Abstract: A method for controlling printing of pixels corresponding to multi-level image data includes determining, based on multi-level image data for a target pixel and multi-level image data for pixels adjacent to the target pixel, whether the target pixel should be printed using a dye-based ink or whether the target pixel should be printed using a pigment-based ink. In a case that it is determined that the target pixel should be printed using the dye-based ink, a printer is instructed to print the target pixel using the dye-based ink. On the other hand, in a case that it is determined that the target pixel should be printed using the pigment-based ink, the printer is instructed to print the target pixel using the pigment-based ink.

Abstract: A two-layer image compression device is disclosed with a halftone circuit, an inverse halftone circuit and a quantization circuit. In this circuit, the halftone circuit converts the input gray-scale image into a binary image and rearranges the binary image output sequence to serve as a base layer of the input gray-scale image. The inverse halftone circuit recovers a predicted image from the binary image using the LMS algorithm and multi-table look-up methods. The quantization circuit then compares the input gray-scale image with the predicted image and encodes the difference between them to obtain an enhancement layer of the input gray-scale image.

Abstract: An edge detection method employs binary morphological erosion. A binary image is generated from the gray-scale-value input image. A structure element is guided in a step-by-step manner across the binary image and generates an eroded binary image in accordance with an erosion rule. By forming the difference between the binary image and the eroded binary image, an output image containing the edges is generated. An output image which contains masked edges is generated through the use of a further erosion rule. The further erosion rule is based on a gray-scale value threshold and is applied to the eroded binary image to form a twice-eroded binary image. The difference between the twice-eroded binary image and the binary image forms the image which contains masked edges.

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

Abstract: A facsimile apparatus contains transfer modes such as a standard mode, a fine image quality mode, a super fine image quality mode which are different from one another in resolution. A signal representing each transfer mode is transmitted from the transmission side to the reception side before the transmission and reception of facsimile image data. A control unit detects the resolution of reception data according to the transfer mode signal to switch over methods for conversion into high-tone in a high-tone conversion unit or to set the magnification of conversion of a resolution conversion unit according to the detected resolution. In this case, when high resolution is detected, the unit for conversion into high-tone executes conversion into multi-value using an area of 17.times.17 picture elements around candidate picture elements for processing. When low resolution is detected, the unit executes the conversion into multi-value using an area of 11.times.

Abstract: An apparatus and method of producing enhanced digital imaging for printing data, in flexographic and other types of printing environments, combines halftone screens which represent continuous "gray tone" (grey tone) levels, wherein the transition from one screen to the other is not visually detectable by an observer of the reproduction results. The digital processing method includes combining an (FM generated) dispersed dot screen with an (AM generated) cluster dot screen, with an overlay interval of both screens of acceptable resultant dot size (percent coverage), to obtain enhanced overall definition over the grey scale range of 1 to 100 percent (i.e., where 100 is equal to "255" in 8-bit environment), specifically over the more visually perceptive gray scale range of 1 to 20 (i.e., out of 0-255 value). The apparatus which implements the method algorithm is positioned intermediate a desktop publishing system and an image setter.

Abstract: In order to print an image sensed by a digital camera using a printing apparatus for forming an image on a print medium, image data corresponding to the sensed image is converted into print data, and the converted data is transmitted to the printing apparatus, thereby providing an image processing system which can print an image sensed by the digital camera using the printing apparatus without the intervention of any computer, and a digital camera and printing apparatus suitable for the image processing system.

Abstract: An input density for a subject pixel position (x, y) is retrieved in S230. A modified density value I'(x, y) is calculated in S240 based on the input density value I(x, y) and the error e(x, y) stored in the corresponding error buffer. Then, in S250, a discrimination value for the subject pixel position (x, y) is retrieved from the bilevel threshold value matrix Mat2( ) which is produced through the blue noise characteristic method. One of two threshold values is assigned to the retrieved discrimination value. Thus, a threshold value T is determined for the subject pixel (x, y). Then, an output density value O(x, y) is determined based on the modified density value I'(x, y) and the threshold value T in S260, S270, and S280. Then, an error value E(x,y) is calculated based on the output density value O(x, y) and the modified density value I'(x, y). The error value E(x,y) is distributed to the error buffer 16 in S300 dependently on the error distribution matrix Bat( ).

Abstract: When a subject pixel has been turned OFF, an accumulated error value is calculated based on binary conversion. Then, the sum of the accumulated error value and the binary conversion error for the subject pixel is compared with a predetermined value. When the sum is less than the predetermined value, the binary conversion error for the subject pixel is multiplied with a coefficient so that the absolute value of the binary conversion error is decreased. Then, the absolute-decreased error is distributed to unprocessed neighboring pixels according to an error distribution matrix. Then, the binary conversion error for the subject pixel is stored in a working memory as a binary conversion error for the s-th pixel to be used in the process of the next pixel.

Abstract: A method and apparatus for halftoning utilizes a truly aperiodic mask with memory requirements much smaller than the mask itself. The mask is constructed of several smaller compatible masks and a selector which selects between the smaller masks. In this way the computation of a large aperiodic mask is replaced by the computation of several much smaller masks. Using this technique, watermarks may be embedded for encrypting information in such a way that the quality of the image is not compromised.

Abstract: Two-dimensional barcodes surrounded by a quiet zone of white space which may or may not include a border, each barcode having encoded digital information in a bitmap representing preferably randomized encoded data bits, are printed onto a printed medium. To extract the encoded digital information from the printed medium, the printed medium is scanned, then the bitmap is located within the printed medium by moving a window, in stepwise fashion in a predetermined pattern across the printed medium. At each step the portion of the printed medium which is encompassed by the window is tested to determine whether it conforms to one or more characteristics of the bitmap. The skew of the bitmap, if any, is determined, by using a finite-state recognizer in combination with a Hough Transform calculation. In one embodiment, the candidate region is divided into a plurality of horizontal regions, preliminary skew angles are calculated for each region, and the actual skew angle is selected using a voting scheme.

Abstract: A high performance halftone shape for embedding machine readable data in printed documents is based on a hyperbola to accommodate the embedded data over an extended dynamic tone range. The shape enables precise tone control and can used for color printing. By rotating the shape 45-degrees, two alternate "ortho-serpentine" structures can be constructed which can be added to the diagonal structures, creating an embedded data system with four orientations. The quadrature system also allows more and varied patterns, but has the disadvantage of additional noise.

Abstract: An image data processing apparatus comprises output means for outputting an image data for each pixel and compression means for compressing the image data supplied from the output means to an image data of a predetermined number of bits. The compression means compresses the image data in accordance with a dot pattern having a predetermined number of tone levels.

Abstract: An image processing method and system for generating enhanced binary image data from greyscale input image data. The method includes the steps of (a) receiving first image data, the first image data being greyscale image data defining an input image, (b) performing a high frequency boost operation on the first image data to produce second image data, (c) performing a linear interpolation operation on the second image data to produce third image data, the third image data having a resolution higher than the resolution of the second image data, (d) performing a contrast enhancement operation on the third image data to produce fourth image data, and (e) thresholding the fourth image data to produce fifth image data, the fifth image data being binary image data defining an output image. The techniques find application, for example, in over-the-desk scanning of documents, and in video-conferencing.

Abstract: A multi-tone-level image is converted into an M-tone-level image using M-1 threshold values, where M-1.gtoreq.2. Middle-tone-level pixels in the M-tone-level image are treated as unknown pixels, tone levels other than the middle tone levels are given to the unknown pixels based on the states of pixels in the neighborhood of the unknown pixels, and thus produces an N-tone-level image, where M>N.gtoreq.2. Two threshold values of the M-1 threshold values are used for determine the middle-tone-level pixels, the two threshold values corresponding to the lightest tone level of a first image region and the darkest tone level of a second image region respectively. The first image region has tone levels which are darker than the middle tone levels and the second image region has tone levels which are lighter than the middle tone levels.

Abstract: An optical character recognition system recognizes character images in a document image comprised of character areas and non-character areas. The system includes a step of obtaining multi-value image data representing the document image, the multi-value image data having a first resolution and comprising plural pixels each having a pixel density value. The system binarizes the multi-value image data to produce binary image data having a second resolution for the document image, the second resolution being greater than the first resolution. The target pixel in the multi-value image data is binarized based on pixels adjacent to the target pixel.

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

Abstract: A video compression method and system including object-oriented compression with object boundaries described by maps of 2.times.2 (or larger) blocks of pixels in which at least a fraction of the pixels of such blocks are in the object.

Abstract: The invention relates to the halftoning of grey values of pixels obtained by a photoelectric scanning of an image. The grey values of the pixels for processing are thresholded, the quantisation error which occurs in these circumstances being added to the grey value of an adjacent yet to be thresholded and situated in a first or second direction of the image. The selection of a pixel in the first or second direction is determined in these conditions by the differences in grey values of not more than two pixels arranged in both directions and situated in the vicinity of the thresholded pixel. The pixel is preferably selected in the direction in which the smallest difference in grey value is encountered, i.e. not in the direction of the grey value gradient but exactly perpendicularly to it. It has been found that the edge transitions can be reproduced most sharply in this way.

Abstract: The present invention reduces the amount of data sent to a printer from a printer driver. Data reduction is achieved by using a dither matrix that is designed to produce compressible images, then using a lossless compression scheme that matches the dither matrix.

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

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

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

Abstract: A set of image feature extraction techniques to locate and group documents based upon appearance in a database management system. The system automatically determines visual characteristics of document images and collects documents together according to the relative similarity of their document images. The system is operable on both binary and grayscale images.

Abstract: An image processing apparatus includes an input unit for entering a plurality of color image signals, an image processing unit for subjecting the plurality of entered color image signals to processing based upon an algorithm of a cellular neural network, and a comparison decision unit for deciding output color data based upon results of processing by the image processing unit. Since input multivalued color image data based upon the algorithm of a neural network are converted to output color image data, it is possible to obtain a high-quality output color image that is faithful to the input color image.

Abstract: A method for compressing the bit data of an alpha mask image frame composed of an array of pixels having bit data indicative of a level of brightness includes selecting a modifying function identifier which represents a mathematical transformation, applying a threshold function to the alpha mask image frame to generate a binary image frame, and encoding the binary image frame and the modifying function identifier for transmission. The method may include receiving an encoded signal containing the binary image frame and the modifying function identifier, decoding the encoded signal to extract the binary image frame and the modifying function identifier, selecting the mathematical transformation represented by the modifying function identifier, and then transforming the bit data of at least one pixel in accordance with the mathematical transformation.

Abstract: A halftone screening method includes a method of moire suppression, in which the input image is first screened in a trial screening module. The input image is then subtracted from the trial screened image to produce an error image which contains both the trial screen pattern and the moire pattern introduced by the trial screening process. The error image is filtered in a lowpass filter to remove the trial screen pattern, leaving only the moire pattern, which is then subtracted from the input image to produce a compensated image. Finally, the compensated image is then screened in a final screening module. The moire image component of the compensated image tends to cancel the moire pattern introduced by the final screening module so as to suppress moire patterns in the final screened image. In two alternate embodiments, filter refinements are provided to reduce grayscale distortions and improve moire suppression in the extreme light and shadow regions of the image.

Abstract: A method and apparatus for resizing or processing images initially retrieves a one-dimensional sample of the image, such as a line of pixels. The image can be of a machine-readable symbol, or other data. A moving window having, for example, five pixels, includes a center "hard core" and four surrounding pixels. Two or more structural sets or multisets are applied to the window to produce a set of pixels greater than the set of pixels in the original image. For example, the center pixel is repeated three times, while immediately adjacent left and right pixels are repeated twice. Thus, a series of nine pixels results. The resulting nine pixels are then sorted based on descending gray scale levels. The n-th largest pixels is selected, such as the third largest. The image is updated, the window moved, and the method repeats again. Pyramid filtering, cubic convolution interpolation, or other techniques can be used to reduce the size of an image, and more complex windows and structural sets can be employed.

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

Abstract: In processing an image represented by binary data and an image represented by multivalue data, multivalue picture information is converted into a binary pattern corresponding to a value of the multivalue picture information, and stored in a memory. A binary pattern corresponding to multivalue picture information is detected from binary picture information stored in the memory to recover the original multivalue picture information.

Abstract: An idealized clustered screen is characterized spot clustering which is optimized so that clusters are about the same size and shape as they grow and are approximately equally distanced though an image. Pixels are swapped within the screen to vary its appearance. An optimization process iteratively checks a quality metric based on the optimum conditions, as pixels are swapped until an optimum screen appearance is obtained.

Abstract: An image processing method for determining a characteristic of image data in each area in whole image area and performing binarization processing appropriate for the characteristic, the method comprises the steps of: calculating gradation levels around a pixel in the image data; selecting a threshold value matrix appropriate for the pixel, in response to the calculating step, from the group consisting of a threshold value matrix consisting of single threshold value elements for simple binarization, a threshold value matrix comprising different threshold value elements for halftone processing, and at least one threshold value matrix comprising interpolation of both the threshold value matrixes; and binarizing the pixel by a systematic dither method using the threshold value matrix which is selected in the selecting step.

Abstract: In a picture-information processing apparatus, information of an edge in a picture is generated from information of luminances in the picture. Data of a mask corresponding to the edge is generated from the information of the edge. Information of feature points on an equal-luminance line in the picture is generated from the information of the luminances in the picture. The equal-luminance line is composed of segments extending between the feature points. A decision is made as to whether or not each of the segments of the equal-luminance line agrees with an edge line segment in response to the data of the mask and the information of the feature points. An edge decision signal is generated which represents the result of the decision. The edge decision signal is added to the information of the feature points.

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: A method for compression and decompression of dithered images is disclosed. Logical units (tiles) of the binary representation are classified into equivalence classes which are then compressed. Each equivalence class represents tiles having similar gray levels (i.e. the same number of black pixels), but which may have different sequences of black and white pixels. Each equivalence class has associated with it a predefined set of rendering exemplars. Each of the exemplars has a similar gray level. Upon decompression, each instance of an equivalence class takes on the value of one of the rendering exemplars which is selected pseudo-randomly.

Abstract: A printer driver operates a printer capable of multiple dot-placement geometries or resolutions and multiple inks per color channel. It maps a continuous-tone cyan pixel-component value to continuous-tone light- and dark-cyan values, which it separately halftones to respective binary pixel values that respectively indicate whether an associated pixel will receive light- and dark-cyan ink dots. It similarly generates binary values that respectively indicate whether an associated pixel will receive light- and dark-magenta ink dots. In performing the halftoning, the driver separately performs error diffusion through different interleaved sub-images of the image to be printed so that the error-diffusion process is performed for images whose pixel geometry is that for which the process was designed even though the overall image's pixel geometry is not.

Abstract: An improved display of a color image is achieved by an optimum placement of color dots using an efficient stochastic screening process in which display elements are formed according to a priority ranking of color and according to a spatial-priority matrix. Various combinations of basic colors are ranked in priority according to visibility such that elements in a stochastic screen are first formed for the most visible colors. The number of elements in the screen that are used to represent more than one basic color is minimized. In preferred embodiments, a spatial-priority matrix is used to control the placement of colors in a stochastic screen such that an optimally uniform distribution of colors is achieved. A process for generating a spatial priority matrix for display devices that do not have a one-to-one display aspect ratio is described.

Abstract: An image processor determines a binarization threshold value used for binarizing a multi-valued image, and performs binarization processing on the multi-valued image. The multi-valued image is input line-sequentially, the binarization threshold values are determined sequentially in units of predetermined size blocks each including a plurality of pixels, and the multi-valued image data is binarized line-sequentially. The inputting of data, determining the threshold value, and binarization of the multi-value image data is performed by pipeline processing.

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

Abstract: A method for halftoning an image to be rendered onto a media sheet includes the steps of: classifying data portions of a received data stream into one of plural image types, each image type to be subjected to a particular halftone procedure; assigning to each data portion of a common image type, a common identifier and then converting the data portions into a raster representation; subjecting segments of the raster representation to individualized halftone procedures, each segment of the raster representation that is assigned a common identifier being subjected to an identical halftone procedure; and rendering the raster representation onto a media sheet, subsequent to the halftone process. The apparatus for performing the halftone method places the halftone operation subsequent to the rasterization operation and thereby avoids anomalies which occurred in the prior art.

Abstract: A method and apparatus for separating picture image areas in facsimile machines, scanners, and other picture processing equipment, and more particularly to a method and apparatus for separating picture regions by extracting features of graphic image and characters includes a vertical contouring circuit for producing vertical contour data by combining vertical components of an original picture and binary picture data; a horizontal contouring circuit for producing horizontal contour data from horizontal components of the binary picture data; a logic combiner for combining outputs from the vertical and horizontal contouring circuits and a halftone picture; a mode discriminator for selecting between a binary picture and contouring mode; an image area separator for separating image areas with an output from the logic combiner and a halftone picture, and a counter for executing pixel counting from a halftone picture to determine the probability of the presence of a character.

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 of generating halftone output on an output device. The method includes retrieving at least one table which associates gray levels with halftone results for a region of an output frame including more than one pixel, determining a reference gray level for a tile of an output frame including more than one pixel, using the at least one table to determine a halftone result for the reference gray level, storing the halftone result for the reference gray level to the tile of the output frame, and delivering the output frame to the output device. The table may be generated from a set of thresholds, which may be a threshold array. A first table may associates gray levels with codes and a second table may associates codes with halftone results, and the method may include converting the reference gray level to a reference code with the first table and converting the reference code to the halftone result for the reference gray level with the second table.

Abstract: An image processing system having programmable keys for recording frequently used procedures is disclosed. The scanner comprises a scanning module for scanning an document, a plurality of programmable keys for recording frequently used procedures and a program key. The computer comprises a script file generation program for generating a script file of the programmable key. The script file is generated by using the following steps: (1) press the program key to generate a script file, (2) press a programmable key to relate the script file to the programmable key, (3) generate a plurality of control signals sequentially through various control keys of the scanner, (4) store the control signals in the script file, and (5) press the program key to complete the script file.

Abstract: Extended lossless imaging method and system, useful for medical and other imaging, where a succession of values of optical density or other feature of interest may be obtained by scanning an image as an array, or may be selected otherwise. Image data values in binary form are linked end to end into a concatenated number, partitionable into a set of ordered (non-repeating) numerical terms summing to it. Position counts of such a concatenated number also may be summed, as to give a "characteristic" whole part of a real number, and may be encoded arithmetically to give a "mantissa" fractional part thereof. The derived numbers are electronically stored for retrieval directly or by reverse computation, to yield reconstituted image data values, from which a lossless replica of the original image is readily made.

Abstract: A supercell is divided into halftone dot cells each with a highlight point at center and halftone dot cells each with a shadow point at center. Thresholds 0, 1, 2, 3, . . . assigned to pixels in the halftone dot cells each with a highlight point at center and thresholds N, N-1, N-2, N-3, . . . assigned to pixels in the halftone dot cells each with a shadow point at center are alternately determined, i.e., determined in the order of 0.fwdarw.N.fwdarw.1.fwdarw.N-1.fwdarw., . . . .fwdarw.3.fwdarw.N-3. When the density of an original image is high, the number of blackened pixels in the halftone dot cells each with a highlight point at center and the number of blank pixels in the halftone dot cells each with a shadow point at center are equalized to each other, thus preventing moire stripes from being produced which would otherwise be caused by a periodic change in the number of blackened pixels in the halftone dot cells.

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

Abstract: The present invention generates a first threshold value constituting a first threshold pattern and a second threshold value constituting a second threshold pattern. The first threshold pattern is to reproduce a relatively large number of tones and is relatively small in size, while the second threshold pattern has a relatively small number of tones and is relatively large in size. An arithmetic operation is carried out on the first threshold value and the second threshold value so as to generate a third threshold value. The third threshold value is compared with an image signal to generate a dot signal representing a halftone dot.

Abstract: A technique combines most of the advantages of both blue noise and clustering in generating a clustered aperiodic mask and using it in a dither array algorithm for halftoning. The method of halftoning of grey scale images utilizes a pixel-by-pixel comparison of the image against a clustered aperiodic mask in which the clustered aperiodic mask is comprised of a partly random and partly deterministic single valued function which is designed to produce visually pleasing dot configurations when thresholded at any level of grey.

Abstract: To perform processing to increase the number of pixels of inputted image data, the inputted image data having low resolution is converted to image data having high resolution. For this conversion, one pixel of the low resolution data is interpolated, a difference value between a predetermined value and image data included in an interpolating-pixel block which corresponds to a pixel of interest of the low resolution data, is calculated, and pixel values of pixels in the interpolation-pixel block are determined in accordance with the difference value. Furthermore, multi-level image data on which pixel values have been determined is binarized by the dither method, to determine pixel values such that the smaller the absolute value of the difference value is, the larger the difference from the predetermined value.