Abstract: The present invention discloses methods and systems for printing by superposing a metallic ink and transparent inks. These methods and systems are useful for color separating images into superpositions of a metallic ink and transparent inks both for design purposes and for the creation and authentication of security documents, such as banknotes, checks, diploma, corporate documents, passports, identity cards, credit cards, product labels, optical disks, CDs, DVDs, packages of medical drugs, cosmetics, and alcoholic drink bottles. By combining a metallic ink and transparent inks, one may create printed images behaving dynamically: an image viewed under specular reflection may be considerably different from the same image viewed under non-specular reflection. Patterns which are either dark or hidden become highlighted under specular reflection, yielding interesting visual effects. Metallic inks allow therefore to create visually appealing dynamically changing color images.

Abstract: A scan line profile characteristic representing the distortion of a scan line is detected. Dot image data undergoes the screen process using a dither matrix. At this time, the quantization process is done by shifting a dither matrix element in the sub-scanning direction opposite to the direction of the scan line changing process at a scan line changing point in the scan line changing process in accordance with the profile characteristic. The image data after the screen process undergoes the scan line changing process, and the interpolation process smooths the scan line changing point.

Abstract: A method for processing an image includes a screen generator (31) which allows a user to define parameters (15) that determine the characteristics of a stochastic halftone screen (32). The screen generator (31) dynamically generates the screen (32) prior to an image processor (20) producing halftone image data (24) from the screen (32) and a supplied image (11). The screen generator (31) is based on an efficient parameterized algorithm whose parameters are selected to allow a user to easily customize a screen (32) that is suited for one of a wide range of reproduction processes.

Abstract: A method for generating a stochastic halftone screen (32) includes a parameterized screen generator (31) whose parameters (15) control aspects of the generated screen (32). Some parameters (15) control the size of a generated threshold array (300). A variety of threshold array sizes can be generated quickly including larger arrays (300) wherein the generation time is proportional to the natural logarithm of the threshold array size. Some parameters control a set of shaping functions used to determine the distribution of minority pixels (302) for a wide variety of printing conditions. These include controls for edge-to-area ratio, cluster size, anticipated dot gain and modeled human visual response.

Abstract: A method of screening a continuous tone image into a halftone representation for a flexographic printing operation can compensate for characteristic printing problems in highlight areas by selectively placing non-printing dots or pixels proximate highlight dots. The non-printing dots or pixels raise the printing relief floor in the highlight areas providing additional support for marginally printable image features.

Abstract: Filtering image information to generate a dithered image includes receiving input image information corresponding to an image generated using a first array comprising a first number of smaller pixels. Intermediate image information is generated from the input image information. The intermediate image information is generated to produce the image using a second array comprising a second number of larger pixels, where the second number less than the first number. A frequency response associated with the image produced using the second array exhibits effects. The intermediate image information is repeatedly filtered to generate updated image information from the intermediate image information and to compensate for the effects. Sub-image information is generated from the updated image information, the sub-image information corresponding to a dithered image.

Abstract: A programmable system for dithering video data. The system is operable in at least two user-selectable modes which can include a small kernel mode and a large kernel mode. In some embodiments, the system is operable in at least one mode in which it applies two or more kernels (each from a different kernel sequence) to each block of video words. Each kernel sequence repeats after a programmable number of the blocks (e.g., a programmable number of frames containing the blocks) have been dithered. The period of repetition is preferably programmable independently for each kernel sequence. The system preferably includes a frame counter for each kernel sequence. Each counter generates an interrupt when the number of frames of data dithered by kernels of the sequence has reached a predetermined value. In response to the interrupt, software can change the kernel sequence being applied. Typically, the system performs both truncation and dithering on words of video data.

Abstract: A printer uses a dithering mask having a width that is 1/N (where N is a nonzero positive integer) times a number of pixels corresponding to the layout pitch of print head tips, so as to always have an identical positional relationship between the dithering mask and the connecting portions of the print head tips, so as to perform a half toning process and print image data. The dithering mask DM is a dithering mask that is optimized so as to be able to obtain dot dispersion characteristics that are somewhat good regardless of the positional shift patterns between the print head tips. Doing so enables the suppression of degradation of printed image quality that stems from differences in characteristics of the plurality of print heads in a line printer that performs printing using a plurality of print heads that are arrayed across a printing range.

Abstract: A plurality of types of positional shift postulated patterns are postulated wherein the positional shift of print head tips in a printer are postulated to have positional shift directions and distances. For each of the postulated positional shift postulated patterns, a base dithering mask is generated considering the ability to produce excellent dot dispersion characteristics when this postulated positional shift has occurred. Additionally, optimal dithering masks are generated through multiply combining the sets of threshold values that comprise the base dithering masks. Doing so enables the suppression of degradation of printed image quality, even when there are positional shifts between the print heads, in a half toning process for printing using a printer that is provided with a plurality of print heads that are arranged in a line across a printing range.

Abstract: An image forming apparatus, for forming an image with plural types of dots having different densities per unit area in a same hue, including: a section to compare between a pixel value of a target pixel and a value of a prescribed threshold value matrix, and to determine, based on the comparison, whether to form a first type of dot at a position corresponding to the target pixel; a section for calculating a corrected threshold value matrix from the prescribed threshold value matrix; a section for calculating a second determining condition by reflecting the corrected threshold value matrix; and a section for determining whether to form the second type of dot, based on a target pixel value added an error with an error diffusion process and the second determining condition, at the position where the first type of dot has been determined not to be formed.

Abstract: A dithering pattern that is generated based on a spatial operation is used for a Bit-Depth Extension (BDE) technique for preventing contouring artifacts in an image displayed by a display having a bit-depth that-is less than the bit-depth of the image. The dithering pattern can be based on achromatic visual model or a spatio-chromatic visual model. The dither pattern is formed by shaping a pseudo-random noise signal by an equivalent noise visual model that is based on an array of pixels. Alternatively, the array of pixels is based on an image, or a determinate array of pixels.

Abstract: Methods, apparatus, software, and systems of the present invention allow for optimization of color and shades of gray documents prior to their conversion to a monochrome format. If color/gray elements are identified in the document, the distance between them and their intensity is determined. If there are elements with the same or similar intensity in close proximity to each other, colors of some of the elements may be replaced with solid monochrome colors, and/or dithered surfaces, and/or monochrome patterns. Further, the elements may be outlined. These improvements make elements in the document more distinguishable after its conversion to a monochrome format. The described color optimization and outlining may have wide applicability in the Internet Fax technology.

Abstract: In a matrix area (720), a plurality of highlight-side dot centers (731) and a plurality of shadow-side dot centers (741) are regularly arranged and a plurality of reference points (751) are set while being distributed almost uniformly. Each of the dot centers (731, 741) is rotated about a nearest reference point (751). Threshold values of the matrix area (720) are determined so that halftone dot areas should be changed around a plurality of highlight-side dot centers (731) after being rotated in accordance with the variation in gray level on the highlight side and a halftone dot area (i.e., joined dot areas) should be changed around a plurality of shadow-side dot centers after being rotated in accordance with the variation in gray level on the shadow side. In a halftone dot image generated by using the matrix area which is thus generated, it is possible to suppress moire and graininess.

Abstract: An algorithm for modulating printer half-tone screening based on the tonal values of the region being reproduced is provided. The algorithm determines the tonal values for a particular region and assigns real number constants to that region. As the clustering screen is applied, the threshold values in the clustering screen are reduced (divided) by the real number constants thereby modulating the effect of the application of the clustering screen. For deep tonal regions, the clustering screen is applied at full strength, while in light tonal regions no clustering effect is applied. The algorithm results in a an image that has a greater dynamic range without the appearance of stair stepping while eliminating clustering artifacts from the lighter regions.

Abstract: In a first process, initial dot pattern of a predetermined dot rate “a” is created in a first process, and a gradation value corresponding to the dot rate “a” is arranged as a threshold value in the position of the pixel of the threshold value matrix corresponding to the initial dot pattern. Then in a second process, the initial dot pattern or the dot pattern having occurred prior to the second computation is used as the dot pattern of dot rate “b”, and new dots including the dots of the dot pattern of dot rate “b” is generated or any of the dots is removed from the dot pattern of the dot rate “b” by the error diffusion method. Thus, the dot pattern of the next dot rate “b?” with its dot rate having been increased or decreased in the aforementioned procedure is generated.

Abstract: When the input value becomes close to the medium dot relative density value (Den_M), the large dot threshold value (Thre_L) and medium dot threshold value (Thre_M) become close to each other. It is possible to prevent output values from being converged to the particular medium-dot output value. When the input value becomes close to the small dot relative density value (Den_S), the medium dot threshold value (Thre_M) and the small dot relative density value (Den_S) become close to each other. It is possible to prevent output values from being converged to the particular small-dot output value.

Abstract: Halftone cells each serving as a unit for formation of a dot are arranged in irregular shapes at random and divided into two groups. The halftone cells (720) in the first group are fewer than the halftone cells (730) in the second group and dispersed, and the area of each of the halftone cells (720) in the first group is set larger than that in the second group. The dot growth speed of the halftone cells (720) in the first group is higher than that of the halftone cells (730) in the second group. This allows formation of fine halftone dots consisting of the halftone cells in the first and second groups, and it is possible to reduce banding appearing in a main scan direction during recording of the halftone dots, with low-frequency components in spatial frequency of the halftone dots caused by the halftone cells (720) in the first group.

Abstract: A half-toner compositor to composite image plane data, for use in an ink drop print head, the half-toner compositor comprising at least one dot merger 58 receiving data from more than one buffer 42, and a color mask register 48 holding masking bits in number equal to the number of image planes, wherein input data to the at least one dot merger 58 is combined with the masking bits to form an output data corresponding to a type of ink in the print head.

Abstract: An organized dither matrix is composed of a main matrix having dispersibility and a sub-matrix having randomness, and the intensity of a frequency characteristic of an output image relatively increases from a low frequency component, through an intermediate frequency component, to a high frequency component in respective tone levels.

Abstract: Techniques for generating dither masks are provided. A dither mask is generated by selecting a sequence of at least three original patterns comprising pixels of at least one of a first color and a second color. At least two patterns are interpolated to generate interpolated patterns in the sequence between the at least three original patterns. If a pattern having at least one specified characteristic exists in the sequence, the steps of interpolating between at least two patterns, and determining if a pattern having at least one specified characteristic exists in the sequence, are repeated. The interpolation is between at least one pattern from each side of the pattern having at least one specified characteristic in the sequence.

Abstract: An image processing apparatus includes: a recording rate determining section for determining a recording rate of each of a plurality of dot types having different densities per unit area from each other according to an input value including a multi-gradation image data, the input value being quantized for forming a dot of the plurality of dot types; a dot formation judging section for judging whether the dot is to be formed on each pixel based on a sum total of each recording rate of the plurality of dot types; and a dot selecting section for selecting a dot type among the plurality of dot types having different densities per unit area from each other to a pixel on which the dot formation judging section judges that the dot is to be formed, wherein an image is formed according to an arrangement distribution of the dot.

Abstract: The invention provides a printing method of printing on a printing medium. The method includes: generating dot data that represents state of dot formation at each print pixel of a print image to be formed on the printing medium by performing a halftone process on image data that represents an input tone value of each pixel making up an original image; providing a print head capable of selectively forming N types of dots having mutually different sizes on a region of one pixel on the printing medium, N being an integer of at least 2; and generating the print image according to the dot data by mutually combining a plurality of dot groups in a common print region, each of the plurality of dot groups being formed on each of a plurality of pixel groups that assume mutually physical differences in a process of dot formation.

Abstract: A method for generating a dither mask is disclosed using a local stochastic technique for use for the halftoning of grey scale images by a pixel by pixel comparison of the images against the dither mask. The dither mask is generated by producing a sequence of dot profiles (each dot profile of the sequence corresponding to a grey scale level) using a stacking constraint with incremental grey scale level such that for each dot profile of the sequence the same pixels are selected compared to the preceding dot profile and the increment in the or each dot profile is realized by selecting at least one additional pixel. When determining the position of an additional pixel, the aspect ratio between the dot pitch in a predetermined direction and a direction perpendicular thereto when rendering images is taken into account.

Abstract: A circuit structure has multiple comparator circuits connected in series. Each comparator circuit compares an input tone value with a medium value of table data input from a preceding comparator circuit. When the tone value is greater than the medium value, the comparator circuit selects table data of greater than the medium value and outputs the selected table data to a subsequent comparator circuit. In this state, the comparator circuit outputs a value ‘1’ as a resulting bit representing a result of the comparison. When the tone value is not greater than the medium value, on the other hand, the comparator circuit selects table data of not greater than the medium value and outputs the selected table data to the subsequent comparator circuit. In this state, the comparator circuit outputs a value ‘0’ as the resulting bit. The circuit structure arrays the resulting bits output from the respective comparator circuits in an output order from its upper bit position and outputs the array of the resulting bits.

Abstract: A method of printing with a personal computer and connected printer includes the step of rendering contone data to a pixel level and subsequently compressing the contone data in the personal computer. The bi-level data is rendered to a dot level and subsequently compressed in the personal computer. Compressed page data is communicated to the printer. The contone data and the bi-level data are expanded in the printer. The contone date is halftoned in the printer. The bi-level data is composited in the printer. The halftoned and composited data is printed.

Abstract: A method for generating a dither matrix for converting a gray scale image having N gray levels into a halftone image, which includes using a parametric filter to generate a dither halftone pattern for each gray level Gi>Gt, where N>2, Gt represents a transition gray level, the lightest gray level is G0, the darkest gray level is GN?1, and Gt?G0, the parametric filter based upon a desired spot profile function of the halftone image, and using the generated dither halftone pattern to generate the dither matrix.

Abstract: A super dithering method of color video quantization maintains the perceived video quality on a display with less bit depth of color than the input video. Super dithering relies on both the spatial and temporal properties of human visual system, wherein spatial dithering is applied to account for human eye's low pass spatial property, while temporal dithering is applied to achieve the quantization level of the spatial dithering.

Abstract: A plurality of types of basic tiles are arranged in a matrix area while prohibiting an arrangement of only ON or OFF elements in two rows and two columns, to acquire an element matrix representing an arrangement of dots in a gray level of 50%. After one element is specified in each of a set of the ON elements and a set of the OFF elements, a process of specifying an element farthest from specified elements is repeated to acquire a turn-on order of dots with increase in gray level on a highlight side and a turn-off order of dots with decrease in gray level on a shadow side, and a threshold value of each element is determined in accordance with these orders. With this operation, it is possible to generate a threshold matrix which is capable of reducing graininess in an image generated by halftoning an original image.

Abstract: This invention is a printing control method of generating print data to be supplied to a print unit which is capable of forming dots on a print medium by ejecting at least one type of colored ink containing a color material and a quality-enhancing ink for enhancing quality of a printed material. The printing control method comprises a color conversion step of converting pixel values into multiple gradation data of each ink, the pixel values representing color of each pixel of given image data, the multiple gradation data of each ink expressing the color of the pixel by using the colored ink and the quality-enhancing ink available in the print unit and a gradation-reduction step of generating at least part of colored dot data and transparent dot data by ordered dither method.

Abstract: The invention provides a printing method of printing on a printing medium. The method includes: providing a print head that includes a plurality of nozzle arrays for ejecting at least N colors of inks, N being an integer of at least 3; performing a halftone process with a dither matrix on image data that represents a tone value of each pixel making up an original image to generate dot data that represents a state of dot formation at each of print pixels of a print image to be formed on the printing medium; and generating the print image by combining at least N colors of dot groups formed in at least one scan of the print head in a common print area, the plurality of nozzle arrays respectively forming dot groups having different colors each other in the each scan of the print head according to the dot data.

Abstract: A dithering method and apparatus are disclosed for image data. At least two different weighting numbers are provided, and the sequence characteristic of the current frame is determined. One of the weighting numbers is then selected as the effective weighting number according to the sequence characteristic. After comparing at least one least significant bit (LSB) of the image data with the effective weighting number, at least one most significant bit (MSB) of the image data is adjusted according to the comparing result.

Abstract: A method and system are provided for processing digital multi-colour images for the reproduction thereof on a colour printing and/or copying system. Particularly, the printing and/or copying system is capable of complementary forming registered composite multi-colour images of coloured marking particles. This means that the separation images of coloured marking particles are formed contiguous to each other rather than in a superimposed relationship. The digital multi-colour images are processed such that during reproduction thereof any adverse effects on image quality caused by register errors in a predetermined direction are eliminated or at least limited. To accomplish this, a particular halftoning technique is used wherein with gradually increasing input density value of the image pixels, a linear growth pattern is generated in the predetermined direction by alternately adding image dots to both sides.

Abstract: A disclosed dither matrix is used in halftone processing for converting input image data having M input halftone levels into output image data having N (M>N>2) output halftone levels. In the halftone processing, a concentration type dither matrix is used as the dither matrix when an input halftone level is within a range of input halftone levels corresponding to an output halftone level that is lower than a predetermined threshold level T (N>T>1), and a dispersion type dither matrix is used as the dither matrix when the input halftone level is within a range of input halftone levels corresponding to an output halftone level that is equal to or higher than the predetermined threshold level T.

Abstract: The invention provides a printing method of printing on a printing medium. The method includes: performing a halftone process with a dither matrix on image data that represents a tone value of each pixel making up an original image to determine a state of dot formation at each of print pixels of a print image that is to be formed on the printing medium, and generating dot data that represents the determined state of dot formation; and generating a print image by mutually combining each of dot groups that are formed at each of a plurality of pixel groups in a common print region according to the dot data, the plurality of pixel groups being assumed to have different physical conditions with respect to the dot formation. The dither matrix stores each threshold value such that a number of dots to be allocated to each of the plurality of dot groups is determined according to a dot formation order of each of the plurality of dot groups in the common print region in the halftone process.

Abstract: The invention provides a printing method of printing on a printing medium. The method includes: generating dot data that represents state of dot formation at each print pixel of a print image to be formed on the printing medium by performing a halftone process on image data that represents an input tone value of each pixel making up an original image; and generating the print image by forming dots on each of the print pixels according to the dot data. The halftone process determines the state of dot formation by using a dither matrix that stores a plurality of threshold values, the plurality of threshold values being used for determining state of dot formation at each of print pixels of the print image to be formed on the printing medium according to an input tone value.

Abstract: A printer has a head where outlets are arranged in a width direction perpendicular to a predetermined scan direction, and a printing paper moves under the head in the scan direction. In a basic dither matrix which is an array where element values are arranged in a column direction corresponding to the scan direction and a row direction corresponding to the width direction and positions in the row direction are associated with the outlets in the head, respectively, the element values are modified on the basis of variation in print densities with respect to the width direction caused by ejection from the outlets. In the printer, printing is performed with the modified dither matrix, it is therefore possible to print an image at high speed and easily, where unevenness caused by variation in ejection amounts of droplets from the outlets or the like is suppressed.

Abstract: A method for multi-level halftoning an input digital image to form an output digital image which includes a multi-level error diffusion halftoning process incorporating periodic dither signals whose amplitudes are adjusted as a function of the error-diffusion texture characteristics.

Abstract: A drawing instruction processor refers to a bit map line table that shows whether the bit arrays in the row unit are the same in the order of concentrations. The drawing instruction processor decides whether dither patterns to be used for the adjacent specified drawing ranges are the same, by referring to the BLT, and links the drawing ranges to which the same pattern can be applied. Based on this, the drawing processor carries out a batch writing using a dither pattern prepared in advance into the specified range in the page memory. The dither pattern to be used for the drawing is prepared by linking a plurality of the same basic patterns to have a length corresponding to the length of the word length. As a result of such an arrangement, it is possible to achieve a high-speed processing.

Abstract: A method of generating a dither matrix for an output device having sub-pixel addressability that permits the attenuation of tone for less than whole pixels. An original representative pixel grid is expanded to a super-resolution by replication of the pixel grid in both directions by the sub-pixel factor S. Halftoning methods for generating dither patterns are then applied using the super-resolution grid to create dither or filter outputs, which are converted to a corresponding output for a sub-pixel resolution grid. Selection of location for incremental addition (deletion) of tone is made using the sub-pixel grid output. The cycle of output generation, conversion to sub-pixel resolution, and tone modulation selection is repeated iteratively until a desired gray level is reached. The process is further repeated for each desired gray level to produce the multiple dither patterns that comprise the desired dither matrix.

Abstract: Xerox Reference No. D/A0639A system and method for improving xerographic halftoning by magnifying a threshold array, interpolating the in-between values, enabling multiple thresholds to be accessed simultaneously and presented to multiple comparators, to cause multi-bit output. A threshold array is sampled at distinct locations separated by the sparse sampling distance to allow warping of the threshold array dots by adjusting the sampling distance in small, fractional portions (deltas) of the magnified distance. By adding more thresholds, amplitude or intensity modulation is used to move dot edges in a process direction for further flexibility in printing irrational or warpable screens.

Abstract: A method for dithering image data is provided. The method is suitable for representing A-bit grayscale values with a B-bit resolution, where A and B are positive integers and A>B. The main steps of the method include calculating 2A target grayscale values with decimals within an interval from 0 to (2B?1)*2A?B, and then representing the target grayscale values with the decimals through 2-dimensional dithering or 3-dimensional dithering.

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: Methods and apparatus are provided for converting a full color image to a two-color image for printing at a two-color printer capable of printing black pixels and alternate color pixels. Black pixels and alternate color pixels of the full color image will be printed as corresponding black and alternate color pixels in the two-color image. Printing in pixel areas of the two-color image which correspond to white pixels of the full color image will be inhibited, such that the white pixels of the full color image appear as corresponding background colored pixel areas of the substrate in the two-color image. A dithering algorithm is used for converting other color pixels of the full color image into the two-color image by utilizing either a combination of corresponding background colored pixel areas of the substrate and printed alternate color pixels or a combination of corresponding printed black and alternate color pixels.

Abstract: A method and circuit for generating an M-bit digital dither signal with a substantially uniform probability density function and high-pass spectrum are disclosed. The circuit includes a linear feedback shift register (LFSR) with N storage elements where N>M, and a high-pass filter. The method involves sampling at least M storage elements of the LFSR with each clock cycle to form an M-bit LFSR output and high-pass filtering and the M-bit LFSR output to provide the M-bit dither signal.

Abstract: An image forming device that has a function for suppressing a document background and performs binary coding of scan data using a dithering matrix, including a dithering matrix construction unit to divide the scan data into areas, set a threshold for each of the areas, and reconstruct a default dithering matrix using the threshold for each of the areas so as to generate a reconstructed dithering matrix for each of the areas; and a binary coding unit to compare the scan data with the reconstructed dithering matrix for each of the areas, and generate binary coded data based on a result of the comparison.

Abstract: Methods for choosing and combining colors from a color palette to render an image color tone are disclosed. A set of up to four palette colors are chosen and the weighted factors for combining the chosen palette to render the image color are determined. The weighted factors of the chosen palette colors are ordered according to an ordering criterion or criteria. The color output of a display pixel is the chosen palette color associated with the interval in which the threshold value falls. Color data compression may also be achieved by eliminating at least one color from the set of chosen palette colors used to render an image color that fails to exceed a specified threshold value. Also disclosed are methods for designing uniform and non-uniform color palettes.

Abstract: Techniques for securely displaying text on a display panel involve destroying spatial and temporal correlations in an otherwise uniform visual field. The techniques render the displayed text secure with respect to attempts to copy the text using a video capture device or still-picture camera. The techniques also render the displayed text unreadable to casual over-the-shoulder viewing by strangers outside of a certain narrow reading area.

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: A four-time resolution refinement of 3D-dither algorithm is provided in this present invention. A 4×2 pixel-block is treated as an observed unit in this present invention, which includes two 2×2 pixel-blocks. In order to eliminate moving lines and dithered edges, the two least significant bits (LSBs) of the pixels are treated depending on cases. For the first 2×2 pixel-block, when 2-bit LSBs being 01 and 11, the pixel being assigned a carry is an upper-left, lower-right, lower-left, and upper-right sequence in a 2×2 pixel-block for four sequential frames. For the second 2×2 pixel-block, when 2-bit LSBs being 01 and 11, the pixel being assigned a carry is a lower-left, upper-right, upper-left, and lower-right sequence in a 2×2 pixel-block for four sequential frames. For both 2×2 pixel blocks, no pixel is treated for 2-bit LSBs being 00. For 2-bit LSBs being 10, the pixel row of the 4×2 block switches between the upper and the lower row for every frame.

Abstract: A multi-tone image processing method and apparatus in which mutually dissimilar tone levels are realized by changing the additive condition of recording energy by means of different recording positions, even when the number of recording operations within a specific range is identical. For example, in an electrophotographic apparatus, when the number of irradiation by a light spot within a specific range remains constant as the irradiation position is changed in the specific range, there is a change in the additive condition of the optical energy within said specific range. Thus, the area rendered visible within the aforesaid specific range also changes, thereby changing the tone level.