Abstract: Provided is an image forming apparatus for forming a toner image including: a first light source emitting a beam corresponding to image information; a first photosensitive member; a first developing means for developing a latent image with a first toner; a second light source; a second photosensitive member; and a second developing means for developing a latent image with a second toner, in which the coloring agent contained in the first toner and the coloring agent contained in the second toner are substantially of the same hue, with the content of the coloring agent contained in the second toner being smaller than the content of the coloring agent contained in the first toner, and in which an oscillation wavelength of at least the first light source ranges from 370 to 500 nm. With the image forming apparatus structured as described above, an improvement in terms of granularity is achieved.

Abstract: It is an object of this invention to prevent a false edge phenomenon in quantization processing for a multilevel image. In order to achieve this object, according to the invention, (1) a reference threshold (Cthreshold) to be used for error diffusion for a cyan (C) component is obtained on the basis of a density value M of a magenta (M) component. (2) A threshold modulation amount table is referred to by using a combination of a density value C of the C component and the density value M of the M component. (3) A correction threshold modulation amount Cthreshold′ is determined by adding the threshold modulation amount obtained in the second step to the reference threshold Cthreshold to be used for error diffusion for the C component. (4) A density Ct after error diffusion for the C component is compared with the correction threshold Cthreshold′. If the density Ct is higher, a quantization value binDataC of the target pixel is set to 255.

Abstract: A color printing system and method for reducing bidirectional hue shift in ink-jet printing. A set of data channels for the ink colors of the system is generated, including at least one print-direction-independent data channel, and at least one pair of print-direction-dependent data channels. A print controller receives the set of data channels for printing, and selects the print-direction-independent data channels, and one of each pair of print-direction-dependent data channels, to provide the data for printing in each pposite scanning direction of the print engine.

Abstract: Disclosed are two novel techniques for digital color halftoning with green-noise stochastic dither patterns generated by homogeneously distributing minority pixel clusters. The first technique employs error diffusion with output-dependent feedback such that the overlapping of pixels of different colors can be regulated for increased color control. The second technique uses a green-noise mask which is a dither array designed to create green-noise halftone patterns. The green-noise mask is constructed to also regulate the overlapping of different colored pixels. As is the case with monochrome image halftoning, both techniques are tunable, allowing for large clusters in printers with high dot-gain characteristics, and small clusters in printers with low dot-gain characteristics.

Abstract: The invention provides methods for using single-cell non-orthogonal cluster screens to satisfy the moiré-free conditions for color halftoning. The invention also provides methods that combine single-cell non-orthogonal cluster screens and line screens for moiré-free color halftoning. Particularly, the selection of these single-cell halftone screens is determined by satisfying moiré-free conditions provided in the respective spatial or frequency equations.

Abstract: An image reproduction engine which causes toner to adhere to a development region of certain area located at a certain position within dots according to image reproduction data is utilized for image processing, wherein a halftone is expressed by means of halftone spots formed from a plurality of dots. The centroid of the halftone spot formed from a single dot or a plurality of adjacent dots is shifted from the center of the dot to an arbitrary position, thus achieving desired screen angles or desired pitches of halftone spots. As a result, screen angles related to an irrational tangent can be realized, and the pitches of halftone spots of a plurality of color screens can also be made uniform.

Abstract: A method and system for generating dither matrices for halftone printing. The design of the dither matrices involves modifying a human visual system model cost function to be color-blind and the addition of a cluster cost function. The cluster fluctuation function has a clustering factor for specify the clustering effect in the halftone image. The clustering factor is preferably gray-level dependent and may be implemented with a look-up table that specifies a clustering factor for each specific gray level. The cluster fluctuation function may optionally include a structure suppression term for suppressing the formation of long horizontal structures or long vertical structures. The structure suppression term includes a symmetry factor for specifying the symmetry of the cluster cost function. The symmetry factor is preferably gray-level dependent and may be implemented with a look-up table that specifies a symmetry factor for each specific gray level.

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: There are disclosed a halftone dot conversion apparatus capable of creating a halftone dot image that is small in an interference between periodical noises occurred at the time of output and a periodical structure of halftone dots, and contributing to avoiding the graininess and prevention of the disorder in geometry on halftone dots; a halftone dot conversion program storage medium storing a halftone dot conversion program; and a dot matrix capable of readily creating the halftone dot image. A halftone dot conversion section forms the halftone dots by sets of drawing pixels number of which is associated with the tone values obtained by the tone value obtaining section, and scatters blanks of the drawing pixels about the halftone dots, on at least a predetermined range of tone values.

Abstract: An image processing apparatus that processes image data and transmits processed image data to an external unit includes a content determination unit that determines content of image processing to be applied to image data for each image data, an image processing unit that applies the image processing of the content determined by the content determination unit to the image data, and a transmission unit that transmits the image data processed by the image processing unit to an external unit.

Abstract: A color image halftoning apparatus and method for creating a color bilevel image from a color output device, and mask generation apparatus and method used in the color image halftoning apparatus and method are provided. The color image halftoning apparatus includes: an address generator that receives a pixel in an image intended for halftoning and generates an address corresponding to the position of the pixel in a mask memory storing mask threshold values for one color channel; a mask generator that receives a mask threshold corresponding to the address from the mask memory and generates a mask threshold value for each of a plurality of color channels; and a comparison unit that sequentially receives the mask threshold value generated for each of the plurality of color channels and the pixel value in the image intended for halftoning, compares both values, and outputs a bilevel value according to a predetermined rule.

Abstract: The present invention is a method of adjusting a color in a color proof (112) printed with primary colors cyan, magenta, yellow, and black.

Abstract: A method for printing multiple binary bitmaps (10) with an original density level (12a) and a color (18), wherein the color (18) is the same for all the multiple binary bitmaps (10), by combining “n” number of binary bitmaps into “p” bits of a multibit image forming a “p” bit image (20), identifying at least one overprint (24a), predicting an overprint density (26a) for each overprint, calculating a set of exposures (28) needed to image each overprint density (24a) and original density (12a), setting a maximum exposure level (30) that is a number greater than or equal to the maximum of the set of exposures (28), calculating pulse width modulation levels (30) for the set of exposures (28) using the set maximum exposure level (30), and printing the color (28) at the set maximum exposure level (30) using the pulse width modulation levels (30) for each level of the “p” bit image (20) in a single pass.

Abstract: The invention is a method for printing a color proof from an initial halftone bitmap file (10) having individual dots (10a, 10b, 10c, 10d) using a spatial filter (20) which is created from a calibration curve (30) for a printing press (380). The method further consists of sending an initial halftone bitmap file consisting of individual dots to the spatial filter creating a filtered output (40), quantizing the filtered output from the spatial filter to “n” levels to create a quantized image (50), transmitting the quantized image to a color printer (70), and printing a halftone color proof (80) on the color printer.

Abstract: Image data is corrected in a device or system using multiple halftones by predicting a second tone transfer curve corresponding to a second halftone based on a first tone transfer curve corresponding to a first halftone. First and second tone transfer curve compensate for application of the first halftone and the second halftone, respectively, to image data. The first tone transfer curve is determined by measuring image data halftoned with the first halftone and developing a first tone transfer curve that linearizes the measured image data. To produce the second tone transfer response curve, measured values of image data halftoned with the second halftone are estimated based on a predetermined relationship between the measured image data that is halftoned with the first halftone and image data that is halftoned with the second halftone. The second tone transfer curve is then developed as the curve that linearizes the estimated measured values of image data halftoned with the second halftone.

Abstract: A method and apparatus for performing ink reduction error diffusion are described.

Abstract: A system and method for printer control and color balance calibration. The system and method address the image quality problems of print engine instability, low quality of color balance and contouring from the calibration. The method includes defining combinations of colorants, such as inks or toners that will be used to print images, defining a desired response for the combinations that are to be used and, in real time, iteratively printing CMY halftone color patches, measuring the printed patches via an in situ sensor and iteratively performing color-balance calibration based on the measurements, accumulating corrections until the measurements are within a predetermined proximity of the desired response. The calibration is performed on the halftones while they are in a high quantization resolution form.

Abstract: A method and apparatus for multi-level color error diffusion employs semi-vector quantization. When operating on image data comprising three color separations, the method employs a vector quantization for the two separations with the most visually perceptive color output to generate a multi-level output pixel for each separation based on the sum and a difference of the input pixel values for the two separations. The method generates multilevel output pixels for the third color separation using scalar error diffusion.

Abstract: Methods embed a digital watermark into a halftone image. One method derives halftone thresholds from a watermark image, and then uses these thresholds to convert target images into watermarked halftone images. A method for measuring digital watermark strength is used for a variety of applications, such as distinguishing original printed documents from copies. In this method, a watermarked signal is processed to extract estimates of error correction encoded bits embedded into the watermarked signal. Then, the error correction encoded bits are decoded to compute a message payload. The message payload is re-encoded to compute error correction encoded bits. A measure of watermark strength is computed from the error correction encoded bits and the estimates of error correction encoded bits.

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 method is disclosed for calibrating the half-tone operation of a color marking engine for creating images formed in bi-level or quad-level dot density formats. In the first step, a test pattern is run to provide an output image of a plurality of gray patches formed of first, second and third color toners. The gray patches of the output image include first, second and third sets of patches reproduced respectively at dot density levels of 25%, 50% and 75% of a maximum dot density. The relative color toner levels in the gray patches within each set of patches varies a predetermined increment in value above or below the toner levels in a median valued gray patch. The remaining steps of the method include visually selecting an output image of a selected color marking engine having a minimum color shift; determining a correction factor defined for each color at the maximum dot density; and storing the correction factor as an offset from maximum density for images created at the bi-level and quad-level formats.

Abstract: Printing masters are produced by use of an inkjet printing system.

Abstract: A method permitting an end user to recalibrate a color reproduction device. The color reproduction device includes a device for converting the native color values of the scanner into a device independent color space, a test target, and the desired values of each patch of the test target. The method includes printing the test target and scanning it with a scanner that forms a part of the color reproduction device. The device compares the desired values with the values obtained from scanning the printed test target to obtain a set of adjustment values to compensate for drift in the output of the color reproduction device. The compensation emphasizes restoration of the overall gray balance of the color reproduction device and can be implemented by modifying the tone reproduction curves or the halftone process used in the color reproduction device.

Abstract: An image processing apparatus executes an error diffusion process to multivalue image data consisting of a plurality of density components. A first processor executes the error diffusion process by changing at least one of a quantization threshold value and a quantization diffusion coefficient which are used for the error diffusion process based on a value of the multivalue image data of the density components or a value calculated from the multivalue image data value. A second processor executes the error diffusion process by setting the quantization threshold value and the quantization diffusion coefficient which are used for the error diffusion process into fixed values. An error diffusion processing controller controls to execute the error diffusion process to at least one color among the density components by the first processor and execute the error diffusion process to other density components by the second processor.

Abstract: A system and method for detecting alteration of a document. The invention evaluates markings in half-tone fields by ascertaining a first dot count of dots isolated from the marking in the half-tone field of the document; forming an image of the marking; superimposing the image on a blank half-tone field having the same predetermined pattern as the half-tone field of the document; ascertaining a second dot count of dots isolated from the image superimposed on the blank half-tone field; and determining whether the marking has been altered by comparing the first dot count to the second dot count. An alteration is indicated where the first dot count and second clot count are different.

Abstract: A method of one embodiment of the invention is disclosed that determines to output an output pixel for a color component of an image pixel. In response to determining to output the output pixel for the color component of the image pixel, the method outputs this output pixel, and at least substantially precludes output of output pixels for other color components of the image pixel.

Abstract: A method of one embodiment of the invention is disclosed that determines to output an output pixel for a color component of an image pixel. In response to determining to output the output pixel for the color component of the image pixel, the method outputs this output pixel, and spaces out the output of output pixels for other color components of the image pixel.

Abstract: A method for printing a halftone digital image using the same binary digital data to make a printing plate and a color proof.

Abstract: In an error diffusion halftoning process a clusters of adjacent pixels can be placed at any arbitrary position of the pixel grid.

Abstract: A method for modeling color halftones that reduces both the number of parameters and the number of measurements needed to characterize an inkjet color printer. The method is based on the eigenanalysis of sample reflectance data and a probabilistic analysis that considers light scattering on the paper substrate as a breakage process governed by a log-normal distribution. The method estimates the reflectance of a print color by characterizing colors as a multiplicative composition of primary color reflectances rather than as an additive mixture of primary and secondary color reflectances as suggested by the theory of Neugebaeur.

Abstract: Selective edge softening and selective edge dithering is introduced into an image representation to improve local control where halo problems are expected. Selective areas of dilation are isolated and separately dithered or halftoned, the result of which is then swapped back into or substituted for the stored original image. In this manner misregistration and color plane-to-plane interactions can be compensated for in plural image forming station architecture systems. The same technique is also valuable in monochrome systems as an aid to overcoming edge displacement and slow toner problems when the selective edge softening is selectively applied to edges which are in particular perpendicular to the fast scan direction.

Abstract: A method for reducing image noise is provided. The procedure of the method is provided in the following steps. First, the color level scale of a scanned image of a document is reduced by a plurality of bits in order to subtract a noise level from the scanned image. Then the color level scales of all pixels of the image are recombined by a halftone pattern method in order to recover the color level scales. Finally the missing codes of the image are filled out by bit enhance method. Because of the color level scales of the proceeding image are not reduced, the scanned image quality does not be blurred by the method. Because the method does not minimize the color level of the proceeding image, the image noise can be reduced without blurring the scanned image and the quality of the image can be increased after the process thereof. And because each color level of the pixel in the image is subtracted by a noise level, some of the bits are removed and the capacity of the image file is decreased.

Abstract: This invention provides a system which can obtain the same output irrespective of a reading system by previously storing different parameters used at the image processing times for respective reading systems and performing image processing operation by selectively using one of the parameters corresponding to the reading system used even in a case where different reading systems such as a through read system and document table fixed type system are provided to read a color document.

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: An integrated circuit fabricated on a single substrate. The integrated circuit includes a data bus and purpose-specific functional units connected to the data bus. The functional units include a JPEG decoder, a compressed bi-level expander, a halftoner, and a printhead interface. A general-purpose processor may also be connected to the data bus for controlling the functional units. The processor may be connected to run software that coordinates the functional units to receive, expand and print pages.

Abstract: An image rendering system and method use a sum-and-difference error diffusion technique that may be utilized in conjunction with image rendering using more than three colorants, e.g., inks. The colorants may be arbitrary and/or redundant. The sum-and-difference error diffusion technique involves two sets of steps. First, steps for performing specification of a colorant amount are separated from steps for determining colorant placement. Colorant placement is then performed by first summing the total number of colorant requests, including any associated error adjustments, and determining how many units of colorant will be rendered. Second, the adjusted colorant requests are sorted to fulfill the image rendering.

Abstract: By using negative feedback, moiré patterns can be reduced, or virtually eliminated, from input black-and-white or color original images. In particular, by feeding back an image containing the difference between the original input image and the halftone output with possible moiré patterns, and subtracting the low-frequency part of this image from the original input image, a resultant halftone image can be achieved that has reduced moiré patterns.

Abstract: ROM stores an 8×8 base matrix of 64 sequential threshold values (1-64), hexadecimal data for a specified pattern to be rendered on an output image, and a threshold address table in which the thresholds of the base matrix are arranged in ascending order of threshold value. The MPU generates a second threshold matrix used to render the specified pattern when the matrix is used by dithering unit to dither a source image having a wide range of gray-scale levels.

Abstract: A method of printing and the related printer architecture for receiving compressed page data that includes both contone data and foreground bi-level data. Both the contone data and the foreground bi-level data are decompressed. The contone data is halftoned to bi-level color data. The foreground bi-level data is composited over the bi-level color data to create composited bi-level color image data that is then printed. The related printer architecture includes an integrated circuit that includes a processor bus and purpose-specific functional units each connected to the processor bus. The functional units include a JPEG decoder, a bi-level decoder, a halftoner, and a program ROM. A general-purpose processor is connected to the processor bus for controlling the functional units. The processor runs software that coordinates the functional units to receive, expand and print pages.

Abstract: There is provided an image processing apparatus which enables high-speed processing with simplified multiplications and divisions even in the case of error diffusion comprised of a combination of processes of two or more colors. The image processing apparatus performs error diffusion on multivalued image data composed of a plurality of density components and outputs the result of the error diffusion. A plurality of error tables are stored in a storage device. One error table is selected from the plurality of error tables according to a density value of a first density component among the plurality of density components and a density value of at least one other density component when performing the error diffusion on the first density component. A CPU performs the error diffusion on the multivalued image data using the selected error table.

Abstract: It is one objective of the present invention to provide an image forming apparatus that increases the printing stability for a highlighted portion, and that can form a high quality image without causing a barrier due to the application of excessive energy to a shadow portion. In an image forming apparatus that, when gray level image data are input, divides the data into a plurality of blocks and, for gray level recording, converts the gray level image data into multi-valued data, in accordance with a gray level transformation characteristic determined in accordance with relative pixel positions in each of the blocks, the gray level transformation characteristic is so set that B<0.

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 method for converting an original halftone bitmap image to a color converted halftone bitmap image by morphological filtering of the original image to compensate for tone and color reproduction characteristics comprising: providing an original halftone bitmap image. The method includes providing a set of asymmetrical morphological filters that have the property that when they are applied recursively in order, the features in the halftone bitmap image are dilated or eroded by varying amounts by extending or reducing the edges first in one direction, then in two directions, etc.

Abstract: An image data processing apparatus determines whether an input element provided by a computer is either a command for processing continuous tone data or continuous tone data. When the input element provided by the computer is a continuous tone data processing command, a parameter (period, angle, form of a macroscopic dot) received by a parameter input unit is replaced by an approximate value realized by a multiple-valued recorder, a continuous tone screen threshold-valued matrix is selected on the basis of the parameter replaced by the parameter replacement unit, and continuous tone data is converted to multiple-valued data in accordance with the selected threshold-valued matrix for outputting halftone data to the multiple-valued recorder.

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: There is provided an image processor for obtaining a correction curve used in a gradation correcting process smoothly and quickly. In the image processor, a curve storing section stores reference correction curves and a correction amount storing section stores correction amounts corresponding to a plurality of specified input density values. A halftone output gradation processing section calculates the correction value to the specified input density value by using the reference correction curve and the set of correction amounts in copying original and calculates a correction value to the remaining input density value by means of interpolation operation for moving one part of the reference correction curve in the direction parallel to the axis of density value and for expanding or compressing in that direction.

Abstract: A method of rendering colors in a printing system using a set of colorants, includes, for each color to be rendered, a selection of a subset of colorants and for each colorant of the subset, a selection of a halftone screen and a coverage fraction. The method includes defining discrete color points in at least a portion of a color space, determining for the defined discrete color points, different subsets of colorants and associated coverage fractions thereof, rendering each of the color points, calculating for each of the subsets an associated graininess value, determining lists of colorant subsets rendering the defined discrete color points where the lists are consistent with respect to the attribution of a halftone screen to a colorant within a subset over the portion of the color space, and selecting one of the lists of subsets of colorants on the basis of a total graininess calculated for the lists.

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 for color correcting an original halftone bitmap image by a predefined color correction function to produce a color corrected halftone bitmap image comprising: providing an original halftone bitmap image; estimating the dot area percentage of the original halftone bitmap image in a set of sub-image blocks; calculating an aim dot area percentage, based on a predefined color correction function, for each sub-image block in the original halftone bitmap image, calculating the number of halftone bitmap image pixels to convert to on or off states to produce a modified original halftone bitmap image that has the aim dot area percentage where said value is designated by N, for each sub-image block in the original halftone bitmap image, and converting N pixels in the original halftone bitmap image to either on or off states depending on whether the aim dot area percentage is greater or less than the dot area percentage of the original halftone bitmap image respectively, for each sub-image block in the origina

Abstract: There is provided an image processing apparatus that can reduce the overlap of dots to thereby enable achievement of favorable visual characteristics, and reduce the amount of pseudo outlines in half tone and reduce the quantity of inks to be shot to thereby suppress an increase in the running cost. When performing the error diffusion on a first density component of the plurality of density components, a threshold to be used for the error diffusion is determined based on a density value of at least one second density component of the plurality of density components. The error diffusion on the first density component is executed based on the determined threshold. A result of the executed error diffusion is outputted.