JP2009060316A - Image data encoding apparatus, image data encoding method, image forming apparatus, and image forming method - Google Patents

Abstract

An image data encoding apparatus capable of encoding multi-value image data mainly including graphics at a higher compression rate than conventional ones.
In an image data encoding device 110 that encodes color information of individual pixels in multi-valued image data into multi-value run-length data indicating at least the color information and the run length thereof, the first pixel of the run is used. In the process of comparing the pixel located on the rear end side of the run with respect to the first pixel from the first side as the target pixel in order from the first pixel, if the first pixel and the target pixel have the same color information or match If the color difference between the two pixels is within the allowable range, the run length is calculated with both pixels as the same run, while the color difference between the two pixels is outside the allowable range without matching. The image data encoding device 110 is configured to execute the process of obtaining the run length with both pixels as separate runs.
[Selection] Figure 4

Description

  The present invention relates to an image data encoding device and an image data encoding method for encoding multi-value image data. The present invention also relates to an image forming apparatus and an image forming method for encoding image data acquired from an external device using the image data encoding apparatus and the image data encoding method.

  In recent years when personal computers (hereinafter referred to as personal computers) and digital cameras have been widely used in the general market, there has been an increase in the opportunity to output color images such as color photographs and color paintings using image forming apparatuses. . In an image forming apparatus such as a printer, an image is formed while image data sent from a personal computer or the like is stored in a temporary memory. However, multivalued image data representing a color image represents black and white. The capacity is much larger than the value image data. For this reason, in order to process a large amount of multi-value image data without waiting for transmission from an external device such as a personal computer, a large-capacity memory must be installed in the image forming apparatus, resulting in an increase in cost. End up. Therefore, a plurality of multi-valued image data sequentially sent from an external device are temporarily stored in the memory while being compressed by encoding, and sequentially decoded at the time of image forming processing, so that the memory capacity can be reduced. It is desirable to reduce the size.

  A run length method has been widely known as a method for encoding image data. The run-length method is a method of converting a group of continuous pixels of the same color composed of a plurality of pixels that are continuous in the same color into a code indicating a series (run) and length (length) in a pixel row composed of a plurality of pixels. It is. For example, in the binary image data, a pixel row in which pixels are arranged in the order of “black black black black black black black white white black and white white white white white” is replaced with a symbol “7314”. In the case of binary image data, there are only two colors, white and black, so by determining which color the first run will be handled in, it is possible to express a pixel column with only the number indicating the run length. It is. For example, the previous symbol “7314” is an example in which the first run is determined to be treated as black. However, when the first run is determined to be treated as white, it may be expressed as “07314”. . In the case of multi-value image data, in addition to the run data indicating the run length of each run, color data indicating the color information of each run is required.

  According to such a run length method, the capacity of image data can be greatly reduced for an image having many pixels of the same color or an image having a large margin. In addition, lossless compressed image data that is the same as the original image can be obtained. As an image data encoding method to which the run length method is applied, the one described in Patent Document 1 is known.

JP 2005-27081 A

  However, when multi-valued image data mainly consisting of graphics rich in color change is encoded by the run length method, the data capacity after encoding cannot be greatly reduced compared to the capacity of the original data. There was a problem. This is because in multi-value image data rich in color tone change, the run is long and difficult to continue. Specifically, in information processing apparatuses such as personal computers in recent years, it has become mainstream to express a color image in full color. In full color, by dividing the brightness of the three primary colors of R, G, and B (or Y, M, and C) into 256 different gradations, it is possible to express an enormous variety of colors of 16777216 colors. In such full-color expression, if the multi-value image data is rich in color tone change, the run is interrupted even if there is a slight color difference that is hardly visible. For this reason, the number of runs included in the run data after encoding becomes very large, which hinders reduction in data capacity.

  The present invention has been made in view of the above background, and an object of the present invention is to encode image data capable of encoding multi-value image data mainly including graphics at a higher compression rate than before. It is to provide a device or the like.

In order to achieve the above object, the invention of claim 1 reads reading means for reading color information of individual pixels in multivalued image data, and based on the color information read by the reading means, at least color information and In an image data encoding device comprising multi-value run length encoding means for encoding multi-value run length data indicating the run length, the image data encoding device is located on the rear end side of the run from the start pixel which is the start pixel of the run In the process of comparing pixels with the first pixel in order from the first pixel as the target pixel, if the color information of the first pixel and the target pixel match each other, or the color difference between both pixels is within the allowable range In some cases, the run length is determined with both pixels as the same run, while the run length is determined with both pixels as separate runs when they do not match and the color difference between both pixels is outside the allowable range. The fruit As to, is characterized in that constitute the multi-level run-length data encoding means.
According to a second aspect of the present invention, in the image data encoding device of the first aspect, the color information of the first pixel and the pixel of interest do not match each other and the color difference between the two pixels is within an allowable range. However, if the run length when both pixels are set to the same run exceeds the upper limit, the multi-value run length data code is set so that the process for obtaining the run length is performed with both pixels as separate runs. The present invention is characterized in that it comprises a conversion means.
The invention of claim 3 is the image data encoding device according to claim 1 or 2, wherein, as the color difference, a difference in the first primary color component between the leading pixel and the pixel of interest in a color representation method using three primary colors, The multi-value run length data encoding means is configured to obtain the sum of the difference between the second original color components and the difference between the third original color components.
According to a fourth aspect of the present invention, in the image data encoding device according to any one of the first to third aspects, as the color difference, a first primary color component of the first pixel and the target pixel in a color representation system using three primary colors is used. The multi-value run length data encoding means is configured to obtain the maximum difference among the difference between the second color component, the second color component difference, and the third color component difference. It is.
According to a fifth aspect of the present invention, in the image data encoding device according to the first or second aspect, the color difference is based on a lightness difference and a hue difference between the head pixel and the target pixel in a color expression method based on lightness and hue. The multi-value run length data encoding means is configured to obtain difference data.
According to a sixth aspect of the present invention, there is provided image data acquisition means for acquiring multivalued image data, image data encoding means for encoding image data acquired by the image data acquisition means, and the image data encoding An image forming apparatus comprising: image data decoding means for decoding data encoded by the means; and image forming means for forming an image based on the multivalued image data decoded by the image data decoding means The image data encoding device according to any one of claims 1 to 5 is used as the image data encoding means.
Further, the invention of claim 7 is a reading step for reading color information of individual pixels in multi-valued image data, and based on the color information read in the reading step, at least color information and a run length indicating the run length. An image data encoding method for performing a multi-value run-length encoding step for encoding value run-length data, wherein in the multi-value run-length encoding step, a run is performed more than a first pixel that is a first pixel of a run. In the process of comparing the pixel located on the rear end side with the first pixel as the target pixel in order from the first side, if the color information of the first pixel and the target pixel match each other, If the color difference between the two pixels is within the allowable range, the run length is obtained by setting both pixels as the same run, but if they do not match and the color difference between the two pixels is outside the allowable range, Run head as run It is characterized in that the finding.
The invention of claim 8 encodes multi-valued image data by an image data encoding method, decodes the multivalued image data by an image data decoding method, and then forms an image based on the decoded image data In the image forming method, the image data encoding method according to claim 7 is used as the image data encoding method.

  In these inventions, although the color information does not completely match, the first pixel and the target pixel whose color difference is within the allowable range are combined as the same run, thereby increasing the run length in each run. And reduce the number of runs. Thereby, multi-value image data mainly including graphics can be encoded at a higher compression rate than in the past.

Hereinafter, an embodiment in which the present invention is applied to a full-color printer (hereinafter simply referred to as a printer) that is an electrophotographic image forming apparatus will be described.
First, a basic configuration of the printer according to the embodiment will be described. FIG. 1 is a schematic configuration diagram illustrating a printer according to an embodiment. In the figure, an endless belt-like photoconductor 1 as an image carrier is stretched so as to be endlessly movable in the clockwise direction in the figure by rotating rollers 2 and 3, and in the same direction by the rotational drive of one of the rotating rollers. Move endlessly.

  Around the photosensitive member 1, there are a charging device 4 as a charging unit for uniformly charging the surface of the photosensitive member 1, a neutralizing lamp L as a neutralizing unit for neutralizing the photosensitive member 1, and a surface to be described later attached to the surface of the photosensitive member 1. A cleaning device 16 and the like for cleaning the transfer residual toner are disposed.

  On the downstream side of the uniform charging position by the charging device 4 in the belt moving direction, the photoconductor 1 is scanned with laser light by the optical writing device 5 serving as a latent image writing means. Along with this scanning, the potential of the exposed portion of the photoreceptor 1 is attenuated, so that the photoreceptor 1 carries an electrostatic latent image.

  A rotary developing device 6 is disposed on the left side of the photosensitive member 1 stretched in a vertically long posture with a space in the vertical direction rather than in the horizontal direction. The rotary image device 6 uses a C developing unit that uses C (cyan) toner, an M developing unit that uses M (magenta) toner, and a Y (yellow) toner as a holder that can rotate around a rotation axis. The Y developing unit is held at a position that is out of phase by a rotation angle of about 120 [°]. The developing color of the electrostatic latent image on the photoconductor 1 can be switched between C, M, and Y by moving any of the developing units to a development position facing the photoconductor 1 by the rotation of the holder. it can. By sequentially switching the developing devices that contribute to development, it is possible to form a C toner image, an M toner image, and a Y toner image on the photoreceptor 1. In addition, it is possible to make the development by the rotary developing device 6 ineffective by rotating the holding body to a position where none of the developing units is positioned at the development position.

  A Bk developing device 7 using Bk (black) toner is disposed above the rotary developing device 6 in the figure, and the electrostatic latent image on the photoreceptor 1 is developed to black to obtain a Bk toner image. be able to. The Bk developing device 7 generates an electrostatic latent image on the photosensitive member 1 by urging means such as a spring that urges the Bk developing device 7 away from the photosensitive member 1 and the abutting of the cam surface of the rotatable cam 45. It is possible to reciprocate between a position where development is possible and a position where development is impossible.

  The optical writing device 5 reflects laser light emitted from a light source such as a semiconductor laser (not shown) based on image information on a mirror surface on the side surface of a polygonal polygonal mirror 5B that is rotationally driven by a polygon motor 5A. By doing so, it is deflected in the main scanning direction (direction corresponding to the photosensitive member axial direction). Then, the surface of the photoconductor 1 is optically scanned by reaching the surface of the photoconductor 1 through the fθ lens 5C, the reflection mirror 5D, and the like.

  An endless intermediate transfer belt 10 is stretched by rotating rollers 11 and 12 on the right side of the photoconductor 1 in the drawing, and is endlessly moved in the counterclockwise direction in the drawing by the rotational drive of one of the rotating rollers. A transfer unit is provided. The transfer unit transfers the intermediate transfer belt 10 to the intermediate transfer belt region on the back side of the primary transfer nip while forming the primary transfer nip by bringing the front surface of the intermediate transfer belt 10 into contact with the front surface of the photoreceptor 1. A primary transfer means such as a brush is brought into contact with or in close proximity. By this primary transfer means, a primary transfer electric field is formed in the primary transfer nip to electrostatically move the toner of the toner image on the photoreceptor 1 from the photoreceptor 1 side to the intermediate transfer belt 10 side. The toner image on the photoreceptor 1 is primarily transferred onto the intermediate transfer belt 10 by the action of the primary transfer electric field and nip pressure.

  First, an electrostatic latent image for C is formed on the surface of the photoreceptor 1 by optical scanning of the optical writing device 5, and this is developed by the C developing device of the rotary developing device 6 to become a C toner image. . At this time, the Bk toner developing device 7 is retracted to a position where development is impossible. The C toner image developed on the photoreceptor 1 is primarily transferred onto the intermediate transfer belt 10 at the primary transfer nip.

  When the optical scanning for forming the C electrostatic latent image is completed, writing of the M electrostatic latent image by the optical scanning of the optical writing device 5 is started. Then, after the rear end of the electrostatic latent image for C on the photosensitive member 1 passes through the position facing the rotary developing device 6, the leading end of the electrostatic latent image for M on the photosensitive member 1 is positioned at the same opposing position. In the meantime, the holder of the rotary developing device 6 is rotated about 120 [°]. As a result, the M developing unit of the rotary developing device 6 moves to the developing position, and the electrostatic latent image for M can be developed with M toner. The M toner image developed on the photoreceptor 1 is primary-transferred superimposed on the C toner image on the intermediate transfer belt 10 at the primary transfer nip.

  When the optical scanning for forming the M electrostatic latent image is completed, writing of the Y electrostatic latent image by the optical scanning of the optical writing device 5 is started. Then, after the rear end of the electrostatic latent image for M on the photosensitive member 1 passes through the position facing the rotary developing device 6, the leading end of the electrostatic latent image for Y on the photosensitive member 1 is positioned at the same opposing position. In the meantime, the holder of the rotary developing device 6 is rotated about 120 [°]. As a result, the Y developing device of the rotary developing device 6 moves to the developing position, and the electrostatic latent image for Y can be developed with Y toner. The C toner image developed on the photoreceptor 1 is primarily transferred to the C and M toner images on the intermediate transfer belt 10 at the primary transfer nip.

  Although it is possible to reproduce black by superimposing the three colors C, M, and Y, in this printer, black with high output frequency is reproduced with black toner regardless of superposition. It has become. Therefore, when the optical scanning for forming the Y electrostatic latent image is completed, the writing of the K electrostatic latent image by the optical scanning of the optical writing device 5 is started. Then, after the rear end of the Y electrostatic latent image on the photosensitive member 1 passes through the position facing the rotary developing device 6, the front end of the K electrostatic latent image on the photosensitive member 1 is located at the same facing position. In the meantime, the holder of the rotary developing device 6 is rotated about 60 [°]. At substantially the same time, the rotation of the cam 45 causes the Bk developing device 7 to move to a position where development is possible. As a result, development processing by the rotary developing device 6 is stopped and development by the Bk developing device 7 becomes possible. The Bk toner image developed on the photoreceptor 1 is primarily transferred to the C, M, and Y toner images on the intermediate transfer belt 10 at the primary transfer nip.

  The transfer unit described above has secondary transfer means 14 such as a secondary transfer roller outside the loop of the intermediate transfer belt 10. The secondary transfer unit 14 is disposed so as to be in contact with or close to a portion where the intermediate transfer belt 10 is wound around the rotating roller 11 to form a secondary transfer position. As a result, a secondary transfer electric field for electrostatically moving the four-color superimposed toner image on the intermediate transfer belt 10 from the intermediate transfer belt 10 side to the secondary transfer means 14 side is formed at the secondary transfer position.

  At the bottom of the printer, there is a paper feed cassette 17 that holds a plurality of recording papers in a stack of sheets. The top recording paper is fed by the rotational drive of the paper feed roller 18. Send out to paper path 31. The fed recording paper is conveyed while being sandwiched between the conveyance nips of the conveyance roller pair 19 disposed in the paper feed path 31, and reaches the registration roller pair 20 disposed near the end of the paper feed path 31. . When the registration roller pair 20 sandwiches the leading edge of the recording paper in the registration nip, the rotational driving of both rollers is temporarily stopped. Then, the rotational driving of both rollers is resumed at a timing at which the recording paper can be superimposed on the four-color superimposed toner image on the intermediate transfer belt 10, and the recording paper is sent out toward the secondary transfer position.

  The four-color superimposed toner image is secondarily transferred collectively to the recording paper that is brought into close contact with the four-color superimposed toner image on the intermediate transfer belt 10 at the secondary transfer position by the action of the secondary transfer electric field described above.

  On the intermediate transfer belt 10 after the secondary transfer process, transfer residual toner that has not been secondarily transferred to the recording paper is adhered. This transfer residual toner is removed by the cleaning device 16 in which the cleaning blade 16A is in contact with the intermediate transfer belt 10 on the downstream side in the belt movement direction from the secondary transfer position.

  In the primary transfer process of superposition, the intermediate transfer belt is caused to travel at least four times to form a four-color toner image on the intermediate transfer belt 10. At this time, if the cleaning blade 16A is kept in contact with the intermediate transfer belt 10, the toner images of the respective colors primarily transferred onto the intermediate transfer belt 10 are removed from the belt surface by the cleaning blade 16A. A color superimposed toner image cannot be obtained. Therefore, this printer has a contact / separation mechanism (not shown) that moves the cleaning device 16 between a cleaning position where the cleaning blade 16A is brought into contact with the belt and a retracted position where the cleaning blade 16A is separated from the belt. In the primary transfer process of superposition, the cleaning device 16 is retracted to the retracted position. When the secondary transfer unit 14 that contacts the intermediate transfer belt 10 to form the secondary transfer nip is used, toner image transfer from the intermediate transfer belt 14 to the secondary transfer unit 14 is avoided. For the purpose, a contact / separation mechanism for separating the secondary transfer unit 14 from the belt is also required in the primary transfer process.

  The recording paper on which the full-color image is formed by batch secondary transfer of the four-color superimposed toner images at the secondary transfer position is sent to the fixing device 50 to fix the full-color image, and then the recording paper 51 It is discharged out of the machine via the discharge nip. And it is stacked on the stack part 52 formed outside the housing.

  The transfer residual toner scraped off from the surface of the intermediate transfer belt 10 by the cleaning device 16 is dropped into a collection container 15 disposed below the cleaning device 16 in the direction of gravity.

  FIG. 2 is a block diagram showing an electrical component in the printer together with a personal computer PC which is an external device. FIG. 3 is a block diagram showing the flow of image data in the electrical equipment section. As shown in FIG. 2, the electrical unit of the printer includes a communication processing device 101, a main memory 102, a CPU (Central Processing Unit) 103, an encoding device 110 that is an image data encoding device, and a decoding that is an image data decoding device. A device 140, a color processing device 170, an engine controller 180, a printer engine 190, and the like are provided.

  The communication processing apparatus 101 communicates with an external personal computer PC via a network cable, a printer cable, a wireless LAN, or the like. PDL (page description language) data is sent as multi-value image data from the personal computer PC to the communication processing apparatus 101. The PDL data received by the communication processing apparatus 101 is temporarily stored in the PDL data memory area 102 b of the main memory 102 and then sent to the CPU 103.

  The CPU 103 sends the obtained RGB band data to the RGB band data memory area 102c of the main memory 102 while dividing the PDL data sent from the PDL data memory area 102b into predetermined page areas. The RGB band data is sequentially sent to the encoding device 110 and subjected to encoding processing, and then is grouped for each page and sent to the encoded page memory area 102d of the main memory 102.

  The encoded page data for each page temporarily stored in the encoded page memory area 102 d is converted into RGB data for each page by the decoding processing by the decoding device 140 and then sent to the color processing device 170.

  As shown in FIG. 3, the color processing apparatus 170 includes an RGB → CMY color conversion processing unit 171, a UCR (Under Color Removal) processing unit 172, a gradation processing unit 173, and the like. The RGB data sent from the decoding device 140 to the color processing device 170 is converted from RGB format to CMY format by the RGB → CMY color conversion processing unit 171. The UCR processing unit 172 performs undercolor removal processing to reduce the amount of C, M, and Y toner attached to the Bk pixels of the image, and then performs gradation processing in the gradation processing unit 173. . Thereafter, the data is sent from the color processing apparatus 170 to the printer engine 190 via the engine controller 180. The printer engine 190 drives the optical writing device (5), the photoreceptor (1), various developing devices, the intermediate transfer belt (10), and the like based on the image information for each page sent from the engine controller 180. Control.

  FIG. 4 is a flowchart showing the flow of data processing in the encoding device 110. The encoding device 110 first executes a read process (step a: hereinafter, step is denoted as S) for reading the RGB band data stored in the RGB band data memory area (102c) of the main memory. Then, after executing the multi-value run-length encoding process (Sb) for encoding the read RGB band data into multi-value run-length data, the iterative encoding process (Sc) is executed. In this iterative encoding process (Sc), regular repetition of the same color and the same length run in the multi-value run length data is detected, and the RGB data (color information) and run length data of the run that repeatedly appear are repeated information. A process for repetitive encoding is performed. Thereafter, color information encoding processing (Sd) for encoding RGB data of each run in the multi-value run length data into index data and code format generation processing (Se) for generating a code format are executed. Further, after executing a code writing process (Sf) for temporarily writing codes based on a plurality of RGB band data in a storage area, the codes are collectively output in a predetermined number as encoded page data.

  FIG. 5 is a block diagram showing the main part of the internal configuration of encoding apparatus 110. As shown in the figure, the encoding device 110 includes a memory arbiter I / F 111 as a data storage unit, a hand data reading unit 112, and a band address generation unit 113. Also, the line memory control unit 114, the band data temporary storage unit 115, the multi-value run length encoding processing unit 116 as multi-value run length encoding means, the repetitive encoding processing unit 117 as repetitive encoding means, and color information encoding means A color information encoding processing unit 118 is also provided. Furthermore, it also includes a code format generation unit 119, an encoded band data writing unit 120, an encoded band address generation unit 121, an image quality mode setting unit 122, and the like.

  The band data reading unit 112 as reading means performs processing for reading RGB band data stored in the RGB band data memory area (102c) of the main memory as the first half of the image reading processing shown in FIG. Specifically, in FIG. 2 described above, the PDL data for one page sent from the personal computer PC to the electrical component of the printer is rendered in RGB for each band unit by the CPU (103), and a plurality of RGB data Band data. The RGB band data memory area 102c of the main memory 102 stores the RGB band data. The band data reading unit 112 shown in FIG. 5 reads the RGB band data in order from the top.

  The CPU (103) analyzes the PDL data sent from the personal computer PC and draws an RGB band. In the RGB band data stored in the RGB band data memory area (102c) of the main memory, information of each pixel is stored in the above-described order. For hardware reasons, the information of each pixel in the RGB band data in the RGB band data memory area (102c) cannot be read in an order different from the order described above. For this reason, the band data reading unit 112 shown in FIG. 5 reads the RGB band data in the order described above. Then, the information of each pixel of the RGB band is read by a predetermined number of horizontal lines. For example, as shown in FIG. 6, the leading pixel in line 0, the 0th horizontal line, the rearmost pixel, the leading pixel in line 1, the first horizontal line, and so on. Information of each pixel is read in the order of pixels.

  The code | symbol attached | subjected in each pixel of FIG. 6 has shown the color of the pixel, and the pixel with the same code | symbol is mutually the same color. In the conventional encoding apparatus, the run length of each run in the run length is determined in the reading order indicated by the arrows in FIG. Then, in the illustrated example, the run length is “3, 3, 4, 3, 1, 1, 2,..., 4, 4, 3, 1, 2.” The color information is “Ca, Cb, Cc, Cb, Cd, Cc... Ca, Cb, Cc, Cb, Cd, Cc”.

  On the other hand, the encoding device (110) of this printer temporarily stores the RGB band data read in the order shown in FIG. 6 and then generates run lengths while re-reading them in a different order. Yes. This process is the latter half of the image reading process (Sa) shown in FIG. 4, which is performed by the line memory control unit 114 and the band data temporary storage unit 115 shown in FIG. That is, in this printer, the combination of the line memory control unit 114 and the band data temporary storage unit 115 functions as a re-reading unit.

  In the re-reading by the re-reading means, in the pixel matrix of the read RGB band data, the process of scanning the pixels in the section where two or more pixels are arranged in the vertical direction and the horizontal direction in a predetermined order, This is performed in a predetermined order of division. As such scanning, for example, scanning in a zigzag direction as shown in FIGS. 7 and 8 can be exemplified. In the figure, after the pixel information for two lines is read in the horizontal line direction from the RGB band data, the pixel in the first column of line 0, the pixel in the first column of line 1, and the two columns of line 0 Scanning in a zigzag direction as indicated by an arrow in the figure is performed, such as the pixel of the eye, the pixel in the second column of line 1. As a result, the matrix partition region of 2 vertical pixels × 2 horizontal pixels is scanned from the first column toward the last column. Then, as shown in FIG. 9, the run length becomes “5, 7, 8, 8, 4...”, The run length of each run is nearly twice as large as before, and the number of runs is approximately halved. It becomes possible to make it. If the number of runs is reduced by half, the data capacity of the color information corresponding to each run will be reduced by half, so that significant savings in memory capacity can be expected.

  Note that the re-reading of the RGB data of each pixel into multi-value run length data is performed by the multi-value run length encoding processing unit 116 shown in FIG.

  Further, in FIG. 8, among the color information data represented by 9-digit numbers, the 3 digits from the left, the next 3 digits, and the next 3 digits represent the brightness of R, G, and B, respectively, from 000 to It is shown in 256 ways of 255.

  In addition, the example of performing re-reading while scanning in the zigzag direction has been described. It may be a direction scan. For example, the pixel in the first column of line 0, the pixel in the second column of line 0, the pixel in the first column of line 1, the pixel in the second column of line 1, the pixel in the third column of line 0, etc. It may be a scan in the direction. Also, a pixel in the first column of line 0, a pixel in the first column of line 1, a pixel in the second column of line 1, a pixel in the second column of line 0, a pixel in the third column of line 0, etc. It may be a scan in the meandering direction.

  The multilevel run length data obtained by the multilevel run length encoding processing unit 116 is repeatedly encoded (Sc in FIG. 4) by the iterative encoding processing unit 117. In this repetitive encoding process, regular repetition of the same color and the same length in the multi-value run length data is detected, and the repetitively appearing run is encoded into repetitive information. For example, it is assumed that the first to ninth runs have a multi-value run length as shown in FIG. In this multi-valued run length, the first run is a Cd color run consisting of four pixel blocks having a run length of 4. The second run is a Cc color run consisting of four pixel blocks with a run length of 4. The third, fifth and seventh runs have the same color and the same length as the first run. The fourth, fifth, and eighth runs have the same color and the same length as the second run. In such a multi-value run length, the pattern of the third to eighth runs is a pattern in which the first run and the second run are alternately repeated five times. Therefore, for the third to eighth runs, the run length and color information data are encoded into repetition information indicating five repetitions as shown. Thereby, the memory capacity can be further reduced.

  The multi-value run length data that has been subjected to the repetitive encoding process is subjected to the color information encoding process (Sd in FIG. 4) by the color information encoding processing unit 118 shown in FIG. Specifically, the electrical unit of this printer has a dictionary data storage circuit (not shown) as dictionary data storage means, and this dictionary data storage circuit is color information and index information of the color information. The dictionary data associated with the index value is stored. The color information encoding processing unit 118 encodes color information in each run of the multi-value run length data into an index value associated with the color in the dictionary data. As a result, the 9-digit color information, which requires a data capacity of 24 [bit] for each color, is converted into an index value that suffices with a data capacity of half or less, thereby further reducing the memory capacity.

  The multi-value run-length data that has been subjected to the color information encoding process is further encoded by the code format generation unit 119 shown in FIG. 5 into codes of a predetermined bit format such as run length, repetition information, and index value. Then, it is sent to the memory arbiter I / F 111 via the encoded band data writing unit 120. Then, it is output to the main memory arbiter 102F of the main memory as encoded page data collected for each page.

  FIG. 11 is a flowchart showing a flow of data processing performed by the multi-value run length encoding processing unit 116. In this data processing, first, after the run length data is set to the initial value “1” (S1), it is the first pixel of the run in the RGB data of each pixel re-read by the above-described re-reading means. A pixel located on the rear end side of the run with respect to the first pixel is compared with the first pixel as a target pixel in order from the front side. Then, it is sequentially determined whether or not the RGB data of the first pixel and the RGB data of the pixel of interest match (S2). In this determination, if it is determined that they match (Y in S2), “1” is added to the run length data (S3). On the other hand, if it is determined that they do not match (N in S2), the run length data and the corresponding RGB data (RGB data of the first pixel) are stored in the temporary storage area (S4). The long data is initialized to “1” (S5). After the process of S3 or S5, after determining whether or not the end of the line has been reached (S6), if the end of the line has been reached (Y in S6), a plurality of data stored in the temporary storage area After the multi-value run length data composed of the run length data and RGB data is output to the next process (S7), a series of processing flow is returned. If the line end has not been reached (N in S6), the target RGB data, which is the RGB data of the target pixel, is shifted by one to the rear end side of the run length (S8), and then the determination process of S2 is performed. Again. The multi-level run length encoding processing unit 116 includes an ASIC (Application Specific Integrated Circuit) for implementing the above-described series of processing flows in hardware.

  FIG. 12 is a flowchart showing the flow of data processing performed by the iterative encoding processing unit 117. In this flow, run length data indicating the run length of each run in the multi-value run length data and an RGB data string indicating the RGB data of each run are processed in parallel. The run length data is used in a determination process (S1) for determining whether the run lengths match or do not match between the target run included in the run length and the run that is two positions before the run. If the run lengths match (Y in S1), the run length repeat flag is set to 1 (S2), but if they do not match (N in S1), the run length repeat flag is set to 0. (S3). On the other hand, the RGB data string is a determination process for determining whether or not the RGB data matches or does not match between the RGB data of the target run included in the RGB data string and the RGB data of the run two positions before this. Used for S4). If the RGB data match (Y in S4), the color repetition flag is set to 1 (S5), whereas if they do not match (N in S4), the color repetition flag is set to 0 ( S6).

  When the parallel processing of the groups S1 to S3 and the groups S4 to S6 is completed, it is next determined whether or not both the run length repeat flag and the color repeat flag are 1 (S7). If it is determined that at least one of them is not 1 (N in S7), it is determined whether or not the line end has been reached. If the line end has been reached (Y in S8), a series of Is returned. If the end of the line has not been reached (N in S8), the target run and the previous two runs are shifted one by one to the lower side (S9), and the parallel processing described above is performed again. To be implemented.

  On the other hand, if it is determined in the determination process of S7 that any of the repetition flags is 1 (Y in S7), the run length data of the target run and the corresponding RGB data indicate that it is a repeated run. The encoded data is encoded (S10). And after the process of S8-S9, the parallel process mentioned above is implemented again. The iterative encoding processing unit 117 includes an ASIC for performing the above-described series of processing flows in hardware.

  FIG. 13 is a conceptual diagram showing dictionary data stored in the dictionary data storage circuit described above. In the figure, the dictionary data is RGB data indicated by 9-digit numbers 010030045, 100150200, 105030060, 101020050, 025060050,..., 100200230, 0, 1, 2, 3, 4,. It is stored in association with an index value of n.

  The color information encoding processing unit 118 shown in FIG. 5 encodes the RGB data of each run into an index value by MTF (Move To Front) method while referring to such dictionary data. Specifically, first, it is determined whether or not the RGB data of the target pixel is stored in the dictionary data. In the illustrated example, RGB data of a 9-digit pixel of interest of 010020050 is stored in the dictionary data in association with an index value of 3. Then, the color information encoding processing unit 118 encodes the RGB data of the target pixel into an index value of 3. Next, as shown in FIG. 14, the index value of the RGB data in the same dictionary data as the RGB data of the target pixel is set to 0 which is the highest value. At the same time, the index values of the RGB data (010030045, 100150200, 105030060 in the illustrated example) associated with the higher index values than the previous index values in the RGB data are shifted one by one.

  On the other hand, when the RGB data of the target pixel is not stored in the dictionary data, the data is output to the next process as it is without being encoded into an index value. Further, as shown in FIG. 15, the RGB data 100200230 associated with n which is the lowest index value in the dictionary data is deleted from the dictionary data. Next, after shifting the index values of the remaining RGB data one by one downward, the dictionary is created by associating the RGB data 100200230 previously determined not to be stored in the dictionary data with the highest index value of 0 Write to data.

  In such a configuration, dictionary data can be reliably stored in the limited memory capacity of the dictionary data storage circuit. Instead of the MTF method, a FIFO (First-In First-Out) method may be adopted.

  The color information encoding processing unit 118 uses a comparison circuit that compares the RGB data of the run in the multi-value run length data and the RGB data in the dictionary data, and stores the number of RGB data (dictionary RGB data) in the dictionary data ( N). Then, by these comparison circuits, the process of comparing the RGB data of one run with all the dictionary RGB data in the dictionary data is performed in parallel.

  FIG. 16 is a block diagram showing an example of the circuit configuration of the dictionary management unit in the color information encoding processing unit (118). In the figure, the dictionary management unit includes an addition & update control device 119a, a register unit 118b, a comparison circuit group 118c, an index generation device 118d, a control device 118e, and the like. The register unit 118b includes a plurality of RGB data registers for storing RGB data, a repetition data register for storing repetition data, and a run-length data register for storing run-length data. Yes. The comparison circuit group 118c has a plurality of comparison circuits.

  The above dictionary data is composed of N + 1 RGB data from RGB data 0 to RGB data N, and RGB data 0 which is the first RGB data is stored in the RGB data 0 register. Also, RGB data 1 as the second RGB data is stored in the RGN data 1 register. Also, RGB data N, which is the (N + 1) th RGB data, is stored in the RGB data N register. Thus, the RGB data register has N + 1 RGB data registers, and different RGB data are stored in the respective RGB data registers.

  The comparison circuit group 118c includes N + 1 comparison circuits (COMP 0 to COMP N). COMP 0 compares the RGB data stored in the RGB data 0 register with the RGB data of the pixel of interest, and outputs information indicating whether or not they match. COMP 1 compares the RGB data stored in the RGB data 1 register with the RGB data of the pixel of interest, and outputs information indicating whether or not they match. COMP N compares the RGB data stored in the RGB data N register with the RGB data of the pixel of interest, and outputs information indicating whether or not they match.

  The RGB data of the pixel of interest in the RGB band data is first input to each comparison circuit (COMP 0 to COMP N) in the comparison circuit group 118c. At the same time, RGB data in the RGB data 0 register, RGB data 1 register,... RGB data N register are input to COMP 0, COMPM 1. Is judged. The RGB data 0 register, RGB data 1 register,..., RGB register N correspond to index 0, index 1,. When there is a match result, the index generation device 118d outputs the COMP number corresponding to the result as an index value, as shown in the flowchart of FIG. For example, if the output from COMP 3 is a match, “3” is output as the index value.

  This index value is output not only to the code format generation unit (119) but also to the addition & update control device 118a. As shown in the flowchart of FIG. 18, the add & update control device 118a shifts the FLAG to the multiplexer (MUX) provided individually for each RGB data register based on the received index value. Output data. Specifically, when the index value received from the index generation device 118d is a value corresponding to any of the RGB data registers, a multiplexer corresponding to the RGB register, and a higher order than this. The shift FLAG data is output to the multiplexer corresponding to the RGB register (except the RGB data 0 register). If no index value is sent from the index generator 118d, that is, if the RGB data of the pixel of interest does not match any RGB data in the dictionary, shift FLAG data is output to all the multiplexers. To do.

  The RGB register that has received the shift FLAG data from the add / update control device 118a, the multiplexer stores the RGB data stored in the RGB register that is one level higher than the RGB register that corresponds to itself. Then, it is rewritten as RGB data in the RGB register corresponding to itself. In addition, the RGB data in the RGB data 0 register is rewritten to the RGB data of the target pixel regardless of whether or not it matches the target pixel. Thereby, the dictionary data is updated by the MTF method.

  The multi-value run length data output from the color information encoding processing unit 118 shown in FIG. 5 is encoded by the code format generation unit 119 into the bit format shown in FIG. 19 and output to the memory arbiter I / F 111. Is done.

  FIG. 20 is a flowchart showing the flow of data processing in the decryption apparatus 140 shown in FIG. The decoding device 140 decodes the encoded page data into RGB data by a flow reverse to the data processing flow by the encoding device 110. Specifically, first, a code reading process (Sg) for reading the encoded page data stored in the encoded page memory area (102d) of the main memory is executed. Then, after executing the code format analysis process (Sh) for analyzing the code format of the read encoded page data, color information decoding for decoding the index value in the multi-value run length data into RGB data Process (Si) is executed. Next, after performing iterative decoding processing (Sj) for decoding the repetition information in the multi-value run length data into run length and RGB data, the run length data and RGB data in each run of the multi-value run length data Is subjected to RGB band decoding processing (Sk) for decoding the data into RGB band data. Thereafter, the RGB band data is output to its own memory arbiter I / F 111 by the band data writing process (Sl), and then written to the main memory as RGB data collectively for each page.

  FIG. 21 is a block diagram illustrating a main part of the internal configuration of the decoding device 140. As shown in the figure, the decoding device 140 includes an RGB band code reading unit 141, an RGB band code address generating unit 142, a code format analyzing unit 143, a color information decoding processing unit 144, an iterative decoding processing unit 145, A value image decoding processing unit 146, a memory arbiter I / F 149, and the like are included.

  The RGB band code reading unit 141 reads the encoded page data in order from the top, and passes it to the code format analysis unit 143. The multi-value run length data whose code format has been analyzed by the code format analysis unit 143 is decoded into RGB data by the color information decoding processing unit 144 serving as color information decoding means. Next, each repetition information is decoded into a plurality of run lengths and RGB data by the iterative decoding processing unit 145 serving as an iterative decoding means, and then transferred to the multi-value image decoding processing unit 146. A multi-value image decoding processing unit 146 as multi-value image decoding means decodes the multi-value run length data sent from the iterative decoding processing unit 145 into RGB band data. The arrangement of the individual pixels in the RGB band data is an arrangement in the zigzag direction by scanning of the line memory control unit (114) of the encoding device. In such an arrangement, since processing by the printer engine cannot be performed, it is necessary to convert the arrangement in the horizontal line direction.

  Therefore, the line memory control unit 146 of the decoding device 140 writes the information of each pixel of the RGB band data in the zigzag direction in the 2-line virtual matrix area of the RGB line data storage unit 148 as shown in FIG. Go. When the writing for two lines is completed, as shown in FIG. 23, each pixel information in the two-line virtual matrix area is read in the horizontal line direction and sequentially output to the memory arbiter I / F.

  The color information decoding processing unit 144 illustrated in FIG. 21 shares dictionary data with the color information encoding processing unit 118 illustrated in FIG. Specifically, the dictionary data storage circuit stores a plurality of dictionary data individually corresponding to the plurality of RGB band data, and each dictionary data includes RGB band data that contributes to encoding. Address information is associated. The color information decoding processing unit 144 detects the address information of the multilevel run length data sent from the line memory control unit 114, and uses the corresponding dictionary data to calculate the index value in the multilevel run length data. Decode into RGB data. At this time, as shown in FIG. 24, the index value in the multi-value run length data is decoded into RGB data having the same index value in the dictionary data. Next, as shown in FIG. 25, the index value of the RGB data in the dictionary data is set to 0, which is the highest value, and is associated with a higher index value than the previous index value of the RGB data. The index value of the RGB data that has been shifted is shifted down by one. Through such processing, a plurality of index values encoded by the color information encoding processing unit 118 of the encoding device 110 shown in FIG. 5 can be decoded into RGB data, respectively.

  FIG. 26 is a block diagram illustrating an example of a circuit configuration of the dictionary management unit in the color information combination processing unit (144). This dictionary management unit performs a dictionary update process as shown in FIG. 27 with the same configuration as the dictionary management unit of the color information encoding processing unit (118) shown in FIG. Update by method.

  FIG. 28 is a block diagram illustrating an example of a circuit configuration in the iterative combination processing unit 145. As shown in the figure, the iterative combination processing unit 145 repeats the repetitive data, run length data, and RGB data output from the color information composite processing unit (not shown), and the run length data from which the repetitive codes are removed. To RGB data.

Next, a characteristic configuration of the printer will be described.
In FIG. 5 described above, the image quality mode setting unit 122 of the encoding device 110 changes the image quality mode in the encoding process in the multi-value run length encoding processing unit 116 from the normal image quality mode and the image quality based on the operation by the user. It plays a role of switching between modes. Specifically, when a mode switching command is issued by a user operating an operation panel (not shown), or when a mode switching command is issued from a personal computer as printer driver setting information, the CPU displays mode setting information corresponding to the commanded mode. The data is sent to the memory arbiter I / F 111. The image quality mode setting unit 122 reads the mode setting information sent to the memory arbiter I / F 111 during the encoding process by the encoding device 110, and sends it to the multi-value run length encoding processing unit 116 as mode data. Further, when the set mode is the normal image quality mode, the data of the maximum difference threshold value, the total difference threshold value, and the run length upper limit value stored in advance in the memory arbiter I / F 111 is read, and these are also multivalued. This is sent to the run-length encoding processing unit 116.

  The encoding process by the multi-value run length encoding processing unit 116 described so far is executed when the high image quality mode is set. When the mode data sent from the image quality mode setting unit 112 is data in the normal image quality mode, the multilevel run length encoding processing unit 116 performs an encoding process slightly different from that described above. To do.

  FIG. 29 is a flowchart showing the flow of encoding processing by the multi-value run length encoding processing unit 116 when the normal image quality mode is set. In this flow, first, after the mismatch flag is set to zero (S1), ORG-RGB data (RGB data of the first pixel) and RGB data of interest in the RGB data of each pixel re-read by the above-described re-reading means. The R difference, which is the difference between the R components, and the G difference, which is the difference between the G components, and the B difference, which is the difference between the B components, are obtained (S2 to S6). Next, a difference sum that is the sum of these three differences and a maximum difference value that is the maximum value among the three differences are obtained (S7, S8). When the ORG-RGB data and the target RGB data match, that is, when the first pixel and the target pixel are the same color, the R difference, the G difference, the B difference, the difference sum, and the maximum difference value are all 0. Become.

  Thereafter, when the ORG-RGB data matches the target RGB data (Y in S11), 1 is added to the run length (S14). Even if the two do not match (N in S11), if the maximum difference value is smaller than the predetermined maximum difference threshold value and the total difference is smaller than the predetermined total difference threshold value (Y in S9). 1 is added to the run length (S14). However, even if the maximum difference value is smaller than the predetermined maximum difference threshold value and the total difference is smaller than the predetermined total difference threshold value, if the run length exceeds the run length upper limit value (S13) Y), the run length is output without being counted up (S15). With this output, the top pixel and the target pixel are divided into separate runs.

  Further, when the ORG-RGB data and the target RGB data do not match and the maximum difference value is equal to or larger than the predetermined maximum difference threshold value, or when the difference does not match and the total difference is smaller than the predetermined total difference threshold value Regardless of the relationship between the run length and the run length upper limit value, the run length is output. With this output, the top pixel and the target pixel are divided into separate runs.

  In addition, when the ORG-RGB data and the target RGB data include the same and all the RGB data in the run including the ORG-RGB data and the target RGB data match, the run length upper limit value is affected. Instead, 1 is added to the run length. Therefore, if all the pixels have the same color, the run length may be longer than the run length upper limit of 6.

  In the encoding process for the normal image quality mode described above, when the RGB data of the first pixel and the target pixel that are continuous with each other match each other, or when the color difference between both pixels is within the allowable range even if they do not match. Also, both pixels are regarded as the same run and reflected in the run length. As a result, the encoded data is irreversible and has a slightly different image quality from the original image. However, the run length in each run is increased and the number of runs is reduced, which is higher than before. It can be encoded with a compression rate.

  Also, even if the color difference between the first pixel and the target pixel is within the allowable range, if the run length exceeds the run length upper limit value, the following situation can be avoided by dividing both pixels into separate runs. can do. That is, in an image in which the color gradually changes with a slight color difference toward a predetermined hue over a wide range, all of the wide range become the same color.

  For reference, FIG. 30 shows a block diagram illustrating an example of a circuit configuration capable of executing the flow of FIG. 29 in hardware.

  FIG. 31 is a schematic diagram for explaining the relationship between the re-read RGB band data and the multi-value run length data corresponding thereto. In the figure, the color information of each pixel is scanned in a zigzag direction as indicated by arrows in the figure. More specifically, the color information is reproduced in the order of the pixel in the first column of line 0, the pixel in the first column of line 1, the pixel in the second column of line 0, the pixel in the second column of line 1, and so on. It will be read. In the figure, the leftmost run is composed of six pixels arranged in a color arrangement of Cd1, Cd1, Cd1, Cd2, Cd1, and Cd1. The color of the fourth pixel in this run is Cd2, and although it has a slight color difference from Cd1 of other pixels, it is within the allowable range, and therefore is grouped as the same run. The run color is stored as Cd1 of the first pixel.

  In the figure, the second run from the left is composed of six pixels arranged in a color sequence of Cd1, Cd2, Cd2, Cd1, Cd1, and Cd1. The color of the first pixel of this run is Cd1, which is the same as the color of the last pixel in the leftmost run. Originally, these two pixels should be combined into one run. However, in this printer, when two or more pixels having acceptable color differences are combined into one run, The upper limit is limited to 6 (S13 in FIG. 29). For this reason, these pixels are divided into separate runs.

  In the figure, the third run from the left is composed of eight pixels arranged in a color sequence of Ca, Ca, Ca, Ca, Ca, Ca, Ca, and Ca. Since all the pixels have the same color, even if the length exceeds the run length upper limit value of 6, those eight pixels are combined into one run.

  FIG. 32 is a schematic diagram for explaining the multi-value run length data when the RGB band data of FIG. 31 is combined. In the same figure, the pixels in the second column of line 1 were originally in the color Cd2, but as a result of being combined into one color run Cd1 as shown in FIG. 31, they were combined into a color Cd1. The

  In the encoding process shown in FIG. 29, as the color difference between the first pixel and the target pixel, the difference between the R components that are the first primary color components of both pixels in the RGB color representation method, the second original Although the sum of the difference between the G component as the color component and the difference between the B component as the third primary color component is obtained, other three primary colors may be employed. For example, instead of RGB, a color expression method using the three primary colors YMY may be employed. Further, a method different from the color expression method using the three primary colors may be adopted. For example, as the color difference, difference data based on the brightness difference and the hue difference between the head pixel and the target pixel in the color expression method based on the brightness and the hue may be employed. As such a color expression method, the Lab method is widely known. In this method, colors are expressed by lightness (L), hue from green to red (a), and hue from blue to yellow (b). For reference, FIG. 33 shows a processing flow in encoding processing employing the Lab method. The overall data processing flow in the encoding device 140 is shown in FIGS.

  Up to this point, a description has been given of a printer having a structure in which toner images of different colors sequentially formed on the photosensitive member 1 are transferred onto the intermediate transfer belt 10 to obtain a multicolor image. The present invention can also be applied to an image forming apparatus that forms an image. That is, a tandem method is used in which toner images of different colors respectively developed on the surfaces of a plurality of latent image carriers are transferred onto a transfer body such as a recording sheet. Further, although an example in which the present invention is applied to an electrophotographic printer has been described, the present invention can also be applied to an image forming apparatus that forms a color image by a direct recording method. This direct recording method is not related to the latent image carrier, but forms a pixel image by directly adhering a toner group that has been ejected in a dot shape from a toner flying device to a recording medium or an intermediate recording medium. In this method, a toner image is directly formed on an intermediate recording medium. It is employed in the image forming apparatus described in JP-A No. 2002-307737. The invention can also be applied to an image forming apparatus that forms a color image by an inkjet method.

  As described above, the encoding apparatus 110 of the printer according to the embodiment detects a regular repetition of the same color and the same length run in the multi-value run length data and encodes the repeatedly appearing run into the repetition information. An iterative encoding processing unit 117 serving as a conversion unit is provided. In such a configuration, as already described, by encoding run length data and RGB data of runs that repeatedly appear in the same color and length, the multi-value image data is compressed at a higher compression rate. Further, the memory capacity can be further reduced.

  In the printer encoding apparatus 110 according to the embodiment, the dictionary data that stores only a predetermined number of RGB data (color information) is used. Then, it is determined whether or not the RGB data of each run in the multi-value run length data is stored in the dictionary data. If it is stored, the RGB data is encoded into an index value. If not stored, the RGB data is output as it is without being encoded, and after deleting one of the other RGB data in the dictionary data, the RGB data that could not be encoded is The color information encoding processing unit 118 serving as color information encoding means is configured to execute processing for writing in the dictionary data. In such a configuration, dictionary data can be reliably stored in a limited memory capacity of the dictionary data storage circuit.

  In addition, when the color information encoding processing unit 118 of the encoding apparatus 110 of the printer according to the embodiment determines that the RGB data of each run in the multi-value run length data is stored in the dictionary data, respectively. In the dictionary data, the RGB data associated with the index value higher than the previous index value of the RGB data while setting the index value of the RGB data to 0, which is the highest value, in the dictionary data The process of shifting the index value of 1 to the lower position is executed. On the other hand, if it is determined that it is not stored in the dictionary data, the RGB data associated with the lowest index value in the dictionary data is deleted from the dictionary data and the remaining RGB data index values Are shifted one by one to the lower order, and RGB data that has been previously determined not to be stored in the dictionary data is written to the dictionary data in association with the highest index value. In such a configuration, the index value after encoding the RGB data having a relatively high appearance frequency is made smaller than the index value after encoding the RGB data having a relatively low appearance frequency, thereby further reducing the memory capacity. Can be achieved.

  In addition, in the color information encoding processing unit 118 of the encoding apparatus 110 of the printer according to the embodiment, the RGB data of the run in the multi-value run-length data is individually separated from the different RGB data stored in the dictionary data. A plurality of comparison circuits are provided as a plurality of comparison units for comparison. In such a configuration, the encoding processing speed from RGB data to the index value can be increased as compared with the case where only one comparison circuit is provided.

  Also, in the printer encoding apparatus 110 according to the embodiment, a band data reading unit 112 serving as a reading unit that reads pixel information in RGB band data, which is multi-valued image data, by a predetermined number of horizontal lines, is read by this. Re-reading means (line memory control unit 114 and band data temporary storage) for re-reading the pixel information so as to sequentially scan the matrix partition area in which a plurality of pixels are arranged in the vertical direction and the horizontal direction in the group of the selected pixels. Part 115). And the multi-value run length encoding process part 116 which is a multi-value run length encoding means is comprised so that the information re-read by the re-read means may be encoded into multi-value run length data. In such a configuration, by reflecting the vertical and horizontal alignments of the pixels in the run length, the compression rate of the image data compared to a conventional encoding device that reflects only the horizontal alignment in the run length. To further reduce the memory capacity.

  Also, in the printer decoding apparatus 140 according to the embodiment, color information decoding that decodes the index value generated by the color information encoding processing unit 118 of the encoding apparatus 110 into RGB data based on dictionary data. A color information decoding processing unit 144, multi-valued run-length data having decoded RGB data and corresponding run lengths, are decoded into multi-valued image data RGB band data. A multi-value image decoding processing unit 146 as a value image decoding unit. With such a configuration, multi-value run length data encoded by the encoding device 110 including the color information decoding processing unit 118 can be decoded into RGB band data.

  In the printer decoding apparatus 140 according to the embodiment, the repetition information encoded by the iterative encoding processing unit 117 serving as the iterative encoding unit of the encoding apparatus 110 is converted into run lengths and RGB data of a plurality of runs. An iterative decoding processing unit 145 is provided as iterative decoding means for decoding. With such a configuration, multi-value run length data encoded by the encoding device 110 including the iterative code processing unit 117 can be decoded into RGB band data.

  Also, in the printer decoding apparatus 140 according to the embodiment, the index value in the data that has passed through the color information encoding processing unit 118 of the encoding apparatus 110 is converted into the RGB corresponding to the index value in the dictionary data. After decoding into data, while setting the index value of the RGB data to the highest value, the index value of the RGB data associated with the index value higher than the previous index value of the RGB data is changed. The color information decoding processing unit 144 is configured to execute a process of shifting down by one. In such a configuration, the multi-value run length data encoded by the encoding device 110 including the color information encoding processing unit 118 can be decoded into RGB band data.

  Also, in the printer decoding device 140 according to the embodiment, the two-line virtual matrix area, which is a pixel area having a predetermined number of horizontal lines, is partitioned so that a plurality of pixels are arranged in the vertical and horizontal directions. The multi-value run length data encoded by the multi-value run length encoding processing unit 116 of the encoding device 110 is sequentially developed for a plurality of matrix partition areas, and then the multi-value run length data is converted into units of horizontal lines. Re-reading means (line memory control unit 146 and RGB line data storage unit 148) is provided for re-reading so as to scan. In such a configuration, pixel information is arranged in a format that cannot be processed by the printer engine (zigzag alignment), and information on each pixel in the multi-value run length data is converted into a pixel alignment (horizontal line alignment) that can be processed by the printer engine. Then, it can be transferred to the printer engine.

1 is a schematic configuration diagram illustrating a printer according to an embodiment. The block diagram which shows the electrical equipment part in the printer with personal computer PC which is an external apparatus. The block diagram which shows the flow of the image data in the same electrical equipment part. The flowchart which shows the flow of the data processing in the encoding apparatus of the same electrical equipment part. The block diagram which shows the principal part of the internal structure of the encoding apparatus. The schematic diagram for demonstrating the data scan of a horizontal line direction. The schematic diagram for demonstrating the data scan of a zigzag direction. The schematic diagram which shows the state which scans RGB band data in a zigzag direction. The schematic diagram for demonstrating the relationship between the RGB band data scanned in the zigzag direction, and the multi-value run length data corresponding to this. The schematic diagram for demonstrating the relationship between the RGB band data in the repetition encoding process, and the repetition information corresponding to this. The flowchart which shows the flow of the data processing performed by the multi-value run length encoding process part of the encoding apparatus. The flowchart which shows the flow of the data processing performed by the repetition encoding process part of the encoding apparatus. The conceptual diagram which shows the dictionary data stored in the dictionary data storage circuit. The conceptual diagram for demonstrating the index update process of the dictionary data by MTF method based on the dictionary data. The conceptual diagram for demonstrating the data addition process and index update process of the dictionary data by MTF method based on the dictionary data. The block diagram which shows an example of the circuit structure of the dictionary management part in a color information encoding process part. The flowchart which shows the processing flow in an index production | generation process. The flowchart which shows the processing flow in a dictionary update process. The conceptual diagram which shows the code format by the code format production | generation part of the encoding apparatus. The flowchart which shows the flow of the data processing in the decoding apparatus of the printer. The block diagram which shows the principal part of the internal structure of the decoding apparatus. The schematic diagram for demonstrating the expansion | deployment process of the RGB band data with respect to 2 line virtual matrix area | region performed by the line memory control part of the decoding apparatus. The schematic diagram for demonstrating the rereading direction of the RGB band data after an expansion | deployment process. The schematic diagram for demonstrating the decoding process from the index value to RGB data performed by the color information decoding process part of the decoding apparatus. The schematic diagram for demonstrating the index update process of the dictionary data performed by the same color information decoding process part. The block diagram which shows an example of the circuit structure of the dictionary management part in a color information composite process part (144). The flowchart which shows the processing flow in the dictionary update process implemented by the dictionary management part. The block diagram which shows an example of the circuit structure in the repetition composite process part 145. FIG. 6 is a flowchart showing a flow of encoding processing by a multi-value run length encoding processing unit when the normal image quality mode is set. The block diagram which shows an example of the circuit structure which can perform the flow of FIG. 29 by hardware. The schematic diagram for demonstrating the relationship between the re-read RGB band data and the multi-value run length data corresponding to this. The schematic diagram for demonstrating the multi-value run length data at the time of the RGB band data of FIG. 31 being compounded. The flowchart which shows the process flow in the encoding process which employ | adopted the Lab system. The flowchart which shows the whole data processing flow in the encoding apparatus. FIG. 30 is a flowchart showing a continuation of FIG. 29. FIG.

Explanation of symbols

110: Encoding device (image data encoding device)
112: Band data reading unit (reading means)
114: Line memory control unit (part of re-reading means)
115: Band data temporary storage unit (part of re-reading means)
116: Multi-level run length encoding processing unit (multi-level run length encoding means)
117: Repetitive encoding processing unit (repetitive encoding means)
118: Color information encoding processing unit (color information encoding means)
140: Decoding device (image data decoding device)
144: Color information decoding processing unit (color information decoding means)
145: Iterative decoding processing unit (iterative decoding means)
146: Multilevel image decoding processing unit (multilevel image decoding means)
147: Line memory control unit (part of re-reading means)
148: RGB line data storage unit (part of re-reading means)

Claims (8)

Reading means for reading color information of individual pixels in multi-valued image data, and multi-value run length data indicating at least color information and its run length based on the color information read by the reading means. In an image data encoding device comprising a value run length encoding means,
In the process of comparing the pixel located on the rear end side of the run with respect to the first pixel as the first pixel of the run from the first side as the target pixel in order, the color information of the first pixel and the target pixel is mutually compared. If they match, or if they do not match and the color difference between the two pixels is within the allowable range, the run length is obtained with both pixels as the same run, while the color difference between the two pixels does not match and the color difference is within the allowable range An image data encoding apparatus characterized in that the multi-value run length data encoding means is configured to execute a process for obtaining a run length when both pixels are separate runs when they are outside. The image data encoding device according to claim 1, wherein
Even if the color information of the first pixel and the pixel of interest do not match each other and the color difference between the two pixels is within the allowable range, the run length when both pixels are set to the same run has an upper limit. An image data encoding apparatus characterized in that the multi-value run length data encoding means is configured to execute a process for obtaining a run length when both pixels are separated from each other when the number of pixels exceeds the maximum number. In the image data encoding device according to claim 1 or 2,
As the color difference, the sum of the difference of the first primary color component, the difference of the second primary color component, and the difference of the third primary color component between the first pixel and the target pixel in the color representation method using three primary colors is calculated. An image data encoding device comprising the multi-value run length data encoding means as described above. The image data encoding device according to any one of claims 1 to 3,
As the color difference, a difference between a first primary color component, a second primary color component difference, and a third primary color component difference between the first pixel and the target pixel in the color representation method using three primary colors, An image data encoding apparatus comprising the multi-value run length data encoding means for obtaining a maximum difference. In the image data encoding device according to claim 1 or 2,
The multi-value run length data encoding means is configured to obtain difference data based on the lightness difference and hue difference between the first pixel and the target pixel in the color expression method by lightness and hue as the color difference. An image data encoding device. Image data acquisition means for acquiring multivalued image data, image data encoding means for encoding the image data acquired by the image data acquisition means, and decoding of the data encoded by the image data encoding means An image forming apparatus comprising: an image data decoding unit that converts the image data; and an image forming unit that forms an image based on the multivalued image data decoded by the image data decoding unit.
An image forming apparatus using the image data encoding device according to claim 1 as the image data encoding means. A reading process for reading color information of individual pixels in multi-valued image data, and a multi-value run length data indicating at least color information and its run length based on the color information read in the reading process. An image data encoding method for performing a value run length encoding step,
In the above multi-value run length encoding process, in the process of comparing the pixel located on the rear end side of the run with respect to the first pixel, which is the first pixel of the run, as the target pixel in order from the first side, If the color information of the target pixel matches that of the target pixel, or if the color difference between the two pixels is not within the allowable range, the run length is calculated with the two pixels as the same run, but the two match. In addition, when the color difference between the two pixels is out of the allowable range, the run length is obtained by using the two pixels as separate runs. In an image forming method in which multi-valued image data is encoded by an image data encoding method and then decoded by an image data decoding method, and then an image is formed based on the decoded image data.
8. The image forming method according to claim 7, wherein the image data encoding method according to claim 7 is used as the image data encoding method.

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