Abstract: An image processor includes: a color conversion unit for converting an input signal to color signals of at least four colors; a gamma correction unit for performing gamma correction on the color signals; a binarization unit for binarizing the color signals through comparison with a threshold value; a superimposing unit for superimposing a color signal of at least one color but of the binarized color signals on another color signal to convert the signals to a superimposed color signal; logical operation unit for performing a logical operation previously defined for an image of three or fewer colors on the superimposed color signal; and a separator for separating color signals as an output of the logical operation unit into separated color signals of at least four colors.

Abstract: A threshold mask for converting a contone image to a halftone image defines halftone cells that define halftone dots that undergo a growth in population as tone levels increase. After some growth in population, the halftone cells define halftone dots that then grow in size from a first predetermined size as tone levels increase further. During the growth in population, the halftone dots having a second predetermined size are placed into halftone gaps. The second predetermined size is smaller than the first predetermined size. In the simplest implementation, FM screening is used up to a tone level where the FM dither pattern holes begin to become visible. At this point AM screening is applied only to the remaining dot centers (corresponding to those holes) until they reach the stable dot size. Then, the dots are further grown according to the method used outside of the FM regime (e.g. the conventional AM process). In the FM regime, two types of visual disturbances can arise.

Abstract: The invention provides a printing method and apparatus which can reduce moirés and artifacts. The printing method includes an expanding step of expanding a multi-value image in a storage area, and an image forming step of binarizing the multi-value image expanded in the storage area based on a binarization dither matrix pattern wherein the turn-on order of pixels is set so that dots having shapes same as each other individually grow in order from a plurality of points and forming an image based on a result of the binarization.

Abstract: A color data converter includes a plurality of memories configured to store lattice points for a color space. The lattice points of the first axis are assigned to memories in a sequential manner. The lattice points along the other two axes are assigned to memories in an alternating manner.

Abstract: A system and method are provided for processing digital multi-colour images for the reproduction thereof on a colour printing and/or copying system. Image dots of marking particles of the respective colours associated with the respective colour separation images are positioned contiguous to each other as long as the print area corresponding to the image part to be reproduced is not fully covered so as to create a first layer of marking particles. If the area is fully covered and the image is not yet completely rendered, a second and any following layer of contiguously positioned marking particles is formed on top of the first layer of image dots. The halftoning of the digital image is such that within the same layer all images dots, irrespective of their colour, are obtained using a raster of the same matrix structure, while image dots associated with different layers are obtained using rasters of different matrix structures.

Abstract: A technique is described to greatly reduce or avoid the quantization errors that occur when mapping a relatively linear RGB color space into a greatly non-linear printer CMY color space of equal precision, avoiding the contouring or banding that occurs when printing color gradients in a non-linear printing system. The technique performs a dither-like process on the original RGB continuous tone data. The RGB values are dithered to create a range of values that, when mapped to the non-linear printer continuous tone CMY values, creates a range of CMY values that, on average, represent the correct average tone of the input RGB values. The generated CMY continuous tone values are then halftoned and printed.

Abstract: A print engine/controller (10) configured to be coupled with others to drive an ink drop printhead (33). It has an interface (27) at which to receive compressed page data. Image decoders (28, 88) decode compressed image planes in the received compressed page data. A half-toner/compositer (29) a half-toner/compositer composites respective strips of the decoded image planes by halftoning a contone layer to a bi-level version and compositing a spot1 bi-level layer over an appropriate halftoned contone layer. A printhead interface (32) interfaces with the printhead. A synchronization signal generator (89,90) outputs a synchronization signal that is used to synchronize print engine/controllers. In some embodiments, one printhead interface (32) acts as master generating the synchronization signal to synchronize all the print engine/controllers to drive the printhead at any one or more of higher speed, higher input resolution, higher outlet resolution or wider format.

Abstract: A printer with synchronized engine/controllers is disclosed. The printer has a multi-segment printhead. Each engine/controller (10) configured to be coupled with others to drive the printhead (33). Each engine/controller (10) has an interface (27) at which to receive compressed page data. Image decoders (28, 88) decode compressed image planes image decoders to perform an expansion, in pipeline fashion, for the received compressed page data. A half-toner/compositor (29) composites respective strips of the decoded image planes and sends output to a printhead interface (32). A printhead interface (32) interfaces with the printhead. A synchronization signal generator (89, 90) may output a synchronization signal that is used to synchronize print engine/controllers.

Abstract: A printer with a multi-segment printhead has multiple engine/controllers (10) configured to be coupled with other engine/controllers to drive the printhead (33). The controllers each have an interface (27) at which to receive compressed page data. Image decoders (28, 88) decode compressed image planes image decoders to perform an expansion, in pipeline fashion, for the received compressed page data. A half-toner/compositer (29) composites respective strips of the decoded image planes and sends output to a printhead interface (32). A printhead interface (32) interfaces with the printhead. A synchronization signal generator (89,90) may output a synchronization signal that is used to synchronize print engine/controllers. One printhead interface (32) preferably acts as master generating the synchronization signal to synchronize all the print engine/controllers to drive the printhead at any one or more of higher speed, higher input resolution, higher outlet resolution or wider format.

Abstract: A print engine/controller (10) configured to be coupled with others to drive an ink drop printhead (33). It has an interface (27) at which to receive compressed page data. Image decoders (28, 88) decode compressed image planes image decoders to perform an expansion, in pipeline fashion, for the received compressed page data. A half-toner/compositer (29) composites respective strips of the decoded image planes and sends output to a printhead interface (32). A printhead interface (32) interfaces with the printhead. A synchronization signal generator (89, 90) may output a synchronization signal that is used to synchronize print engine/controllers. One printhead interface (32) preferably acts as master generating the synchronization signal to synchronize all the print engine/controllers to drive the printhead at any one or more of higher speed, higher input resolution, higher outlet resolution or wider format.

Abstract: A method for processing an input digital image having an x,y array of input pixels having associated input pixel values, to produce a multichannel multitoned output image having two or more colorant channels, wherein at least two of the colorant channels are similar, having substantially the same color but different densities, including determining continuous-tone pixel values for each colorant channel of the input digital image in response to the input pixel values using an ink manifold processor; for each colorant channel, selecting a multitone process from a plurality of multitone processes in response to an input pixel value using a multitone process controller; for each colorant channel, applying the selected multitone process to the continuous-tone pixel value to produce a multitoned output pixel value; and repeating steps a)-c) for each input pixel in the input digital image to produce the multichannel multitoned output image.

Abstract: A printing technique wherein pixel locations that are requested to be marked with only black are identified, black is applied to the identified pixel locations, non-black color is applied to a subset of the identified pixel locations that have an associated black half-tone threshold level that is darker than a predetermined non-white threshold level, such that only black is applied to identified pixel locations having an associated black half-tone threshold level that is lighter than or equal to the predetermined non-white threshold level.

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: 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: The invention relates to a method for representing the halftone of an image. The invention is based upon a combined scanning method with a dither matrix and an error diffusion method. According to the invention, when a halftone value of an image is determined, the colour value of image points which are not arranged next to the image point whose halftone value is being determined are corrected. Several colour values in particular are corrected. According to the inventive method, errors existing when determining a halftone value are distributed over a larger area, enabling predetermined point forms to be substantially maintained by the dither matrix.

Abstract: While a general large layer dither volume provides great flexibility in dither cell design, by decoupling different intensity levels, they are inefficient to access since each colour component requires the retrieval of a different bit from the volume. Therefore in a multi threshold dither volume for digital halftoning a contone colour image, in the form of an array of contone colour pixel values to bi-level dots, there is allocated for each dither cell location a fix set of n thresholds defining n+1 intensity intervals within which said dither cell location is defined to be alternatively not set and set.

Abstract: While a general large layer dither volume provides great flexibility in dither cell design, by decoupling different intensity levels, they are inefficient to access since each colour component requires the retrieval of a different bit from the volume. Therefore in a multi threshold dither volume for digital halftoning a contone colour image, in the form of an array of contone colour pixel values to bi-level dots, there is allocated for each dither cell location a fix set of n thresholds defining n+1 intensity intervals within which said dither cell location is defined to be alternatively not set and set.

Abstract: While a general large layer dither volume provides great flexibility in dither cell design, by decoupling different intensity levels, they are inefficient to access since each colour component requires the retrieval of a different bit from the volume. Therefore in a multi threshold dither volume for digital halftoning a contone colour image, in the form of an array of contone colour pixel values to bi-level dots, there is allocated for each dither cell location a fixed set of n thresholds defining n+1 intensity intervals within which said dither cell location is defined to be alternatively not set and set.

Abstract: An image to be printed is stored in an image storage memory of approximately 1.3 Mbytes. An image access unit accesses the image and transfers the image to a printhead interface on command from the central processing unit. The printhead interface transforms the image to a 1600 dpi dithered bi-level CMY image for printing by a monolithic printhead.

Abstract: It is necessary that paper be moved past the printhead at a constant velocity to obtain artifact-free printing. Therefore the printhead requires a constant stream of data during printing. Whilst it is possible to rasterize the page using a page description language directly to the printhead, it is uneconomical. Hence the redering is carried out in the PC. However, the standard USB peripheral connection is the standard connection on PCs, which places a constraint on the limit of data per page that can be transmitted to the printer and still obtain a reasonable rate of printing. Thus the contone images and graphics are rendered in the PC to a pixel level, and the black text and graphics are rendered in the PC to a dot level, where the rendered data is compressed and transmitted to the printer. The transmitted data is decompressed and combined and the images overlaid and printed.

Abstract: A controller for a printer module having a printhead that prints an image on printable media including a low speed central processing unit with associated program memory storing program steps for execution by the central processing unit to operate the printer module and associated scratch memory to store program variables. An image to be printed is stored in an image storage memory of approximately 1.3Mbytes. An image access unit accesses the image and transfers the image to a printhead interface on command from the central processing unit. The printhead interface transforms the image to a 1600 dpi dither CMY image for printing by a monolithic printhead. The controller also includes one or more interface units communicating with components of said printer module under control of the central processing unit. A Serial Bus interface communicates with the Serial Bus of a compact printer system to transfer data and power between modules.

Abstract: A method of, and apparatus for, dithering an image to be printed. Color component values of odd and even pixels of an image are stored in a dither cell. The dither cell is mapped to a staggered dither cell such that lines of odd pixel component values are staggered relative to lines of even pixel component values. Addressing of the staggered dither cell is determined by an address generator that also addresses a buffer storing an up-interpolated image. Corresponding values in the staggered dither cell and the buffer are compared to determine which nozzles of a printhead are fired.

Abstract: A method of, and apparatus for, dithering an image to be printed. Color component values of odd and even pixels of an image are stored in a dither cell. The dither cell is mapped to a staggered dither cell such that lines of odd pixel component values are staggered relative to lines of even pixel component values. Addressing of the staggered dither cell is determined by an address generator that also addresses a buffer storing an up-interpolated image. Corresponding values in the staggered dither cell and the buffer are compared to determine which nozzles of a printhead are fired.

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 sampling a Bayer image having two dimensional planes of red, green and blue pixels, the method including the steps of: rotating the green plane by 45 degrees; sequentially sampling an m×m pixel block of the rotated image, where m is an integer greater than 1; providing an address for the m2 samples by determining a starting address for a first of the samples and thereafter applying a predetermined fixed sequence of offsets to obtain the addresses of the remaining samples.

Abstract: A circuit for generating a threshold bias signal for processing n color separations representing a color image includes a threshold bias register which holds and outputs the current threshold bias signal.

Abstract: A method and system are provided for processing digital multi-colour images for the reproduction thereof on a colour printing and/or copying system. Particularly, the printing and/or copying system is capable of complementary forming registered composite multi-colour images of coloured marking particles. This means that the separation images of coloured marking particles are formed contiguous to each other rather than in a superimposed relationship. The digital multi-colour images are processed such that during reproduction thereof any adverse effects on image quality caused by register errors in a predetermined direction are eliminated or at least limited. To accomplish this, a particular halftoning technique is used wherein with gradually increasing input density value of the image pixels, a linear growth pattern is generated in the predetermined direction by alternately adding image dots to both sides.

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 color image is converted into a dot pattern for display by a color printer. The image is separated into Cyan, Magenta and Yellow color planes; a dither matrix is applied to the Cyan plane; an inverse of the dither matrix is applied to the Magenta plane; and either the dither matrix or the inverse dither matrix is applied to the Yellow plane.

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: A color correction table which contains a correspondence relationship between a discrete input color signal and an output color signal is employed. An inputted color signal is corrected by a signal correcting unit, and an approximating unit acquires a discrete input color signal approximated to the corrected input color signal. A table referring unit refers to the color correction table to output an output color signal which corresponds to the input color signal approximated by the approximating unit. An approximate error producing unit calculates an approximate error from difference between the input and output signals supplied to the approximating unit, and then stores this calculated approximate error into a data holding unit. The stored approximate error is supplied to a signal correcting unit to be used in the correction of the input signal.

Abstract: For M (magenta) and C (cyan), in case of generating, e.g., ternary data of C0 to C2 and M0 to M2 respectively by using a look-up table on the basis of an error diffusion method, in a highlight portion of input M and C data (errors Ce and Me have been added respectively), a conversion space of correlating these data is used, while in a high-density portion, a conversion space of equivalent to ordinary error diffusion is used. Thus, in case of converting multivalued color image data into data of a less number of bits than the number of bits of color components constituting the multivalued color image data, it is possible to maintain excellent tonality on an entire image, and particularly to control graininess by preventing image quality deterioration in the highlight area.

Abstract: A method for performing a digital multistage screening of a half-tone image with a screen having any desired screen resolution and any desired screen angle, in which the screening is carried out by reading out threshold values and comparing the threshold values read out with the color values of the half-tone image. Threshold value matrices are used in which the threshold values represent one or more screen dots of a given screen, with which the desired screen resolution and the desired angle are approximated. While the threshold values are being read out, an error between the coordinates of the desired screen and of the given screen is determined, and the error is compensated for by correcting the read address for the threshold value matrix, as soon as the error exceeds a predefined limiting value. Instead of the threshold value matrices, printing-value matrices can also be used.

Abstract: An object is to provide a print proof that takes account of halftone dots and operating conditions of a printing press. To achieve the object, a color image processing apparatus for producing the print proof comprises: a dot gain processing unit for receiving an input of halftoned binary image data, and for converting the binary image data to multi-value image data corresponding to the amount of dot gain of each color; a first color-converting unit for converting the multi-value image data to image data in a device-independent color space; a resolution converting unit for changing the resolution of the multi-value image in the device-independent color space to match the resolution of an output device; and a second color-converting unit for converting the multi-value image data, converted into the device-independent color space, to image data in a color space associated with the output device.

Abstract: This invention concerns high performance color printers which typically use page-width drop-on-demand inkjet printheads. In particular it concerns a halftoner/compositor unit for digitally halftoning a contone color layer to bi-level dots, and compositing a black layer over the halftoned contone layer. In another aspect it concerns a method of halftoning and compositing. The unit comprises: An input port to receive a contone color layer in the form of a series of contone color pixel values, and an black layer in the form of a series of black dot values. A dither unit to dither each contone color pixel value received at the input port and determine the value of a bi-level output dot for each color component.

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 color image is converted into a dot pattern for display by a color printer. The image is separated into Cyan, Magenta and Yellow color planes; a dither matrix is applied to the Cyan plane; an inverse of the dither matrix is applied to the Magenta plane; and either the dither matrix or the inverse dither matrix is applied to the Yellow plane.

Abstract: A method is provided for creating a binary-coding pattern to be used in binary-coding a multi-value image. The method includes the steps of: creating a basic pattern shape of the prospective binary-coding pattern by a first arithmetic operation; determining the sequence of lighting pixels composing such basic pattern by a second arithmetic operation; and creating a rectangular pattern, which serves as the prospective binary-coding pattern, based on the resultant basic pattern. Hereby, it is possible to automatically create a centralized type of binary-coding pattern, and also it is possible to facilitate creating a minimum-sized binary-coding pattern.

Abstract: A method of authenticating a video image created by a camera (V) or similar video device. The image is formed into a first 2-dimensional pixel array (A1) with each pixel (pm,n) represented by a data word of a predetermined length. Additional data words including event information are added to this 2-dimensional array (A1). The formatted array is converted into a second 2-dimensional array (A2) which may be made smaller than the first array by eliminating rows and columns from the formatted array. A first linear vector (A3) is created using the data words in the second array, and a second linear vector (A4) is created by repositioning the data words from the first linear vector in a random pattern. A checksum is created by summing the contents of all of the data words in the second linear vector beginning at a location established by a pre-established formula. A header (H) is formed using the resulting checksum, information identifying the device used to create the image, and the time the image is formed.

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 processing method and apparatus for improving both gradation and resolution in a screening process. The apparatus comprises an image memory for storing multi-valued image data in pixel units; a pixel data acquiring portion for acquiring image pixel data from the memory; a threshold value matrix constituted by a density area by which dots of a high number of lines are produced and another density area by which dots of a low number of lines are produced; a threshold value data acquiring portion for acquiring from the matrix threshold value data corresponding to image data acquired by the pixel data acquiring portion based upon the image data address; and a comparator for comparing the acquired image data with the acquired threshold value data to thereby output a consequent binary signal.

Abstract: The present invention discloses a method of reducing intermediate data to provide very portable intermediate data, and keeping in balance loads on an analysis processor and a print processor. For this purpose, in an image data transfer method of the present invention, the analysis processor creates image analysis intermediate data including a matrix element of a transformation matrix for transformation of a position of each pixel of image data into an actual print position, and color information of the pixels arranged in the order in which the pixels of the image data are arranged, and transfers the image analysis intermediate data created in the analysis processor to the print processor. The present invention can be applied to transfer, when a certain processor requests a print processing-dedicated processor to print image data, the image data in, for example, a client server system.

Abstract: This invention relates to a color image dithering method and apparatus for producing an output point in an output color space corresponding to a selected vertex in a tetrahedron of a three-dimensional cubic subinterval of a pixel point in a source color space.

Abstract: An image forming apparatus includes an image reader for reading images, a memory for storing images read by the image reader, a compression circuit for compressing an arbitrary portion of an image placed on a page memory, a compressed image memory for storing images compressed by the compression circuit, a decompression circuit for decompressing images placed on the compressed image memory, a page memory for developing images decompressed by the decompression circuit, and a printer for outputting images on the page memory. When a plurality of images stored in the memory are to be screened, combined on the page memory and to be output, the images are developed such that screen patterns of respective images to be combined are superposed on the page memory. As a result, an image forming apparatus which is capable of screening, combining and printing a plurality of stored images without increasing memory capacity is provided.

Abstract: This is a halftone circuit which, in addition to the usual counting and addressing mechanisms, has control over the phase, angle and direction of the addressing circuitry of the array in memory so that regular dots, mirror images of dots and out-of-phase dots can be created from a single array, thus saving memory hardware. The mirror images can be made by counting rows in either direction, the angle can be varied by varying the number of pixels shifted between scans, and the phase can be varied by setting the starting point to any row and column. In this way, a single array can be used to create a number of dots.

Abstract: A method of generating artifact-free threshold matrices for digital printing devices is provided. The method includes, for example, the steps of establishing a threshold matrix by examining at least one color level for artifacts and removing the color level from the threshold matrix if it has artifacts. The method further includes the steps of examining a range of color levels for artifacts and removing the color levels from the threshold matrix which have artifacts and evenly distributing the remaining color levels over a range of color levels from a first color level to a last color. The examination of color levels for artifacts may be implemented manually or through an automated computer controlled process. The automated process includes digitally acquiring the color level and performing a Fourier transform on the color level to determine its spectral components. The spectral components are analyzed to determine the presence or absence of artifacts.

Abstract: When a color image is converted to binary format using a dither pattern, a plurality of dither patterns are first prepared. Then, saturation and hue of the original image are used as parameters in selecting the most appropriate dithering pattern among a plurality of candidates. Therefore, even if the lightness of two original images is the same, these images are converted to different black-and-white images as long as their saturation and hue are different. Such black-and-white images look naturally when compared with the original color images.

Abstract: A printing control system is composed of a computer and a printing apparatus connected via a communication line. The computer forms a dither matrix, which is employed in binarization processing to deal with misregistration of color planes, by rotating a reference dither matrix through a predetermined angle in dependence upon printing orientation and paper transport direction, and binarizes print data using the dither matrix that has been formed. Print data that has been corrected, by the computer, for misregistration of color planes is printed by the printing apparatus.