Abstract: Halftone processing section carries out a halftone processing using a dither threshold plane on which thresholds in a predetermined threshold range corresponding to the tone range of input image data are arranged, and provides halftone-processed image data. Image output section has intrinsic, basic tone characteristics and outputs an image corresponding to the halftone-processed image data provided from the halftone processing section. The dither threshold plane consists of a plurality of same unit threshold matrixes and each of the unit threshold matrix consists of a plurality of sub-matrixes. An array of relatively low thresholds in the predetermined threshold range is equal among the plural sub-matrixes, and relatively medium thresholds and high thresholds in the predetermined threshold range are arranged periodically to extend over series of sub-matrixes.

Abstract: A method and system for de-screening an image signal utilizing a bank of filters to provide several increasingly blurred versions of the original image signal is disclosed. At any given time, only two of these blurred versions are created, on a pixel-by-pixel basis. The outputs from the selected pair of blurred signals are then blended together to create a variable blending output that can vary smoothly from no blurring to maximum blurring in a smooth and continuous manner. In addition, the method provides the capability to enhance text and line art by using a variable un-sharp masking mechanism with independent post-blur sharpening control, and the capability to detect and enhance neutral (no-color) output pixels.

Abstract: Apparatus defines a dither mask (DM) and printmask (PM) with corresponding dimensions. In one invention form the DM dimension is not an integral factor or multiple of the PM dimension. The two dimensions may be lengths or widths; preferably the apparatus manages both; the corresponding dimensions differ by at least three pixels, and by a multiple of two pixels—more preferably eight or a multiple of eight. Preferably one dimension is an integral multiple of 256 pixels differing by eight pixels from the other. Another invention form has a scanning printhead making multiple passes across a print medium to form swaths of marks, a mechanism to define an offset smaller than at least one of the two dimensions, and a unit to index one mask by that offset between forming of successive swaths. This is valuable if DM and PM are established by preprogrammed circuits (e.g.

Abstract: When a halftone dot image structure reproduction mode is selected in a proof image data generating apparatus, color image data are generated using threshold matrixes having respective screen angles which are essentially equal to the screen angles of printing plates for a color print and screen ruling ratios between the threshold matrixes which are essentially equal to the screen ruling ratios between the printing plates for the color print, and the processed color image data are supplied to a color printer. The color printer outputs a color proof having a rosette pattern similar to the rosette pattern in the color print based on the supplied color image data.

Abstract: A method for removing color moire pattern noise having known chromaticities from a digital image is disclosed. The chromaticities are used to determine the region of color moire. The chromaticities within the region of color moire are then changed in accordance with the chromaticities of the located pixels in the region of color moire so that the color moire pattern noise is reduced.

Abstract: Dot cells are made up of halftone threshold data of color images of C, M, Y, K. At least the dot cells of color images of C, M, K are set under the condition of a non-rational tangent. Halftone screen periods and screen angles of said three color images of C, M, K are set such that a period and an angle of a primary moiré pattern produced when two of the three color images of C, M, K are superposed are substantially equal to a halftone screen period and a screen angle of the remaining one of the three color images of C, M, K. A halftone image is generated using dot cells thus produced.

Abstract: The present invention is a method and apparatus for reducing two-color moiréoften found during the rendering of full color images using halftoning techniques, by providing shared screen angles between distinct color separations.

Abstract: When clustered-dot dithering is employed in laser printers a banding effect sometimes results from the interaction of the dither matrix with non-uniform line spacing in the printer. We have found that we can lessen the effect of this interaction if we change the dither matrix as it moves over the image. We do this by modulating the dither matrix (halftone cell) as a function of the spatial position of the sub-area in the image. Halftone cells can be formed in a variety of patterns (e.g. vertical, horizontal, etc.) but generally their threshold values grow from a minimum value to a maximum value. Our process is to modulate the halftone cell according to a function: f (s, h) where s is the spatial position of the sub-area of the image and h is the halftone cell. We modulate the cell by altering the relative positions of the threshold values in the cell as we move the cell over the image.

Abstract: A method for automatic prevention of vertical streaks involves processing output signals from a plurality of photosites to determine what gain is appropriate for each output signal. An exemplary preferred method distinguishes between different types of output signals for which a first type of gain is appropriate and other output signals for which a second type of gain is appropriate. The first type of gain is a proportionate gain. The second type of gain is determined from at least one gain which is appropriate for output signals generated by neighbor photosites. The second type of gain is applied to the output signals when the processing indicates that a light-absorbing optical obstruction associated with the photosites generating the output signals appears to be positioned in an optical path of the photosites on or between a scan surface area over which an object to be imaged by the photosites is positioned and a calibration strip facing the scan area surface.

Abstract: A color image reading apparatus reads an original image by a line sensor through sequentially lighting respective light sources of a plurality of colors with respect to a scan line. An analog-to-digital converter converts an analog image signal read by said line sensor to digital image data. A lighting frequency ratio setting part sets the lighting frequency ratio for the light sources such that not all of the light sources are equally lighted. A thinning control part performs thinning control of lighting lines according to the lighting frequency ratio at which the light sources are lighted. A read data combining part combines read data of the plurality of colors according to a predetermined combination, said read data being obtained by the thinning control.

Abstract: Stripe patterns caused by grids having different pitches can be reduced when image data obtained by reading images photographed by using the grids are reproduced. A radiation image is read from a stimulable phosphon sheet on which the radiation image has been recorded by photographing using a grid of 3.4 lines/MM. Filtering processing by filtering means is carried out on digital image data obtained by the reading. The coefficients of a filter used in the filtering processing are −1, −1, 4, −3, −14, 0, 43, 68, 43, 0, −14, −3, 4, 1, −1. This filter is to reduce a response of a spacial frequency equal to or more than 3.3 cycles/mm to equal to or less than 5%, preferably to equal to or less than 2%. In processed image data obtained through filtering processing using such a filter, a response of 3.4 cycle/mm or 4.0 cycle/mm frequency corresponding to the grid of 3.4 lines/mm or 4.

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 method for halftoning a multi-channel digital color image having an x,y array of color pixel values, wherein at least two color channels are similar having substantially the same color but with low- and high-densities, includes the steps of: providing a matrix of dither values for each group of similar color channels wherein two or more of the matrices of dither values are designed jointly to minimize a visual cos t function; for at least one group of similar color channels, forming an inverted matrix of dither values by subtracting the value of each element of the matrix of dither values for that group from a predetermined maximum value, associating the inverted matrix of dither values with one of the low- or high-density color channels, and associating the matrix of dither values for that group with the other low- or high-density color channel of that group; for each color channel of the multi-channel digital color image modularly addressing the matrix of dither values associated with that color channel u

Abstract: An inkjet printer comprises a printhead that includes a number of printhead segments that span a print area so that portions of consecutive printhead segments overlap in common print areas. Each printhead segment defines a lead-in area in one common print area and a lead-out area in a consecutive common print area. An interface is configured to receive image data. A memory device stores data relating to characteristics of the printhead. A dithering unit communicates with the interface and the memory device. The dithering unit is configured to generate a lead-in dither matrix associated with the lead-in area and a lead-out dither matrix associated with the lead-out area, to generate lead-in/lead-out dither matrices for each common print area, to generate a variable probability value that is dependent on a scalar value that corresponds to a position along a line spanning each common print area and to interpolate the lead-in/lead-out dither matrices with the variable probability value.

Abstract: In an image processing method, a tone of a target pixel and tones of peripheral pixels around the target pixel are detected. Also, a tone difference between the target pixel and each peripheral pixel is detected. Then, smoothing processing is executed upon image data of the target pixel, based on the tone differences between the target pixel and the peripheral pixels, in such a way as to reduce a change of the tone of the target pixel.

Abstract: By simulating the interference-generated image fine structures with a continuous-tone printer or a display, the image fine structures can be predicted as faithfully as can be achieved by high quality machines. This is done without sacrificing the advantages of the continuous-tone printer or display (i.e., convenience in handling and the low costs of materials and machine), while ensuring that moiré, line discontinuities, imperfections in straight lines and other image fine structures that may appear in a printed document are predicted on a hard or soft proof accurately and conveniently and within a short time. The intensity of moiré and other peculiar patterns that occur when simulating the image fine structures in a printed document can be freely adjusted in accordance with the type of the printing machine which is to be employed to produce the printed document. Pixel values of an original image are separated, processed, and subjected to weighted averaging with adjustable weights.

Abstract: The result of integrating a halftone dot-shape can be clustered. When the edge of the halftone dot-shape extends across a “vertical” edge of a window, the window is altered until the edge of the halftone dot-shape no longer crosses either vertical edge of the altered window. The image density of the portion of the halftone dot-shape contained within the altered window is determined. The block of image density of the portion of the halftone dot shape contained within the altered window is aligned with the right edge, the left edge, split between the left and right edges, or clustered in the “center” of the altered window. An amount of the determined block that extends into the original sample window is determined. This amount extending into the original window determines the amount of image density to be generated in the final output image based on that sample location of the window.

Abstract: Image defects in a digital image are reduced by a process comprising:

Abstract: An apparatus and method for dither matrix design for color halftoning using dispersed dot clusters where the dot cluster centers are arranged in a homogeneous and isotropic pattern, in order avoid the moiré effect. The method requires that the size of the array and the number of dot seeds that will be in the array be predetermined.

Abstract: A method for opto-electronic scanning, by pixel and by line, of screened master photographic images with a sensing device. From the actual scanning, at least one master photographic image area that contains the grid scale is detected in the screened master photographic image. Subsequently, the picture values present in the local area of the detected grid scale area of the master photographic image are transferred by Fourier transformation to the frequency range as a spatial frequency spectrum, and, from the spatial frequency spectrum, the screen ruling and raster angle of the raster of the master photographic image are determined. For the determined raster angle and the determined screen rulings of the grid scale of the master photographic image, the optimal scan frequencies for Moiré-free scanning are determined from the spatial frequency spectrum.

Abstract: A maximum color identifying portion 41 identifies a maximum color from coloring material colors used to reproduce a color of a line segment after color conversion into coloring material colors by a character/line color converting portion 31 is applied to the rasterized image signal. A structure deciding portion 42 outputs a screen parameter flag that controls a screen parameter in compliance with the identified maximum color and a drawing direction of the line segment such that the screen process in the maximum color is executed at a screen angle, that is different from the drawing direction of the line segment, in a character/line screen processing portion 35. The character/line screen processing portion 35 applies the screen process to the image in accordance with the screen parameter flag by using the screen parameter at the screen angle that is different from the drawing direction of the line segment. Accordingly, disappearance of the line segment due to the screen process is avoided.

Abstract: An image processing apparatus prepares dot cluster within block by pixel value shift to determine phase quantity every pixel value block at the time of constituting stripe pattern or texture of dots by set of dot clusters within respective blocks to control value of pixel shifted from respective pixels within block to shifted pixel designated within block in accordance with phase quantity thereof. Thus, it is possible to control position within block of dot cluster within corresponding block by level smaller than pixel size. In addition, an image processing system includes at least an image reading unit in addition to such an image processing apparatus and preferably comprises an image forming unit to thereby obtain high picture quality and stable image.

Abstract: An additional motion is introduced into a scanning operation. This additional motion is in addition to the motion that is inherent in any document scanning operation. For example, in a flatbed scanner a linear array of scanning devices is positioned across the document in a first or “x” direction and this array is moved across the document in a perpendicular or “y” direction. In a flatbed scanner the position of the scanning devices are fixed in the “x” direction. In a drum scanner a light beam moves across the document in an “x” direction and the document is moved in the “y” direction. The light reflected from the document is directed to a fixed photoreceptor. With the present invention an additional vibratory motion is introduced into the scanning process. With a flatbed scanner the array of detector devices is moved or vibrated. The vibratory motion can for example be in the “x” direction.

Abstract: An image printing method, wherein one pixel is formed from a plurality of dots arranged in a primary scanning direction, in which printing elements are arranged, and in a secondary scanning direction perpendicular to the primary scanning direction; wherein the tone of one pixel is expressed by changing the overall printing area in accordance with whether or not the dots are printed; and wherein a multicolor image is printed by combination of one yellow pixel, one magenta pixel, one cyan pixel, and one black pixel, the method comprising the step of: setting to a nonintegral multiple a dimensional ratio among one yellow pixel, one magenta pixel, one cyan pixel, and one black pixel in the secondary scanning direction.

Abstract: In order to reproduce a gradation image of a plurality of colors with dither method, a plurality of patterns including first and second patterns are provided which makes dot in the reproduced image grow as lines and as lumps as gradation level increases with increase in gradation level. One of the patterns for a color of the received image data is selected, and received multi-level image data are screened with the selected pattern to generate bi-level image data for reproducing the image. In a different way, a plurality of patterns including first and second patterns are provided which make dots to be reproduced grow discretely along lines at low gradation levels as the gradation level increases. Screen angles of the first and second patterns are different by 90° from each other. One of the patterns is selected based on a color of received image data, and the received image data are screened with the selected patterns to generate bi-level image data.

Abstract: An image printing method, wherein one pixel is formed from a plurality of dots arranged in a primary scanning direction, in which printing elements are arranged, and in a secondary scanning direction perpendicular to the primary scanning direction; wherein the tone of one pixel is expressed by changing the overall printing area in accordance with whether or not the dots are printed; and wherein a multicolor image is printed by combination of one yellow pixel, one magenta pixel, one cyan pixel, and one black pixel, the method comprising the step of: setting to a nonintegral multiple a dimensional ratio among one yellow pixel, one magenta pixel, one cyan pixel, and one black pixel in the secondary scanning direction.

Abstract: A data carrier with at least one halftone images 10 represented by structural elements 12, whereby a predetermined symmetrical widening of structural elements 12 represents a corresponding gray level of halftone image 10. Image 10 has predetermined areas 14, 16 and 22 each having a predetermined number or screen frequency of structural elements 12, the screen frequency of structural elements 12 per unit area of area 14, 16 and 22 being different between at least two areas 14, 16 and 22 and/or structural elements 12 being offset from each other in at least two areas 14, 16 and 22. A data carrier with such a halftone image 10 acquires a moiré pattern in at least predetermined areas of halftone image 10 when copied, so that a copy of the data carrier is recognizable immediately and with the naked eye (FIG. 1).

Abstract: Lines or sections of lines on a scanned CRT display are checked to determine whether a moire pattern exists. The existence is determined by comparing the number of pixels occurring on a line or a section of a line to a reference count corresponding to a moire pattern. Substantial equality of the pixel count and the reference count enables a moire correction circuit for the section of the display containing the moire pattern. In sections of the display where the moire pattern does not occur, i.e., the pixel count and the reference count are not substantially equal, the moire correction circuit is automatically disabled.

Abstract: A processing system for preparing a plural separation document image for printing, including a process for mitigation or reduction of three color moiré. An approximation of moiré amplitude is calculated, and compared to a reference. Where three color moiré mitigation is desirable, black is removed and replaced with other separation colors.

Abstract: A method of operating a printing system that can print any of several different colors onto a point on a sheet of printer media. The method includes using a halftoning screen with a matrix of assorted threshold values, along with image data having a matrix of image data elements. For each data element and each color, a density value is determined to establish the amount of each color needed to produce the color associated with the original data element. Then a calculation determines which of the colors will be printed to the particular location. In a selected sequence of colors, density values of the colors are added one by one to generate a density sum that increases until it exceeds the threshold value. The last color added, which caused the sum to exceed the threshold, is then printed to the media sheet at a corresponding point.

Abstract: A system provides a halftone image having reduced moire patterns by applying a screen function of the type having a first function exhibiting symmetry about a point and a second function exhibiting symmetry about a line. In a progression of tone levels, such a screen function creates first dots, then lines, then dots. For example, a screen function may include the sum of a first function of the type (1−cos(pi*(x+y))*cos(pi*(y−x))) and a second function being a piecewise linear function of x, where {x,y} is a coordinate location in a unit cell mapped to a halftone cell mapped to the image pixel grid. In other embodiments, a unit cell is defined on the grid by a vector. The vector has a component along an axis of the grid. The component has a noninteger length. Unit cells of the type so defined implement rational tangent angles not possible with conventional halftone cells.

Abstract: A circuit for moiré suppression detects the Nyquist frequency in an input video signal. Based on detected alternating structures indicative of the Nyquist frequency, the circuit fades between outputting the input video signal and a low-pass filtered version of the input video signal. When the output signal is applied to a video display, moiré is suppressed.

Abstract: A method for calibrating a multi-chip image sensor, and an imaging system having a multi-chip sensor that includes color correction factors generated by such a method. The image sensor is successively controlled to image three different test targets. After imaging each target, a set of correction factors is generated and used to correct image signals generated when imaging the next test target. A first set of correction factors corrects for pixel-to-pixel variations between imaging elements in the array. The second set of correction factors corrects for chip-to-chip variations between chips in the array. The third set of correction factors corrects for array-wide variations compared to a standard color chart.

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: 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 image recording method in which a head, in which a plurality of recording elements are arranged in the main scanning direction, is moved in the sub-scanning direction, one of densities and area rates of respective pixels is varied in accordance with image densities, respective colors of yellow, magenta, cyan and black are combined so as to record multicolor images, the method including the step of: setting a ratio of dots, whose longitudinal direction period is in the sub-scanning direction, of the respective colors of yellow, magenta, cyan and black to 1:3/4:3/5:1/2, where any of these colors may be used as a standard for the ratio.

Abstract: A recording apparatus includes a recording unit having a nozzle line comprising a plurality of nozzles arranged along a sub-scan direction for recording a band having a record width corresponding to a length of the nozzle line onto a recording medium in accordance with an input image signal by discharging ink from the nozzles along a main scan direction orthogonal to the sub-scan direction, a transport unit for intermittently transporting the recording medium in the sub-scan direction, and a control unit for controlling the drive of the recording unit and the transport unit. The control unit sets a transport distance of the recording medium by the transport unit to a distance smaller than the record width when the image to be recorded on the recording medium comprises a plurality of bands. Each of the bands has at least one end having an image pattern complement to an image pattern at an end of adjacent band along the sub-scan direction.

Abstract: Disclosed is a method of producing a multicolored image in which the image is produced through the aggregation of a multiplicity of color dithering passes (CMYK). The method uses a dither matrix for at least one pass (C) which is of a different size relatively prime in relation to dither matrices used for the other passes.

Abstract: A screening system comprises at least one screen of which the phase is tone or image level dependent. This tone dependent phase shift influences the rosette structure and can be used to improve the neutral balance and color fidelity in multi-color reproduction and to minimize the visibility of such rosette structures in highlight and shadow areas.

Abstract: A screening system comprises at least one screen of which the phase is tone or image level dependent. This tone dependent phase shift influences the rosette structure and can be used to improve the neutral balance and colour fidelity in multi-colour reproduction and to minimise the visibility of such rosette structures in highlight and shadow areas.

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: An image processing arrangement is described that minimizes moire patterns in scanned halftone images of a scanned image while maintaining the resolution of the scanned image. The arrangement includes a filtering processor that has a modified median filter with a specially shaped (e.g., cross-shaped) filter window. The filter window allows the modified median filter to preserve scanned text images of the scanned image when processing the scanned halftone images to minimize the moire patterns. In addition, the filtering processor determines if an image pixel of the scanned image appears to belong to scanned continuous tone images of the scanned image prior to processing the image pixel. The filtering processor does not process that image pixel and the pixel value of that image pixel is left unchanged if the image pixel appears to belong to the scanned continuous tone images.

Abstract: An image recording method in which a head, in which a plurality of recording elements are arranged in the main scanning direction, is moved in the sub-scanning direction, one of densities and area rates of respective pixels being varied in accordance with image densities, respective colors of yellow,. magenta, cyan and black are combined so as to record multicolor images, the method including the step of: recording the respective colors in a pattern in which a dot pitch was randomly arranged only in the sub-scanning direction. Further, recording a color in a pattern in which a dot pitch was ordinarily arranged in the sub-scanning direction, and recording the other colors in a pattern, in which the dot pitch was randomly arranged only in the sub-scanning direction, could also be performed.

Abstract: An image processor performs emphasis processings suitable for materials to be copied to produce clear copy outputs. The image processor has a digitizing circuit which outputs a digital signal produced by digitizing an image. The processor further has a first detecting circuit which detects an area of the digital signal including a periodic component, a second detecting circuit which detects a character area of the digital signal, and a smoothing circuit which smoothes the digital signal to output a smoothed signal. Either the digital signal or the smoothed signal is selected and outputted by a changeover circuit according to an output of the first detecting circuit. The output of the changeover circuit is differentiated into a plurality of differentiated signals by a differentiating circuit by use of a plurality of different coefficients. One of the differentiated signals is selected and outputted according to the outputs of the first and second detecting circuits.

Abstract: The dot patterns which may be used to reduce dot gain and moire effects in halftone images involve printing areas which have inwardly curved edges and variable elongation. Colored images having screens which use these patterns may be printed with the screens at 45.degree. relative angular separations. Alternatively the dot patterns may be regarded as reversed variable oval patterns with varying elongation of the generally oval shaped non-printing areas.

Abstract: A solid state imaging apparatus includes two-dimensional frequency process which is applied to an output signal from each pixel of a progressive scan-type CCD. The CCD has an an arrangement of color separation filters without making carriers in the horizontal and vertical directions of the two-dimensional frequency to obtain chrominance signals with less moire in the horizontal and vertical directions of the two-dimensional frequency. A luminance signal with less moire in the horizontal and vertical directions of the two-dimensional frequency can be obtained by interpolating with the ratio of a chrominance signal with less moire.

Abstract: Image characteristics of a finally generated printed image that is reproduced from YMCK halftone dot percentage data from an image editor by an image output unit B are simulated highly accurately taking into account periodic noise and random noise, and the simulated image is outputted from an image output unit A. Specifically, the YMCK halftone dot percentage data from the image editor are converted into color image data corresponding to image characteristics of the image output unit B by an LUT combiner/converter, and periodic noise and random noise that can be produced by the image output unit B are applied to the color image data. The noise-applied color image data are then outputted from the image output unit A.

Abstract: An image data generating circuit of a color image processing apparatus generates multivalued image data for each color in accordance with density of each color of magenta (M), cyan (C) and yellow (Y). An M-screen threshold value generating circuit outputs a plurality of first threshold values, a C-screen threshold value generating circuit outputs a plurality of second threshold values, and a Y-screen threshold value generating circuit for outputting a plurality of third threshold values. A comparing circuit compares the multivalued image data outputted from the image data generating circuit with the first to third threshold values outputted from the M-, C- and Y- screen generating circuits for each color to output a comparison result in the form of a binary signal. The first and second threshold values is assigned to each pixel of an M multi-cell and a C multi-cell constituted by square matrixes having screen angles of .+-.tan.sup.-1 (q/p) and each side of .beta..multidot.p.multidot.q, respectively.

Abstract: A method of generating an output device control signal having portions representing the content of pixels of an image including at least two types of image content, in which data defining the content of each pixel of the image at a lower, first resolution and a higher, second resolution are passed respectively through a pair of processing paths, one corresponding to each image content type. A binary control signal is generated from the first resolution data in the first path by applying a stochastic screen. The binary control signal resulting from the stochastic screen is adapted to conform with the data at the second resolution, and the output device control signal is generated by combining data from the two processing paths.

Abstract: Halftoned frequency modulated color separations are produced from continuous-tone multicolored artefacts. The continuous tone values of the pixels of the scanned artefact are simulated by once and for all fixed halftone dot patterns within the pixels (tiles) of the halftoned reproduction. The dot patterns of the different tone levels are different for each individual color separation but are connected with each other through criteria specifying an overlapping dot ratio in conjunction with a translation prohibition, thereby substantially suppressing moire, disturbing effects of mis-register (e.g. color shifts) and graininess that is often seen in the highlights and midtones of reproductions with stochastic distribution of the halftone dots.