Abstract: An image processing apparatus has a memory device for storing pixel image data including both halftone image data such as data of image of a photograph having a gradation and line image data such as data of text containing characters. The storage is conducted on the basis of blocks each having a predetermined number of pixels. The mean information quantity of the halftone image data per pixel stored in the memory means is not greater than the information quantity of the line image data per pixel stored in the memory means. The halftone image data being compressed on the basis of the block. Therefore, both the halftone image data and line image data can be stored in a small memory by using common addresses, without causing any degradation of the image quality.

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 method of color halftone reproduction with reduced moire patterns and simplified calculations of color densities is disclosed. The method entails dividing a reproduction surface into an array of abutting halftone cells having centers aligned at a screen angle, preferably 45.degree. , with halftone cells in adjacent rows. The halftone cells each cover an area of M abutting horizontal dots long by N abutting vertical dots wide. The various system colors are applied to the pels, as required, in color patterns centered within the halftone cells. The patterns overlap one another to adjust the hue of the reproduction at the halftone cell location to the desired hue. The method is usable with permanent reproductions, such as printed paper, or with transient reproductions, such as the image on a CRT screen.

Abstract: A method for image processing includes the steps of scanning an image within a first grid of pixels, determining a grayscale value for each pixel scanned in the first grid of pixels, and, for each pixel scanned, activating a number of pixels of a second grid of pixels corresponding to the grayscale value determined. Data representing the second grid of pixels can be compressed, and stored for use in facsimile transmission or photoreprographic image production.

Abstract: In order to prevent a line break phenomenon in reproduction of an image of an original in halftone dots, RGB signals of an original (2) are contour-enhanced by a USM circuit (10), and inputted in a halftone dot signal producing circuit (30) and an edge signal producing circuit (40). The halftone dot signal producing circuit (30) converts image signals (Y-IMA to Bk-IMA) to halftone dot signals (DOT1 to DOT10) at the timing of a clock signal (CL1), to output the halftone dot signals (DOT1 to DOT10) to a synthesizing circuit (11) in response to a first output start signal (ENST). However, an output start time is delayed from the time of receiving the signal (ENST) by a time required for the halftone dot processing.

Abstract: The present invention is a method and apparatus for processing a color document for moire-free printing, the color document including a plurality of color separations each defined with a set of image signals representing optical density with m possible density levels, while a printer is capable of rendering density with n density levels. The invention employs a spatial resolution scaler to produce m-bit signals at a spatial resolution that is a function of the halftone screen angle, base dot pitch, and desired halftone cell size. Subsequently, the m-bit signals at the desired spatial resolution (frequency and angle) are halftoned to produce n-bit signals that are printed with a raster output scanning-type printer suitable for printing at selectively variable spots per inch in both the fast and slow scan directions.

Abstract: In an image forming apparatus according to the present invention, characteristics 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 are inputted by inputting means. At the time of image formation processing, input gray level-output gray level characteristic data are corrected on the basis of each of the characteristics correcting data inputted by the inputting means.

Abstract: A full-color image printing method and apparatus operate to form mono-color toned images of individual color components using multiple, e.g., four, mono-color imaging units provided in correspondence to the color components and single-lined screen processors provided in correspondence to the imaging units, and overlap the mono-color toned images sequentially to produce a full-color image on a sheet of print paper. The screen angle is made different among the mono-color toned images and the line pitch of the screen is made virtually equal for all mono-color toned images with the intention of retaining a high-grade color quality and preventing the degradation of picture quality such as a degraded tone quality.

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: An image processing apparatus, which stochastically binary-converts lower-bit data of a pixel of interest to improve image quality in a highlight portion, as well as in a low-density portion, is provided. In an image processing apparatus for quantizing multi-value image data to binary data, multi-value image data of a pixel of interest is divided into upper- and lower-bit data by a calculator (24). The lower-bit data is binary-converted by a comparator (25) using a normalized uniform random number generated by a random number generator (26) as a threshold value. The binary-converted data is added to the upper-bit data of the image signal of the pixel of interest by an adder (22), and the sum data is binary-converted by a comparator (18) using one of a plurality of weighted average values of a plurality of pixels near the pixel of interest, which values are calculated by a calculator (600), on the basis of binary data of pixels, which have already been binary-converted before the pixel of interest.

Abstract: Apparatus and method for descreening and for performing resolution changes and correction of misregistration on a color half-tone image in order to produce a color continuous tone image. The apparatus includes filter apparatus for removing screen information from the half-tone image including a plurality of different filters each providing interpolation and screen removal functions and a controller for selecting per pixel of the continuous tone image and in accordance with sensed misregistration and as a function of desired resolution changes, one of the filters for operation on a neighborhood of the pixel.

Abstract: A method for enhancing the contour fidelity of printed images of two or more colors is described, which includes obtaining a digital representation of the color image and finding color separations of each color. Each color separation is enhanced by a single set of inverse symmetrical templates, the set including templates in which the second template is always the inverse of the first, and the third and fourth templates are 180 degree rotations of the first two. The resulting smoothed color separations are recombined into an enhanced image without separation error.

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 tonal is carried out to produce a reproduced picture of a halftone from a color photographic original picture of a continuous tone. Density values of a designated highlight area (H) and an area in the vicinity thereof on the color photographic original picture are measured and density values of a designated shadow area (S) and an area in the vicinity thereof on the color photographic original picture are measured to obtain respective representative density values (DH.sub.av, DS.sub.av) from the measured density value. Also, measuring density values (D.sub.n) of pixels of a range extending from the highlight area (H) to the shadow area (S) are measured. Using a density characteristic curve of a photosensitive material of a color film with which the color photographic original was taken, the density characteristic curves being defined in a D-X orthogonal coordinate system of which vertical axis (i.e., D axis) represents density values and of which horizontal axis (i.e.

Abstract: A method of reproducing on a substrate an image incorporating metallic inks involves scanning (18) the image to be reproduced and creating (20) four color separations of the scanned image. Metallic gold and/or metallic silver color separations (22, 24) are created by electronically selecting any color area where the effect is desired. Next, the color separations are edited by creating (26) an electronic yellow mask of the image and adjusting (28) the desired tonal range of the metallic areas. The mask edges of each color separation can also be softened (34). The scanner then outputs (36, 38) the separations to film. The image is then reproduced by printing each of the process color separation films (44, 48) and the metallic separation films (42, 46) onto a substrate.

Abstract: A method and apparatus for printing a multi-colored image is provided. The image is composed of a plurality of single-color images, each of which is printed by an inking means in a base color ink. The reflectance of the image is measured by a spectrophotometer. Based upon the reflectance of the image and the full-tone reflectance of the base colors in the image, the effective dot density of each of the base colors are determined. The effective dot densities of the base colors of the image are compared to the effective dot densities of the base colors of an exemplary image. Based on the comparison, control signals are sent to the inking means to adjust the amount of ink used to print the single-color images. The effective dot density of the base colors of the image are determined from the reflectance of the image using a prediction process that incorporates a modified form of Neugebauer's model.

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: Method and apparatus for processing color document images to determine the presence of particular image types in order to designate areas for optimal image processing thereof. A multi-separation image defined in terms of color density for each separation is converted to a luminance-chrominance definition, where one component of the image represents image intensity. An image segmentation process operates on the image intensity signal, the results of which are used to determine processing of the multi-separation image.

Abstract: An image formation apparatus for performing a gradation recording by changing a size of a dot on the basis of an image data inputted to the apparatus. The apparatus divides an image into a plurality of blocks each comprising a predetermined number of pixels and gives a preferential order with respect to a position within each of the plurality of divided blocks. When the preferential order is higher, the size of the corresponding dot is first enlarged on the basis of a density of the image data. This arrangement can prevent generation of a texture and deterioration of the image resolution irrespective of the case that characters or line drawings are mixed with half-tone pictures in the image.

Abstract: Apparatus and method for descreening and for performing resolution changes on a half-tone image in order to produce a continuous tone image. The apparatus includes filter apparatus for removing screen information from the half-tone image including a plurality of different filters each providing interpolation and screen removal functions and a controller for selecting per pixel of the continuous tone image and as a function of desired resolution changes, one of the filters for operation on a neighborhood of the pixel.

Abstract: A method for improving the quality of full-color images is disclosed. An original image is divided into a plurality of pixels. A neutral intensity value is determined for each pixel. A desired black-color intensity value is determined from the neutral intensity value. A printer-producible black value is determined from the desired value. The printer-producible black-color intensity value is used to rescale the original color intensity values of the pixels. The rescaled color intensity values are used to generate output color intensity values. The output image comprising the output color intensity values and the printer-producible black-color intensity value may then be converted to a continuously varying or halftone output image and output to an image output apparatus.

Abstract: An image processing apparatus has a memory device for storing pixel image data, including both halftone image data such as data of image of a photograph having a gradation, and line image text data such as data, containing characters. The storage is conducted on the basis of blocks each having a predetermined number of pixels. The mean information quantity of the halftone image data per pixel stored in the memory means is not greater than the information quantity of the line image data per pixel stored in the memory means. The halftone image data is compressed on the basis of blocks. Therefore, both the halftone image data and line image data can be stored in a small memory by using common addresses, without causing any degradation of the image quality.

Abstract: A halftone screen with precisely controlled angles and rulings, including irrational screen angles and rulings, for screening photographic images is generated by representing a desired screen pattern in an irregular or non-grid like array of screen elements. In one embodiment, a random array of screen elements is used. In another embodiment, a Poisson-disk distribution of screen elements is used to improve quality. The error between an ideal screen point and an actual screen point in the transformed UV space is calculated and used as the basis for selecting an actual screen point as having the least error between the ideal and actual screen points in UV space. The number of error calculations may be reduced by storing pointers the nearest points to each screen point in transformed UV space, and by storing a plurality of successive screen values at a given angle and screen ruling corresponding to each point in the transformed UV space.

Abstract: A technique for use in a direct digital color proofing (DDCP) system (500) for printing a "modelling" color(s) in a halftone color proof image such that the modelling color simulates a ("special") color that does not lie within a gamut of colors reproducible through only primary color (e.g. cyan, magenta, yellow and black) halftone printing. Specifically, a wide range of such modelling colors can be produced by independently and appropriately setting dot size, particularly in combination with solid area density, for the halftone dots (110, 120, 130, 140) produced for different primary colors and then printing the resulting dots on an overlaid dot-on-dot basis with proper registration. Appropriate dot gain and density look-up tables (230, 720; 240, 940) are respectively used to transform continuous tone separation values and bit-mapped data to vary dot size and solid area density of these halftone dots for each such primary color prior to printing these dots using a proofing engine.

Abstract: A halftone screen pattern generation system for computing halftone screened images with rotated screens including multiple angle and ruling combinations, including irrational tangent angles, is disclosed. A screen pattern is generated by storing an oversized strip from an ideal angled screen pattern, and then assembling a sequence comprising selected scan line segments of the oversized strip. Each selected scan line segment corresponds to one of a plurality of offsets of the oversized strip. The error between the actual generated screen and ideal desired screen is computed. Each subsequent scan line segment is selected from the plurality of scan line segments corresponding to the plurality of offsets so as to minimize the accumulated error. In accordance with one aspect of the present invention, the measure of error between the actual generated screen and the ideal angled screen is the length of a vector in a transformed UV space between the actual screen sample point and the ideal screen sample point.

Abstract: Cyan, magenta, yellow and black ink are each used to print a color patch to obtain four color patches. Two of each pair of the three colorants cyan, magenta and yellow are used to print a red, a green and a blue patch. These seven color patches together with a patch formed by the printing medium with no colorant form eight color patches. A color monitor is adjusted until its screen color matches one of the eight color patches and the appearance values of the monitor are noted. This is repeated for each of the eight patches in order to compile a lookup table for the colors in each of the eight color patches. For softproofing, each square in a color grid pattern printed by the printer will contain portions, each of which has a color identical to one of the eight color patches. Using the lookup table, the values of the appearance signals corresponding to the colors of these portions in the square area are obtained for displaying a color patch on the color monitor of the same color.

Abstract: A method and apparatus for color screening combines existing halftone pixel matrices into a super cell. Images of different intensities are displayed using such a super cell by selectively illuminating pixels in the super cell in an order that depends both on the illumination order of the original cells and a visitation order for the halftone cells that make up the super cell.

Abstract: A printing system is disclosed. The system includes a scanner which produces an RGB signal corresponding to a scanned image. The RGB signal is compressed in accordance with a tone curve which is built in reliance upon input provided by the user. The resultant compressed RGB signal is conveyed to a computer. The RGB signal may be modified by a number of interface controls. The RGB signal is driven through a separation engine to produce individual CMYK signals. The separation engine relies upon the interface controls in converting the signal. Image sharpening, or unsharp masking, is performed on resultant CMYK signals to produce a sharp printed image. The image sharpening procedure includes sharpening pixels, calculating T-sums for pixels, calculating gradients for pixels, and smoothing pixels in response to the T-sums and gradient calculations. The resultant CMYK signals may be exported for further data processing, such as integration with text, or they may be sent to a printer to produce high-quality prints.

Abstract: A scheme for the color display of images on a device with a moderate sized color table first builds halftoned binary images for each of the three color components at a multiple of the display resolution. By summing bit values it then determines average values for display resolution pixels. The average values are then mapped to a color table. An example of the scheme uses the YES color model as the color coordinates. The colors are separated into luminance and chrominance components, allowing more weight to be given to the luminance from which the eye extracts most of the information. An example of the scheme yields 275 real colors for a 17.times.9 .times.9 grid of coordinate values, which is close to the size of a 256 entry color table. The scheme provides both anti-aliasing of solid areas, such as lines and text, and color halftoning to give the appearance of colors between those available from the color table.