Abstract: A method and system for estimating color separation misregistration of a printing system. The method may include marking a substrate to form a misregistration estimation patch. The misregistration estimation patch being formed by first and second color separations. The first color separation marking the substrate with a first halftone pattern. The first halftone pattern has a first halftone-frequency vector in a first direction and a second halftone-frequency vector in a second direction. The second color separation marking the substrate with a second halftone pattern. The second halftone pattern has a first halftone-frequency vector in a first direction and a second halftone-frequency vector in a second direction. The first and second halftone patterns form a moiré pattern. A deviation in at least one the halftone frequency vectors and/or the moiré pattern can be indicative of a color separation misregistration.

Abstract: An image reading apparatus for reading an image on an original document by irradiating it with light and photoelectrically converting reflected light from it by an image pickup unit, including: an original document guide member positionable opposite to the image pickup unit, with a conveyance position of the original document therebetween; a white reference member that is positionable, the same as the original document guide member, and has a reference white color; an achromatic constant-density reference member that is positionable, the same as the original document guide member, and has a reference achromatic constant-density; a drive unit that moves one of the three members so as to be positioned opposite to the image pickup unit; and a control unit that controls execution of detection processings for dust detection from data obtained by moving, as described above, the achromatic constant-density reference member and the white reference member by reading them.

Abstract: In an apparatus for performing printing using a color ink-jet head having a plurality of ink-discharge-port strings corresponding to ink materials having different color tones, a high-quality image having excellent gradation can be recorded, while reducing the cost of the apparatus and increasing the data processing speed by reducing the capacity of a memory for storing dot arrangement patterns.

Abstract: A system and method for printing an image on a document by generating RGB data from a scanned image, converting the RGB data to CMYK data and identifying one of a first and a second type of screening. The type of screening is identified for a first one of the CMYK data based upon the density of the first one of the CMYK data and the density of at least one of the other CMYK data.

Abstract: An efficient method and system for eliminating halftone screens from scanned documents while preserving the quality and sharpness of text and line-art is disclosed. The method and system utilizes one or more independent channels with different sensitivities (e.g., Max, High, and Low) to provide high quality frequency and magnitude estimation. The most sensitive channel (Max) derives the frequency estimate, and the remaining channels (e.g., High and Low) are combined to create the screen magnitude. The Max channel is the most sensitive and will usually report the existence of frequencies even when the screen is very weak. Therefore, the screen frequency must be additionally qualified by the screen magnitude. The screen magnitude can be interpreted as the level of confidence that the local neighborhood represents half-toned data.

Abstract: A method for determining lattice points to be referenced to prepare the correspondence defining data, said method including steps of prescribing a smoothness evaluation function which evaluates smoothness of arrangement of lattice points in the device-independent color space and contains a constraint condition that the arrangement of lattice points becomes nonuniform at a certain position in the device-independent color space and which has as a variable the lattice point position information in the low-dimensional color space which is prescribed by less color components than the number of inks used by the printing apparatus, optimizing the arrangement of lattice points in the device-independent color space by improving the rating of the smoothness evaluation function, with the lattice point position information in the low-dimensional color space varied, and determining lattice points to be referenced to prepare the correspondence defining data in the optimized state.

Abstract: A print engine/controller suited to use with a drop on demand print head. The print engine/controller works with compressed page data having both JPEG contone image layers and a bi-level image plane compressed using a Group 4 facsimile protocol. It receives compressed image plane's and effects expansion and printing in a pipeline fashion. It consists of a high speed serial interface (27) (such as a standard IEEE 1394 interface), a standard JPEG decoder (28), a standard Group 4 Fax decoder (39), a halftoner/compositor unit (29), a tag encoder (30) by which to place infrared tags into a printed page, a line loader/formatter unit 31 feeding an interface 32 to the print head (33). The decoders (28, 39) and encoder (30) are buffered to the halftoner/compositor (29).

Abstract: A method for converting an original halftone bitmap image to a color converted halftone bitmap image. A set of asymmetrical morphological filters is provided. The original halftone bitmap image is segmented into blocks and for each block: apply the set of morphological filters to the original halftone bitmap image to produce a set of modified halftone bitmap images; estimate the percent dot area of the original halftone bitmap image and the set of modified halftone bitmap images; a predetermined dot-gain to the percent dot area of the original halftone bitmap image to produce a modified percent dot area; select the modified halftone bitmap image whose percent dot area is closest to the modified percent dot area to produce a block of the color corrected halftone bitmap image; and replace the original halftone bitmap image with the combined blocks of selected modified halftone bitmap image.

Abstract: A method for multi-toning an input digital image having input pixels with two or more color channels to form an output digital image having modified output levels. The method includes producing an error signal for each color channel, combining the error signals to produce a combined error signal, sorting the error signals to produce a set of sorted error signals, and determining modified output levels responsive to the set of sorted error signals and the combined error signal.

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 of adjusting primary color data values including producing color saturation adjusted primary color data values that depend on a relative amount of chroma in the initial primary color data values.

Abstract: An improved color-image error diffusion process for use in conjunction with the operation of a multi-level, halftone, color-image output device. This process involves, first, performing output-device-dependent color error diffusion on color-image input data utilizing a halftone, output-device-dependent color palette containing output-device-dependent output color values. Thereafter, and with respect to the selection for pixel outputting of a pixel utilizing one of the output colors in the palette, and in relation to infeeding of that pixel to the output device for outputting, the process features applying a predetermined, dot-gain correction curve which corrects the infeed intensity value of the pixel in accordance with (a) the selected output color for the pixel, and (b) assessment of the pixel in terms of its association with a predetermined neighborhood pattern of adjacent pixels.

Abstract: The present invention relates to expanding the range of image densities over which the manipulation of differential gloss as may be inherent in halftoned images may be achieved. By selectively applying halftones with anisotropic structure characteristics which are significantly different in orientation while remaining identical in density, a gloss image may be superimposed within an image without the need for special toners or paper. This technique may be enhanced across low and high density areas by application of clear toner. Further, in color systems, light color toner may be applied to low density image areas and dark under-color applied in high density image areas, to expand the range of image densities over which a desired glossmark image will bear an effect.

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×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 seco

Abstract: An image processing device connected to a display device and a printing device, the image processing device includes an image data acquiring module that acquires image data; a setting module that sets a print image quality adjustment condition that is a condition for adjusting image quality for a print image; a print image data generating module that performs a image quality adjustment process on the acquired image data on the basis of the set print image quality adjustment condition, and generates print image data; a display image data generating module that performs a image quality adjustment process on the acquired image data on the basis of the set print image quality adjustment condition, and generates display image data; a display image adjusting module that adjusts the display image data so as to conform or approximate characteristics of a display image reproduced by the display device using the display image data to characteristics of a print image reproduced by the printing device using the print ima

Abstract: A data processing method for a color management module (CMM), applying to image processing, including dividing an object data respectively into a meta file data, a CMM profile data and a screening/half-toning table. The meta file data is processed by a firmware of a printer, while the CMM profile data and the screening/half-toning table are processed by an application specification integrated circuit in the printer, thereby shortening the total time of data processing and thus improving the printing speed.

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. If the density Ct is lower, the quantization value is set to 0.

Abstract: This invention proposes a method and a control device for controlling a medical imaging system's inner cavity color. The control device comprises a colored light source for lighting up the inner cavity of a medical imaging system so as to control its color tone. This colored light source is a base color light source and each base color light source is connected respectively to a regulator for regulating its brightness. A doctor or a patient can produce a mixture of lights of a desired color tone by controlling the brightness of each base color light source, while by illuminating the inner cavity of said medical imaging system with the mixture of lights said color tone will be presented therein. This invention can be widely used in all kinds of medical imaging systems, especially in magnetic resonance imaging systems and computerized tomography imaging systems.

Abstract: A color tone setting window 100 that includes an ink color circle 110 is displayed in order to set a color tone of a monochrome image. By specifying a point Pcc in the ink color circle 110, intensities of color components representing three chromatic primary color inks are specified. The color component intensities representing three chromatic primary color inks are determined as parameters defining the color tone of the monochrome image in accordance with the position of the specified point Pcc in the ink color circle 110. The ink color circle 110 is configured such that the color component intensities representing three chromatic primary color inks can be visually recognized from the position in the ink color circle 110. Alternatively, ink color sliders can be used in lieu of the ink color circle 110.

Abstract: The present invention relates to error diffusion logic in which three partial diffusion error values are produced in a pipelined manner and then summed together when the last partial error value is produced. The resulting summed error can be used to adjust a target pixel in a sequence of pixels or stored in a buffer until further corresponding partial error is produced for adjusting the target pixel.

Abstract: A method of embedding an image into two images by performing a digital halftoning process on a Cartesian product of color spaces to embed the image into the two images. A digital halftoning process includes an iterative isotropic halftoning process. The iterative isotropic halftoning process for each iteration if Outimage has not changed between two iterations or maximum number of iterations reached, then exit the iterations loop.

Abstract: In a computer generation of a dither mask for conversion of a continuous-tone image into a halftone image, a pixel array having a size in accordance with the dither mask is partitioned into blocks. Initial pixel values are determined such that the occurrences of pixel values will be substantially uniform in the blocks. A pair of exchange target pixels are selected at random from the pixels in one of the blocks and function values of a predetermined evaluation function that indicates a characteristic of the pixel value configuration of the pixels in this block are computed for the two cases where pixel values are exchanged among the exchange target pixels and where not exchanged. These function values are compared to judge whether exchange should be performed.

Abstract: The present invention relates to the segmentation of an image into a main area and a image segment for variable data differential gloss image control. A single color is selected. Two or more different color definitions are created by combining the selected single color with two or more halftones having anisotropic structure characteristics which are significantly different in orientation to each other while remaining identical in density. By alternatively assigning the color definitions to the image segment in accord with the variable data content, a variable data differential gloss image may be superimposed within an image having reduced data processing and storage requirements.

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: A method for processing color image data to generate multi-level image data with arbitrary output levels and arbitrary level spacing. The method identifies a gray level spacing for each of a first and second color separation pixels and scales the gray level for each of the first and color separation pixels scaled to a common level spacing in relation to their corresponding gray level spacing. The scaled gray levels are then be thresholded to one of the two multi-level output values corresponding to the bounds of the gray level spacing.

Abstract: Provided herein are teachings directed to calibrating an output device such as a color display, using a visual method of determining the gamma for the blue primary that is easier to perform and more consistent than methodologies employing a luminance-matching task. The methodology is based on the insight that accurate gamma estimation for blue is important not for luminance reproduction, but for proper color-balance, and most importantly grey-balance. Thus, it follows to use grey-balancing, rather than luminance-matching, as the criterion for selecting the blue gamma value. One variant as taught herein is to provide a user visual task to find a patch best representing neutral, given previously determined calibrated digital values for the red and green primaries that produce 50% fractional luminance. A large patch is displayed within a larger surround containing both a white border and either a checkerboard or a line pattern, so as to establish a reference for the neutral axis.

Abstract: A method of receiving image data indicative of an image and providing to a printer print data, corresponding to said image data, the print data being in a predetermined print format and having a predetermined print resolution, the method including the steps of receiving the image data, converting the image data into first format data having a first predetermined resolution, converting the first format data into the print data and making the print data available to a printer for printing.

Abstract: An error diffusion processing method includes determining a binary value of an input pixel according to a grayscale level of the input pixel, searching a nearest pixel that has the same binary value as the input pixel, and comparing a measured actual distance with an ideal distance between the two pixels, so as to compute a first adjustment value. By applying a noise array to an input image, a second adjustment value is also computed according to a noise value of the input pixel. Based on the first and second adjustment values, a threshold is adjusted to determine the binary value of the input pixel. The adjusted threshold is compared with the grayscale level of the input pixel, and according to the comparison result, the binary value of the input pixel is determined. By diffusing an error value, which is a difference between the grayscale level and the determined binary value of the input pixel, to neighboring pixels, the grayscale level of the neighboring pixels is changed.

Abstract: An improved method of encoding and compressing digital halftones that utilizes a “none-of-the-above” method for designating variable-length runs. A monochrome input bitmap is rearranged slightly to reduce the patterns possible in contained digital halftone cells. This revised monochrome bitmap is parsed into subfiles to optimize run-lengths. The parsed subfiles are combined into a single file whose alternating runs of 1's and 0's are converted into successive variable-length binary numbers. One of the permutations of an antecedent binary is designated “none-of-the-above” and its use triggers a subsequent variable-length binary. All other permutations within each variable-length binary may designate a specific contained run-length and such use triggers a return to the initial binary in the series. The above method is reversed to decode and uncompress the encoded file to reproduce the original revised monochrome bitmap for display by a computer monitor or printer.

Abstract: The present invention relates generally to digital watermarking. In one embodiment, a method of detecting copying of a printed object is provided. In another embodiment, a method is provided to measure digital watermark strength. In yet another embodiment, and for printing applications, an embedded digital watermark may be used to carry printer information that is later decoded by a watermark decoder and used to examine a digital scan of a printed object and determine whether the printed object is authentic. Other embodiments are provided as well.

Abstract: A printer is capable of expressing halftones by forming halftone spots in cells each having a plurality of pixels by irradiating an exposure beam. The printer comprises a halftone processing section for converting M-bit image data into N (M>N)-bit drive pulse width data for driving the exposure beam. The halftone processing section includes a threshold matrix including a plurality of threshold values corresponding to the plurality of pixels, and a converter circuit which compares a plurality of threshold values output from the threshold matrix with image data, and generates drive pulse width data in accordance with the comparison result. Random noise is superposed on the plurality of threshold values or the image data, and the resultant is subjected to the comparison, whereby generation of tone jump is suppressed.

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: 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 of receiving image data indicative of an image and providing to a printer print data, corresponding to said image data, the print data being in a predetermined print format and having a predetermined print resolution, the method including the steps of receiving the image data, converting the image data into first format data having a first predetermined resolution, converting the first format data into the print data and making the print data available to a printer for printing.

Abstract: There has been a demand to accelerate image data conversion through the use of the error diffusion method. To convert image data, it is determined whether a specified block process condition is satisfied on the basis of a gradation value for each pixel in a target block. When the block process condition is true, a process is performed to diffuse a gradation error for the entire target block and convert image data for pixels in the target block at a time. Even when the block process condition is false, it is determined whether to form a dot in the target block. When it is determined that no dot should be formed, a process is performed to diffuse a gradation error for the entire target block to the unconverted pixels in another block and convert image data for pixels in the target block.

Abstract: A method of adjusting positions of dots in an original halftone image for improving quality of printed images, the original halftone image including a plurality of pixels containing either dots to be printed or blank spaces. The method includes selecting a pixel in the original halftone image containing a selected dot to be printed, analyzing pixels in the original halftone image neighboring the selected pixel to determine if the neighboring pixels contain dots to be printed, adjusting the position of the selected dot in the selected pixel to increase an average distance between the selected dot and the dots in the neighboring pixels, and creating a modified halftone image in which the position of selected dot has been adjusted.

Abstract: CPU 150 performs a matrix operation on image data GD, and then increases the effective digit place number of the color values of the image data GD to increase the tone number of the image data GD from 8-bit tone to 18-bit tone. CPU 150 performs a gamma correction process, a matrix operation N?1M, and an inverse gamma correction process, and then restores the tone number of the image data GD to the original 8-bit tone, and performs automatic quality adjustment. As a result, the 8-bit tone of the original image data GD is preserved throughout image processing, and reproductive color number of the image data GD is preserved as well.

Abstract: In an image data producing apparatus for producing proofing halftone dots image data representative of a proof image in which an image obtained by a printing system is simulated, the image data producing apparatus has: a halftone dots pattern data storage section for storing a plurality of sorts of halftone dots pattern data representative of a plurality of sorts of halftone dots patterns; an image data obtaining section for obtaining the multi-tone level image data; a halftone dots pattern selecting section for selecting a single halftone dots pattern according to an operation from among the plurality of sorts of halftone dots patterns represented by the plurality of sorts of halftone dots pattern data stored in said halftone dots pattern data storage section; a halftone dots image data producing section for producing the proofing halftone dots image data by means of subjecting the multi-tone level image data obtained by said image data obtaining section to the halftone dots processing based on the halftone

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 and apparatus for performing ink reduction error diffusion are described. In one embodiment, the method comprises performing vector error diffusion and mapping anchors to printing colors, where performing vector error diffusion includes quantizing each input pixel value to a closest anchor in an anchor set, calculating errors based on differences between the input pixel values and the anchors, and performing error filtering based on calculated errors.

Abstract: Conventional design tools were not developed for designing square zero-shift supercells. Conventionally, solutions that enable square zero-shift supercells were found by trial and error or by exhaustive analysis. According to a first design criterion of this invention, a non-square supercell in a first frame of reference has a diagonal that is equal in length to the diagonal of a square supercell in a second frame of reference rotated at a desired screen angle to the first frame of reference. The screen angle is a function of the lengths of the sides of the non-square supercell in the first frame of reference. According to a second design criterion, if the area of the corresponding square supercell in the second frame of reference is an integer, a square zero-shift supercell can be designed based on the lengths of the sides of the non-square supercell in the first frame of reference.

Abstract: An improved digital halftoning method that uses an input image's global gray levels to determine the local gray levels of a monochrome output image. Input multi-bit pixels grouped into two-pixel-by-two-pixel local subcells are variously aggregated into one or more larger supercells. The size of said supercell(s) is related to and limited by the size of the global input bitmap. A final monochrome gray level is derived from said supercell(s) and distributed within contained subcells. Subcell gray levels are expressed as interim whole monochrome pixels and gray level remainders. A comparison is made of the final supercell and the summed interim subcell monochrome gray levels. An ordering of the remainders is used for assignment of additional monochrome pixels, if necessary, to yield final subcell monochrome gray levels. Gray level rounding errors thus are quantized by reverse diffusion until a monochrome gray level for each of the global image's two-pixel-by-two-pixel local subcells is derived.

Abstract: A number of lasers (402) used to image a bitmap file (630) of a halftone screen is comprised of generating a first bitmap file (630) for a first color. A first image (710) is printed with the first bitmap file for the first color with n lasers. A second image (720) is printed with the first bitmap file for the first color with n?1 lasers. An optimum number of lasers is selected for printing the first bitmap file based on the image with the least number of defects (700).

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: 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.

Abstract: An image data of M-gradations in a pixel is converted into multivalued image data of N-gradations (M>N>2) in a pixel. A remarked pixel converted into the multivalued data is determined whether to be a predetermined gradation TJ (N>TJ>2) in which a tone jump occurs. When the remarked pixel converted into the multivalued data is determined to be the predetermined gradation TJ, it is determined whether a pixel of the predetermined gradation TJ exists in pixels being adjacent to the remarked pixel. When the pixel of the predetermined gradation exists, the gradation of the remarked pixel is changed to the gradation other than the predetermined gradation so as to prevent the tone jump, and an average density after multivalued image data conversion is preserved.

Abstract: A method is provided for rendering a color image with a plurality of separations with a multi-level successive-filling halftoning process using a single screen for a plurality of separations. For a separation to be processed, first, from the possible multiple levels for the separation, the set of levels that would be used and the number of dots corresponding to the different levels are decided. These decisions are based on the input level for the separation and input levels for the prior process separations. The location of the dots to be printed for the different levels for the separation is then decided by using the halftone screen, while simultaneously taking into account the placement of printed dots for the prior separations. The selection is done so as to best disperse dots and minimize overlap.

Abstract: An edge pixel is extracted from an input image by an edge determination section, an object image section is extracted by an object-image extraction section, and a first characteristic amount of the object image section in a first local pixel block containing a first target pixel is calculated by a first-characteristic-amount calculation section. A classification is made as to whether the first target pixel is a character edge pixel or a dot edge pixel by an edge-class determination section on the basis of the result of extraction for the edge pixel and the first characteristic amount. A second characteristic amount of a second local pixel block containing a second target pixel is calculated by a second-characteristic-amount calculation section on the basis of the edge classification result. The image of the second target pixel is classified by an image-class determination section on the basis of the second characteristic amount.

Abstract: The present invention relates to an image processing method, an image processing apparatus and a recording medium that convert a grey scale image into an area gradation image. The present invention intends to provide an image processing method, an image processing apparatus and a recording medium capable of increasing processing speed in a state where high image quality is maintained. In the image processing method and the image processing apparatus according to the present invention, image data of a C component and image data of an M component in grey scale image data are converted into halftone image data in accordance with an error diffusion method, and image data of a Y component are converted into halftone image data in accordance with a blue noise mask method.

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