Abstract: An image processing apparatus for converting a color image into an image of an N (N=2, 3, . . . ) number of colors, i.e., black and other colors, is disclosed. In the image processing apparatus, a gray-component extracting unit extracts a gray component signal from input color image signals, and produces remaining-color-component signals. A black signal generating unit generates a black signal by using the gray component signal and the remaining-color-component signals. A color signal generating unit generates a color signal by using the remaining-color-component signals.

Abstract: A halftone processing method is disclosed in which, after receiving three or more monochrome digital images which collectively represent a color image having three colors, processing takes place. Processing is by a separate stage for each of the monochrome digital images to provide halftone output images, wherein at least one of the stages uses a different processor algorithm from the other halftone processing stages so as to increase processing speed.

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: A method of and system for rendering a halftone image of a gray scale image by utilizing a pixel-by-pixel comparison of the gray scale image against a blue noise mask is disclosed in which the gray scale image is scanned on a pixel-by-pixel basis and compared on a pixel-by-pixel basis to an array of corresponding data points contained in a blue noise mask stored in a PROM or computer memory in order to produce the desired halftoned image. Both digital and optically implemented halftone methods are disclosed. Application specific modifications of the blue noise mask as well as its use for producing halftoned color images are also disclosed.

Abstract: Input chromatic densities IC, IM, and IY are first converted into corrected chromatic densities I'C, I'M, and I'Y based on the input density IK. The input density IK is then added with the corresponding weighted error sum EK, so that a modified density IKmod is obtained. Similarly, the corrected chromatic densities I'C, I'M, and I'Y are added with the weighted error sums EC, EM, and EY, respectively, so that modified densities ICmod, IMmod, and IYmod are obtained. Then, the modified density IKmod is compared with the threshold T, and an output OK is determined. When the obtained output OK is zero, the ICmod, IMmod, and IYmod are compared with the threshold T, and output data OC, OM, and OY are obtained. On the other hand, when the obtained output OK is a dot-forming data, the output data OC, OM, and OY are forcibly set to a non-dot forming data.

Abstract: A method of printing an image onto a substrate includes the steps of determining a difference in intended color intensity between a first pixel and a second pixel; adjusting the intended color intensity of the second pixel based on the determined difference; and depositing a colorant onto the substrate at the first pixel and at the second pixel at the adjusted intended intensity, so as to enhance the appearance of the image on the substrate. The current system has particular utility in enhancing the appearance of fine images such as one pixel wide, vertical and diagonal lines in a printing system which utilizes printhead heating elements that are larger in the vertical direction than in the horizontal direction.

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 technique for screening an image for half-tone reproduction by image reproduction apparatus including a marking device which is operative to mark a medium along a multiplicity of parallel marking lines including the steps of providing a digital representation of density values of an original image, storing dot shape information representative of a screen function in a line-by-line, input density-by-input density arrangement and extracting the dot shape information from storage for the density values in the form of information that designates on and off points for each marking line. Apparatus for carrying out the technique is also disclosed.

Abstract: To produce a correction table to be referred to when a quantum level data (QL data) as an input image data to a given image output device is converted into an image having a halftone dot percentage, reference QL data having a plurality of data values arranged at predetermined data intervals are inputted to the image output device; the halftone dot percentage of an output image from the image output device are measured; an approximation formula of a desired function form is determined to approximate the measured halftone dot percentage by the method of least squares, on the condition that the formula should go through preset starting and ending points; and the correction table is produced based on the resulted approximation formula.

Abstract: An image rendering system for generating discrete tone image data for representing continuous tone image data to be rendered by a rendering device. The continuous tone image data includes a plurality of pixel values each associated with a pixel. The rendering device renders a colorant in a plurality of colorant densities. The image rendering system comprises a threshold array, preferably stochastic, a colorant density array, and a colorant density supply arrangement. The threshold array comprising a plurality of threshold values. The colorant density array comprises a plurality of array elements, each associated with one of said pixel values and one of said threshold values. Each of the array elements identifies a particular one of a plurality of colorant density values each associated with one of the colorant densities rendered by said rendering device.

Abstract: A basic gradation curve, a gray balance, and a black curve are selected, and a tone reproduction curve is generated based on a combination of the basic gradation curve, the gray balance, and the black curve which have been selected. Using the generated tone reproduction curve, a sample image is color-separated to generate a proof. The proof is checked, and, if necessary, the tone reproduction curve is corrected until an optimum tone reproduction curve is generated.

Abstract: A technique for screening an image for half-tone reproduction by image reproduction apparatus including a marking device which is operative to mark a medium along a multiplicity of parallel marking lines including the steps of providing a digital representation of density values of an original image, storing dot shape information representative of a screen function in a line-by-line, input density-by-input density arrangement and extracting the dot shape information from storage for the density values in the form of information that designates on and off points for each marking line. Apparatus for carrying out the technique is also disclosed.

Abstract: Apparatus and a method for random screening including an exposure select operator which receives two-dimensional coordinate information relating to a screen and input density information relating to an image to be screened, the operator being characterized in that for a constant input density it provides a constant exposure output over each of a multiplicity of groups of contiguous coordinate regions, at least some of which groups are mutually non-aligned.

Abstract: A method of printing an image onto a substrate includes the steps of determining a difference in intended color intensity between a first pixel and a second pixel; adjusting the intended color intensity of the first pixel based on the determined difference; and depositing a colorant onto the substrate at the first pixel at the adjusted intended intensity, so as to enhance the appearance of the image on the substrate. The current system has particular utility in enhancing the appearance of fine images such as one pixel wide, vertical and diagonal lines in a printing system which utilizes printhead heating elements that are larger in the vertical direction than in the horizontal direction.

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 vivid color correction technique eliminates artifacts from a predetermined tonal area of a halftone image to thereby improve the color vividness of that image. According to this technique, pixel tonal values associated with input colors are initially examined to determine a maximum color value. After error diffusion halftoning, the resulting binary pixel values are collectively processed to generate inter-color information for comparison with a selected harmonic color cluster. If the inter-color information specifies a color that does not match one of the colors of the selected harmonic cluster, the inter-color information is "corrected" to reflect an acceptable output color.

Abstract: In a method of producing a digital half-tone representation of an original image, wherein the representation is constituted by an array of output cell values representing the colour content of pixels of the original image, cell values are determined for successive output cells, for which cell values have not previously been determined. An output cell value is generated with reference to an input cell value related to the colour content of a corresponding pixel in the original image, and any error values propagated from previous iterations. Where the output cell value satisfies a predetermined condition, the effective colour content of a neighbourhood of previously determined output cell values is determined by addressing a look-up table containing a single value for each neighbourhood. An error value constituted by the difference between the effective colour content and the corresponding input cell value is determined and propagated for use in subsequent iterations.

Abstract: This system selectively enables a printer to deposit primary or black color dots at pixel locations on a sheet to produce a color image--in such a way as to increase the overall number of dots used in the image, thereby minimizing contrast between dots on the sheet and adjacent areas and so providing a better simulation of a continuous-tone image. The result is print quality often near that of error diffusion, usually better than any dither technique, but with the greater speed of a dither technique. The system includes a memory for storing a first color vector for each pixel in the image, respectively, and a processor coupled to the memory for determining a second color vector from each of the first vectors, respectively. The processor accomplishes this determination by replacing a fraction of the black color component of the first vector with primary colors.

Abstract: A system for printing an image onto a substrate includes a print controller that determines a difference in intended color intensity between a first pixel and a second pixel; adjusts the intended color intensity of the first pixel based on the determined difference; and deposits a colorant onto the substrate at the first pixel at the adjusted intended intensity, so as to enhance the appearance of the image on the substrate. The current system has particular utility in enhancing the appearance of fine images such as one pixel wide, vertical and diagonal lines in a printing system which utilizes printhead heating elements that are larger in the vertical direction than in the horizontal direction.

Abstract: A method for increasing the speed of color conversion from a plurality of color spaces to a single color space by reducing the number of color pixels by a factor of two prior to the color conversion step. This pixel reduction constitutes a lossy data compression scheme which takes advantage of the advance knowledge that the pixels will later undergo anti-aliasing by averaging subsequent to the color conversion. First the pixels are grouped into pairs, and one pixel of each pair is eliminated to form a pseudo halfpixel. The eliminated pixel is replaced with a tag identifying either the previous, current or next pseudo halfpixel. Then each pseudo halfpixel is color converted. Finally the indicated previous, current or next pseudo halfpixel, now color converted, is averaged with the current pseudo halfpixel to form a halfpixel, which is then averaged with the halfpixel above or below it to form an anti-aliased full pixel which can be displayed.

Abstract: When an image is input, that input image is separated into a halftone region, such as a photograph, and a binary region, such as a character/line. Contour vector data along an edge of the separated binary image region is extracted. Regarding the binary image region, when the input image is to be enlarged or reduced and then output, individual coordinates in the extracted contour vector data are enlarged or reduced to reproduce the binary image.

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: A multi color printing method employing a color printer capable of non-overlapping color printing using M colorants, where M is greater than two, includes the steps of: providing a digital color image having multi-bit color pixels; separating the digital color image into three multi-bit color primary components; converting each multi-bit component into a 1-bit component using a digital halftoning technique; assigning a single printer colorant to each output image pixel based on the 1-bit color components. The printer colorants are assigned by: dividing the image into n-tuples, each pixel in an n-tuple having a unique designation N; assigning N-member combinations of N-1 printer colorants and no colorant that appear as combinations of 1-bit color components; and setting an output to the Nth member of an N-member combination based on the corresponding combination of 1-bit color components. The image is then printed using the assigned colorants.

Abstract: In a printer for printing text of one color over a background of another color, a method and circuit for allowing the text character outline boundaries to pass through the color halftone dots, creating partial dots in the process, the partial dots within the character boundaries being of the color of the text, and the partial dots outside of the character boundaries being the color of the background. To use a numerical example, to produce an eight bit output dot through which a boundary passes, fifteen halftone bits in the first color are produced for each dot clock, and the rightmost seven bits are latched for the next cycle. On the next clock, fifteen bits are produced, and the leftmost 7 are aligned with the latched seven. If the bits are to the left of the boundary, bits from the first cycle are output, and if the bits are to the right of the boundary, bits from the second cycle are used.

Abstract: An image processing apparatus prevents an increase in random noise and the like produced by distributing a transformation error, which is produced at the time of a level-number transformation, to unprocessed pixel data. Error data X.sub.n is added to pixel data, which has entered via an input unit, by an adder. Thereafter, the resulting data is subjected to a level-number transformation by a binarizing circuit. Transformation error produced at the time of the level-number transformation is calculated by an error arithmetic unit. The transformation error thus calculated is distributed to unprocessed pixel data by an error-diffusion unit, and the error is accumulated in a line buffer memory as error data. When processing of a prescribed number of lines has ended, a line-number discriminating circuit clears the error data that has been accumulated in the line buffer memory. As a result, an increase in random noise is prevented.

Abstract: A color printing system includes a discrete CMY color printer, a LAB color error diffuser, and a LAB/CMY converter. The diffuser includes an image compensator, a vector color space reverter, an error calculator, and an error diffuser. The vector color space reverter provides for error diffusion in a LAB color space that is different from the CMY color space of the printer. The perceptual linearity of the LAB color space provides for enhanced color fidelity in the printed image. In addition, color conversion and error diffusion are performed together, minimizing computational error accumulation and maximizing computational throughput.

Abstract: An image processing method and apparatus which inputs a color image signal, and generates and outputs pattern data corresponding to the color of the image signal. The color of each pixel of the input color image signal is discriminated by a color discrimination circuit and the pattern data which corresponds to the color is output from the pattern generation circuit according to the result of discrimination. The brightness of the pattern data is adjusted according to a shift, which is the difference between the discriminated color and the color of the pixel. In the instance where the discriminated color is different from the predetermined color, or the proper color is not discriminated, the brightness signal of the pixel data is output as is. In this way, the coexistence of the pattern data at the border of the colors is de-emphasized.

Abstract: In an image forming apparatus according to the present invention, characteristic correcting data for correcting input gray level-output gray level characteristics for each of a plurality of steps into which input gray levels are divided is inputted by an inputting device. At the time of image formation processing, input gray level-output gray level characteristic data are corrected on the basis of the characteristic correcting data inputted by the inputting device. Further, when there occurs at the boundary between adjacent steps such a reversal phenomenon that an output gray level in the step having relatively low input gray levels is higher than an output gray level in the step having relatively high input gray levels in input gray level-output gray level characteristic data obtained by correction using a correcting device, the input gray level-output gray level characteristic data are so corrected that output gray levels gradually increase with higher input gray levels in the vicinity of the boundary.

Abstract: A method of halftoning over a region of output pixels by defining large halftone cells corresponding to regions of contiguous pixels and partitioning the larger halftone cells into smaller halftone cells is disclosed. The number of levels of gray determined by the number of pixels within the larger halftone cell while resolution is defined by the size of the smaller halftone cells within the larger halftone cells. A predetermined level of gray determines the number of pixels to darken within the larger halftone cell and the pixels are darkened within the smaller halftone cell according to a spot function. The larger halftone cells are partitioned into smaller halftone cells such that the larger halftone cell has exactly one center smaller halftone cell.

Abstract: This invention provides an information recording apparatus, which can save the consumption amount of a toner without thinning out an image in units of pixels, and can realize smoothing processing with high image quality. In input data, a pixel corresponding to an edge portion is subjected to smoothing processing. Data of a black pixel which is not subjected to smoothing processing is recorded while saving toner by controlling the print pulse width or the print pulse number upon recording of the black pixel on the basis of a print density command.

Abstract: An image processing system for preparing a document for printing which receives multi separation color documents 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 such a system, each separation of the image is separately processed with an error diffusion process which takes into account the processing of another separation, if any. Output signals from a separation are used to determine threshold values for at least one other separation. The varying thresholds are used to vary the likelihood of the current pixel being a spot or no spot.

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: An image processing apparatus includes a bit conversion part for converting an input multilevel image signal obtained via raster scanning into an output multilevel image signal through an MTF correction processes; a bi-level rendition part for performing a bi-level rendition processes with respect to the output multilevel image signal so that a first bi-level image signal is produced, and for performing a pseudo halftone rendition process with respect to the input multilevel image signal to generate a second bi-level image signal; a discrimination part for detecting whether a picture element indicated by the input multilevel image signal is located in a halftone region of an original image or in a bi-level region thereof, and an image synthesizing part for outputting the first bi-level image signal to an output device when the picture element is detected as being located in the bi-level region of the original image and for outputting the second bi-level image signal to the output device when the picture eleme

Abstract: Each image area in a total image is assigned with a screen angle mode Ms indicating whether screen angles of magenta and cyan separations are to be adjusted or not. Screen angle data representing screen angles of magenta and cyan are produced according to the screen angle modes Ms. A dot signal for recording a halftone image of each of the magenta and the cyan separations is generated by comparing screen pattern data of a certain screen angle specified by the screen angle data with image data for each color separation. Accordingly, the present invention effectively prevents a moire in any image area included in a printing image.

Abstract: A method of and system for rendering a halftone image of a gray scale image by utilizing a pixel-by-pixel comparison of the gray scale image against a blue noise mask is disclosed in which the gray scale image is scanned on a pixel-by-pixel basis and compared on a pixel-by-pixel basis to an array of corresponding data points contained in a blue noise mask stored in a PROM or computer memory in order to produce the desired halftoned image. Both digital and optically implemented halftone methods are disclosed. Application specific modifications of the blue noise mask as well as its use for producing halftoned color images are also disclosed.

Abstract: An exposure signal representing a halftone image is generated by executing tone correction on at least either of an image signal and n pieces of dot pattern signals, and by comparing the image signal with the n pieces of dot pattern signals after the tone correction. The tone correction characteristics are set to compensate for a difference in dot gain characteristics between dot types. The halftone image is accordingly reproduced with the compensated dot gain characteristics.

Abstract: The invention is for use with a visible medium capable of light reflection etc., and for use with a color-image source that defines a desired color. Here a device for causing the medium to appear colored includes a gray-scale subsystem to achromatically suppress a stated fraction of the reflection; and at least two device-primary subsystems to cause selective reflection of light of two associated device-primary colors. Even if the device, as originally made, in effect uses the gray-scale subsystem to help construct colors, or the device-primary subsystems to help form gray-scale "values", such cross-dependency is essentially removed. A programmed processor resolves the desired-rendition information into Fraction-Black, Fraction-Colorant, and hue.

Abstract: A multifunction device having at least a facsimile function, a scanner and an image processing circuit is provided. The image processing circuit includes a circuit for applying a TRC correction to gray values derived at the scanner, before a halftoning circuit quantizes the gray values for printing. The TRC correction circuit includes at least two stored TRC correction functions that can be applied by the TRC correction signals. In making a call to transmit a document via the facsimile function to a called station, the exchange of signals required for establishing the facsimile connection includes identification of a preferred TRC correction function preparatory to printing at the called station printer. In accordance with the identification of a preferred TRC correction function, the image processing circuit operates on image signals derived at the scanner, to provide TRC correction of the image signals preparatory to printing at the destination printer.

Abstract: A method and reproduction system for generating image information signals of a second type for each image point, upon supply of digital image information signals of a first type generated in a multi-bit form by a first and second signal source and making use of the information content concerning the density value present in the signals. The second signal source is adapted to generate image information signals in accordance with a predetermined density value. The image information signals of the second type are converted, by the application of grey value processing, to image reproduction signals which are used to control an image reproduction system such as a printer.

Abstract: Adaptive preprocessing is performed on the three primary color signals generated during the scanning of a color image in order to enhance the perceived saturation of the dominant primary color. This preprocessing is performed by removing a small increment from the least intense primary color and adding the same increment to the most intense primary color. In this manner the overall brightness of the pixel is preserved, but the perceived saturation is increased. The increment that is effectively transferred from the least intense primary color value to the most intense primary color value is based on the relations of the three primary color values to each other in order to avoid visible color artifacts.

Abstract: A method for generating a screened reproduction of an image including the steps of providing a representation of an original having input density values representing the grey levels of various locations of the original for a given color separation, defining a desired irregular screen function for the image and writing screen segments in a line by line fashion, wherein each screen segment is a line whose length and location is determined by employing the input density values of the original and the desired irregular screen function.

Abstract: In an image processing apparatus, when a hard copy of image data displayed on a display with reduced gradation and non-image data displayed on the display is simultaneously produced, the image data are automatically printed as data having original high gradation while being synthesized with the non-image data. When a hard copy of image data and non-image data displayed on a bit-map display having low gradation is produced, the image data having high gradation is printed by a full-color printer by reading original-image data having the high gradation from a hard disk and synthesizing the read data with the non-image data in an image memory by a printer control unit according to image control information stored in an image control table.

Abstract: A gray pixel encoding scheme is used in combination with a halftoner and an imager to produce halftoned images. A halftoner and an imager can be totally separate because the gray pixel encoding allows the imager to decode them at any time. The encoded gray pixels require less bandwidth than explicit gray pixels and can be decoded by the imager in an optimal fashion for the characteristics of the specific printer being used. An imager produces a small partial pixel within a spot boundary. The subpixel produced is called a gray pixel. The gray pixel is allowed to grow from a zero width to a full spot width and is allowed to start anywhere within the spot. The pixel codes describe the starting positions of the gray pixels, the locations of the gray pixels within the spot, and the gray pixel width required. The imager uses the encoded gray pixel from the halftoner to produce a final halftoned image.

Abstract: A method of and system for rendering a halftone image of a gray scale image by utilizing a pixel-by-pixel comparison of the gray scale image against a blue noise mask is disclosed in which the gray scale image is scanned on a pixel-by-pixel basis and compared on a pixel-by-pixel basis to an array of corresponding data points contained in a blue noise mask stored in a PROM or computer memory in order to produce the desired halftoned image. Both digital and optically implemented halftone methods are disclosed. Application specific modifications of the blue noise mask as well as its use for producing halftoned color images are also disclosed.

Abstract: Finishing requirements are set (S31) and points of image data at each of which the finishing requirements should be met are specified (S32). The magnitude of correction of each of set-up parameters related to gradation is set based on halftone % data at each specified point and target halftone % data corresponding to the finishing requirements (S35). The halftone % data at each specified point is re-calculated based on the corrected set-up parameters (S36). The result of correction is evaluated and each of the set-up parameters is repeatedly corrected so as to reach the optimum value (S37). As a result, the most suitable set-up parameters can be obtained. Thus, the optimum image in which the finishing requirements are met can be obtained by image processing under the optimum set-up parameters.

Abstract: A model-based printing method and system for generating color halftone output images corresponding to color input signals. Models for individual printer types allow predicted printer error signals to be generated which can be used to modify the color signals in such manner as to produce output signals which, when applied to the printer, create color halftone images of enhanced quality. In an alternative embodiment, output image signals are selected which minimize an error function based on the difference between (i) a predicted perceived image corresponding to the color image input as filtered by an eye-model filter and (ii) the color halftone image resulting from filtering of the output image by a filter modeling the printer followed by the eye-model filter.

Abstract: Provided is a system and method for selectively enabling a printer to deposit on a sheet cyan, magenta, yellow and black (C,M,Y and K) primary or black color dots at each of the plurality of pixel locations to produce a color image. The system comprises a memory for storing C, M, Y and K values for each pixel in the color image and a processor for controlling selective deposition of the C, M, Y and K colors. The system includes a memory for holding a color vector for each pixel, respectively in the color image; a memory for storing parameters of a dither cell; and a processor coupled to the memory for comparing the dither cell with each color vector, to select a color component to print at the corresponding pixel location based on the comparison. The system provides a halftoning technique that produces print quality near error diffusion quality with the speed of a dither by dithering on a color vector.

Abstract: In an apparatus for forming an electrostatic latent image in a form of dot for each pixel on a photoreceptor, each pixel has plural color component signals and a dot is formed for each of color component signals in the same imaging unit area. A signal processing circuit processes specific color component signals of pixels neighboring a target pixel to obtain a density distribution around the target pixel, and determines a recording position of the dot in the recording unit area for each of the plural color component signals on the basis of the density distribution.

Abstract: A gray balance correction technique eliminates artifacts, caused by the accumulation of diffusion errors, from a predominantly "gray" tonal area of a halftone image. According to the technique, pixel tonal values associated with three input colors are initially examined to detect a condition that specifies production of a gray image area. Upon detecting this condition, errors from previously processed pixels are averaged prior to being "diffused" among these input color pixels. Thereafter, the input pixels are processed in accordance with conventional halftoning operations and the resulting binary pixel values are passed to an output buffer for printing. Averaging of the errors prior to error diffusion ensures that the detected condition is maintained throughout preprocessing of those input color pixel values.