshold value, Dmp.sub.vi is a video dependent dampening factor, and Mod.sub.Eff is a modulation multiplication factor. An interpolator converts the screened multi-level grey scale pixel value to a second resolution, the second resolution being higher than the first resolution, and a binarization circuit binarizes the converted multi-level grey scale pixel value so as to output a binary signal and an error value, the error value having a resolution equal to the first resolution.

Abstract: The invention relates to a method and device for reproducing grey values by reproducing pixels with specific dimensions and degrees of coverage. Use is made of a method based on error diffusion, wherein no clustering of identical pixels is the objective in edge zones while such clustering is the objective outside such zones.

Abstract: Upon gradation converting input m-bit image information into n-bit image information (m and n are integers; m>n), random numbers, the maximum values of which are changed in accordance with the input values of the m-bit image information, are generated at periods of two or more pixels, and the random numbers are selectively output while switching their signs to positive/negative within the period of two or more pixels. The output signal values and the input values of the m-bit image information are added to each other, and the sum signal values are converted into n-values by a density preservation type quantization method. With this control, the problems of sweeping, texture, and the like of the conventional density preservation type quantization method can be solved without emphasizing the granularity of an image.

Abstract: A printing system for rendering marks on a recording medium receives a multi-level grey scale pixel value representing a pixel having a first resolution. A screening circuit generates a screened multi-level grey scale pixel value equal to (G.sub.L -V.sub.i)+(S.sub.i -Th)*Dmp.sub.vi *Mod.sub.Eff wherein G.sub.L is the maximum grey level value of the pixel, V.sub.i is equal to the multi-level grey scale pixel value of the first resolution, S.sub.i is equal to a screen value corresponding to a position of the pixel, the image classification of the pixel and a brightness/darkness setting, The threshold value, Dmp.sub.vi is a video dependent dampening factor, and Mod.sub.Eff is a modulation multiplication factor.

Abstract: Coupled to an error variance circuit 11 is an emission luminance characteristic acquisition circuit 20 that counts up, at a display number counter 21, the display number in the single or plural frames of the respective bits of image data by the counters, M in number, corresponding to said bits, then solves for display area percentage (Sk) dividing, at a display area percentage operation part 22, the display dot number as counted at a display number counter 21, by total dot number, and acquires the luminance deviation characteristic for each bit by means of an emission luminance deviation characteristic measuring part 24. The luminance deviation thus obtained is renewed for each frame and transferred to the error variance circuit 11, and processed for error variance on the basis of the emission luminance characteristic to be output at PDP.

Abstract: An image processing apparatus includes a circuit for correcting a first image data of a target pixel corresponding to a correction amount, a circuit for generating a third image data on the basis of the second image data and a preset threshold value, the third image data having a gradation value less than one of the second image data, a circuit for comparing the second image data with the third image data to output a difference value therebetween, and a circuit for deriving the correction amount. based on the difference value to randomly diffuse the difference value to the peripheral portion of the target pixel and supplying the correction amount to the correcting circuit.

Abstract: A printing system for rendering marks on a recording medium receives a multi-level grey scale pixel value representing a pixel having a first resolution. A screening circuit generates a screened multi-level grey scale pixel value equal to (G.sub.L -V.sub.i)+(S.sub.i -Th)*Dmp.sub.vi *Mod.sub.Eff wherein G.sub.L is the maximum grey level value of the pixel, V.sub.i is equal to the multi-level grey scale pixel value of the first resolution, S.sub.i is equal to a screen value corresponding to a position of the pixel, Th is the threshold value, Dmp.sub.vi is a video dependent dampening factor, and Mod.sub.Eff is a modulation multiplication factor. An interpolator converts the screened multi-level grey scale pixel value to a second resolution, the second resolution being higher than the first resolution, and a binarization circuit binarizes the converted multi-level grey scale pixel value so as to output a binary signal and an error value, the error value having a resolution equal to the first resolution.

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: A lossless image compression encoder/decoder system having a context determination circuit and a code generator. The image compressor uses the context of a pixel to be encoded to predict the value of the pixel and determines a prediction error and maps the prediction error to a mapped value having a distribution suitable for Golomb encoding. The image compressor contains a context quantizer that quantizes the context of pixels. The image compressor determines a Golomb parameter based on the context and historical information gathered during the coding of an image. To avoid systematic prediction biases in an image, the image compressor adjusts the distribution of prediction residuals to a distribution suitable for Golomb coding. As it encodes a particular pixel, the encoder uses the Golomb parameter to determine a Golomb code for the prediction error and encodes that value. To decompress an image, the decompressor determines and quantizes the context of each pixel being decoded.

Abstract: An image processing apparatus 30, which can solve the problems of delay in dot generation in beginning portions of areas of low or high density and tailing after finishing areas of low or high density and carry out speedy binary coding image processing without accompanying side effects of quality depletion and without the need to utilize a complicated processing circuit: includes error correction means 34 which corrects multigradation image data 200 and outputs it, threshold error setting means which sets a binary coding threshold value based on the gradation value of said target pixel multigradation image data 200 and binary coding means 36 which, based on the set threshold value, converts the previously mentioned corrected pixel data into the previously mentioned bigradation image data and outputs it; the gradation value of the previously mentioned target pixel multigradation image data being data, the median value of the previously mentioned first gradation value and second gradation value being m and the

Abstract: A system, which converts a continuous tone value undergoing conversion to an output value, generates first and second errors and an output. The first error is based upon (i) the continuous tone value undergoing conversion, (ii) output values corresponding to previously converted continuous tone values, output values predicted for continuous tone values yet to be converted, and an output value having an assumed first level for the continuous cone value undergoing conversion, and (iii) a matrix value based upon the continuous tone value undergoing conversion. The second error is based upon (i) the continuous tone value undergoing conversion, (ii) the output values corresponding to the previously converted continuous tone values, the output values predicted for the continuous tone values yet to be converted, and an output value having an assumed second level for the continuous tone value undergoing conversion, and (iii) the matrix value based upon the continuous tone value undergoing conversion.

Abstract: In an image processing apparatus in which digital data of a certain number (m) of levels are converted into digital data of a larger number (n) of levels, then subjected to certain desired editing processing, and again digitized to data of the original number (m) of levels. The redigitization to m levels is conducted by determining the average density of a predetermined area, utilizing data of pixels already redigitized to m levels, and redigitizing the data of n levels into m levels, utilizing the average value. This process significantly reduces the amount of data processing required without formation of an unpleasant texture on the image resulting from errors in digitization.

Abstract: An error diffusion method suitable for producing an output image from an input image having a set of digitized continuous-tone pixels is disclosed. The method includes the steps of computing an image activity signal; computing a set of activity weights from the image activity signal; computing a filtered input value for a digitized continuous-tone input pixel responsive to the activity weights and computing a filtered output value responsive to the activity weights for each of the possible output levels. The method further includes selecting the output level in response to the filtered input value and the filtered output value for each of the possible output levels according to an error criterion; determining an error signal between the filtered input value and the filtered output value for the selected output level; and weighting the error signal and adjusting the filtered input values for nearby pixels which have not yet been processed.

Abstract: An adaptive filtering and thresholding arrangement provides a set of error filters having different sizes and associated weighted coefficients for diffusing quantization errors among neighboring pixels in predetermined tonal areas of an image to achieve a smooth halftone image quality. Each error filter circuit is optimally applied to a particular pixel area depending upon the grayscale tone of that area and the desired output print resolution. The arrangement further provides for the addition of "noise" errors to threshold values at selected input image pixel ranges and at the intersection of two differently filtered areas to eliminate visible pattern distortion.

Abstract: A system and method for processing image data converts a pixel of image data having a first resolution to a plurality of subpixels, the plurality of subpixels representing a second resolution, the second resolution being higher than the first resolution. The plurality of subpixels are thresholded to generate a group of subpixel values for each pixel and a threshold error value. It is then determined if the group of subpixel values from the thresholding process produce a pattern containing an isolated subpixel. If the group of subpixel values from the thresholding process produce a pattern containing an isolated subpixel, the group of subpixel vales is modified to produce a pattern without an isolated subpixel. The modification process produces a subpixel error value which is diffused in the slowscan direction to adjacent pixels.

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 image processing apparatus and method which can be selectively used in a variable mode and a fixed mode. In the variable mode, the quantizing values and thresholds for converting high valued image gradation into low valued image gradation can be changed so as to vary the surface gray levels of a printable image at a fixed laser gradation value. In the fixed mode, constant thresholds and quantizing values are used. The use of selectable operation modes enables easy printing operation with increased quality. Also, constant quality of printable images despite environmental changes may be realized by sensing and comparing currently read reference data with initially stored reference data and subsequently correcting quantizing values and thresholds in accordance with the compared result.

Abstract: An image processing method for converting multi-gradation image data into two-gradation image data by employing an error diffusion method, the image processing method comprises the steps of: (1) adding a diffusion error derived from at least one pixel which has already been binary-coded and is located near a pixel of interest to multi-gradation image data of this pixel of interest to thereby obtain corrected data; (2) comparing the corrected data with a threshold value and converting the corrected data into two-gradation image data for indicating any one of a dot ON and a dot OFF; (3) calculating a quantizing error corresponding to a difference between the corrected data and a first evaluation value corresponding to the two-gradation image data; (4) diffusing the quantizing error to a plurality of pixels which have not yet been binary-coded and are located near the pixel of interest; and (5) varying the first evaluation value corresponding to the two-gradation image data indicative of the dot ON in accordance

Abstract: A technique for calibrating the hardware and software of a digital printing apparatus relies on making seven component test patches which completely characterize the printing system, and then measuring the actual reflectance of these seven test patches. The measured reflectances are then converted, by the Yule-Nielsen equation, to values representative of the ink area coverage characteristic of each component test patch, because ink area coverage is the parameter that can be directly controlled by the digital printer. This conversion step takes into account the non-linear relationship between the reflectance of a halftone area and the amount of ink area coverage on the halftone area.

Abstract: An image processing apparatus of a digital copying machine, a digital facsimile, or a printer comprises an input unit to input multi-level data; an arithmetic operating circuit for adding error data to the input multi-level data and for calculating error correction data; a selector to select a predetermined dot pattern on the basis of the error correction data; an error calculation circuit to calculate a difference between the representative value for each dot pattern and the error correction data; a storage memory for storing the difference as error data into a memory; and a dot pattern memory in which dot patterns corresponding to a plurality of colors have been stored. The input unit inputs multi-level image data of a plurality of colors and the selector selects the dot pattern whose dot arrangement differs in accordance with the color of the multi-level image data.

Abstract: A printer driver for a color printer employs an error-diffusion-type half-toning process in which different quantization thresholds are employed for different ones of the color components. The color component whose value is highest after augmentation by accumulated error is compared with a relatively low threshold to determine the binary output value for that component. The lowest error-augmented component value is compared with a relatively high quantization threshold, and the component whose value is between those of the other two is compared with an intermediate-valued quantization threshold. Varying the thresholds in this manner tends to discourage coincidences of different-colored imaging agents at the same pixels and thus tends to result in light colors' having a smoother appearance.

Abstract: An enhanced error diffusion for color and/or black-and-white halftone reproduction of gray scale, color and/or black-and-white images, features enhancements in obtaining the thresholds that are used in error diffusion halftoning as well as enhancements in how to distribute error. Thresholds according to the invention are derived by applying a standard error-diffusion technique, using a fixed threshold value of 0.5, to a constant gray level image patch which has a gray level value corresponding to an irrational number. Thresholds so-derived are well dispersed in a threshold mask and have only a limited number of threshold values; use of such thresholds in error diffusion has been found to reduce significantly the presence of structural artifacts in halftone images.

Abstract: An image processing system for displaying pixel data on a screen performs a binary-encoding method using error diffusion with edge enhancement. In the method for binary-encoding the image data, pixels to be binary-encoded are divided into normal and edge regions, and the pixel data is binary-encoded in accordance with the divided regions. By using the method, bars on the display screen which are unpleasant to the eye can be removed and an image with good edge sharpness can be obtained.

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 an effective spot area value is generated when the modified input grey value is equal to or greater than the predetermined threshold value. The effective spot area value is retrieved from a look-up table having a plurality of effective spot area values based on the input grey image value.

Abstract: A method and system implements a redistributive characteristic into an error diffusion process. A grey level value representing a pixel is received. A threshold circuit thresholds the received grey level value and generates an error value as a result of the threshold. A portion of the error value is diffused to adjacent pixels on a next scanline. All the error for a single pixel on the next scanline is accumulated. Since this accumulated error has a greater number of bits than can be stored in a buffer, a portion of the accumulated error is truncated and redistributed to a down stream pixel for inclusion in the downstream pixel's error accumulation process. The grey level value has a first resolution which corresponds to an original input resolution. In a high addressabilty environment, the received grey level value is interpolated to subpixel grey level values before thresholding.