Abstract: A multi-color image forming apparatus and method to form a color image by overlapping multiple gradation pattern images formed for each of the recording colors based on the input color image information, wherein the screen angles of the unit gradation patterns of the multiple gradation pattern images are set such that they are separated from one another by 20 degrees or more, and in which the first unit gradation pattern is formed using a line pattern in which the colored dot patterns are made to extend in the direction corresponding to a first screen angle and the second unit gradation pattern is formed using a line pattern in which the colored dot patterns are made to extend in the direction corresponding to a second screen angle which is different from the first screen angle by 90 degrees.

Abstract: A method and apparatus are disclosed which permit a seamless halftoning of an image by halftoning regions of the image independently and/or in parallel. Each region of the image being arbitrarily determined, and being halftoned on the basis of halftoned pixel results of pixels within a predetermined neighborhood of the region. The arrangement providing a greater flexibility in the independent halftoning of the regions, while providing substantially seamless joins between abutting halftoned regions of the image. Further, the arrangement also provides a mechanism for parallel processing (halftoning) of abutting regions of an image with substantially seamless results.

Abstract: A ROM in the control circuit of a color printer stores a threshold matrix. The individual elements of the threshold matrix correspond to print dots, the number of which is X.times.Y and which form 1 pixel in the original image. Values t (x, y) which are integral numbers not less than 0 are assigned one to each of the individual elements in a predetermined order. Using the threshold matrix, the CPU of the control circuit creates mask patterns for representing halftones. A value of 1 is subtracted from the tone number allotted to the tone of color of a pixel in an image to be printed, and the resultant value is substituted for a variable G. When a gradation for image data representing the pixel is given as "g", the condition required for setting ON (transferring toner to print) the dot specified by the coordinates (x, y) in the pixel in the case of the gradation "g" is expressed by the following formula (6):t (x, y).ltoreq.g.times.X.times.

Abstract: Dither patterns are generated for use in converting a gray-scale image to a bi-level image. The dither patterns simulate halftone screen patterns with arbitrary screen angles. The dither patterns are made up of unit patterns, and have sizes calculated so that the unit patterns match up at the edges of the dither pattern.

Abstract: A method for halftoning a multi-channel digital color image having an x,y array of color pixel values, includes the steps of: providing a matrix of dither values for each color channel of the digital color image wherein two or more of the matrices of dither values are designed jointly to minimize a visual cost function; for each color channel modularly addressing the matrix of dither values with the location of a pixel in the digital color image to obtain an addressed dither value; comparing the addressed dither value for each color channel with the pixel value for the corresponding color channel to determine an output halftone image value for each color channel; and repeating steps b and c for each pixel in the digital image.

Abstract: The invention seeks to reduce amount of image data without detracting from picture quality, thereby lowering processing speed and holding down memory cost. While preserving the density of color image data, a computer compresses the color image data, which has been outputted by an image scanner, to a prescribed number of colors on the basis of the colors of inks. An image processor binarizes the results of compression, while preserving density, on the basis of ink colors. A main unit repeatedly prints a basic image, which is represented by the binarized image data, on cloth supplied from a supply unit.

Abstract: In a printer for printing an image by a distribution of dots having different densities per unit area or dots having different hues, the structure of the present invention accurately determines the on/off state of the different dots and ensuring high quality of printing. Recording ratios Rn and Rt of deep dots and light dots corresponding to input tone data DS in a target pixel are read from a map representing the relationship between the recording ratios and the tone data. The systematic dither method is adopted to determine formation or non-formation of a deep dot in the target pixel. This method compares the recording ratio Rn of deep dots with a threshold value Dref corresponding to the target pixel and read from a threshold matrix TM. In case that a deep dot is not formed, the recording ratio Rt of light dots is corrected by adding the recording ratio Rn of deep dots and subsequently compared with the same threshold value Dref to determine formation or non-formation of a light dot in the target pixel.

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: 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: 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: A gray component replacement method for each pixel of a continuous tone image, first obtains intermediate halftone colorant values by applying any suitable halftoning technique to continuous tone colorant values. Halftone output values at each pixel, including a black output value, are determined based on the intermediate halftone values. If desired, halftone output values can be determined based on both the intermediate halftone values and the continuous tone colorant values.

Abstract: A technique for reducing image artifacts is described. The technique includes utilizing a clustered-dot dither matrix having a plurality of layers with each of the layers arranged in one of a plurality of complementary patterns within the dither matrix. By using a dither matrix which generates layers of dots in complementary patterns, image banding artifacts and ink bleeding characteristics resulting from a printer generating a halftone image using a clustered-dot dithering technique are reduced.

Abstract: The binary, on-or-off commands for a binary scan-line-oriented display are obtained by half-toning through the use of a dither matrix of the clustered-dot variety. But in "tiling" the display surface with the replicated dither matrix, successive columns of the dither matrices are offset from each other, in the direction transverse to the scan direction, by a fraction of the cluster-row spacing. This reduces the banding artifacts that otherwise result from non-uniform scan-line spacing.

Abstract: A bitmap-based digital color printing method and system is described which automatically detects when a black object is commanded to be printed, and changes the Bit Block Transfer (BitBlt) method so that the resultant composition of the black color at each point in the bitmap is responsive to the amount of non-black colorants already existing in the background color at that position on the page. For many printing systems the resulting prints exhibit fewer visual defects. Single-color black objects printed on top of a color field are printed as process black responsive to the background color. Therefore, they exhibit a greater density and gloss and show fewer problems caused by the misregistration of separations or other printer defects, such as white fringes around the black objects. They also avoid problems caused by excessive ink coverage differences between foreground black and background color.

Abstract: A hybrid system for digitally screening black and white and/or color images using a number of imaging techniques is disclosed. Cyan, yellow, magenta and black color separation may be processed according to the same or different methods according to gray levels or other factors, in order to optimize output print quality.

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 method and apparatus for selectively depositing ink on a recording medium is described. The method and apparatus implement a technique in which portions of a clustered-dot dither matrix are identified and no ink is deposited under any circumstances in the so-identified portions. The portions are organized into a relatively large dispersed distribution matrix within the clustered-dot dither matrix.

Abstract: A method for halftoning a multi-channel digital color image having an x,y array of color pixel values, includes the steps of: providing a matrix of dither values for each color channel of the digital color image wherein two or more of the matrices of dither values are designed jointly to minimize a visual cost function; for each color channel modularly addressing the matrix of dither values with the location of a pixel in the digital color image to obtain an addressed dither value; comparing the addressed dither value for each color channel with the pixel value for the corresponding color channel to determine an output halftone image value for each color channel; and repeating steps b and c for each pixel in the digital image.

Abstract: The present invention provides a system and method for generating halftone patterns. Typically the generated halftone patterns are used for generating dither matrices to halftone a image with improved visual quality. The steps for generating a plurality of color halftone patterns include: defining a color path from a color concentration level p to a color concentration level q; and generating a halftone patterns f.sub.j for each color concentration level j along the defined color path. After the halftone pattern f.sub.j is generated for the color concentration level j, the color fluctuation of the halftone pattern f.sub.j is minimized. A key contribution of the current invention is the decomposition of a color halftone pattern which occurs during the step of minimizing the color fluctuation for halftone pattern f.sub.j, and which allows simultaneous optimization of underlying color halftone patterns. After the step of minimizing the halftone pattern f.sub.

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: A system and method for halftoning multi-level pixels preferably uses a threshold array divided into two or more classes. The classes are ordered in a visitation order. Each class contains at least one element. A halftone cell comprised of a plurality of pixels corresponds to the threshold array. As the intensity level for the halftone cell increases, the pixels corresponding to the elements in the first class are halftoned by fractional values of pixels until all of the pixels in that class reach saturation. As the intensity of the halftone cell increases, none of the pixels corresponding to the elements in any other class change state. Once the pixels corresponding to the elements in the first class are saturated, the pixels corresponding to the elements in the second class are halftoned by fractional values of pixels. In more general terms, the next class in the class visitation order is not addressed until the pixels corresponding to all of the elements in the previous class are saturated.

Abstract: To convert the multiple-bit-resolution intensity information for a color component of a given pixel into the ink-on or ink-off command required to control a printer, the source values for different pixels are compared with thresholds in a "dither matrix" of different thresholds for different pixels, and a given pixel is printed if the source value exceeds the dither-matrix value for that pixel. Different dither matrices are employed for different color components, with the result that lighter-color areas have a smoother appearance than they would result if a common dither matrix were employed for all color components.

Abstract: The shift register 43Y is written with four bits of data for recording dots of yellow color, the shift register 43M is written with four bits of data for recording dots of magenta color, the shift register 43C is written with four bits of data for recording dots of cyan color, and the shift register 43Bk is written with four bits of data for recording dots of black color. The recording head 29 is scanned relative to the recording paper 33 in dot intervals D in a scanning direction. In the recording head 29, the recording units 30Y, 30M, 30C, and 30Bk for recording the four colors are aligned in the scanning direction with an interval P equal to a sum of one dot interval D and a multiple of four dot intervals 4D. With this arrangement, the shift registers 43 are supplied with the four bits of data at timings shifted from one another by an amount corresponding to one recording timing period T.

Abstract: Halftone-dot area percentage data generated from an image document for at least three plates including three primaries are converted into respective bit map data with referring to respective threshold matrix. The bit map data are simultaneously referred to with respect to each of the pixels of a color printer which is to output a color proof, and thereby the area percentages are counted. Then, predetermined colorimetric data of the respective colors are processed by the area percentages as weighting coefficients, and the average tristimulus value data are calculated. The calculated tristimulus value data are used as pixel data of input image data of the color printer.

Abstract: Methods and apparatus generate, and use in printing, a dither matrix that incorporates a vivid-response function, that follows a generally S-shaped response curve. Printing with this pregenerated dither cell is just as fast as with a conventional cell, but printed color has a slightly exaggerated vividness, more pleasing to most users than more-accurately reproduced color. Color printed with this curve alone, however, is found unsatisfactorily dark; the invention also encompasses including in the overall response another function to lighten the colors--particularly at the low end of the brightness range. We define both functions as so-called "gamma functions", but with different arguments and exponents, and construct the S-shaped curve as two separate sections blended at a generally central point. Preferably the argument of the first (low-brightness) section is an expression that is proportional to an input color signal; the function raises this argument to a power greater than unity (ideally 1.6).

Abstract: An image forming apparatus discriminates a color of an inputted color image for each pixel and generates a first color component and a second color component. The apparatus compares values of the first and the second color components, and selects and outputs the color component having a larger value. Meanwhile a color component which is not selected is diffused to neighboring pixels. When pixels neighboring a pixel of interest in a predetermined area are filled with one color component, the other color component is selected and outputted regardless of the values of the first and second color components.

Abstract: A printing system that uses a halftone processor is driven to halftone selected areas of an image based on a selected halftone dot, wherein the halftone dot has the properties of maintaining a dot fill order of a desired dot, while also maintaining a preselected percentage of the dot as untilled space.

Abstract: In a method for creating at least five to seven color separations for input into a raster image processor for creation of at least five screen separations for use with at least a five color press to create at least a five color printed page, a scanned digitized image is created represented by at least three digitized color image signals. These at least three digitized color image signals are input into a digital color separation computer. The digital color separation computer is used to create at least five single color unscreened image separations in the form of computer files. The computer files are input into a raster image processor to create at least five single color screen separations in the form of electronic signals. The electronic signals are then fed to a film recorder to create at least five single color screen separation films used in conjunction with a five color press to create the at least five color printed page.

Abstract: A method for applying FM screening, also known as stochastic screening, to a digital image in a computer. The method permitting manipulation and editing "on-screen" of a CMYK image having a random dot pattern (FM screening) applied. The method permitting the "on-screen" editing of each of the four color separations (cyan, magenta, yellow, and black) of the CMYK FM screened image while viewed as a single composite image. The "on-screen" editing of the CMYK image performed and viewed before the image is directed to an imaging device.

Abstract: A system and method usable in producing a display image limited to a lesser number of colors from an input image having a greater number of colors. The invention is particularly useful in a computer system utilizing a video monitor capable of simultaneously displaying a selected number of colors stored in a lookup table. The system and method receive data representative of respective colors at a multiplicity of individual pixels in the input image. This input image data is then temporarily stored in an input buffer. An appropriate processor receives the input image data and performs image quantization thereon. Specifically, the processor first determines the selected colors to be included in the display image. Next, the processor determines which of the selected colors respectively correspond to individual pixels of the display image.

Abstract: Halftone screens are generated for each separation in accordance with the goal of avoiding overlapping whenever possible. Initially, the black separation is halftoned, generating a dot pattern with a number of ON pixels and OFF pixels in accordance with the area density of the black separation. Next, a first color separation is halftoned, setting a number of the previous OFF pixels to ON. Then, if any white pixels remain, the second color separation is halftoned, setting a number of the previously OFF pixels to ON. If during the processing of the second and third separations, it is determined that no OFF pixels exist to be turned ON, a second layer of color is started, respectively superimposed over the first layer. The third color separation is halftoned in reverse fill-in order, setting a number of the previous OFF pixels to ON. Each layer is started and arranged so that the additional colors forming the dot pattern are not placed on any black areas.

Abstract: A catalogue card and a document card are used for a file system. The document card indicates a predetermined document. The catalogue card indicates a catalogue of the document. Since the catalogue of the document is input to the file system via the catalogue card instead of a keyboard, a user who is not used to operating a keyboard can easily input the catalogue and manage the document.

Abstract: This invention discloses an improved method and apparatus for generating a screened reproduction of an image. The apparatus comprises a matrix defining an arrangement of a plurality of areas within a printing dot, each having an assigned reference value. The screening logic apparatus receives input density information with respect to an image and includes apparatus for assigning to each input density a corresponding plurality of reference values. The apparatus also includes a method for combining with each of the plurality of reference values a random additional reference value, thereby defining a randomized plurality of reference values. The apparatus also causes the exposure of those areas in the matrix having reference values which correspond to the randomized plurality of reference values.

Abstract: In a method for transforming a color signal, a target output color signal component (X, Y, Z) is transformed into an input signal component (B, G, R) by referring to a look-up table, and a target output color signal component, which is not stored in the look-up table, is transformed into an input signal component by an interpolating process. In an output color signal space, a local coordinate system is set by using a successive approximation process, and a desired output color signal component is subjected to linear interpolation in the local coordinate system. A three-dimensional interpolating process is thus carried out quickly and accurately and over the entire color reproduction range.

Abstract: A half-tone mask is characterized by an N.times.M array of mask value locations associated with at least a portion of the pixels of the digital image. The size of the mask array may contain a relatively small number of pixel locations, which is applied spatially to mutually contiguous subsets or sub-arrays of pixels of a relatively high resolution digital image. Although the mask may also be made large enough to encompass the entire image of interest, respective threshold values of the mask may be computed `on the fly`, so as to obviate the need to prestore all of the threshold values of the mask. Each of the locations of the mask array is assigned a respectively different grey scale/half-tone conversion threshold value. These threshold values are distributed among the locations of the mask array such that as one proceeds through the mask array, the next sequential location is specified in accordance with fractional parts of integral multiples of a two-dimensional analog of the Golden Mean.

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.

Abstract: A system and method for representing a multi-color, halftone image on a multi-color, continuous-tone device can be configured to employ an approximation technique for determining areas of overlap regions produced by adjacent device spots in a printed halftone image based on a halftone device model. The approximation technique enables consideration of the effects of a variety of halftone device characteristics such as addressability, device spot size, and color values on the appearance of a printed halftone image. The system and method can be configured to employ the approximation technique in a manner that also enables consideration of the effect of misregistration between color separations on the appearance of a printed halftone image. As an alternative, the system and method can be configured to employ a geometrical abstract that effectively centers device spots on the corners of addressable units.

Abstract: The present invention relates to a method of enhancing a digital color video image comprised of separating a source pixel into individual component parts, for each component part, generating a random number having the same length as the corresponding component part, adding each random number to its corresponding component part to form resultant component parts, and combining the resultant component parts to form a destination pixel.

Abstract: An image processing system for preparing a color document for printing, each discrete area or pixel in the image described by a signal having a number of possible states greater than can be rendered by a selected printer, in which each separation of the image is halftoned, with at least one of the separations processed with a non-periodic halftoning method, and at least one of the remaining separations processed with a periodic pattern. Preferably, in a printer printing with colorants approximating cyan, magenta, yellow and black, one of the non-yellow separations is processed with the non-periodic halftoning method.

Abstract: A method for the point-by-point and line-by-line recording of rastered images, whereby, in order to avoid discontinuous changes of the raster density, a modulation signal that increases the raster density to be recorded and a modulation signal that reduces the raster density are superimposed, at least in one direction of an image coordinate, on the image signal which determines the raster density to be recorded. As a result, at least one reduced and one enlarged raster point is recorded in respective alternating fashion in at least one expanse of the raster between the raster points that reproduce the raster density to be recorded. An apparatus for implementation of the method comprises a modulator which combines an image signal with a modulation signal. The modulator is connected to a modulation generator that generates the modulation signal and in which the amplitude of the modulation signal is influenced, dependent on the amplitude of the image signal.

Abstract: The method approximates full color resolution by combining dot-on-dot (DOD) and dot-next-to-dot (DND) techniques in printing images received from a computer. The method prints with DOD at the edge of an image or in a depleted area within an image and prints with DND elsewhere within the image to conserve printing time and ink. In the method, the color for each dot of the image is stored, and the image is divided into subgroups of four dots each. Each dot is then tested for significance by looking at whether other dots within the group or adjacent to the group are white. The color for each dot is mapped to one or more colors for printing, the mapping depending on the significance status of at least one dot within the subgroup. In this manner the image is checked for solid and depleted areas of color so that the minimum number of dots are printed within each subgroup.

Abstract: Apparatus and associated methods employed therein, for objectively providing an accurate appearance match between images produced by two imaging systems (e.g. a target image produced by one such system, e.g. a press sheet (140) generated by a printing press (130), which is to be matched by a replica image produced by another such system, e.g. a proof (120) generated by a color halftone proofing system(110)) and thereby calibrate the performance of one imaging system, e.g. the proofing system, to that of the other system, e.g. the printing press. Specifically, measurement data, such as illustratively densitometric N,R,G,B measurements, is obtained for the same portions of the press sheet and proof. This data is then transformed into a color space which encodes color information in a pre-defined manner that approximates color preferences inherent in human color interpretation.