Abstract: The present invention relates to methods of coalescing device independent bitmaps (“DIBs”) into images for rendering onto a printed page such that artifacts induced by global techniques for image enhancement are avoided. The present invention distinguishes three classes of DIBs for separate treatment. One group of DIBs constitute a single and sole image on the page for which full coalescence and subsequent image enhancement is appropriate. Another class of DIBs may constitute separate images on a multiple-image page for which intra- (but not inter-) image coalescence is appropriate followed by separate image-by-image global enhancements. The third class of DIBs are recognized by the present invention as unsuitable for global enhancements and, rather than risk introduction of image artifacts, no global enhancements are applied.

Abstract: A grayscale patch is formed using a uniform density signal on the entire surface of a recording paper sheet corresponding to a print region of a photosensitive drum, and a plurality of such grayscale patches corresponding to different gray levels are output (S3501). The entire surface of each of the plurality of output grayscale patches is scanned by a scanner unit to obtain luminance data for respective pixel positions (S3502). The scanned luminance data for the entire surface are converted into reflection density values using a predetermined table (S3503), and a two-dimensional &ggr; correction LUT corresponding to the print region is obtained on the basis of the converted density values (S3504).

Abstract: The image processing apparatus has nonlinear processing device that performs nonlinear processing on a digital color signal. The nonlinear processing device comprises gray region discriminating device which discriminates whether the digital color signals are present in a gray proximate region including gray signals and region correspondence nonlinear processing device which performs the nonlinear processing differently in accordance with cases where the digital color signals are discriminated as signals inside the gray proximate region being present in the vicinity of the gray signals or as signals outside the gray proximate region being not present in the vicinity of the gray signals by the gray region discriminating device.

Abstract: An image forming apparatus having a plurality of halftone tables to store a toner quantity value corresponding to a displacement of a gradation grade value of a pixel of image data in different patterns, respectively. The image forming apparatus also has a controller to output print image information by selecting any one of the halftone tables and by fetching a toner quantity value corresponding to a gradation grade value of each pixel of original image data in the selected halftone table, and an engine to print an image corresponding the print image information as output in the controller in recording media. Therefore, it is possible to enhance quality of the print image by extending a range of gradation representation in a desired region according to the characteristics of the printed image.

Abstract: The reproduced image quality of a shuttle scanner is enhanced by automatically compensating for the scanner's assembly tolerances, using a method for correcting vertical alignment error in a shuttle scanner. The method includes the steps of: (a) initializing a block count of a document to be scanned to a value of N; (b) scanning the Nth block and rasterizing the scanned block into a dot image; (c) shifting each dot of the dot image formed by the rasterized block according to a set of pre-stored correction values; and (d) incrementing the block count and performing the steps (b) through (d) until reaching the end of the document being scanned. The set of pre-stored correction values is produced by the steps of: scanning at least one block of a reference pattern formed on the document to be scanned; comparing the scanned reference pattern with an ideal reference line to calculate a shift value for each dot of the scanned at least one block; and storing the calculated shift values in a memory device.

Abstract: A system and method of removing background noise from a digital image of a scanned document is described. The system and method is a reversible background noise removal technique that allows a user to select whether background noise is removed or not. In addition, since the present invention divides the background noise removal operations into a two phase process, the overall efficiency of the system and method are significantly improved.

Abstract: An image processing device for processing an input image so as to reproduce a halftone, includes: a matrix setting section for setting a threshold matrix having a plurality of elements arranged in M columns X N rows, at least two threshold values being stored in each of the elements; an element specifying section for specifying a corresponding element of the threshold matrix in accordance with a position of a pixel in the input image; and a multilevel signal generating section for fetching the threshold values from the specified element and for generating a multilevel signal by transforming an input pixel value to one of multiple levels in accordance with the fetched threshold values; wherein the multilevel signal generating section outputs a constant value Doutmin as the multilevel signal when a first condition that the input pixel value is smaller than or not larger than a minimum value of the threshold values, is satisfied; the multilevel signal generating section outputs a constant value Doutmax when a se

Abstract: The efficient use of memory devices is crucial in processing a large amount of data. In particular, the buffer memory is used in an efficient manner by the use of a buffer memory control unit. The efficient use of the buffer memory is implemented in a high-speed color data processing unit in a color image processing device such as copiers, facsimile devices and printers.

Abstract: There is generated a virtual tile set which virtually covers color planes of an original image without any clearance or overlap by combination of Penrose-type virtual tiles to be non-periodically provided on the planes. The respective tiles are subjected to raster conversion in accordance with predetermined gradation levels, thereby generating a raster image. Since the virtual tiles can be laid non-periodically, iteration of the same dot pattern on the raster image can be prevented.

Abstract: A method which enables high-accuracy color conversion. On condition that conversion from a second color space into a first color space can be made accurately, target coordinates in the first color space are determined and coordinates in the second color space are arbitrarily determined. The coordinates in the second color space are converted into coordinates in the first color space and the difference between the resulting coordinates and the target coordinates is calculated. A trial for moving the coordinates in the second color space is repeated until the difference becomes smaller than a prescribed threshold. Therefore, the correlation between the first and second color spaces can be defined by repeating only the accurate conversion process so that color conversion can be accurately made over the whole color gamut according to the correlation thus defined.

Abstract: In multi-level error diffusion in an image processor, a quantization error data table is accessed at an address of data from a feedback adder, to output the data at the address as quantization error data. By using the table, the error is detected at high speed with an access time for the table. The quantization error is added to an input data by an adder after error integration with weights. Thus, the feedback calculation in multi-level error diffusion is performed at high speed, while the circuit structure thereof is simplified.

Abstract: An image formation apparatus includes an aperiodic data generating unit for generating aperiodic data between pixel areas having a neighboring relation every pixel area comprising a plurality of pixels having an interlocking relation of the image data, a threshold value deciding unit for converting the aperiodic data into a plurality of threshold data for forming a systematic dot array in the pixel area, and a gradation conversion processing unit for performing a gradation converting process by comparing the image data with the threshold data, thereby reducing a signal processing amount as compared with that in case of performing the propagating process on a pixel unit basis.

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: A method of color conversion includes providing a first color domain input signal set having plural input signals; sorting the input signals of the first color domain input signal set according to signal intensity; designing and generating plural 1-D look-up table sets for color polyhedrons; selecting a set of look-up tables for use with a specific color polyhedron, wherein said selecting is a function of a section of the polyhedron determined as a function of the input signal set; looking up values in the look-up table set as a function of the input signal set; generating weights as a function of the sorted signal intensities; and interpolating the output from the selected look-up tables as a function of the selected look-up table and the generated weights to produce a color domain signal set which is converted to a desired color domain signal set.

Abstract: Color printheads in a color inkjet printer are in a fixed order in the scanning carriage, which causes the colors to be printed in a different order when the carriage is scanned in an opposite direction. The different print order may result in a perceptible change in hue between passes in bi-directional printing. Depleted shingle masks are substituted for the nominal ones, based on print direction, at the shingle masking stage, to compensate for print-direction-induced hue shift. A look-up table indexed by a composite color tone value providing a depletion probability and a halftoning error diffusion value are used in determining when depleted shingle masks are to be invoked.

Abstract: Color processing architecture and algorithms (CPAA) for color laser printers process and handle incoming RGB image data effectively to achieve high performance, high quality image printing with low memory requirements. CPAA supports a new data structure for faster raster operation processing (ROP) for color laser printers. The CPAA architecture advantageously improves the flow of data through the processing pipeline to provide high speed at higher resolutions, e.g., at 600 and 1200 dpi. An advance quantizer using multilevel dithering flexibly reduces bits to support fast ROP and to enable fast conversion to CMYK data with only a simple look-up table (LUT) operation by a color matching module, while an adaptive filter maintains high image quality.

Abstract: The image processing apparatus disclosed performs as follows:

Abstract: For blending two color transformation look-up tables, the weights used for combining the tables are designed such that transitions from one look-up table to another are smooth and do not create objectionable artifacts. Building the individual weights includes obtaining the position of a given input point from the input color space, both in the input device and an output device gamut. Weight calculation is obtained by (1) if the input color falls in the intersection of predefined percentages of both the input gamut and the output gamut, then a pictorial LUT is used and the weight is set to 1.0; (2) if the input color falls outside the input and/or output gamut, then a graphics LUT is used and the weight is set to 1.

Abstract: An image forming apparatus having first and second basic cells each containing a predetermined number of cells in a main scanning direction and a sub-scanning direction and disposed adjacent to each other in the sub-scanning direction, a gradation processing portion arranged to perform a gradation expressing process for each basic cell in accordance with a density of a supplied image and a dot forming portion capable of forming dots on a recording medium to correspond to each pixel subjected to the gradation expressing process by the gradation processing portion. The gradation processing portion performs the gradation expressing process in such a manner that enlargement of dots in the first and second basic cells adjacent to each other in the sub-scanning direction is inhibited in the sub-scanning direction until the dots are enlarged and connected to each other in the main scanning direction.

Abstract: The present invention is a method and apparatus for improving the appearance of electronic images, and more specifically, to the efficient use of template rotation within a template matching process to enhance such images. The invention reduces the number of entries that are stored in a look up table by eliminating identical patterns that differ only by the angle at which they are output. The appropriate templates are then rotated it by the required angle for output subsequent to their retrieval from the lookup table.

Abstract: A method, apparatus, article of manufacture for transmitting data to a facsimile presentation device is disclosed. In one embodiment of the invention, the method comprises the steps of receiving a presentation job comprising input data associable with at least one input grayscale value, retrieving at least one of a plurality of threshold matrices, each threshold matrix selected to control a grayscale rendering characteristic of the facsimile presentation device associated with the threshold matrix, applying the grayscale values to the retrieved threshold matrix to rasterize the input data, and transmitting the rasterized input data to the facsimile presentation device. This invention can be practiced in several embodiments, and permits the user to select the threshold matrix according to the presentation device and/or a selected presentation quality.

Abstract: If there is considerable difference in volume between the color gamut of one image processing device and the color gamut of the other image processing device, high-rate compression occurs and changes chroma to a great degree, resulting in color unbalancing. For example, if an image of the leaves of a plant including shadows is transferred from an image input device to an image output device and reproduced, the shadows discolor and look dark brown. According to the invention, the color gamut of the first image processing device is rotated by a predetermined hue angle and compressed to fall within the color gamut of the second image processing device and color values in the former gamut are mapped to those in the later gamut. By color transformation based on the thus defined mapping, color transformation is executed. Thereby, second color image data determined by rotating the hue angle of first color image data can be obtained.

Abstract: An open color management system allows any of a plurality of input color devices to share data with any of a plurality of output color devices. The color management system includes a networked connection space for input and output device communication, an input color profile for each input device, an output color profile for each output device, and an open color manager which links a given input device with a selected output device. When linking devices, an input color space dataset having black plus multiple color channels is parsed with the input and output color profiles at a job time to create an output color space dataset having black plus multiple color channels for imaging by the output device without degrading color accuracy while preserving black channel information. A method for open color management and an open color manager for use in an open color management system are also provided.

Abstract: The present invention provides a mapping method and apparatus of look-up table in an imaging system. The mapping method implemented by the apparatus comprises receiving a digital signal having a high-bit portion and a low-bit portion. The high-bit portion of the digital signal is subjected to a curve table for look-up mapping to get a high-bit signal. The partial high-bit portion is subjected to a slope table for getting a factor. The low-bit portion of the digital signal is calculated with the factor to get a low-bit signal. The high-bit signal is combined with the low-bit signal to get an output signal. The curve table and slope curve can reduce the memory usage of the imaging system.

Abstract: An image which has been color-converted in correspondence with the output characteristics of a printing press as a target for the purpose of proof may often be printed by a copying machine or printer. Prior to the proof, a generation history of a generated profile of an output device is preferably managed. The operator sets whether or not to save parameters (saving location and profile name) associated with saving of a file and colorimetric values, whether or not to save history management information, and the like.

Abstract: Methods and systems for automatic color calibration result in a cluster of printers having more uniform color output. Each printer within the cluster prints a color target. Each color target is measured, typically by sensors located in the print path. The data is sent to a central location for processing. Color look-up tables are constructed for each color and for each printer. The color look-up tables are formulated on a baseline characteristic of the printer in the cluster having the least dynamic range. That is, for each printer in the cluster, there is an input value for each color (e.g. cyan) wherein that input value results in the same output ink density as the baseline printer. Each printer in the cluster receives a color look-up table for each color, and incorporates that table in its color data flow.

Abstract: An image processing apparatus according to the present invention comprises an unsharp weighting image forming section (50, 54, 56) for forming from image data an unsharp weighting image which connects a principal subject region and a background region smoothly, a color reproduction parameter forming section (48) for forming at least one of color reproduction parameters of the principal subject region and the background region, an output image forming section (46) for forming the output image data from image data by using at least one of the color reproduction parameters of the principal subject region which is weighted with weight of the unsharp weighting image and the background region which is weighted with the remainder obtained by subtracting the weight of the unsharp weighting image from a reference value.

Abstract: The image processing incorporates a regional difference such as an outline/edge area vs. a non-outline area in determining an appropriate correction coefficient. The image processing additionally includes any combination of an intensity level, a sharpness level and predetermined user input values. The input values include a user specified intensity level, a user specified document type, a user specified background removal level and other customized values.

Abstract: A method for calibrating a printer includes printing a set of color samples with the printer, the set of samples or calibration target generated dynamically in response to selected printer variables, and reflecting at least a portion of the printer gamut. Each printed color sample in the set of samples is measured calorimetrically, to determine the printer's response thereto, so that a calibration table can be generated, taking into account printer variables selected by a user.

Abstract: A method of determining colorant amounts to be laid down in a color printer includes determining an initial set of cyan, magenta and yellow (CMY) values; ordering the initial set of CMY values to determine the largest, middle and smallest values of the three values and generating an ordering vector; selecting a gamut center black generation LUT and two gamut boundary black generation LUTs from a set of black generation LUTs from a selection table; indexing the selected black generation LUTs to determine black values for each black generation LUT as a function of the minimum of the CMY values; interpolating a final output black colorant amount from the black values, and interpolating final output CMY colorant amounts from the TO initial set of CMY values, the maximum CMY ink limit constraint, and a set of boundary threshold values.

Abstract: An original reference value table containing converted values of image data on the entire color space is made based on known look-up tables of a printer and a correction printer, and a reference value table is wholly or partly corrected adequately so that the results of printing performed by the correction printer by referring to the original reference value table may be similar to the results of printing performed by the printer while the mutual non-linearity of converted values held in the reference value table is maintained, thus making a reference value table with an improved precision of color reproduction.

Abstract: A method for calibrating a printer includes printing a first set of color samples with the printer, reflecting at least a portion of the printer gamut. Each printed color sample in the set of samples is measured calorimetrically, to determine the printer's response thereto. The colorimetric response is compared with a predictive model of printer behavior for that portion of the printer gamut. In a portion of the printer gamut wherein the calorimetric response differs from predicted printer behavior, the printer generates a new set of color samples, for printing. The new set of color samples is secondarily measured to determine the printer's colorimetric response thereto; and using the initial measurements and the secondary measurements, a color calibration table is generated for use by the printer in converting device independent colors to device dependent colors.

Abstract: The present invention relates to an image processing method using the error diffusion method to prevent jumps in a highlight part and darkening in a shadow part at high resolution. The image processing method comprises a step of calculating an average value of density values of N×M (N, M>1) pixels, a step of adding the average value and a diffused quantization error value, a step of quantizing the addition result with a predetermined number of tones, a step of selecting a quantization pattern corresponding to the quantization result, and a step of calculating the diffused quantization error value from the quantization error. The error diffusion algorithm has flexibility in outputting dots. In other words, error diffusion processing is performed in N×M pixel units, and a plurality of quantization patterns are provided, and a quantization pattern is selected based on the quantization result.