WO2005104525A1 - 複数画素ずつ多値化を行う画像処理装置 - Google Patents
複数画素ずつ多値化を行う画像処理装置 Download PDFInfo
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- 238000006243 chemical reaction Methods 0.000 title claims abstract description 118
- 238000013139 quantization Methods 0.000 claims description 252
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- 238000007639 printing Methods 0.000 claims description 58
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Classifications
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
- H04N1/40—Picture signal circuits
- H04N1/405—Halftoning, i.e. converting the picture signal of a continuous-tone original into a corresponding signal showing only two levels
- H04N1/4055—Halftoning, i.e. converting the picture signal of a continuous-tone original into a corresponding signal showing only two levels producing a clustered dots or a size modulated halftone pattern
- H04N1/4057—Halftoning, i.e. converting the picture signal of a continuous-tone original into a corresponding signal showing only two levels producing a clustered dots or a size modulated halftone pattern the pattern being a mixture of differently sized sub-patterns, e.g. spots having only a few different diameters
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
- H04N1/41—Bandwidth or redundancy reduction
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2340/00—Aspects of display data processing
- G09G2340/04—Changes in size, position or resolution of an image
- G09G2340/0407—Resolution change, inclusive of the use of different resolutions for different screen areas
Definitions
- Image processing device that multi-values each pixel
- the present invention relates to a technology for outputting an image based on image data, and more particularly, to a technology for outputting an image by performing predetermined image processing on image data to generate dots at an appropriate density.
- Image output devices that output images by forming dots on various output media such as print media and liquid crystal screens are widely used as output devices for various image devices.
- images are handled in a state subdivided into small areas called pixels, and dots are formed in these pixels.
- dots are formed in pixels, of course, if one looks at each pixel, one can only take the state of whether dots are formed or not. However, if we look at the area with a certain size, it is possible to cause the density of the dots to be formed to be uneven, and by changing the density of the dots, we can output multi-tone images. It is possible.
- the dot formation density is appropriately controlled, it is possible to output a multi-tone image.
- the process of controlling the formation of dots to obtain an appropriate formation density is generated by performing predetermined image processing on an image to be output.
- these image output devices have been required to have higher quality and larger image output images. To meet the demand for higher image quality, it is effective to divide the image into smaller pixels.
- An object of the present invention is to provide a simple image processing technology that can be executed without using a device having a high processing capability such as a personal computer.
- the image processing device of the present invention employs the following configuration. That is, the present invention processes image data representing an image represented by a predetermined number of gradations, and performs multi-level conversion of each pixel constituting the image with a number of gradations smaller than the predetermined number of gradations.
- a pixel group gradation value which is a gradation value representing a pixel group in which a plurality of pixels are grouped, and a multi-value quantization result value representing a result of the multi-value quantization for each pixel constituting the pixel group.
- a pixel group gradation value determination unit that extracts a group of pixels corresponding to the pixel group from the image data representing the image, and determines the pixel group gradation value for each pixel group that is the group of the extracted pixels; Means,
- a multi-level conversion unit that obtains a multi-level conversion result value for each pixel group forming the image based on the pixel group gradation value by referring to the correspondence relationship;
- Control data output means for generating and outputting a control data for forming the image from the multi-value quantization result value obtained for each pixel group;
- the gist is to provide Further, the image processing method of the present invention corresponding to the above image processing apparatus processes image data representing an image represented by a predetermined number of gradations, and for each pixel constituting the image,
- An image processing method for performing multi-level conversion with a small number of gradations comprising: a pixel group gradation value that is a gradation value representing a pixel group in which a plurality of pixels are grouped; A correspondence between the pixel and the multi-value quantization result value representing the result of the multi-value quantization is prepared in advance,
- a multi-value halftoning result value for each pixel group constituting the image is obtained based on the pixel group gradation value, Generating and outputting control data for forming the image from the multilevel halftoning result value obtained for each of the pixel groups;
- the gist is.
- a pixel group gradation value that is a gradation value representative of the pixel group is set. It is determined, and the obtained pixel group gradation values are converted into multi-valued values.
- the pixel group may be a group of the same number of pixels at all times, but may be, for example, a group of different numbers of pixels according to a predetermined pattern or a predetermined rule. . Further, when determining the pixel group gradation value, for example, it can be determined based on the image data of each pixel included in the pixel group.
- an average value, a representative value, a total value, and the like of the gradation values of a plurality of pixels can be used as appropriate.
- Control data for forming an image is generated from the multi-value quantization result value obtained for each pixel group in this way, and this is output.
- the multi-value quantization result value can be represented by multi-value conversion of the entire image with a very small amount of data as compared with data indicating whether or not dots are formed for all pixels of the image. Therefore, if the control data generated from the multi-value quantization result value is output, it can be output quickly.
- the image output device that receives such control data determines whether or not dots are formed in each pixel in the pixel group by using a method described later, and then outputs an image based on the determination result. be able to. Therefore, if control data can be quickly supplied to such an image output device, an image can be output more quickly.
- the multi-value conversion is performed while referring to the correspondence between the pixel group gradation values and the multi-value conversion result values. Value can be obtained. For this reason, control data can be generated quickly, and the control data can be output quickly with a better layer.
- multi-value conversion is performed by referring to the correspondence set for each pixel group.
- the correspondence can be set for each pixel group, it is possible to associate the same multi-value quantization result value with different pixel group tone values, so The number of multi-value quantization result values can be reduced as compared with the case where the pixel group gradation value is multi-valued. As a result, the data amount of the control data can be reduced as compared with the case where the pixel group gradation value is simply multi-valued, and the data can be output more quickly.
- the main processing for generating the multi-value quantization result value refers to the correspondence. This is a simple process.
- the pixel group gradation value may be multi-valued as follows. First, a classification number assigned to each pixel group is obtained. Then, the pixel group tone value may be multi-valued by referring to the correspondence set for each classification number.
- the correspondence is set for each classification number, a completely unique correspondence can also be set for each classification number.
- the pixel group gradation value of each pixel group can be appropriately multivalued.
- the pixel group can be identified using the classification number, it is possible to simplify the process of multi-valued the pixel group gradation value.
- the pixel groups may be classified into a plurality of types according to positions in the image, and a classification number may be assigned to each pixel group. By doing so, a classification number can be appropriately assigned as needed without having to assign a classification number to a pixel group in advance.
- the classification number can be assigned appropriately.
- the correspondence relation referred to in multi-value conversion may be the following correspondence relation.
- the correspondence may be such that the multi-value quantization result value for each pixel group is set by the number determined according to the classification number. Since the correspondence referred to in multi-value conversion is set for each pixel group, the number of multi-value quantization result values can be set freely for each pixel group. If the number of multi-value quantization result values can be changed for each pixel group, there is no danger that the multi-value quantization result values are repeated in a fixed pattern as in general multi-value quantization processing.
- the correspondence relation referred to in multi-value conversion may be the following correspondence relation. That is, the multi-value halftoning result value for the pixel group tone value may be a correspondence defined for each classification number. Alternatively, data that can determine the order in which dots are formed in the pixel group is stored for each classification number, and the dots formed in the pixel group are stored as the multi-value quantization result values. The number of dots is obtained, and from the number of dots obtained by the multi-level conversion means and data that can be used to determine the order of dot formation, it is determined at which pixel in the pixel group a dot is formed.
- Control data may be output as data that can be used. In this way, simple data can be used to form dots at any position in the pixel group. It can inform the equipment that forms the dots.
- data of gradation values at which the result of multi-value conversion is switched and the number of dots to be formed in the pixel group at each gradation value may be stored in association with each other. Good. Since the multi-value quantization result value takes the same value in a predetermined gradation range, it can be processed by storing the data of the gradation value at which the result of the multi-value quantization is switched. In this way, the amount of data to be stored as the correspondence can be reduced.
- the data which can know the order in which dots are formed may be the value itself given to each pixel in the pixel group, or may be an order value describing the order in which dots are formed.
- the processing can be performed even if the correspondence relationship itself has, for example, the threshold value of the dither matrix as it is, in the present invention, it is said that whether or not to form a dot for each pixel is determined by comparing the gradation value with the threshold value. It does not need to have any thresholds. Therefore, it is sufficient to store the data as a simple order value, and the amount of data to be stored can be reduced.
- the multi-level conversion may be so-called binarization, but may be more than three-level conversion.
- the number of formed dots of each type is obtained as the multi-level quantization result value, and the L types of dots are obtained.
- the control data may be output from the dots having a higher concentration per unit area among the dots in such a manner that the dots are formed in the order described above. This makes it easy to specify the formation of multiple types of dots. 'Furthermore, the following methods can be considered as a method of preparing the correspondence. First, assuming a pixel group consisting of P horizontal pixels X vertical pixels (P and Q are natural numbers of 2 or more) included in a rectangular area, M, N are natural numbers of 8 or more). ⁇
- the global dither matrix stored in a distributed manner is divided into a plurality of rectangular areas corresponding to the pixel groups, and the PXQ thresholds included in each of the divided areas are extracted. S is assigned and managed. Then, for each area to which the classification number S is assigned, the gradation value converted to the recording rate of the finally formed L types of dots is applied and the pixel at any position in each gradation value is applied. Then, information as to which kind of dot is formed is generated, and the correspondence between the position of the dot formation and the gradation value is stored for each classification number S. After such processing, it is not necessary to store the original dither matrix or the thresholds in the rectangular area corresponding to the pixel group.
- the same classification number is not assigned to a plurality of pixel groups adjacent to each other. Therefore, the multi-value quantization result value for the pixel group gradation value is determined for each classification number. In this case, even if the same pixel group gradation value continues over a plurality of pixel groups, the same multi-value quantization result value does not continue. For this reason, when an image is output based on such control data, it is possible to avoid the occurrence of dots in a fixed pattern. Further, in such an image processing apparatus, the pixel group staircase value may be multi-valued with reference to the following correspondence.
- the correspondence in which the pixel group gradation value and the multi-value quantization result value are set may be referred to.
- the number of unions that arrange the classification numbers is not large enough. For this reason, even if multi-leveling is performed based on the correspondence set for each classification number, a certain regularity may appear in the dot generation pattern in some cases. In order to avoid such a risk, it is desirable that the number of classification numbers is large. However, experience shows that if the number of classification numbers is 100 or more, a certain pattern appears in the dot generation.
- the number of classification numbers or the number of pixels per pixel group may be set so as to be at least 0 0 0 or more. If the number of pixels included in the pixel group increases, the pattern of dot generation can take many patterns even within one pixel group. Therefore, even if the number of classification numbers is not sufficiently large, if the number of pixels included in the pixel group is large, this is compensated to suppress the occurrence of a certain regularity in the dot generation pattern. it can.
- the present invention can be realized by using a computer by reading a program for realizing the above-described image processing method in a computer. Therefore, the present invention includes an embodiment as a recording medium on which the following program product or program code is recorded. If such a program product or a program recorded on a recording medium is read into a computer and the various functions described above are realized using the computer, image processing and data transfer can be performed quickly to achieve high image quality. Images can be output quickly.
- control data used by an image output device that forms a dot and outputs an image to control the formation of the dot is generated by applying predetermined image processing to the image data representing the image.
- a pixel group gradation value determination unit that determines a pixel group gradation value which is a gradation value representing the pixel group for each pixel group in which a plurality of pixels constituting the image are grouped;
- the gradation value and the multi-value quantization result value obtained by multi-value conversion of the pixel group gradation value refer to the correspondence relationship set for each pixel group, thereby obtaining the pixel group gradation value of the pixel group.
- a multivalued means for multivalued the value
- a control data output means for outputting the multi-value quantization result value obtained for each pixel group as the control data
- control data used by an image output device that forms a dot and outputs an image to control the formation of the dot is generated by applying predetermined image processing to image data representing the image and generating an image. Processing method,
- the pixel group gradation value is obtained by multi-leveling the pixel group gradation value, and the multi-value quantization result value obtained by multi-leveling the pixel group gradation value is referred to by referring to the correspondence relationship set for each pixel group.
- An invention as an image processing method including: Brief Description of Drawings
- FIG. 1 is an explanatory diagram for explaining the outline of the present invention using a printing system as an example.
- FIG. 2 is an explanatory diagram illustrating a configuration of a computer as the image processing device of the present embodiment.
- FIG. 3 is an explanatory diagram showing a schematic configuration of the power lapping machine according to the present embodiment.
- FIG. 4 is an explanatory diagram showing the arrangement of the ink jet nozzles in the ink discharge head.
- FIGS. 5 (a) and 5 (b) are explanatory diagrams showing the principle of forming dots having different sizes by controlling the ejection of ink droplets.
- FIG. 6 is a flowchart illustrating an overall flow of the image printing process according to the first embodiment.
- FIG. 7 is a flowchart showing the flow of a multi-value quantization result value generation process performed in the image printing process of the first embodiment.
- FIGS. 8 (a) and 8 (b) are explanatory diagrams showing a method of determining a pixel group classification number.
- FIG. 9 is an explanatory diagram conceptually showing a multi-value quantization table referred to in the multi-value quantization result value generation processing of the first embodiment.
- FIG. 10 is an explanatory diagram exemplifying a state in which the multilevel halftoning result value increases stepwise as the pixel group gradation value increases.
- FIG. 11 is a flowchart showing the flow of the dot formation presence / absence determination processing of the first embodiment.
- FIG. 12 is an explanatory diagram conceptually showing a conversion table referred to in the dot formation presence / absence determination processing of the first embodiment.
- FIG. 13 is an explanatory diagram showing the correspondence between the coded number data and the number of various dots represented by each code data.
- FIGS. 14 (a) to 14 (c) are explanatory diagrams illustrating the order value matrix referred to in the dot on / off state determination processing of the first embodiment.
- 'FIG. 15 is an explanatory diagram conceptually showing how pixel positions forming various dots in a pixel group are determined based on data of the number of dots while referring to an order value matrix.
- FIG. 16 is an explanatory diagram conceptually illustrating a part of the dither matrix.
- Figure 17 shows the dot formation for each pixel while referring to the dither matrix. It is explanatory drawing which showed the mode of judging presence or absence notionally.
- FIGS. 18 (a) to 18 (c) are explanatory diagrams showing a method for determining a classification number for each pixel group.
- FIGS. 19 (a) to 19 (d) are explanatory diagrams showing a method of calculating the classification number of a pixel group.
- Country 20 is an explanatory diagram showing a method of obtaining the classification number from the binary representation of the coordinate value of the pixel group of interest.
- Fig. 21 is a flow chart showing the flow of the half-I-one process, in which it is possible to determine whether large, medium and small dots are formed for each pixel by developing the dither method.
- FIG. 23 is an explanatory diagram conceptually showing a state in which the presence / absence of large, medium and small dots is determined for each pixel in the pixel group.
- FIG. 24 is a flowchart showing the flow of processing for setting the multi-value quantization table.
- FIG. 25 is a flowchart showing the flow of the processing for setting the conversion table.
- FIGS. 26 (a) to 26 (c) are explanatory diagrams showing a method of setting an order value matrix.
- FIG. 27 is an explanatory diagram conceptually showing a rough flow of a process of determining whether or not each of large, medium, and small dots is to be formed for each pixel from the multi-value quantization result value in the process of determining whether or not to form dots in the first embodiment. It is.
- FIGS. 28 (a) to 28 (c) are explanatory diagrams showing a method of determining a classification number from the position of a pixel group on an image.
- ' Figure 29 is an explanatory diagram showing how to determine the position on the dither matrix from the pixel group coordinate values (i, j) to determine the classification number.
- FIG. 30 is an explanatory diagram conceptually showing a threshold value table referred to in the multi-value quantization result value generation processing of the modification.
- Fig. 31 is a flowchart showing the flow of the process for determining the presence or absence of dot formation according to the modification. is there.
- FIG. 32 is an explanatory diagram showing a correspondence table in which code data representing the number of dots is associated with intermediate data.
- FIG. 33 is an explanatory diagram showing a state in which the presence / absence of dot formation is determined by reading data at a location corresponding to the order value from the intermediate data.
- FIG. 34 is an explanatory diagram conceptually showing a conversion table referred to in the dot formation presence / absence determination processing of the second embodiment.
- FIGS. 35A and 35B are explanatory diagrams showing the data structure of dot data set in the conversion table of the second embodiment.
- FIG. 36 is a flowchart showing the flow of the dot on-off state determination process of the second embodiment.
- FIG. 1 is an explanatory diagram for explaining an outline of the present invention by taking a printing system as an example.
- the printing system includes a computer 10 as an image processing device, a printer 20 as an image output device, and the like.
- a predetermined program is loaded and executed on the computer 10
- the computer 10 and The printer 20 functions as an integrated image output system as a whole.
- the printer 20 prints an image by forming dots on a print medium.
- the combination device 10 performs predetermined image processing on image data of an image to be printed, so that the printer 20 generates data for controlling dot formation for each pixel, and Supply 0.
- a typical printing system prints an image as follows.
- image data is converted into data representing the presence or absence of dot formation for each pixel by performing predetermined image processing in the evening. Then, the obtained data is supplied to the printer, and the printer prints an image by forming a dot according to the supplied data.
- the printing system illustrated in FIG. 1 prints an image as follows.
- a plurality of pixels constituting an image are determined by a predetermined number.
- a pixel group is generated collectively for each pixel, and for each pixel group, a pixel group gradation value that is a gradation value representing the pixel group is determined.
- a multi-level halftoning result value is generated by multi-leveling the pixel group gradation value.
- a classification number assigned to each pixel group is obtained, and the pixel group gradation value and the multi-value quantization result value are referred to by referring to a correspondence relationship associated with each classification number. .
- the printer 20 When the printer 20 receives the multilevel halftoning result value for each pixel group, it converts it into number data that is data related to the number of dots to be formed in the pixel group. Such conversion is performed in the multi-value quantization result value conversion module.
- the dot formation presence / absence determination module determines the presence / absence of dot formation for each pixel based on the order of pixels in each of which a dot is formed in the pixel group and the number data.
- the dot formation presence / absence determination module may store an appropriate pixel order in advance. If the order of the pixels is stored, an appropriate order can be quickly determined.
- the image is printed by the dot forming module forming dots at the pixel positions determined in this way.
- the multi-value quantization result value for each pixel group can be a much smaller data amount. Therefore, if instead of supplying data indicating the presence or absence of dot formation for each pixel from the computer 10 to the printer 20 and supplying the multi-value quantization result value for each pixel, the data can be transferred very quickly. Becomes possible.
- the multi-value quantization result value is generated in the computer 10 as follows. First, the pixel group tone value is determined in the pixel group tone value determination module. In determining the pixel group gradation value, for example, the pixel group gradation value may be determined based on image data of each pixel in the pixel group.
- the correspondence storage module a correspondence in which the pixel group gradation value is associated with the multi-value quantization result value is stored for each pixel group classification number.
- the classification numbers of the pixel groups are classified into a plurality of types according to the position in the image.
- an appropriate classification number can be assigned to each pixel group in advance.
- the multi-level conversion module Upon receiving the pixel group gradation value of the pixel group, the multi-level conversion module refers to the correspondence according to the pixel group classification number from the correspondence storage module to increase the pixel group gradation value. Convert to a valuation result value.
- the multi-value quantization result value is generated while referring to the correspondence as described above, the multi-value quantization result value can be generated very quickly. For this reason, the generated multi-value quantization result value can be promptly supplied to the printer 20, and the image can be quickly printed even if the image has a large number of pixels. Also, if the multi-value quantization result value is generated with reference to the correspondence, it can be generated by extremely simple processing. Therefore, in order to generate the multi-value quantization result value, the number data is generated inside the printer 20 or a digital camera without using a device having a high processing capability such as the computer 10. It is also possible.
- various embodiments of the present invention will be described in detail using such a printing system as an example.
- FIG. 2 is an explanatory diagram illustrating a configuration of a computer 100 as an image processing apparatus according to the present embodiment.
- the computer 100 is a well-known computer that is configured by connecting the CPUs 102 and 13 ⁇ 40111 14 ⁇ ⁇ 1 ⁇ AMI06 with each other via a bus 116.
- the computer 100 has a disk controller DDC 109 for reading data from the flexible disk 124 and the compact disk 126, and a peripheral device interface PIF 1 for exchanging data with peripheral devices. 08, Video interface VIF 112 for driving CRT 114 is connected.
- the PIF 108 includes a color printer 200 described later and a hard disk 1 18 and so on are connected.
- FIG. 3 is an explanatory diagram showing a schematic configuration of the color printer 200 of the present embodiment.
- the color printer 200 is an inkjet printer that can form dots of four color inks of cyan, magenta, yellow, and black.
- a total of six ink dots including cyan (light cyan) ink with a low dye or pigment concentration and magenta (light magenta) ink with a low dye or pigment concentration, are used.
- a formable inkjet printer can also be used.
- the cyan ink, magenta ink, yellow ink, black ink, light cyan ink, and light magenta ink are referred to as C ink, M ink, Y ink, K ink, LC ink, and LM ink, respectively. It may be abbreviated.
- the color printer 200 has a mechanism for driving a print head 241, which is mounted on a carriage 240, to discharge ink and to form a dot.
- a control circuit 260 for controlling the conveyance of the printing paper.
- the carriage 240 is provided with an ink cartridge 242 for storing K ink and an ink cartridge 243 for storing various inks of C ink, M ink and Y ink.
- FIG. 4 is an explanatory diagram showing an arrangement of the ink jet nozzles Nz in the ink ejection heads 2444 to 247. As shown in the figure, on the bottom surface of the ink discharge head, there are formed four sets of nozzle rows for discharging ink of each color of C, M, K, and K. The nozzles Nz are arranged at a constant nozzle pitch k.
- the control circuit 260 includes a CPU, a ROM, a RAM, a PIF (peripheral device interface), and the like, which are interconnected by a bus.
- the control circuit 260 controls the main scanning operation and the sub-scanning operation of the carriage 240 by controlling the operations of the carriage motor 230 and the paper feed motor 235. Based on the print data supplied from 0, control is performed to eject ink droplets from each nozzle at an appropriate timing.
- the color printer 200 can print a color image by forming ink dots of each color at appropriate positions on the print medium under the control of the control circuit 260.
- the color printer 200 of the present embodiment can control the size of the ink dot by controlling the size of the ink droplet to be ejected.
- FIG. 5 (a) is an explanatory diagram showing the internal structure of a nozzle for discharging ink.
- a plurality of such nozzles are provided in the ink ejection heads 2444 to 247 of each color.
- each nozzle is provided with an ink passage 255, an ink chamber 256, and a piezo element PE above the ink chamber.
- Carriage 2 4 0 When the ink cartridges 242 and 243 are mounted, the ink in the cartridge is supplied to the ink chamber 256 via the ink gallery 257.
- the piezo element PE is an element that, when a voltage is applied, distorts the crystal structure and converts electric-mechanical energy very quickly.
- the side wall of the ink chamber 256 is deformed by applying a voltage having a predetermined waveform between the electrodes provided at both ends of the piezo element PE.
- the volume of the ink chamber 256 decreases, and ink corresponding to the reduced volume is ejected from the nozzle Nz as an ink droplet Ip.
- the ink droplets Ip penetrate into the printing paper P mounted on the platen 236 to form an ink drop on the printing paper.
- FIG. 5 (b) is an explanatory diagram showing the principle of changing the size of the ink droplet to be ejected by controlling the voltage waveform applied to the piezo element PE. Ink drop from nozzle
- the ink is once sucked into the ink chamber 256 from the step 257, and then a positive voltage is applied to the piezo element PE to reduce the volume of the ink chamber and discharge the ink droplet IP.
- a positive voltage is applied to the piezo element PE to reduce the volume of the ink chamber and discharge the ink droplet IP.
- the suction speed of the ink is appropriate, the ink corresponding to the amount of change in the volume of the ink chamber is sucked, but if the suction speed is too high, the ink gallery 27 Because of the passage resistance, the inflow of ink from the ink gallery 255 cannot be completed in time. As a result, the ink in the ink passage 255 flows back into the ink chamber, and the ink interface near the nozzle is largely retreated.
- the size of the ejected ink droplets is controlled, and three types of ink dots, large, medium, and small, are formed. Is possible. Of course, not only three types but also other types of dots can be formed. Further, the size of the ink drop formed on the printing paper may be controlled by a method of discharging a plurality of fine ink droplets at a time and controlling the number of the discharged ink droplets.
- a printing method is used in which ink dots are formed on printing paper using a phenomenon such as thermal transfer, or a method in which toner powder of each color is attached to a printing medium using static electricity. It is also possible to use
- the color printer 200 having the above-described hardware configuration drives the carriage motor 230 so that the ink discharge heads 244 to 247 of each color are mainly printed on the printing paper P.
- the printing paper P is moved in the sub-scanning direction by moving the paper in the scanning direction and driving the paper feed motor 235.
- the control circuit 260 drives the nozzles at an appropriate timing to eject ink droplets while synchronizing with the main scanning and sub-scanning movements of the carriage 240, so that the color printer 200 prints. You are printing a color image on paper.
- the color printer 200 also has a CPU, RAM, and RO in the control circuit 260. Since the M and the like are installed, it is also possible to execute the processing performed by the computer 100 in the color printer 200. In such a case, the image data of the image captured by the digital camera 120 or the like is directly supplied to the color printer 200, and the necessary image processing is performed in the control circuit 260. It is also possible to print an image directly from 200.
- FIG. 6 is a flowchart showing the overall flow of the image printing process of the first embodiment.
- the combination server 100 starts reading image data (step S100).
- the image data is assumed to be RGB color image data. Not only data but also monochrome image data can be similarly applied.
- a color conversion process is performed (step S102).
- Color conversion processing is a process in which R, G, and B color image data expressed by a combination of R, G, and B gradation values is expressed by a combination of gradation values for each color of ink used for printing. This is a process of converting the image data into converted image data.
- the color printer 200 prints an image using four color inks of C, M, ⁇ , and K. Therefore, in the color conversion processing, the image data represented by each of the RGB colors is converted into data represented by the gradation values of each of the colors C,, Y, and K.
- the color conversion process is performed by referring to a three-dimensional numerical table called a color conversion table (LUT).
- LUT the gradation values of each color of C, M, Y, and ⁇ obtained by color conversion for RGB color image data are stored in advance.
- step S ⁇ 02 by referring to this LUT, it is possible to rapidly perform color conversion of R, G, B color image data into C, M, Y, ⁇ color image data.
- the resolution conversion processing starts (step S104).
- the resolution conversion process is a process of converting the resolution of the image data into a resolution at which the printer 200 prints an image (print resolution). If the resolution of the image data is lower than the print resolution, interpolation is performed to generate new image data between pixels.
- step S106 multi-value quantization result value generation processing
- the number of pixels grouped as a pixel group does not necessarily have to be the same for all pixel groups.For example, a plurality of pixels are regularly switched, or pixels are grouped into a pixel group according to a position in an image. Although it is possible to switch the number, here, for convenience of explanation, the simplest case will be described assuming that all pixel groups have the same number of pixels. In this way, a plurality of pixels are grouped into a pixel group, and a pixel group gradation value which is a gradation value representative of each pixel group is obtained, and then the pixel group gradation value is multi-valued. As a result, the pixel group tone value for each pixel group is converted into a multi-value quantization result value.
- the number of states that can be obtained as a result of the multi-value quantization differs for each pixel group. That is, in general multi-level quantization, for example, there is no switching between binary and ternary conversion in one image, but in the multi-level quantization result value generation processing of this embodiment, the pixel group The number of stages of multi-level conversion is different for each. Then, a result value obtained by converting the pixel group gradation value into a multi-level image with the number of stages for each pixel group is output to the power raster printer 200.
- the amount of data to be output to the color printer 200 is greatly reduced. be able to.
- the multi-value quantization result value for each pixel group can be generated quickly, coupled with the reduction in the amount of data, the multi-value quantization result value can be output very quickly. It is possible to output 0. Details of the multi-value quantization result value generation processing will be described later.
- the multilevel halftoning result value is a value obtained by multileveling the pixel group tone value, and is a value indicating which pixel in the pixel group should form a dot. Absent.
- a so-called density pattern method is used as a method of determining the pixel position at which a dot is formed from the multi-value quantization result value of the pixel group.
- the density pattern method cannot be applied as it is.
- a pixel position at which a dot is formed is determined from the multi-value quantization result value obtained for each pixel group by using a special method as described later.
- the substantial resolution is reduced to the resolution of the pixel group subjected to the multi-value processing, and the image quality tends to be deteriorated.
- the dot on / off state determination processing of the first embodiment the image quality does not deteriorate depending on the size of the pixel group as described later.
- step SI10 a process of forming a dot at the determined pixel position is performed. That is, as described with reference to FIG.
- the ink ejection head is driven to eject ink droplets while repeating the main scanning and the sub-scanning of the carriage 240, so that the ink is printed on the printing paper.
- Form dots By forming the dots in this manner, an image corresponding to the image data is printed.
- FIG. 7 is a flowchart illustrating a flow of the multi-value quantization result value generation process performed in the image printing process of the first embodiment described above.
- the multi-value quantization result value generation processing will be described as being performed in the combo box 100, but as described later, the multi-value quantization result value generation processing can be an extremely simple process.
- Color printer 200 Alternatively, it can be implemented in the digital camera 120.
- description will be given in accordance with the flowchart.
- the pixel group gradation value and the pixel group classification number are determined (step S202).
- the pixel group gradation value is a gradation value representative of the pixel group, and can be easily obtained as follows. For example, the average value of the image data assigned to each pixel in the pixel group can be determined and used as the pixel group gradation value.
- FIG. 8 is an explanatory diagram showing a method of determining a classification number of a pixel group.
- FIG. 8A shows one pixel group generated by combining eight pixels in an image.
- a method of determining the classification number for this pixel group will be described.
- Note that a pixel group of interest for determining a classification number as shown in FIG. 8 (a) is referred to as a pixel group of interest.
- the pixel position is represented by the number of pixels in the main scanning direction and the sub-scanning direction from the origin.
- the position of the pixel group is represented by the pixel position of the pixel at the upper left corner of the pixel group.
- the pixels indicating the position of the target pixel group are indicated by black circles.
- the pixel position of this pixel is (X, Y).
- the classification number of the pixel group of interest can be determined very easily by simply displaying X and Y in binary numbers and reading data stored in predetermined bits. For example, as shown in FIG. 8B, it is assumed that X and Y representing the position of the pixel group of interest are 10-bit data. Then, the value obtained by reading the uppermost 4th to 8th bits of X is N, and the value obtained by reading the uppermost 4th to 8th bits of ⁇ is obtained. Let the value be M. Then, in the case of this embodiment,
- the pixel group gradation value is multi-valued by referring to a multi-value conversion table described later (step S204).
- FIG. 9 is an explanatory diagram conceptually showing a multi-value quantization table referred to in multi-value quantization. As shown in the figure, in the multi-value quantization table, the multi-value quantization result value for the pixel group gradation value is stored in association with each pixel group classification number. It increases stepwise as the pixel group gradation value increases.
- 1D is an explanatory diagram illustrating a state in which the multilevel halftoning result value gradually increases as the pixel group gradation value increases.
- the multi-value quantization result value for the pixel group gradation value is displayed using a line graph in which the horizontal axis represents the pixel group gradation value and the vertical axis represents the multi-value quantization result value.
- the multivalued results for five pixel groups having different classification numbers N1 to N5 are shown, but in order to avoid the polygonal lines of these pixel groups becoming difficult to distinguish.
- the origin position of the multi-value quantization result value is shifted by a small amount in the vertical axis direction.
- the pixel group of classification number N 1 indicated by a thick solid line in the figure will be described. If the pixel group gradation value is in the range of 0 to 4, the multi-value quantization result value is ⁇ 0 ''. , Pixel When the group gradation value is in the range of 5 to 20, the multilevel halftoning result value increases to “1”. Next, when the pixel group gradation value is in the range of 21 to 42, the multi-value quantization result value increases to “2”, and when the pixel group gradation value is in the range of 43 to 69, the multi-value quantization result value is “ 3 ”.
- the multi-value quantization result value increases stepwise, and finally, the multi-value quantization result value increases to “15”.
- the number of pixel group gradation values that can take the range of gradation values 0 to 255 is increased in 16 levels from gradation values 0 to 15. It means that it is priced (in other words, 16-valued).
- the range of gradation values 0 to 255 is taken.
- the obtained pixel group gradation value is multi-valued (18 levels) in 18 steps from gradation values 0 to 17. Furthermore, for the pixel group of classification number N4 incense indicated by a thin solid line and the pixel group of classification number N5 incense indicated by a thin dashed line, the pixel group gradation value is set to 2 in the gradation value 0 to 20. In other words, it is multi-valued (in other words, 21-valued) in one step.
- the number of stages of multi-value quantization (the number of states that can be obtained as a result of multi-value quantization) of each pixel group is not the same, It is multi-valued with a unique number of stages.
- the same pixel group gradation value is multi-valued, if the classification number of the pixel group is different, and if the number of stages of multi-value conversion is different, the multi-valued result will be different.
- the same multi-level quantization result value is not necessarily obtained. For example, as apparent from a comparison between the pixel group of the classification number N2 shown in FIG.
- the number of multi-level quantization stages for these pixel groups is 18 Although it is a stage, the pixel group gradation value at which the multi-value quantization result value is switched is often not the same.
- the number of multi-valued stages in each of these pixel groups is 21 but the pixel group floor at which the multi-valued result value is switched The tone values often do not match. From this, even if the number of multi-level quantization stages of the pixel group is the same, a different multi-level quantization result value can be obtained if the classification number is different. It becomes.
- the multi-value quantization result values for the pixel group tone values are stored for each pixel group classification number.
- the correspondence relationship between the pixel group gradation value and the multi-value quantization result value is a unique correspondence relationship for each classification number as shown in FIG.
- the pixel group gradation value is multi-valued with reference to such a multi-value quantization table, so that multi-value Performs processing to generate the result value.
- the setting method of the multi-valued table shown in FIG. 9 will be described later in detail.
- step S206 when a plurality of pixels are grouped into a pixel group and the multi-value quantization result value of the pixel group is generated, it is determined whether or not the processing has been completed for all the pixels (step S206). If unprocessed pixels remain (step S 206: n 0), the process returns to step S 200 to generate a new pixel group, and a series of processes described later is performed. A multi-value quantization result value is generated for the pixel group. These operations are repeated, and if it is determined that the processing for all pixels has been completed (step S206: yes), the multi-value quantization result value obtained for each pixel group is output to the color printer 200. Then, the multi-value quantization result value generation processing of FIG. 7 ends.
- the amount of data to be supplied to the color printer 200 is significantly reduced as compared with the case where the data indicating the presence or absence of dot formation is output for each pixel. Can be done.
- this point will be described.
- three types of dots, large dot, medium dot, and small dot can be formed, so if the case where no dot is formed is included, four states can be taken for each pixel. Therefore, in order to indicate the presence or absence of dot formation, two bits of data per pixel are required.
- one pixel group is assumed to be composed of eight pixels. Therefore, an attempt is made to indicate whether or not dots are formed for each pixel.
- the number of levels of multi-level quantization is about 15 to 21 although it differs depending on the pixel group classification number (Fig. 9, Fig. 10 See).
- the method of determining the number of levels of multi-level quantization for each pixel group will be described later. However, it is considered that the number of levels of multi-level quantization will not exceed 30 even if it is estimated at large. Therefore, if the pixel group has a multi-valued result value, it can be sufficiently expressed if there is a 5-bit data amount per pixel group.
- the color printer 200 Upon receiving the multi-value quantization result value from the computer 100 in this way, the color printer 200 performs dot formation presence / absence determination processing described below to perform dot formation for each pixel in the pixel group. Determine whether or not.
- C-1 Overview of the process for determining the presence or absence of dots:
- FIG. 11 is a flowchart showing the flow of the dot formation presence / absence determination processing performed in the image printing processing of the first embodiment described above. This process is executed by the color printer 200 after receiving the multi-value quantization result value for each pixel group from the computer 100.
- the dot on / off state determination processing of the first embodiment is started, first, one pixel group to be processed is selected, and a multi-value quantization result value of the selected pixel group is obtained (step S300, S 3 0 2) o Next, the multi-value quantization result value of the pixel group is formed in the pixel group. (Step S304).
- the multilevel halftoning result values take different values even if the pixel group gradation values are the same if the pixel group classification numbers are different. .
- the multi-value quantization result value of the pixel group can compare the magnitude of the result value only with the pixel group of the same classification number. Is data for which the multi-value quantization result values cannot be compared. Therefore, we consider converting the multi-value quantization result value that depends on the pixel group classification number into a multi-value quantization result value that does not depend on the classification number. If the multi-value quantization result value is converted to a value that does not depend on the classification number, it is possible to compare the magnitude of the multi-value quantization result value for all pixel groups.
- step S304 of FIG. 11 based on this concept, the multi-value quantization result value depending on the pixel group classification number is converted into data indicating the number of dots to be formed in the pixel group. I do.
- the actual conversion can be performed extremely quickly by simply referring to a conversion table in which data of the appropriate number of dots is set in advance for each combination of the pixel group classification number and the multi-value quantization result value. it can.
- FIG. 2 is an explanatory diagram conceptually showing a conversion table referred to when converting a combination of a pixel group classification number and a multi-value quantization result value into data indicating the number of dots.
- data of the number of dots corresponding to the multi-value quantization result value is set for each classification number.
- the pixel group of the classification number 1 will be described.
- For the multi-value quantization result value 0 “0” is set as the data of the number of dots.
- the dot number data “0” is code data indicating that the number of large dots, medium dots, and small dots is all zero.
- ⁇ 1 J is set as the dot number data. Yes.
- Dot number data "1 J is code data indicating that the number of large dots and medium dots formed is 0, and the number of small dots formed is 1. Further, the multi-valued result value For 1 5, dot number data “1 6 4” is set. Dot number data “1 6 4 J is code data indicating that eight large dots are formed and medium dots and small dots are not formed. Thus, the data indicating the number of dots is included in the conversion table. In other words, the number data does not directly indicate the number of dots, but any form of data as long as the number of dots can be specified in some way, even if the number data does not directly indicate the number of dots.
- 13 is an explanatory diagram showing the correspondence between the coded number data and the combination of the number of large dots / medium dots / small dots represented by each code data.
- the reason why the number of various dots is coded and handled in this way is as follows.
- one pixel group is composed of eight pixels collectively, so that the number of large dots, medium dots, and small dots formed can take 0 to 8 values each. Therefore, if we try to represent the number of each dot without coding it, we will use 4 bits each to represent the number of large dots, the number of medium dots, and the number of small dots, for a total of ⁇ 2 bits. Data volume is required.
- the total number of dots that can be formed in the pixel group is at most eight.
- a combination of the number of dots, such as four large dots, three medium dots, and two small dots actually occurs because the total number of dots is nine, exceeding eight. I can't get it. Considering these points, it is thought that there are not so many types of dot number combinations that can actually occur.
- the actual calculation is as follows.
- the pixel group contains eight pixels, and for each pixel, "form large dots”, “form medium dots”, “form small dots”, and "do not form dots” There are four possible states. Therefore, the combination of the number of dots that can be formed in the pixel group is equal to the number of combinations when these four states are selected eight times, allowing duplication.
- n H r is an operator that finds the number of overlapping combinations when selecting r times from n objects while allowing overlapping.
- n C r is an operator for calculating the number of combinations when selecting r times from n objects without allowing duplication. ⁇ If there are 65 combinations, 8 bits can be expressed. Therefore, if a code number is set for a combination of the number of dots that can actually occur, the combination of the number of dots to be formed in the pixel group can be represented by 8-bit data. After all, by coding the combination of the number of dots, the required data amount can be reduced as compared with the case where the number of formed dots is represented for each type of dot.
- the quantity data is coded as shown in Fig. 13 and expressed in the conversion table shown in Fig. 12, That is, the data of the number of converted dots is set.
- the method of setting the conversion table as shown in Fig. 12 will be described later in detail with reference to another figure.
- the dot on / off state determination process shown in FIG. 11 by referring to the conversion table shown in FIG. 12, the process of converting the multilevel halftoning result value of the pixel group into code data representing the number of dots is performed.
- a pixel group classification number is required in addition to the multi-value quantization result value.
- the classification number of the pixel group is determined based on the position of the pixel group in the image. Since the multi-valued result value is supplied for each pixel group, based on the order in which the multi-valued result value is supplied, the position of the pixel group of the multi-valued result value to be processed on the image is determined. It is possible to easily determine the classification number. A method of determining the classification number according to the position of the pixel group on the image will be described later. It goes without saying that the classification number may be output together with the multi-value quantization result value from the computer [00] to the color printer 200. Next, a process of reading an order value matrix corresponding to the pixel group is performed (step S306).
- the order value matrix is a matrix that sets the order in which dots are formed for each pixel in the pixel group.
- FIG. 14 is an explanatory diagram exemplifying an order value matrix. As shown in the figure, a different matrix is set for the order value matrix for each pixel group classification number. As an example, the ordinal value matrix of the classification number 1 shown in FIG. 14 (a) will be described. In the pixel group of classification number 1, the pixel at the upper left corner is the pixel where dots are most likely to be formed among the eight pixels that make up the pixel group. The number ⁇ ⁇ ”set in the pixel at the upper left corner of the order value matrix indicates that this pixel is the pixel on which the dot is formed first.
- the numerical value indicating such an order set in the order value matrix is called an order value.
- the order value “2” set in the pixel at the lower right corner of the pixel group indicates that this pixel is the second dot to be formed in the pixel group.
- an order value indicating the order in which dots are formed is set for the eight pixels included in the pixel group.
- These ordinal values matrix have different matrix depending on the pixel group classification number. For example, the ordinal value matrix of classification number 2 shown in Fig. 14 (b)
- the first pixel where the dot is formed (the pixel with order value ⁇ -)) is the second pixel from the bottom left, and the second pixel where the dot is formed (the order value “2”).
- Pixel is the pixel in the lower right corner.
- the pixel where the first dot is formed (the pixel with ordinal value "1") is the second pixel from the right in the upper row. Yes, the pixel where the second dot is formed (the pixel with order value “2”) is the pixel in the lower left corner.
- the order value matrix as illustrated in FIG. 14 is stored in advance for each pixel group classification number. Then, in step S306 of FIG. 11, a process of reading the order value matrix corresponding to the classification number of the pixel group from the ROM is performed. The method of setting the order value matrix for each pixel group classification number will be described in detail with reference to another figure.
- a pixel for forming a large dot is first determined from among the eight pixels constituting the pixel group (step S308). Since large dots are more conspicuous than other dots, it is important to prioritize the pixel positions that form the dots so that the dots are formed as dispersed as possible. desirable. For this reason, first, a pixel for forming a large dot is determined.
- the data of the number of dots obtained by converting the multi-value quantization result value of the pixel group and the ordinal matrix corresponding to the pixel group are used.
- the code data indicating the number of dots to be formed in a pixel group represents a combination of one large dot, two medium dots, and one small dot.
- the order value matrix sets the order in which dots are formed for each pixel in the pixel group.
- a large dot is formed at the pixel for which the order value “1” is set.
- the number of large dots formed is two, large dots will be formed not only on the pixels with the order value “1” but also on the pixels with the order value “2”.
- pixels forming large dots are displayed with fine diagonal lines.
- processing for determining a pixel forming a large dot is performed based on the data of the number of dots and the order value matrix.
- the pixels that form the medium dot are determined (step S310 in FIG. 11).
- the number of medium dots to be formed is two. Since a large dot has already been formed at the pixel with the order value ⁇ ”, the medium dot is formed at the pixel with the order value“ 2 ”and the pixel with the order value“ 3 ”.
- pixels in which medium dots are formed are displayed with slightly coarse diagonal lines.
- a process of determining a pixel for forming a medium dot from among pixels for which a large dot is not formed is performed.
- the pixels that form the medium dot are determined, the pixels that form the small dot are then determined (step S312 in Fig. 11).
- the number of small dots to be formed is one, and pixels with an order value of "1" or "3" have already formed large dots and medium dots. Therefore, the small dot is formed in the pixel having the order value “4”.
- pixels in which small dots are formed are displayed with coarse diagonal lines.
- the remaining pixels in the pixel group may be determined to be pixels that do not form a dot (step S314 in FIG. 11).
- it is determined whether or not dot formation is determined by performing the above-described processing for all the pixel groups (step S 3 16). If an unprocessed pixel group remains (step S 3) 16: n 0), returning to step S 300, selecting a new pixel group, and performing a series of subsequent processes on the pixel group.
- step S316 the dot formation presence / absence determination processing shown in FIG.
- the process returns to the image printing process shown in.
- an image is printed on printing paper by forming a dot according to the result of determining whether or not to form a dot.
- a plurality of pixels are grouped together to form a pixel group, multi-value processing is performed for each pixel group, and the obtained multi-value conversion result value is color-coded. -Output to printer 200.
- the classification number of the pixel group and the pixel group gradation value are obtained, and the multi-value quantization result value can be obtained immediately by simply referring to the multi-value quantization table shown in FIG. Obtainable. Since the classification number of the pixel group and the gradation value of the pixel group can be obtained very easily as described above, the multi-value quantization result value of the pixel group can be obtained very quickly and by a very simple process. Become. In addition, since the multilevel halftoning result value can be represented by a small number of bits per pixel group (at most 5 bits in this embodiment), the data amount is smaller than the data indicating whether or not dots are formed for each pixel. It can be greatly reduced.
- the multi-value quantization result value for each pixel group is output to the color printer 200 instead of the data indicating the presence or absence of dot formation for each pixel, data is supplied promptly as much as the data amount decreases. It becomes possible.
- the color printer 200 receives the multi-value quantization result value for each pixel group, it converts this into data indicating the number of dots to be formed in the pixel group. Such conversion can be performed quickly only by referring to a conversion table as shown in FIG. Next, the data indicating the number of dots obtained by the conversion and the order value matrix After determining whether large dots, medium dots, and small dots are to be formed, print the image by forming the dots.
- the order value matrix it is relatively easy to determine the pixels forming the large dot, medium dot, and small dot. Therefore, even in the color printer 200, upon receiving the multivalued result value for each pixel group, the presence / absence of dot formation for each pixel can be quickly determined with relatively simple processing, and further, It is possible to print an image on a computer.
- the image printing process of the first embodiment not only can images be printed quickly, but also images can be printed with sufficient image quality.
- a so-called blue noise mask or green noise mask can be used.
- the image printing processing of the first embodiment described above is an improvement obtained by developing a so-called dither method. Therefore, as a preparation for explaining the concept of determining the classification number of the pixel group and the setting method of the multi-value table, the conversion table, the order value matrix, etc., first, the outline of the dither method will be briefly described.
- the dither method is a typical method used to convert image data into data indicating the presence or absence of dot formation for each pixel.
- a threshold value is set in a matrix called a dither matrix, and the tone value of the image data is compared with the threshold value set in the dither matrix for each pixel. For large pixels, it is determined that a dot is formed. Judge that no dot is formed.
- FIG. 16 is an explanatory diagram showing an example of an enlarged part of dither matrix.
- the matrix shown in the figure has 128 pixels in the horizontal direction (main scanning direction) and 64 pixels in the vertical direction (sub-scanning direction), for a total of 8192 pixels, with a gradation value of 1-2.
- a threshold value uniformly selected from the range of 55 is randomly stored.
- the reason why the threshold gradation value is selected from the range of ⁇ to 255 is that, in this embodiment, the image data is 1 byte data which can take gradation values of 0 to 255.
- the range in which the threshold can be taken is the range in which the maximum gradation value is excluded from the range in which image data can be taken.
- a dot is always formed in a pixel having a threshold value equal to the minimum possible gradation value of the image data. It will be formed. To avoid this, the range that the threshold can take is the range that the minimum gradation value is excluded from the range that the image data can take.
- the possible gradation values of the image data are 0 to 255, and dots are formed in pixels having the same threshold value as the image data. Therefore, the possible range of the threshold value is 1 to 255. 2 5 5
- the size of the dither matrix is not limited to the size illustrated in FIG. 16, but may be various sizes including a matrix having the same number of vertical and horizontal pixels.
- FIG. 17 is an explanatory diagram conceptually showing a state in which the presence or absence of dot formation is determined for each pixel with reference to a dither matrix. When judging the presence or absence of dot formation, first, the pixel to be judged is selected, and the gradation value of the image data for this pixel and the threshold value stored at the corresponding position in the dither matrix are determined.
- the thin dashed arrow shown in Fig. 17 schematically shows that the gradation value of the image data is compared with the threshold value stored in the dither matrix for each pixel. .
- the tone value of the image data is 97 and the threshold value of the dither matrix is 1, so it is determined that a dot is formed at this pixel.
- the arrow indicated by a solid line in FIG. 17 schematically shows a state in which it is determined that a dot is formed in this pixel, and the result of the determination is written in the memory.
- the tone value of the image data is 97
- the threshold value of the dither matrix is 177, which is larger than the threshold value. to decide.
- the image data is converted into data representing the presence or absence of dot formation for each pixel by determining whether or not a dot is formed for each pixel while referring to the dither matrix. Based on the contents described above, the method of determining the classification number of the pixel group and the method of setting the multi-value table, conversion table, and order value matrix will be described below.
- FIG. 18 is an explanatory diagram showing a concept for determining a classification number for each pixel group.
- Fig. 18 (a) shows that four pixels horizontally and four pixels vertically in the upper left corner of the image. This diagram conceptually shows how one pixel group is generated by putting together a total of eight pixels of two pixels.
- the gradation value of the image data assigned to the pixel is compared with the threshold value set at the corresponding position of the dither matrix to determine the presence or absence of dot formation for each pixel.
- a predetermined number of adjacent pixels are grouped together as a pixel group, so that the blocks set for the dither matrix also generate blocks by a predetermined number corresponding to the pixel group.
- FIG. 18 (b) shows a state in which the threshold values set in the dither matrix shown in FIG. 16 are grouped into four in the horizontal direction and two in the vertical direction to generate a plurality of blocks.
- the dither matrix 16 has a total threshold value of 128 pixels for 128 pixels in the horizontal direction (main scanning direction) and 64 pixels in the vertical direction (sub-scanning direction). Therefore, if these thresholds are grouped into blocks of four in the horizontal direction and two in the vertical direction, the dither matrix will be divided into 32 blocks in each of the vertical and horizontal directions, for a total of 10 24 blocks. Now, as shown in Fig. 18 (b), these blocks are given serial numbers from 1 to 124. Then, when the dither matrix is applied to the image data, the pixel groups are classified according to the serial numbers of the blocks applied to the positions of the pixel groups. For example, as shown in Fig. 18 (C), the block with the serial number 1 in Fig. 18 (b) is applied to the pixel group at the upper left corner of the image. The classification is made into the pixel group of the classification number ⁇ .
- FIG. 19 is an explanatory diagram showing a method of calculating a classification number of a pixel group.
- FIG. 19 (a) shows one pixel group generated in the image. In the following, a method of calculating a classification number using this pixel group as a target pixel group will be described. To do. As described above, the position of the pixel group of interest is represented by the pixel position of the pixel at the upper left corner of the pixel group. In FIG. 19 (a), the pixels indicating the positions of the pixel groups are indicated by black circles. Assume that the pixel position of this pixel is (X, Y). Then, the size of each pixel group is 4 pixels in the main scanning direction and 2 pixels in the sub-scanning direction.
- n and m are positive integers greater than or equal to 0
- n pixel groups are arranged on the left side of the pixel group of interest
- m pixel groups are arranged above the pixel group of interest.
- the pixel groups are classified based on the serial numbers of the blocks applied to the pixel group of interest when dither matrix is applied to the image data (see FIG. 18). ), The same pixel group is classified into different classification numbers depending on the method applied to image data while moving the dither matrix.
- any method can be applied to the image data while moving the dither matrix, but here, for convenience of explanation, the simplest method, that is, moving the dither matrix horizontally.
- Fig. 19 (b) conceptually shows how dither matrices are applied to image data repeatedly while moving them little by little in the horizontal direction.
- Fig. 19 (c) shows how dither matrices are applied to the target pixel group shown in Fig. 19 (a) while using dither matrices repeatedly as shown in Fig. 19 (b). It is conceptually represented. By moving the dither matrix in this way, one of the blocks in the dither matrix is applied to the target pixel group. Here, it is assumed that the block of the M-th row and the N-th column in the dither matrix is applied to the target pixel group. Then, as shown in Fig.
- int is an operator indicating that a value after the decimal point is truncated to be converted to an integer. That is, int (n / 32) represents an integer value obtained by truncating the decimal part of the calculation result of ⁇ / 32.
- the numerical values M and N are obtained from the above-described relational expression shown in Fig. 19 (d), and the block of the block at the Mth row and the Nth column in the dither matrix is obtained.
- the number may be used as the classification number of the pixel group of interest. In practice, however, as described above with reference to FIG.
- FIG. 20 is an explanatory diagram showing a method of obtaining the classification number from the binary representation of the coordinate value of the pixel group of interest.
- the coordinate value of the target pixel group is (X, Y), and X and Y are represented by 10 bits.
- FIG. 20 (a) conceptually shows 10-bit binary data representing a numerical value X.
- serial numbers from 1 to 10 are assigned from the most significant bit to the least significant bit.
- the number n of the pixel groups on the left side of the target pixel group can be obtained by subtracting 1 from the numerical value X and dividing by 4.
- the division by 4 can be performed by shifting rightward by 2 bits, so subtract 1 from the numerical value X and convert the resulting binary data to 2 bits rightward. You only have to shift the pit by the minute.
- the numerical value X does not take an arbitrary value, it can only take a numerical value that can be expressed in the form of 4n + 1, so without subtracting 1, only binary data is shifted rightward by 2 bits.
- the number n of pixel groups can be obtained simply by bit shifting.
- FIG. 20 (b) conceptually shows the number n of binary data obtained by bit-shifting the numerical value X in this way.
- int (n / 32) is calculated. That is, the number n is divided by 32, and the operation is performed to round off the number after the decimal point. Division by 32 can be performed by shifting the binary data bitwise by 5 bits to the right. I will. In the end, ⁇ nt (n / 32) binary data can be obtained by simply shifting the number n of binary data by 5 bits to the right.
- Fig. 20 (c) conceptually shows the binary data of int (n / 32) obtained by bit-shifting the number n. The resulting int (n / 32) is multiplied by 32. Multiplication by 32 can be performed by shifting the binary data by 5 bits to the left.
- the numerical value N it is possible to obtain the numerical value N extremely simply by only applying the mask data as shown in FIG. 20 (f) to the binary data shown in FIG. 20 (b).
- mask data as shown in FIG. 20 (g) is applied to the binary data of the numerical value X indicating the position of the pixel group of interest shown in FIG. 20 (a), and the fourth to eighth bit data are obtained.
- the numerical value N can also be obtained by extracting directly.
- the dither is calculated from the numerical value X of the coordinate value (X, Y) indicating the position of the pixel group of interest.
- the numerical value N indicating the block position in the matrix has been described above, but the numerical value M indicating the block position can also be obtained from the numerical value Y in exactly the same way.
- the position of the pixel group of interest is known, it is only necessary to extract the data of a specific bit position from the binary data, and to know the row and column of the pixel group of interest in the dither matrix
- the classification number of the pixel group of interest can be obtained.
- the method of calculating the classification number described above with reference to FIG. 8 is a method derived in this manner.
- the multi-value quantization table shown in FIG. 9 As described above, in the multi-value quantization table, the multi-value quantization result value for the pixel group gradation value is set for each pixel group classification number, and the multi-value quantization is performed with reference to the multi-value quantization table. As a result, the pixel group tone value is multi-valued in a unique manner according to the pixel group classification number as shown in FIG.
- the multi-value quantization table of the present embodiment is set based on a method developed from the dither method described above so that the presence or absence of dot formation can be determined for each pixel for a plurality of types of dots having different sizes. ing. The detailed contents of such an approach are disclosed in Japanese Patent No.
- FIG. 21 is a flowchart showing the flow of the half-I-one processing, which is based on the development of the dithering method and makes it possible to determine whether large dots, medium dots, and small dots are formed for each pixel.
- the halftone processing is started, first, a pixel for which dot on-off state is to be determined is selected, and image data of the pixel is obtained (step S400). Next, the obtained image data is converted into density data for each of the large, medium, and small dots.
- the density data is data representing the density of dots to be formed.
- the density data indicates that the higher the gradation value, the higher the density of dots formed. It indicates that For example, the tone value “255” of the density data indicates that the dot formation density is ⁇ 100%, that is, that dots are formed in all pixels. “0” indicates that the dot formation density is 0%, that is, no dot is formed in any pixel. Conversion to such density data can be performed by referring to a numerical table called a dot density conversion template.
- FIG. 22 is an explanatory diagram conceptually showing a dot density conversion table which is referred to when converting the gradation value of image data into density data for each of large, medium and small dots.
- density data is set for each dot of small dot / medium dot * large dot with respect to the gradation value of the image data.
- the density data of the medium dot and large dot are all set to the gradation value ro.
- the density data of small dots increases as the tone value of the image data increases, but once the image data reaches a certain tone value, it starts to decrease again, instead of the middle dot. Density data starts to increase.
- step S402 of FIG. 21 referring to the dot density conversion table, the gradation value of the image data is converted into the density data of the large dot, the density data of the medium dot, and the density data of the small dot. Perform processing to convert to.
- the density data of the large, medium and small dots is obtained for the pixel to be processed, it is first determined whether or not a large dot is formed (step S404 in FIG. 21).
- This determination is made by comparing the density data of the large dot with the threshold value of the dither matrix set at the corresponding position of the pixel to be processed. If the density value of the large dot is larger than the threshold value, it is determined that a large dot is formed in the pixel to be processed. Conversely, if the density data is smaller, a large dot is formed. Judge not to. Next, it is determined whether or not it is determined that a large dot is to be formed in the pixel to be processed (step S406). If it is determined that a large dot is to be formed (step S406: yes), the medium dot is determined. The determination of small pixels and small dots is omitted, and it is determined whether or not all pixels have been completed (step S418).
- step S 418 If there remains any pixels for which dot formation has not yet been determined (step S 418: n 0), the flow returns to step S 400 to select a new pixel and perform a series of subsequent processes.
- step S406 ⁇
- the medium dot density data is used to determine whether or not a medium dot is formed.
- the intermediate data for the medium dot is calculated by adding the density data (step S408). The intermediate data for medium dots obtained in this way is compared with the threshold value of the dither matrix. If the intermediate data for the medium dot is larger than the threshold value, it is determined that a medium dot is to be formed.
- a medium dot is formed. It is determined not to be performed (step S410). Next, it is determined whether or not it is determined that a middle dot is to be formed in the pixel to be processed (step S412), and if it is determined that a medium dot is to be formed (step S412: yes) ), Omitting the determination for small dots and determining whether all pixels have been completed (step S418). If it is not determined that a middle dot is to be formed in the pixel to be processed (step S412: n0), a small dot is inserted into the middle data for the middle dot in order to determine whether or not a small dot is formed.
- the intermediate data for the small dot is calculated by adding the density data of the dot (step S414). Then, the obtained intermediate data for small dots is compared with the threshold of dither matrix. And the intermediate data for small dots is better than the threshold If the threshold value is larger, it is determined that a small dot is to be formed. Conversely, if the threshold value of the dither matrix is larger than the intermediate data, it is determined that no dot is to be formed (step S416) ). In other words, for pixels whose threshold value set in the dither matrix is larger than the large dot density data (pixels in which no large dot is formed), the medium dot density data is added to the large dot density data.
- the obtained intermediate data is compared with a threshold value, and if the intermediate data is larger, it is determined that a medium dot is to be formed.
- new intermediate data is calculated by adding the density data of small dots to the intermediate data.
- the intermediate data is compared with the threshold value, and if the new intermediate data becomes larger, it is determined that a small dot is to be formed. Any pixel for which the threshold value is still larger is formed. You decide not to.
- step S418 it is determined whether or not the processing has been completed for all the pixels (step S418), and if there are any undetermined pixels (step S418: n0), the process proceeds to step S410. Return to 0, select a new pixel, and continue —run through the sequence. In this way, it is determined whether a large, medium, or small dot is to be formed for each pixel selected as a processing target. Then, when it is determined that the processing has been completed for all the pixels (step S418: yes), the half
- the method of judging the presence or absence of formation of each of the large, medium, and small dots using dither matrix has been described.
- the pixel groups are collectively multi-valued by representing the image data of each pixel included in the pixel group with the pixel group gradation value. Therefore, when setting the multi-value conversion table, first, assuming that all the pixels in the pixel group have image data of the same value as the pixel group gradation value, the presence or absence of formation of various large, medium, and small dots for each pixel Think about judging. The determination of the presence or absence of formation of various dots is performed by the half I-one process described above with reference to FIG. FIG.
- FIG. 23 is an explanatory diagram conceptually showing a state in which the presence / absence of large, medium, and small dots is determined for each pixel in the pixel group.
- the pixel group of interest for performing the half! ⁇ One processing is indicated by a thick solid line.
- the pixel group is composed of eight pixels, and the image data of each pixel has the same value as the pixel group tone value (tone value 97 in the example shown).
- image data is converted to density data for each dot. Conversion to density data is performed by referring to the dot density conversion table shown in Fig.22.
- the density data of the various dots also have the same value for all the pixels.
- the gradation value of the large dot density data is “2”
- the gradation value of the medium dot density data is ⁇ 95
- the gradation value of the small dot density data is“ 30 ”.
- the threshold value of the dither matrix used for comparison a threshold value set in a portion corresponding to a pixel group of interest from the dither matrix is used. For example, in the example shown in FIG.
- the threshold set for the pixel group at the upper left corner in the dither matrix is used as the threshold. Then, among the eight threshold values set for the pixel group, a pixel having a smaller threshold value than the large dot density data is determined to form a large dot.
- the density data of the large dot has the gradation value “2”
- the pixel where the large dot is formed is only the pixel for which the threshold value ⁇ 1 J is set.
- pixels for which a large dot is determined to be formed are displayed with fine diagonal lines.
- a threshold is set that is larger than the large dot density data “2” and smaller than the medium dot intermediate data “97” obtained by adding the large dot density data and the medium dot density data. It is determined that a medium dot is formed in the pixel. There are only two such pixels, a pixel for which the threshold “42” is set and a pixel for which the threshold “58” is set. In FIG. 23, the pixels for which it is determined that medium dots are to be formed are displayed with slightly coarse hatching. Finally, the intermediate data for small dots “1” which is larger than the intermediate data for medium dots “97” and is obtained by adding the density data for small dots to the intermediate data for medium dots It is determined that small dots are formed for pixels for which a threshold smaller than 27 is set.
- Such pixels are only those pixels for which the threshold “1 0 9” has been set.
- the pixels for which it is determined that small dots are formed are indicated by coarse hatching.
- the pixel group tone value of the pixel group of interest is “97”, one large dot, medium dot Two dots and one small dot will be formed.
- the pixel group gradation values differ greatly, the number of large dots, medium dots, and small dots formed in the pixel group will also differ. Also, if the pixel group gradation value is changed from “0” to ⁇ '255, the number of large dots, medium dots, and small dots should change in several steps.
- FIG. 24 is a flowchart showing the flow of the process of actually setting the multi-value table.
- step S500 one pixel group classification number is selected. For example, here, it is assumed that classification number 1 is selected.
- a threshold value corresponding to the pixel group of the selected classification number is read out from the dither matrix (step S502). For example, here, it is assumed that the classification number 1 is selected. Therefore, from the dither matrix illustrated in FIG. 16, eight of the dither matrices set at the block positions indicated as No. 1 in FIG. 18 (b) are selected. Read the threshold. Then, the multi-value quantization result value RV and the pixel group gradation value BD are set to “0” (step S504), and the number of large dots, medium dots, and small dots formed is reduced to zero. Set (step S506). Subsequently, by referring to the dot density conversion table shown in FIG.
- the pixel group tone values are converted into density data for large dots, medium dots, and small dots (step S50).
- the number of large, medium, and small dots to be formed is determined based on the density data and the threshold value read in advance (step S510). That is, as described with reference to FIG. 21 or FIG. 23, the number of thresholds smaller than the density data of large dots is obtained, and the obtained number is used as the number of large dots formed. Also, the number of thresholds larger than the density data of the large dot and smaller than the intermediate data for the medium dot is obtained, and this is set as the number of medium dots to be formed. Further, the number of thresholds larger than the intermediate data for medium dots and smaller than the intermediate data for small dots is obtained, and this is set as the number of small dots formed.
- step S512 It is determined whether or not the number of formed various dots obtained in this manner has been changed from the previously set number of formed dots (step S512). If it is determined that the formed number has been changed (step S512: yes), the multivalue quantization result value RV is increased by “1” (step S514), and the obtained multivalue quantization is performed. The result value RV is stored in association with the pixel group gradation value BD (step S5 16). On the other hand, if it is determined that the number of formed pixels has not been changed (step S512: ⁇ 0), the value is used as it is for the pixel group gradation value BD without increasing the multi-value quantization result value RV. And memorize it (Step S5 16).
- step S5 18 After storing the multi-value halftoning result value for a certain pixel group gradation value, it is determined whether or not the pixel group gradation value BD has reached the gradation value 255 (step S5 18). . If the gradation value has not reached 255 (step S5 18: ⁇ 0), the pixel group gradation value ⁇ D is increased by ⁇ ”(step S520), and the process returns to step S508 and returns to the pixel group again. After converting the gradation value BD into density data, a series of subsequent processes are performed, and the multi-value quantization result value RV is stored in association with the new pixel group gradation value BD (step S5 16).
- step S516 yes
- step S516 yes
- step S516 it is determined whether or not the above processing has been performed for all the classification numbers. If an unprocessed classification number remains (step S522: no), the step S500 is performed. And the above processing is performed again. This process is repeated, and when it is determined that all the multi-value quantization result values have been set for all the classification numbers (step S522: yes), the multi-value quantization table setting process shown in FIG. 24 ends.
- the multi-value quantization result value is obtained by converting the pixel group gradation value. It is determined by the obtained density data of the large, medium and small dots and the threshold value stored at the position corresponding to the pixel group in the dither matrix.
- the dot density conversion table shown in FIG. 22 refers to the same table even if the pixel group classification numbers are different, the density data of each dot with respect to the pixel group gradation value also has the classification number. The same density data can be obtained regardless of the data.
- the set of thresholds read from the dither matrix differs for each classification number.
- the threshold value should be distributed as much as possible so that the dots do not appear in a fixed pattern on the image, or do not degrade the image quality due to sticking at close positions. And as random as possible. For this reason, when a plurality of threshold values included in the pixel group are viewed as a set, it is considered that the possibility of exactly the same combination is extremely low. For this reason, in the multi-level quantization table referred to in the multi-level quantization result generation processing of the present embodiment, the correspondence between the pixel group gradation value and the multi-level quantization result value differs for each classification number. Also, the number of times that the multi-level quantization result value changes (the number of levels of multi-level quantization shown in Fig. 10) differs depending on the classification number. -
- Such a conversion table is used to convert the multi-value quantization result value into the data representing the number of dots formed in the pixel group by combining the multi-value quantization result value with the classification number during the dot formation presence / absence determination processing shown in FIG. Table to be referenced.
- the multi-value quantization result values set in the multi-value quantization table are large, medium, and small dots formed in the pixel group. Is determined based on the number of However, the multilevel halftoning result value does not immediately correspond to the combination of the number of dots formed in the pixel group.
- FIG. 25 is a flowchart showing a specific processing flow for setting the conversion table. Hereinafter, description will be given according to the flowchart.
- the number of large, medium, and small dots corresponding to the multi-value quantization result value RV is obtained (step S604). For example, if the multilevel halftoning result value is ⁇ ⁇ , then for the pixel group of that classification number, change the pixel group gradation value from “0” to “255” while Judge the presence or absence of formation, and obtain the number of large dots, medium dots, and small dots when the number of dots formed changes the fourth.
- the combination of the numbers of the dots thus obtained is converted into a code data (step S606). Conversion from the combination of dot numbers to code data is performed by referring to the correspondence table shown in Fig.13.
- Step S610 After storing the obtained code data in association with the multi-level quantization result value (step S608), it is determined whether or not the maximum multi-level quantization result for the target classification number has been reached. That is, as described with reference to FIG. 9, the maximum value of the multi-valued Since the classification number differs depending on the classification number, it is determined whether or not the maximum value of the multilevel quantization result for the target classification number has been reached. If the maximum value of the multi-level quantization result has not been reached (step S610: n0), the value of the multi-level quantization result RV is increased by "1" (step S6 12).
- step S610 the number of dots corresponding to the new multi-value quantization result value RV is obtained, and the subsequent series of processing is repeated. These operations are repeated, and when it is determined that the maximum multi-value quantization result value of the target classification number has been reached (step S610: yes), it is determined that all data for the classification number has been set in the conversion table. Become. Therefore, this time, it is determined whether the same process has been performed for all the classification numbers.
- Step S 6 1 4 the process returns to step S600, a new classification number is selected, and the above-described series of processing is performed on this classification number.
- step S614: yes all the data in the conversion table has been set, and the processing shown in FIG. 25 ends.
- the conversion table set in this way is stored in advance in the ROM built in the control circuit 260. Then, in the dot formation presence / absence determination processing shown in FIG. 11, the multi-value quantization result value is converted into the number of pieces by referring to this conversion table.
- the order value matrix is a matrix in which the order in which dots are formed is set for each pixel in the pixel group.
- the order value matrix corresponding to the pixel group is read and the matrix is read.
- the pixels that form large dots, medium dots, and small dots are determined according to the order set in the boxes.
- the order value matrix can be formed by the method disclosed in Japanese Patent No. 3922104 (by developing the dither method to determine whether or not plural types of dots having different sizes are formed).
- the method is set based on That is, when setting the multi-valued table, as described above, it is assumed that all the pixels in the pixel group have the same image data (pixel group gradation value), and the large, medium, and small dots formed in the pixel group are set. While determining the number, change the pixel group gradation value from “0” to ⁇ 255, and set the multi-value quantization result value by paying attention to the change in the number of dots formed at this time. did. Also, as shown in FIG. 12, by combining the multi-value quantization result value and the classification number, it was possible to restore up to the number of large, medium, and small dots formed in the pixel group.
- the ordinal matrix can be thought of as storing information on the pixel positions where various dots are formed in the pixel group. That is, if the method disclosed in Japanese Patent No. 3922104 is applied to a pixel group, as described above with reference to FIGS. 21 to 23, not only the number of various dots formed but also the pixel Although it is possible to determine the pixel position where a dot is formed in a group, in this embodiment, this method is decomposed into two elements, and the information on the number of formed dots is mainly multi-valued.
- Result value (Accurately, a combination of the multivalued result value and the classification number) (It can be considered that this is reflected, and the information on the pixel position where the dot is formed is reflected in the order value matrix.
- Result value matrix can be set relatively easily, and Fig. 26 is an explanatory diagram specifically showing a method of setting an order value matrix.
- FIG. 26 (a) is an explanatory diagram conceptually showing a state where the dither matrix is divided into a plurality of blocks. Now, assuming that the dither matrix has the size shown in Fig. 16 (that is, 128 pixels in the main scanning direction and 64 pixels in the sub-scanning direction), one pixel group consists of the main scanning direction. As shown in Fig.
- FIG. 26 (a) is an explanatory diagram showing, as an example, a state in which an ordinal value matrix is generated from a block having a classification number of one.
- the left half of FIG. 26 (b) shows the threshold of dither matrix included in the block of classification number 1. As described above with reference to FIG. 23, dots are formed in order from the pixel for which a small threshold value is set.
- the pixel in which the dot is formed first in the block of one incense shown in FIG. 26 (b) can be considered as the pixel for which the threshold value “1” is set. Therefore, “1” is set to this pixel as the order value.
- the pixel on which the second dot is formed can be considered to be the pixel for which the threshold “4 2”, which is the second smallest threshold, is set. Therefore, an order value “2” is set for this pixel. In this way, if the order value “1” to the order value “8” are determined in order from the pixel with the smallest threshold set in the block, the classification shown in the right half of Fig. 26 (b) can be obtained. You can get the ordinal value matrix of number 1 incense.
- Fig. 26 (c) shows the classification number 2 by setting the order value M "to the order value” 8 "in order from the discards for which a small threshold is set in the block. It shows how the order value matrix of incense is obtained.
- classification number“ 1 ” 0 2 4 ”An order value matrix up to incense can be obtained.
- the order value matrix set in this way is stored in advance in the ROM built in the control circuit 260 in association with the pixel group classification number. Have been. Then, when performing the dot on / off state determination process shown in FIG. 11, the matrix corresponding to the classification number of the pixel group is read from the stored order value matrix.
- a plurality of pixels are grouped into a pixel group, and the multi-level conversion is performed for each pixel group by referring to the multi-level conversion table illustrated in FIG. Determine the result value.
- the conversion table illustrated in FIG. 12 and the order value matrix illustrated in FIG. 14 pixel positions at which various dots are formed in the pixel group based on the multi-value quantization result value are determined. decide. Even when the positions of the pixels forming the dots are determined in this way, a high-quality image in which the dots are appropriately dispersed can be output.
- the dither matrix to be referred to at this time is a so-called blue noise mask or a matrix taking into account the dispersibility represented by a green noise mask
- a high-quality image in which dots are well dispersed can be obtained.
- image data generally tends to be assigned similar (or identical) gradation values between adjacent pixels.
- the resolution of image data has tended to be higher and higher due to the demand for higher image quality.However, the tendency that adjacent pixels have similar or the same gradation value is more pronounced as the resolution of image data is higher. . For this reason, as described above with reference to FIG.
- the pixel group tone value is multi-valued to generate a multi-value quantization result value depending on the pixel group classification number.
- the multi-value quantization result value thus generated is combined with the pixel group classification number to provide data indicating the number of various dots formed in the pixel group.
- the number of large dots, medium dots, and small dots formed by combining with the pixel group classification number is 1, 2, and 1, respectively.
- a multi-value quantization result value is generated as shown in the following table.
- the dot formation presence / absence determination processing of the first embodiment described above when such a multi-value quantization result value is received, the presence / absence formation of each of the large, medium, and small dots is determined for each pixel in the pixel group.
- Fig. 27 is a conceptual diagram showing the general flow of the process for determining whether or not large, medium, and small dots are formed for each pixel in the pixel group by receiving the multi-value quantization result value in the dot formation presence / absence determination process described above.
- the classification number of the pixel group represented by the result value is obtained, and then the The number of large, medium, and small dots to be formed is obtained based on the binarization result value and the classification number.
- a matrix stored in association with the classification number is read out from the order value matrix stored in advance. A specific method for obtaining the classification number will be described later. If the description is made assuming the pixel group shown in FIG. 23, the pixel group is located at the upper left corner of the image. By combining the multi-value quantization result value of this pixel group and the obtained classification number, it can be seen that one large dot, two medium dots, and one small dot are formed in this pixel group.
- the order value matrix of the classification number 1 is referred to.
- the order value matrix is used to determine whether or not dots are formed for the corresponding portion of the dither matrix used for determining whether or not dots are formed, that is, for each pixel in the pixel group.
- An ordinal value matrix generated from the part. Based on the number of large, medium and small dots obtained in this way and the order value matrix, the pixel positions at which these dots are formed in the pixel group are determined. Since the specific method of determining the pixel position has already been described with reference to FIG. 15, the description is omitted here and only the result is shown.
- the middle dot is formed in the pixel with the order value of 2 and the third pixel, and the small dot is formed in the pixel with the order value of 4.
- Pixel 27 as in Figure 15, pixels forming large dots are finely hatched, pixels forming medium dots are slightly hatched, and pixels forming small dots. Is shown with coarse hatching. Comparing the dot distribution obtained in this way with the dot distribution obtained by judging the presence or absence of dot formation for each pixel shown in Fig. 23, the two dot distributions are complete. It can be seen that they match. That is, even if only the multi-value quantization result value depending on the classification number is received, When the presence or absence of dot formation was determined using the method described above, the above-mentioned Patent No.
- the multi-value quantization table referenced to generate the multi-value quantization result values is set based on the dither matrix (see Figure 25).
- the conversion table or ordinal matrix referred to in the process of determining the presence or absence of dot formation from the multi-value quantization result value is also set based on the dither matrix (see FIGS. 25 and 26). ).
- FIG. 28 is an explanatory diagram showing a method of obtaining a classification number based on the position of a pixel group on an image.
- the target pixel group is the ⁇ ⁇ -th pixel group in the main scanning direction and the j-th pixel in the sub-scanning direction with reference to the upper left corner of the image.
- they are in group position.
- the position of such a pixel group is represented by a coordinate value (i, j).
- the size of the dither matrix is usually not as large as the image, so as described above with reference to Fig. 19 (b), the dither matrix is repeatedly moved while moving in the main scanning direction. Shall be used.
- FIG. 29 is an explanatory diagram specifically showing a method of obtaining the position of the pixel group in the dither matrix from the coordinate value (i, j) of the pixel group.
- FIG. 29 (a) conceptually illustrates a 10-bit binary number representing a numerical value i.
- serial numbers from 1 to 10 are assigned from the most significant bit to the least significant bit.
- int (i / 32) is calculated. This operation can be performed by shifting the binary data of ⁇ to the right by 5 bits (see Figure 29 (b)). Next, int (i / 32) ⁇ 32 is calculated. This operation can be performed by shifting the binary data of int (i / 32) leftward by 5 bits (see Figure 29 (c)). Finally, subtracting int (i 32) X 32 from the number i gives the desired number I. This operation is essentially nothing more than extracting the lower 5 bits from the binary data of the numerical value ⁇ . It is very easy to obtain the numerical value I.
- the classification number can be calculated by using the above equation (2).
- the multi-value halftoning result value generation processing (step S106 in FIG. 6) and the dot formation presence / absence determination processing (step S108 in FIG. 6) performed during the image printing processing of the first embodiment are described above. The contents were explained in detail.
- a pixel group is generated by grouping a predetermined number of pixels, and a result value obtained by multi-leveling the pixel group tone value of the pixel group is generated.
- the multi-value quantization result value obtained in this way is a result value depending on the classification number of the pixel group, but the data amount is much smaller than the data indicating the presence or absence of dot formation for each pixel. Therefore, data can be output very quickly from the computer 100 to the color printer 200. That is, in the above-described multi-value quantization result generation processing, the generation and output of the multi-value quantization result value can be executed at high speed, and the image can be printed quickly by that much. is there.
- the process of generating the multi-value quantization result value is merely a process of referring to the multi-value quantization table, and the classification numbers and pixel group gradation values used to refer to the multi-value quantization table are extremely simple. Therefore, even when a device such as the computer 100 that does not have a high data processing capability is used, the processing can be performed at a sufficiently practical speed. Furthermore, since most of the processing is extremely simple processing of simply referencing a table, it is not executed by software using a CPU, but by using an IC chip incorporating a dedicated logic circuit. It is easy to execute in hardware, and this makes it possible to process at extremely high speed.
- the multi-value quantization result value generation processing is performed inside the digital camera 120 or the color printer 200. Executing in, the image can be printed quickly.
- the dot formation presence / absence determination processing performed during the image printing processing of the first embodiment, when the multi-value quantization result value is received, the presence / absence of dot formation is determined for each pixel in the pixel group.
- the multi-value quantization result value is converted into a combination of the number of dots by referring to a conversion table. Then, by referring to the order value matrix, the formation positions of various dots are determined.
- the pixel positions forming various dots can be quickly determined. Normally, when the types of dots that can be formed increase, the process of determining the pixel positions where these various dots are formed becomes complicated at an accelerated rate.
- the basic processing contents of referring to the conversion table and the order value matrix are the same even when the number of dots increases. The processing content does not become complicated. From this point as well, it can be said that the dot formation presence / absence determination processing of the first embodiment enables simple and quick processing.
- the gradation value 0 to the gradation value 255 For each pixel group gradation value up to, a multi-value quantization table storing the corresponding multi-value quantization result values is referenced. However, the multi-value quantization result value only increases stepwise as the pixel group tone value increases. Therefore, if only the pixel group tone value at which the multi-value quantization result value switches is stored, the pixel group tone value is obtained. A multi-value halftoning result value for the tone value can be obtained. In an image printing process according to a first modification described below, a multi-value quantization result value generation process according to such a modification is performed. FIG.
- FIG. 30 is an explanatory diagram conceptually showing a threshold value table referred to in the multi-value quantization result value generation processing of the modification.
- a threshold value corresponding to the multi-value quantization result value is set in the threshold value table for each classification number.
- This threshold value represents the largest pixel group gradation value that is the multi-value halftoning value when the pixel group gradation value is increased from gradation value 0 to gradation value 255.
- the pixel group of the classification number 1 will be described.
- a threshold “2” is set for the multi-level quantization result value “0”.
- a threshold value of “15 J” is set for the multi-value quantization result value ⁇ . ” This means that, for the pixel group of classification number 1, the pixel group tone value is from 33 to ⁇ 15 If the value is within the range, the multi-value quantization result value becomes ⁇ ”.
- a threshold “2 4 3” is set for the multi-level quantization result value “1 4”
- a threshold “2 5 5” is set for the multi-level quantization result value ⁇ 5 j.
- the multi-value quantization result value will be “1 5”. Indicates that the maximum value of the multi-value quantization result value is ⁇ 5 ”.
- the threshold value for each classification number is set corresponding to the multi-value quantization result value.
- a single set of threshold values may be stored for each classification number without being associated with a multi-value quantization result value. In this case, by counting the number of thresholds smaller than the pixel group gradation value, the multivalued result value can be obtained. The description will be given again using the pixel group of the classification number 1 as an example.
- the pixel group gradation value is “20”.
- the multilevel halftoning result value for the pixel group tone value 20 may be determined to be “3”.
- the multi-value halftoning result value generation processing of the modified example described above after obtaining the pixel group gradation value and the classification number for the pixel group, the multi-value conversion processing is performed by referring to the threshold table illustrated in FIG. Generate the conversion result value.
- the threshold table can be stored with a smaller amount of data than the multi-level quantization table (see FIG.
- the multi-value quantization result value can be immediately obtained only by referring to the multi-value quantization table from the classification number and the pixel group gradation value. That is, since it is not necessary to compare the pixel group gradation value with the threshold unlike the processing in the modified example, it is possible to quickly multi-value.
- the dot formation presence / absence determination process of the first embodiment described above when the classification number of the pixel group and the multi-value quantization result value are received, this is temporarily converted into data representing the number of various dots to be formed in the pixel group. did.
- judging the presence or absence of dot formation whether or not a dot was formed for each pixel in the pixel group was determined for each type of dot. For example, in the flow chart shown in Fig. 11, it is first determined whether or not a large dot is formed, then the medium dot is determined, and finally the small dot is determined. The presence or absence of dot formation was determined for each type of dot.
- the method of determining the presence or absence of dot formation is not limited to such a method.
- FIG. 31 is a flowchart showing a flow of a dot formation presence / absence determination process according to a modification.
- the dot formation presence / absence determination processing of the modified example will be described with reference to a flowchart.
- the dot formation presence / absence determination processing of the modified example similarly to the processing in the first embodiment described above, first, when the processing is started, one pixel group to be processed is selected (step S700).
- the multi-value quantization result value of the selected pixel group is obtained (step S702), and the number of dots to be formed in the pixel group is determined based on the classification number of the pixel and the multi-value quantization result value.
- the data to be represented is obtained (step S704).
- the data of the number of dots can be quickly obtained from the combination of the classification number and the multi-value quantization result value by referring to the conversion table shown in FIG. In the dot formation presence / absence determination process of the modified example, the data of the number of dots thus obtained is temporarily converted into intermediate data having a length of 16 bits (step S706). That is, in the conversion table of FIG. 12, the data of the number of dots is represented as 8-bit length code data in order to reduce the amount of data.
- the data length of the data is 16 bits because the number of pixels included in the pixel group is 8, and the presence or absence of dot formation for each pixel can be expressed with 2 bits By being.
- the intermediate data is data that represents the number of dots using eight sets of data corresponding to the number of pixels, with one set of two bits each. If the number of dots to be formed in the pixel group is expressed in such a format, it is easy to correspond to the pixels as described later, so that it is possible to easily determine whether or not to form dots.
- the correspondence between the code data representing the number of dots and the intermediate data is stored in advance.
- FIG. 32 is an explanatory diagram showing a correspondence table in which code data representing the number of dots is associated with intermediate data.
- code data representing the number of dots is associated with intermediate data.
- the type of the dot is represented by two bits as one set.
- 16-bit data can be obtained.
- the 16-bit intermediate data is data obtained by converting the expression format of the code data in this way. For example, code data "" indicates a combination of 0 large dots, 0 medium dots, and 1 small dot. For reference, the combination of the number of dots indicated by each code data is shown on the right side of FIG.
- the 16-bit data corresponding to the code data. 1 J contains only one set of“ 0 1 ”.
- the two-bit data is data such as “0 0”.
- the 2-bit data “0 0” is data indicating that no dot is formed.
- the code data “1 63” indicates a combination of 7 large dots, 1 medium dot, and 0 small dots.
- the large dot Only one set of “1 1” is set at the right end, two sets of 2-bit data ⁇ 1 0 indicating the middle dot are set next to the left, and further to the left Subsequently, three sets of 2-bit data “0 1” representing a small dot are set, and the remaining two sets are set with 2-bit data “0 0” indicating that no dot is formed. In the end, these 2-bit data may be set left-justified. That is, large dots, medium dots, and small dots may be set in order from the left.
- the combination of the classification number and the pixel group gradation value is once converted into 8-bit code data representing the number of dots.
- the code data is converted to 16-bit intermediate data.
- 16-bit intermediate data is set in the conversion table shown in Fig. 12 instead of 8-bit code data. It is also possible to immediately obtain intermediate data from a combination of the pixel group classification number and the pixel group gradation value.
- step S708 the order value matrix corresponding to the pixel group is read (step S708), and the pixel for which dot formation is to be determined from the pixel group is determined. Is selected (step S710), and the order value set at the pixel position selected in the order value matrix is acquired (step S712).
- step S710 the order value set at the pixel position selected in the order value matrix is acquired (step S712).
- step S710 the presence or absence of dot formation for the selected pixel is determined by reading the 2-bit data set at the location corresponding to the order value from the intermediate data obtained earlier.
- Figure 33 shows that the presence or absence of dot formation is determined by reading the data at the location corresponding to the order value from the intermediate data.
- FIG. 33 (a) shows an example of intermediate data obtained by converting data of the number of dots formed in a certain pixel group.
- the intermediate data is 16-bit data, and is composed of eight sets of data each two bits.
- one set of 2-bit data ⁇ 1 J representing a large dot two sets of 2-bit data ⁇ 10 representing a medium dot
- two sets of small dots Three sets of 2-bit data "0 1" and two sets of 2-bit data "0 0" indicating that no dot is formed.
- the two-bit data consists of large dots, medium dots, and small dots. Right-justified in dot order.
- FIG. 33 (b) conceptually shows a state where 2-bit data in the third set from the right end of the intermediate data is read.
- the read 2-bit data is “1 0”, so it may be determined that a medium dot is to be formed in this pixel. If the sequence value is “1”, the 2-bit data set at the right end of the intermediate data should be read out and determined to form a large dot.
- the presence / absence of dot formation is determined by an extremely simple operation of reading 2-bit data set at a position corresponding to the order value from the intermediate data. Can be determined. This is for the following reasons.
- two-bit data representing large dots, medium dots, and small dots are set right-justified.
- the dots are arranged in the order of large, medium, and small dots. The presence or absence of formation is determined.
- the 2-bit data set in the intermediate data is read in order from the right end, various dots are formed by applying the method described above with reference to FIG. 21 or FIG. In this order, two-bit data representing large dots, medium dots, and small dots are obtained in the same order in which the pixel positions to be determined are determined.
- dots are formed in order from the pixel for which a small threshold is set in the dither matrix.
- the order value set in the order value matrix indicates the order of smaller threshold values set in the dither matrix. Therefore, the order value matches the order in which the dots were formed when the presence or absence of the dot formation was determined using the method described above with reference to FIG. 21 or FIG.
- the order value of the target pixel is known, then when applying the method of Fig. 21 or Fig. 23, it is determined in which order the pixel is the pixel in which the dot is formed in the pixel group If the intermediate data is counted from the right end and the two-bit data of the ordinal value set is read, the presence or absence of dot formation obtained when the method of FIG. 21 or FIG. 23 is applied is obtained. You can know the result of the decision. In the above description, the place where the 2-bit data is read out of the intermediate data is changed according to the order value. However, instead of changing the location to be read in the intermediate data, the location from which the data is read may be fixed, and the intermediate data may be shifted by the number of sets corresponding to the order value.
- FIG. 33 (c) is an explanatory diagram conceptually showing a state in which the presence / absence of dot formation is determined by shifting the intermediate data.
- the 2-bit data at the right end of the intermediate data is read out, and the intermediate data is shifted rightward by the number of sets corresponding to the pixel order value (specifically, the number of sets that is one less than the order value). I'm shifting.
- the two bits set at the same position in the intermediate data are ultimately obtained. This means that data is being read.
- step S714 If there is a pixel in the pixel group for which dot formation has not yet been determined (step S714: ⁇ 0), the process returns to step S710 to select a new pixel. Then, after performing the above-described series of processes on the selected pixel, it is determined again whether or not dot formation is determined for all pixels in the pixel group (step S 716). This operation is repeated until it is determined whether or not dots are formed for all the pixels in the pixel group. If it is determined that all the pixels have been determined (step S 716: yes), then all the pixels in the image are set. It is determined whether or not dot formation is determined for the group by performing the processing described above (step S718).
- step S 718: n 0 If an unprocessed pixel group remains (step S 718: n 0), the process returns to step S 700 to select a new pixel group and perform a series of subsequent processing on the pixel group. . These operations are repeated, and when it is determined that the processing for all the pixel groups is finally completed (step S718: yes), the processing for determining whether or not to form a dot in the modified example shown in FIG. 31 is completed. .
- dot formation can be performed simply by reading 2-bit data set at an appropriate position according to the order value from the intermediate data. Can be determined.
- the presence or absence of the dot formation can be quickly determined in this way, so that the image can be printed more quickly.
- the dot formation presence / absence determination processing of the first embodiment described above when the multi-value quantization result value for each pixel group is received, the number of dots is temporarily determined by referring to the conversion table shown in FIG. After converting the data to represent data, the pixel positions where dots are to be formed within the pixel group were determined with reference to the order value matrix. However, upon receiving the multi-value quantization result value for each pixel group, it is also possible to immediately determine the pixel positions forming various dots.
- D-1 Principle of the process for determining the presence or absence of dot formation in the second embodiment:
- the dot formation presence / absence determination processing of the first embodiment when a multi-value quantization result value is received for each pixel group, a classification number of the pixel group is obtained, and then the multi-value quantization is performed. From the combination of the result value and the classification number, the number of various dots formed in the pixel group was determined. Then, the pixel positions for forming these dots are determined by referring to the order value matrix corresponding to the classification number. That is, if the multi-value halftoning result value and the classification number of the pixel group are determined, the type of dot formed at each pixel in the pixel group can be determined.
- FIG. 34 is an explanatory diagram conceptually showing a conversion table referred to in the dot formation presence / absence determination processing of the second embodiment.
- data representing the type of dot formed in each pixel in the pixel group is associated with the combination of the multi-value quantization result value and the classification number. Is set. In the following, such data will be referred to as dot data.
- dot data can be immediately read out from the combination of the pixel group classification number and the pixel group gradation value. For example, if the classification number is i and the pixel group gradation value is j, the dot data is DD (i, j). The dot data read in this manner describes whether or not a dot is formed for each pixel in the pixel group.
- the dot data is 16-bit long data composed of 8 sets of 2-bit data.
- one dot data is composed of eight sets of data, which corresponds to the fact that one pixel group includes eight pixels in the image printing process of this embodiment. That is what you do. Therefore, for example, when one pixel group is composed of four pixels, one dot data is composed of four sets of data.
- the reason why one set of data consists of two bits is that the color printer 200 of the present embodiment has one pixel, a large dot, a medium dot, and a small dot.
- each of the eight sets of data constituting the dot data is associated with a pixel at a predetermined position in the pixel group.
- the first set of data at the beginning of the dot data shown in Fig. 35 (a) corresponds to the pixel at the upper left corner in the pixel group as shown in Fig. 35 (b). .
- the second set of data from the top of the dot data corresponds to the second pixel from the left in the upper row in the pixel group.
- the eight sets of data constituting the dot data are respectively associated with the pixels at the predetermined positions in the pixel group in advance.
- the content of each set of data indicates the type of dot to be formed in the corresponding pixel. ing.
- the 2-bit data "1 1” means that a large dot is formed.
- Two-bit data "10” means forming a medium dot, "01J means forming a small dot, and" 0 0 "means not forming a dot. ing.
- a large dot is formed in the pixel at the upper left corner of the pixel group, and a medium dot is formed in the third pixel from the left in the upper row.
- a small dot is formed in the second pixel from the left in the lower row, a medium dot is formed in the pixel at the lower right corner of the pixel group, and data indicating that no dot is formed in other pixels.
- FIG. 36 is a flowchart showing the flow of the dot on-off state determination process of the second embodiment. The following is a brief description according to the flowchart.
- the dot data representing the presence or absence of dot formation for each pixel in the pixel group is read out.
- the position corresponding to the dot is By simply reading out the stored dot data, the presence or absence of dot formation can be determined for each pixel in the pixel group.
- it is determined whether or not dot formation is determined for all pixel groups step S806). If an unprocessed pixel group remains (step S806: no), the step is performed. Returning to S800, a new pixel group is selected, and a series of subsequent processing is performed on the pixel group.
- step S806 the dot formation presence / absence determination processing of the second embodiment shown in FIG. 36 is terminated.
- the dot formation presence / absence of each pixel in the pixel group can be determined from the multi-value quantization result value simply by referring to the conversion table on the first floor. You can decide immediately. Therefore, the presence / absence of the dot formation can be determined more quickly even in the process of determining the presence / absence of the dot formation of the first embodiment shown in FIG. It is possible to output.
- the present invention is not limited to all the embodiments described above, and can be implemented in various modes without departing from the gist of the invention.
- the present invention can be suitably applied to a liquid crystal display device or the like that expresses an image whose gradation continuously changes by dispersing bright spots on a liquid crystal display screen at an appropriate density.
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Abstract
Description
Claims
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
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EP05736571A EP1744539A4 (en) | 2004-04-22 | 2005-04-22 | IMAGE PROCESSOR FOR IMPROVED IMPLEMENTATION IN UNITS OF PIXELS |
JP2006512662A JP4375398B2 (ja) | 2004-04-22 | 2005-04-22 | 複数画素ずつ多値化を行う画像処理装置 |
US11/585,014 US20070035772A1 (en) | 2004-04-22 | 2006-10-23 | Image processing apparatus for carrying out multi-value quantization in multiple-pixel units |
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JP2004-126971 | 2004-04-22 | ||
JP2004126971 | 2004-04-22 |
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US11/585,014 Continuation US20070035772A1 (en) | 2004-04-22 | 2006-10-23 | Image processing apparatus for carrying out multi-value quantization in multiple-pixel units |
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WO2005104525A1 true WO2005104525A1 (ja) | 2005-11-03 |
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US (1) | US20070035772A1 (ja) |
EP (1) | EP1744539A4 (ja) |
JP (1) | JP4375398B2 (ja) |
CN (1) | CN1947409A (ja) |
WO (1) | WO2005104525A1 (ja) |
Cited By (3)
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JP2007142848A (ja) * | 2005-11-18 | 2007-06-07 | Seiko Epson Corp | ディザマトリックスを用いたハーフトーン処理 |
US7924464B2 (en) | 2005-11-18 | 2011-04-12 | Seiko Epson Corporation | High-image-quality halftone process |
US8023151B2 (en) | 2005-11-18 | 2011-09-20 | Seiko Epson Corporation | High-image-quality halftone process |
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JP4241823B2 (ja) * | 2004-05-19 | 2009-03-18 | セイコーエプソン株式会社 | ドットデータ処理装置、画像出力システムおよびそれらの方法 |
US8270498B2 (en) * | 2009-03-26 | 2012-09-18 | Apple Inc. | Dynamic dithering for video compression |
US20110135011A1 (en) | 2009-12-04 | 2011-06-09 | Apple Inc. | Adaptive dithering during image processing |
KR102537608B1 (ko) * | 2016-01-28 | 2023-05-30 | 삼성디스플레이 주식회사 | 표시 장치 및 그의 영상 표시 방법 |
JP2018121277A (ja) | 2017-01-27 | 2018-08-02 | セイコーエプソン株式会社 | 画像形成システム、画像形成装置、画像形成方法、プログラム |
CN111950510B (zh) * | 2020-08-26 | 2023-10-03 | 上海申瑞继保电气有限公司 | 高压开关分合指示牌图像识别方法 |
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- 2005-04-22 WO PCT/JP2005/008273 patent/WO2005104525A1/ja not_active Application Discontinuation
- 2005-04-22 CN CNA200580012398XA patent/CN1947409A/zh active Pending
- 2005-04-22 EP EP05736571A patent/EP1744539A4/en not_active Withdrawn
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JP4534963B2 (ja) * | 2005-11-18 | 2010-09-01 | セイコーエプソン株式会社 | 画像形成方法、画像形成装置、画像形成システム、印刷方法、印刷物の生成方法および画像形成装置を制御するためのコンピュータプログラム |
US7924464B2 (en) | 2005-11-18 | 2011-04-12 | Seiko Epson Corporation | High-image-quality halftone process |
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JPWO2005104525A1 (ja) | 2008-03-13 |
CN1947409A (zh) | 2007-04-11 |
US20070035772A1 (en) | 2007-02-15 |
EP1744539A1 (en) | 2007-01-17 |
JP4375398B2 (ja) | 2009-12-02 |
EP1744539A4 (en) | 2008-06-25 |
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