Abstract: The geometric texture and the graininess of an output image are improved in half tone processing using an error diffusion method. An image processing method where halftone processing is performed on input images using an error diffusion method including generating a sine wave where the amplitude and the frequency are modulated according to the average value of the target pixel value and the peripheral pixel values, adding the diffused quantization errors, the target pixel value and the sine wave, quantizing the addition result by a predetermined number of grayscale levels, and calculating the quantization errors of the peripheral pixels from the errors by quantization. By applying a disturbance sine wave by the error diffusion method, diffusion errors can be uniformly dispersed, and geometric texture and graininess can be improved.

Abstract: An adaptive halftoning method where the difference between a digital image and a filtered digital image is introduced into the system on a pixel by pixel basis is disclosed.

Abstract: The image forming apparatus and image forming method according to the present invention have an object of outputting a latent image formed on an intermediate recording medium as a stable image when it is developed with toner on a medium such as paper or the like, to improve more the concentration of pixel values, by adding all of N pixels in N-pixel modulation and rearranging them with a screen-line position as a reference situated at the center, thereby to reduce boundaries between image portions and non-image portions in the sub-scanning direction. Specifically, to concentrate image parts of image signals of N pixels, pixel values of all consecutive pixels in the main scanning direction are added, and the pixels are rearranged with a screen-line position as a reference situated at the center, based on the addition result. If the addition result exceeds the maximum value of one pixel, the exceeding pixel is rearranged and outputted.

Abstract: A method for reducing or eliminating residual error when “blank” pixels are found in the input image data is provided, such as one that can be used in printers of the type which use error diffusion as part of the halftoning process. When a blank pixel is found, the residual error may be immediately reduced in magnitude in one embodiment. In another embodiment, a “hop count” value is increased (or incremented) when a blank pixel is found, and if sufficient consecutive blank pixels exist in the input data, the hop count achieves a threshold and then either decimates or eliminates the residual error, thus limiting the migration of residual error. If a non-blank pixel is found in the input data before the threshold is achieved, the hop count is reset to zero.

Abstract: In order to reduce time required to perform error diffusion processing on one line of image data, one line of multi-tone image data 100 is divided into two or more segments of image data 102 and 103 with an overlapped region 101 provided across the boundary. The two or more segments of image data 102 and 103 are subjected to error diffusion to create binary image data 104 and 105 corresponding to the divided image data 102 and 103, respectively. Then the binary image data 104 and 105 are merged to form binary data 106 corresponding to the original image data of one line. Upon merging the binary image data, binary data b2 obtained from the divided image data 102 located upstream of the line before divided in the direction in which the error diffusion processing progresses is used as binary data corresponding to the overlapped region.

Abstract: An image processing method is provided for reproducing multi-gradation image data in the form of a bi-gradation image as used particularly in a printer, a scanner, a copier, a facsimile, etc. The method comprises acknowledging a pixel arrangement around a target pixel through examining an on/off-state of each pixel of a binary form, calculating error correction data from the pixel arrangement, and carrying out a binary coding of multi-gradation image data. Accordingly, as the error data for a binary form of the multi-gradation image data is corrected depending on the density of its actual printed form, unstable artifacts generated in the reproduction of pixels can be suppressed during the binary coding.

Abstract: A method for halftoning includes the steps of defining a first set of weight sets, and defining a second set of weight sets. A first error associated with a first pixel location of a plurality of pixel locations is diffused to a first neighboring at least one pixel location using a first weight set selected from the first set of weight sets, and a second error associated with a second pixel location of said plurality of pixel locations is diffused to a second neighboring at least one pixel location using a second weight set selected from the second set of weight sets. The first diffusing step and the second diffusing step are alternately performed along each scanline in the image to reduce visual artifacts.

Abstract: The present invention relates to an image processing technique for improving dot dispersion in highlight areas and shadow areas in an error diffusion method.

Abstract: An error adding portion adds together input multi-tone image data and peripheral error information. An adding/subtracting portion adds to or subtracts from multi-tone image data calculated by the error adding portion, a random number in a matrix prepared for each set of pixels of the input multi-tone image data. A quantizing portion quantizes multi-tone image data calculated by the adding/subtracting portion into image data, the number of bits of which image data being smaller than the number of bits of the multi-tone image data calculated by the adding/subtracting portion. An error calculating portion calculates an error based on the multi-tone image data calculated by the error adding portion and the image data quantized by the quantizing portion. An error storing portion stores the error calculated by the error calculating portion for each peripheral pixel.

Abstract: In the error diffusion technique for digital halftoning the output color for a first pixel is selected by comparing an adjusted input color signal to a boundary separating output colors in a pallette for a display device. The error or difference between the selected output color and the input color signal is determined and portions of that difference are added to the input color signals for neighboring pixels diffusing the error throughout the area neighboring the first pixel. Error diffusion can create artifacts in the image as rendered by the display device. Error diffusion artifacts are reduced or eliminated by a higher order error diffusion method where the boundary separating output colors in the device's pallette is adjusted as a function of the error in a previous pixel.

Abstract: Circuits for rendering according to the present invention are operable to function in either halftone mode or error diffusion mode. A pixel multiplexor selects between a rasterized unrendered pixel signal from an input rasterized unrendered datastream in halftone mode and an error diffusion adjusted pixel signal generated by error diffusion hardware in error diffusion mode. A memory stores the current error diffusion state signal and retrieves it as the previous error diffusion state signal during the processing of the appropriate pixel in the next scan line in error diffusion mode. A threshold multiplexor selects between an error diffusion threshold signal and a halftone threshold signal. In halftone mode, the memory is operable to retrieve a halftone threshold signal which is supplied to the threshold multiplexor.

Abstract: A method for eliminating moire in scanned digital image comprises the steps of using an average circuit for taking weighted average and error diffusing a gray level difference between an error diffusion pixel Gij and neighbor pixels to neighbor to obtain output image pixel Y′ij; using a second adder for subtracting the error diffusion pixel Gij from the output image pixel Y′ij to obtain a neighbor image error dij; using a error filter H(z) to process the neighbor image error dij to obtain a corrected pixel error H(d(i,j)); and using a first adder for adding the corrected pixel error H(d(i,j)) and the input image pixel Yij to obtain the corrected error diffusion pixel Gij, and then jumping to first step until all pixels being processed. The method provides real time treatment for eliminating moire and provide smooth image.

Abstract: A color marking system includes a control system for maintaining an accurate representation for approximating color space transformation comprising a set of piecewise homeomorphisms. The homeomorphisms and parametric models are selectively adjustable in accordance with printer/display calibrating data. Preferably the homeomorphisms comprise corresponding tetrahedra with domain and co-domain color spaces. If error above a selected level is detected, the tetrahedra are adjusted by calculating new locations for their vertices having a consequence of recomputation of model parameters and converging parametric model performance in accordance with a predetermined objective of the system. An inverse of the model is used for feedforward control of the marking system.

Abstract: An improved method of digital halftoning using “screens” or dither arrays is provided, including stochastic dither arrays (e.g., stochastic screening). The weakness of ordinary stochastic dithering is its isolated or dispersed dots and the related problems of dot gain and consistent dot formation when used with certain types of printers. However, the inconsistent formation of isolated dots causes unpredictable variations in uniformity and tone. The present invention solves this problem by grouping dots into small clusters, which may be rendered more consistently. Unlike conventional clustered-dot halftoning, however, this method arranges the dot clusters in a stochastic fashion to avoid objectionable periodic artifacts. A novel weighting function is used to generate the dot clusters, in which one function of a first extent is subtracted from another function of a second extent, thereby creating clusters of dots that center at locations where the weighting function chooses to place dots.

Abstract: There is provided an image processing apparatus which enables high-speed processing with simplified multiplications and divisions even in the case of error diffusion comprised of a combination of processes of two or more colors. The image processing apparatus performs error diffusion on multivalued image data composed of a plurality of density components and outputs the result of the error diffusion. A plurality of error tables are stored in a storage device. One error table is selected from the plurality of error tables according to a density value of a first density component among the plurality of density components and a density value of at least one other density component when performing the error diffusion on the first density component. A CPU performs the error diffusion on the multivalued image data using the selected error table.

Abstract: A method for reproducing a continuous-tone image in a reduced medium includes a comparison step, a diffusing step, and determining a threshold value for the comparison step from a matrix of threshold values, wherein the matrix has a spatial-chromatic correlated noise pattern.

Abstract: An image processing apparatus includes an error correcting section for correcting an input image on the basis of a supplied error correction amount and outputting a corrected image, a threshold processing section for processing the corrected image on the basis of a predetermined threshold, further processing the corrected image on the basis of the error correction amount, and outputting an output signal, a correction amount calculating section for calculating in advance a plurality of correction amounts corresponding to possible values of the output signal in parallel with processing of the threshold processing section on the basis of the corrected image output from the error correcting section, and selecting one of the plurality of error correction amounts as the error correction amount in accordance with the value of the output signal actually output from the threshold processing section, and an error correction amount supplying section for supplying the error correction amount calculated and selected by th

Abstract: The invention relates to a method of diffusing error caused by quantizing each pixel within an image formed of a plurality of pixels, each pixel representing a greyscale value of the image at a location (n, l) within the image, and having an original greyscale value associated therewith.

Abstract: An error diffusion processing circuit includes an error diffusion processing unit and a noise signal unit. The error diffusion processing unit generates a first output image signal of a first pixel by carrying out an error diffusion process, based on an inputted first input image signal of the first pixel. The number of gray tones of the first output image signal is smaller than that of the input image signal. The noise signal unit which generates a noise signal and outputs the noise signal to the error diffusion processing unit. The noise signal is inputted into a feedback loop of the error diffusion process.

Abstract: Disclosed are an image processing apparatus and method for the purpose of preventing overlapping of dots between two colors in low-density areas in color pseudo-grayscale processing, thereby obtaining excellent placement of the dots of each color. When a color image is binarized, an error is added to a respective one of color components (I0,I1), after which output decision means (2) decides an output value in accordance with the value of the sum in such a manner that the sum of pixel values after conversion will be rendered constant. Error calculation means (3-0, 3-1) calculate differences between pixel values before and after binarization as errors, and error diffusion means (9-0, 9-1) calculate values to be diffused to a neighboring pixel. Weighting coefficients used at such time are decided in accordance with combinations of values of the color components (I0,I1) of pixel values in the original image. The output value decided by the output decision means (2) is printed out by a printer or the like.

Abstract: A threshold modulation method, includes the steps of: a) determining whether an input pixel value is greater than a threshold of a current input pixel from the original digital image; b) determining whether an output image value is a predetermined high level or low level based on the threshold; c) if the input pixel value is greater than the threshold and the output image value is the predetermined high level, modulating the threshold of the adjacent pixel; d) if the input pixel value is greater than the threshold and the output image value is the predetermined low level, modulating the threshold of the adjacent pixel; e) if the input pixel value is not greater than the threshold and the output image value is the predetermined low level, modulating the threshold of the adjacent pixel; and f) if the input pixel value is not greater than the threshold and the output image value is the predetermined high level, modulating the threshold of the adjacent pixel.

Abstract: Systems and methods for generating graphical bar codes (i.e., images that contain inconspicuous graphical modulations that encode embedded information) by halftoning with embedded graphical encoding are described. In one aspect, a graphical bar code is generated by halftoning regions of an original image. The original image regions incorporate errors diffused among regions of the original image and computed based at least in part upon modulations in the graphical bar code corresponding to a graphical encoding of a message. In another aspect, a graphical bar code is decoded by generating a base image having halftone regions representative of an original image. Regions of the base image are compared probabilistically to a set of graphical code words to obtain a sequence of graphical code words corresponding to a graphical encoding of a message. The sequence of graphical code words is decoded to produce a decoded message.

Abstract: Tone dependent plane dependent error diffusion halftoning takes into account multiple color planes, such as cyan and magenta, when determining the placement of a dot in any of the color planes. The combined tones of the correlated color planes is used to determine the threshold levels against which the combined tones and the accumulated errors for the correlated color planes is compared. Further, tone dependent error weightings are determined based on the combined tones of the correlated color planes. The tone dependent error weightings are used to diffuse the final accumulated errors for each color plane. A prerendered mid-tone bitmap may be used to break up any structured patterns that occur in the mid-tones. 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 to provide a more uniform pattern and to avoid the unintentional overlapping of colors. This technique can be used to augment any existing error diffusion method.

Abstract: A tone dependent error diffusion halftoning system uses tone dependent thresholds and error weightings that are optimized by minimizing a model based cost function. An upper and lower threshold are used to compare with the modified pixel value. If the modified pixel value is greater than the upper threshold, a dot is printed, if less than the lower threshold, no dot is printed, and if between, a binary bitmap is used to determine whether a dot should be printed. For each midtone threshold level, a halftone image is generated by a direct binary search method and an error diffusion method. The magnitudes of the fast Fourier transforms, of the halftone images are compared using a visual cost function and the thresholds and error weightings are altered to minimize the cost function. For highlight and shadow tone levels, a filtered halftone image from an error diffusion system is compared to the continuous tone image after filtering the image via a human visual system model.

Abstract: An image processing method and an image processing apparatus are provided to maintain image quality through simple processing while reducing the number of gradation levels of image data by error diffusion process. In an image processing apparatus, data outputted from a filter is subtracted from input image data x(i, j) at the subtracter. Data outputted from the subtracter is quantized at a quantizer. Data outputted from the quantizer is outputted as output image data y(i, j). Furthermore, the data outputted from the subtracter is subtracted from the data outputted from the quantizer at a second subtracter to produce quantization error e(i, j). At a filter section, filtering process is performed on the quantization error e(i, j). Data outputted from the filter section is inputted to the first subtracter.

Abstract: An adaptive halftoning method where the difference between a digital image and a filtered digital image is introduced into the system on a pixel by pixel basis is disclosed.

Abstract: Methods and apparatus for processing an image is disclosed. First an output value of a first current pixel (inx,y−1), which is not at an edge of the image, is determined using a first influence value (Wx,y−2) for a first current pixel which equals a first sum, over a first set of pixels, of the product of a pixel weight value and a corresponding pixel value, where the pixel weight value is substantially equal to a weight factor (X, Z) raised to the power (i) of the distance of the pixel from the first current pixel.

Abstract: An apparatus (1100) for halftoning an image is disclosed. The apparatus comprises means for determining an output value of a current pixel on a current scanline using a sum of an input value (1102) for the current pixel and a neighborhood error value (1150) at the current pixel, means (1124) for determining an error at the current pixel as the difference between (i) the sum of the input value (1102) for the current pixel and the neighborhood error value (1150) at the current pixel, and (ii) the output value (1120) of the current pixel; and means (1140) for adding a proportion of the error at the current pixel to neighborhood error values at as yet unprocessed pixels of a subsequent scanline in accordance with a next scanline error impulse response; wherein said next scanline error impulse response approximates a function which spreads with self-convolution in proportion to a degree of self-convolution.

Abstract: In order to acquire a good binary image at all levels of gray scale, an image processing apparatus for quantizing input multivalued image data by a multivalued error diffusion method, selecting a predetermined dot pattern based on the quantized image data and outputting a binary image is configured to have an error calculation division for calculating corrected value from a pixel value and a processed pixel diffusion error of an input image, and calculating a quantization error from an output density level corresponding to the corrected value, an image generation division for first acquiring a diffusion coefficient corresponding to a pixel value of the input image, and distributing the quantization error to surrounding pixels according to a weight assignment by the diffusion coefficient to generate the binary image, a diffusion coefficient generation division for generating a plurality of candidate diffusion coefficients, a computing division for acquiring an evaluation value for the binary image generated by

Abstract: Halftoning by error diffusion, enhanced so as to reduce the presence of structural artifacts in the halftoned output while avoiding an artificial increase in halftoning image noise. Specifically, error diffusion according to the invention divides the input gray level intensity range into different segments for purposes of both thresholding and error diffusion. Different error diffusion threshold masks are applied for each respective segment, and different error diffusion weights are applied for each respective segment, with a decision being made as to whether or not to apply a different threshold mask being based on the local image gradient.