JP2010220127A - Image processing apparatus and method, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently compress and encode image data having attribute information for every pixel. <P>SOLUTION: Encoding of image data is performed using predictive encoding and run-length encoding. In generating run length, the change of attribute data corresponding to the image data is detected, a run-length value of the image data is terminated at a change point of the attribute data to encode the run-length value, and the encoded run-length value and a code representing the attribute data are output to a code string of 1. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image processing apparatus, an image processing method, and a program for compressing and encoding image data and decoding the compression-encoded image data.

  In an image forming apparatus such as a printer, input image data is temporarily stored in a memory, and the image data stored in the memory is read at a predetermined timing to perform a printing operation. In this case, if the image data is stored in the memory as it is, a large-capacity memory is required and the cost of the apparatus increases. Therefore, generally, input image data is compression-encoded and stored in a memory.

  By the way, in order to output a color image with good image quality by a printer device, a color image or a natural image (image) such as a photographic image, a graphic or a line drawing (thin line) generated by a computer, a character that varies depending on the type of image, Halftone processing is required. That is, in order to output an image in which different types of images are mixed, a means for performing optimum image processing for each type of image is required. Therefore, conventionally, attribute information indicating the type of image represented by a pixel is added to the image data of each CMYK plate and supplied to the printer apparatus.

  Various methods have been proposed for processing this attribute information. Patent Document 1 discloses a technique for reading an extended image in which an attribute value is added to a pixel and encoding it into one code in one data unit in which the pixel and the attribute information are integrated. Patent Document 2 discloses a technique for embedding attribute information in lower bits of a part of color components (for example, R component) of RGB pixel values when compressing RGB pixels, and compressing the RGB pixels by different compression methods according to the attribute values. It is disclosed.

  In Patent Document 3, image data is separated based on attribute values to generate a plurality of images, and the generated images are compressed by different encoding devices so that the attribute values need not be compressed. Technology is disclosed.

  Patent Document 4 discloses a technology for compressing and encoding attribute information at a high compression rate by packing the attribute information in units of a plurality of pixels. Further, in this Patent Document 4, the drawn multi-value plane data is encoded for each CMYK plate by the compression unit, and the drawn attribute data is encoded by another compression unit. The point that the code | symbol of the multi-value plane image for every version and the code | symbol of an attribute value are decoded sequentially is described.

  Patent Document 5 describes that printing is performed by decoding a code of each plate by a decoding device for each plate in synchronism with the engine of each plate of CMYK during image formation.

  On the other hand, Patent Document 6 describes a technique for compressing image data using run-length encoding. According to Patent Document 6, for example, FIG. 21-2 illustrates a print image in which different types of images such as characters, graphics, and photographic images are mixedly disposed as illustrated in FIG. As shown, the attribute value indicating the image type is run-length encoded.

  The attribute information encoding according to Patent Document 6 will be described in more detail with reference to FIG. The attribute information is associated with each pixel as exemplified by the C version in FIG. In the example of FIG. 22-1, the attribute value indicating the attribute information is 0 to 3 and indicates whether the pixel is a background attribute, a graphics attribute, a character attribute, or a photograph attribute. FIG. 22-2 illustrates an example in which attribute information is encoded using a run length. In this example, the code data of the attribute information is configured by repeatedly arranging an attribute header indicating the start position of the attribute value, the attribute value, and a run length value of the attribute value.

  According to Patent Document 4 and Patent Document 5 described above, rendered multi-value plane data is encoded for each CMYK plate, and printing is performed in synchronization with the print engine of each CMYK plate at the time of decoding. The print engines for each of the CMYK plates sequentially operate with a predetermined delay. Therefore, it is necessary to read the same attribute data from the memory for each version of CMYK.

  Therefore, in Patent Document 4 and Patent Document 5, four DMACs (Direct Memory Access Controllers) for reading attribute codes from the memory for each version of CMYK and 4 for reading image codes from the memory for each version of CMYK. A total of 8 DMACs of the DMACs are required, and there is a problem that the apparatus scale and cost increase.

  In Patent Documents 4 and 5, a decoding device that decodes attribute codes and a decoding device that decodes image codes are required for each version of CMYK. That is, according to Patent Document 4 and Patent Document 5, it is necessary to prepare a total of eight decoding apparatuses, and this also causes a problem that the apparatus scale and cost increase.

  Furthermore, according to Patent Document 4 and Patent Document 5, when decoding at the time of printing, the same attribute code is transferred to the bus at each printing timing of each CMYK plate, so that the bus transfer is wasted. There was a problem that there was. In particular, at the time of printing, since the transfer of multi-value plane data of each version of CMYK must reliably catch up with the processing speed of the printer engine, the waste of bus transfer at the time of decoding at the time of printing must be minimized.

  Furthermore, according to Patent Document 2, since attribute information is embedded in the lower bits of some color components of the RGB pixel values when compressing RGB pixels, the embedded attribute information becomes noise and causes a reduction in image quality. There was a problem that it was. In addition, since the RGB pixels and the attribute values are compressed by different compression methods, it is necessary to prepare a large number of DMACs and decoding devices as in the above-mentioned Patent Literature 4 and Patent Literature 5, which increases the device scale and cost. There was a problem of being invited.

  On the other hand, according to Patent Document 3, compression of attribute values is unnecessary by compressing a plurality of images generated by separating image data by attribute values using different encoding devices. However, the method of Patent Document 3 has a problem in that the number of decoding devices corresponding to the number of types of attribute values is required for each version of CMYK, resulting in an increase in device size and cost. For example, when there are four types of attribute values, four decoding devices are required for each version of CMYK, and it is necessary to prepare 16 decoding devices for the entire device.

  In addition, the total code amount obtained by encoding each of the plurality of separated images is expected to be larger than the code amount when the image is encoded as one image without being separated. Therefore, a large-capacity memory is also required for storing the compression-encoded image data, which increases the cost of the apparatus.

  In Patent Document 1, since attribute information and image information are encoded as one piece of information, the number of DMACs required is increased and the apparatus scale is increased as in the case of Patent Document 4 and Patent Document 5 described above. The problem of doing does not occur. However, since the extended image in which the bit width of the pixel information for adding the attribute value is expanded is encoded, this Patent Document 1 has a problem that the compression encoding process itself becomes difficult.

  That is, for example, when attribute information having a bit width of 2 bits is added to image information having a bit width of 8 bits, the bit width of the extended image becomes 10 bits. However, since general hardware is designed on the assumption that processing is performed in units of 8 bits such as 8 bits and 16 bits, data having a bit width that is not a multiple of 8 bits such as 10 bits is efficiently used. In order to handle it efficiently, a device is required.

  Further, when an extended image in which attribute information is added to image information is handled, a problem may occur particularly when predictive encoding is performed. That is, when bits of attribute information are added to lower bits of pixel data, even if the image is gentle, the value of the lower bits that are the attribute information part in the pixel data does not change unless the attributes of the image change. It will be. Therefore, it is assumed that the change of the pixel data is a change of 2 bits at least, and prediction such as the planar prediction method does not work well.

  On the other hand, it is also conceivable to add a bit of attribute information to the upper bits of pixel data. In this case, if the attribute value of the image does not change, it is considered that prediction such as the plane prediction method works well. However, when the attribute value of the image changes, the pixel data changes, for example, in units of 8 bits corresponding to the pixel data. Even in this case, it is assumed that the prediction using the planar prediction method does not function well. The Therefore, it is considered difficult to increase the compression rate basically.

  The present invention has been made in view of the above, and it is an object of the present invention to provide an image processing apparatus, an image processing method, and a program that can efficiently compress and encode image data having attribute information for each pixel.

  In order to solve the above-described problems and achieve the object, the first invention is an image processing apparatus that encodes pixel data and attribute data corresponding to the pixel data, and generates a run length based on the pixel data. A run length generating means, an encoding means for encoding the run length generated by the run length generating means, and attribute data; and a detecting means for detecting a change in attribute data corresponding to the pixel data, The encoding unit encodes the run length generated by the run length generation unit and initializes the run length when a change in the attribute data is detected by the detection unit, and encodes the attribute data after the change. And the encoded run length are output as one code string.

  The second invention is an image processing method for encoding pixel data and attribute data corresponding to the pixel data, and includes a run length generation step for generating a run length based on the pixel data, and a run length generation step. An encoding step for encoding the generated run length and attribute data; and a detection step for detecting a change in attribute data corresponding to the pixel data. The encoding step includes a change in attribute data by the detection step. Is detected, the run length generated in the run length generation step is encoded and the run length is initialized, and the code indicating the changed attribute data and the encoded run length are set as one code. It is characterized by outputting in columns.

  In the third invention, a run length generated based on pixel data and encoded in accordance with a change in attribute data corresponding to the pixel data, and a code indicating the changed attribute data in one code string An image processing apparatus that decodes included code data, a code processing unit that obtains pixel data, a run length, and attribute data based on the code data, and a length indicated by a run length obtained by the code processing unit, The pixel data output means for outputting the pixel data obtained by the code processing means and the attribute obtained by the code processing means synchronously with the pixel data output means for the length indicated by the run length obtained by the code processing means. And attribute data output means for outputting data.

  According to a fourth aspect of the present invention, a run length generated based on pixel data and encoded in accordance with a change in attribute data corresponding to the pixel data, and a code indicating the changed attribute data in one code string An image processing method for decoding the included code data, a code processing step for obtaining pixel data, run length, and attribute data based on the code data, and a length indicated by the run length obtained by the code processing step, A pixel data output step for outputting pixel data obtained by the code processing means, and a code processing step in synchronism with the output of the pixel data by the pixel data output step by the length indicated by the run length obtained by the code processing step. And an attribute data output step for outputting the attribute data obtained by the above.

  According to the first and second aspects of the present invention, when the run length generated based on the pixel data and the attribute data corresponding to the pixel data are encoded, a change in the attribute data corresponding to the pixel data is detected. If the generated run length is encoded, the run length is initialized and the code indicating the changed attribute data and the encoded run length are output as one code string. Therefore, the image data having attribute information for each pixel can be efficiently compressed and encoded.

  According to the third and fourth aspects, the pixel data, the run length, and the attribute data are obtained based on the code data, and the pixel data is output for the length indicated by the run length, and the length indicated by the run length is determined. Since the attribute data is output synchronously with the output of the pixel data, the run length generated based on the pixel data and encoded in accordance with the change of the attribute data corresponding to the pixel data, and the post-change There is an effect that it is possible to decode the code data included in the code string having one code indicating the attribute data.

FIG. 1 is a schematic diagram illustrating a configuration example of a mechanism unit of an image forming apparatus to which an image processing apparatus according to an embodiment of the present invention can be applied. FIG. 2 is a block diagram illustrating an exemplary configuration of the transmission / control apparatus. FIG. 3A is a schematic diagram illustrating an exemplary format of the CMYKA band data area in the main memory. FIG. 3B is a schematic diagram illustrating an exemplary format of the CMYKA band data area in the main memory. FIG. 4A is a schematic diagram for specifically explaining the CMYK image and attribute information of each version of CMYK. FIG. 4B is a schematic diagram for specifically explaining the CMYK image and attribute information of each version of CMYK. FIG. 4C is a schematic diagram for specifically explaining the CMYK image and the attribute information according to each version of CMYK. FIG. 4-4 is a schematic diagram for specifically explaining the CMYK image and attribute information of each version of CMYK. FIG. 4-5 is a schematic diagram for specifically explaining the CMYK image and attribute information of each version of CMYK. FIG. 5 is a flowchart of an example schematically showing image processing in the color printer having the above-described configuration. FIG. 6 is a schematic diagram illustrating an example of a data flow related to encoding processing in the color printer having the above-described configuration. FIG. 7 is a schematic diagram illustrating an example of a data flow regarding decoding and printing processing in the color printer having the above-described configuration. FIG. 8 is a flowchart for explaining that band data encoding is performed while incorporating band data of attribute A for each version of CMYK. FIG. 9 is a flowchart illustrating an example of decoding and printing processing for one plate. FIG. 10 is a functional block diagram illustrating an example of the operation of the CMYK + A encoding unit according to the embodiment of the present invention. FIG. 11 is a schematic diagram for explaining pixels used in planar prediction. FIG. 12A is a schematic diagram illustrating a format of an example of a code generated by the code format generation processing unit. FIG. 12-2 is a schematic diagram illustrating a format of an example of a code generated by the code format generation processing unit. FIG. 13A is a schematic diagram illustrating a configuration example of a prediction error code, a PASS code, an attribute code, and a run-length code. FIG. 13-2 is a schematic diagram illustrating a configuration example of a prediction error code, a PASS code, an attribute code, and a run-length code. FIG. 14 is a flowchart illustrating an example of encoding processing according to the present embodiment, which is performed by the CMYKA encoding unit. FIG. 15A is a schematic diagram for specifically explaining an example of the encoding process according to the embodiment of the present invention. FIG. 15-2 is a schematic diagram for specifically explaining an example of the encoding process according to the embodiment of the present invention. FIG. 16A is a schematic diagram for explaining another example of the encoding process according to the embodiment of the present invention. FIG. 16B is a schematic diagram for explaining another example of the encoding process according to the embodiment of the present invention. FIG. 17 is a block diagram illustrating an exemplary configuration of a CMYKA encoding unit according to the present embodiment. FIG. 18 is a functional block diagram illustrating an example of the operation of the C + A decoding unit 7 according to the embodiment of the present invention. FIG. 19 is a flowchart illustrating an example of a decoding process performed on the code data encoded by the encoding process according to the present embodiment, which is performed by the C + A decoding unit 7. FIG. 20 is a block diagram showing an example of the configuration of the C + A decoding unit 7 according to the embodiment of the present invention. FIG. 21A is a schematic diagram for explaining encoding of attribute values according to the conventional technique. FIG. 21B is a schematic diagram for explaining encoding of attribute values according to the conventional technique. FIG. 22-1 is a schematic diagram for explaining encoding of attribute values according to the prior art. FIG. 22-2 is a schematic diagram for explaining encoding of attribute values according to the prior art.

  Exemplary embodiments of an image processing apparatus according to the present invention will be described below in detail with reference to the accompanying drawings. First, the image processing according to the present invention will be conceptually described. In the present invention, encoding of pixel data is performed using predictive encoding and run-length encoding. When the run length is generated, a change in the attribute data is detected, the run length value of the pixel data is terminated at the change point of the attribute data, the run length value is encoded, and the encoded run length value and the attribute data are encoded. Are output for one code string. Pixel data and attribute data can be composed of one code string, and only one DMAC for decoding is required for each version of CMYK. In addition, since the run-length code of attribute data is unnecessary, higher compression efficiency can be expected.

<Configuration of image processing apparatus applicable to this embodiment>
Next, the best embodiment of the image processing apparatus according to the present invention will be described in detail. FIG. 1 shows an example of the structure of a mechanism part of an image forming apparatus (referred to as a color printer) to which an image processing apparatus according to an embodiment of the present invention can be applied. In this embodiment, an example in which the image processing apparatus and the image processing method according to the present invention are applied to an image forming apparatus that is a color printer will be described. However, as long as image processing is performed on an image including a character image, However, the present invention is not limited to this. For example, the present invention can be applied to an image processing apparatus such as a copying machine, a facsimile machine, and a multifunction machine.

  A color printer 100 illustrated in FIG. 1 forms images of four colors (Y, M, C, K) by independent image forming systems 1Y, 1M, 1C, and 1K, and synthesizes these four color images. This is a 4-drum tandem engine type image forming apparatus. Each of the image forming systems 1Y, 1M, 1C, and 1K includes a photoconductor as an image carrier, for example, small-diameter OPC (organic photoconductor) drums 2Y, 2M, 2C, and 2K, and the OPC drums 2Y, 2M, and 2C. The electrostatic latent images on the charging rollers 3Y, 3M, 3C, and 3K as charging means and the OPC drums 2Y, 2M, 2C, and 2K are developed with a developer from the upstream side of image formation so as to surround 2K. Developing devices 4Y, 4M, 4C, and 4K that generate toner images of Y, M, C, and K colors, cleaning devices 5Y, 5M, 5C, and 5K, and static eliminating devices 6Y, 6M, 6C, and 6K are arranged. .

  Beside each developing device 4Y, 4M, 4C, 4K, toner bottle units 7Y, 7M, 7C, 7K for supplying Y toner, M toner, C toner, K toner to the developing devices 4Y, 4M, 4C, 4K, respectively. (The image forming systems 1Y, 1M, 1C, and 1K are respectively provided with independent optical writing devices 8Y, 8M, 8C, and 8K. The optical writing devices 8Y, 8M, 8C, and 8K are Optical components such as laser diode (LD) light sources 9Y, 9M, 9C, and 9K as laser light sources, collimating lenses 10Y, 10M, 10C, and 10K, fθ lenses 11Y, 11M, 11C, and 11K, and polygon mirrors as deflection scanning means 12Y, 12M, 12C, and 12K, and folding mirrors 13Y, 13M, 13C, 13K, 14Y, 14M, 14C, and 14K.

  The image forming systems 1Y, 1M, 1C, and 1K are arranged vertically, and the transfer belt unit 15 is arranged on the right side so as to be in contact with the OPC drums 2Y, 2M, 2C, and 2K. The transfer belt unit 15 is rotationally driven by a drive source (not shown) with the transfer belt 16 stretched around rollers 17 to 20. A paper feed tray 21 storing transfer paper as a transfer material is disposed on the lower side of the apparatus, and a fixing device 22, a paper discharge roller 23, and a paper discharge tray 24 are disposed at the top of the apparatus.

  At the time of image formation, in each image forming system 1Y, 1M, 1C, 1K, the OPC drums 2Y, 2M, 2C, 2K are rotationally driven by a driving source (not shown), and the OPC drums by the charging rollers 3Y, 3M, 3C, 3K. The 2Y, 2M, 2C, and 2K are uniformly charged, and the optical writing devices 8Y, 8M, 8C, and 8K perform optical writing on the OPC drums 2Y, 2M, 2C, and 2K based on the image data of each color, so that the OPC drum Electrostatic latent images are formed on 2Y, 2M, 2C, and 2K.

  The electrostatic latent images on the OPC drums 2Y, 2M, 2C, and 2K are developed by developing devices 4Y, 4M, 4C, and 4K, respectively, to become toner images of colors Y, M, C, and K, while the paper feed tray 21 Then, the transfer paper is fed in the horizontal direction from the paper feed roller 25 and is conveyed vertically in the image forming systems 1Y, 1M, 1C and 1K by the transport system. This transfer paper is electrostatically held by the transfer belt 16 and conveyed by the transfer belt 16, and a transfer bias is applied by a transfer bias applying means (not shown), and Y on the OPC drums 2Y, 2M, 2C, 2K, A full color image is formed by sequentially superimposing and transferring toner images of M, C, and K colors. The transfer sheet on which the full-color image is formed is fixed to the full-color image by the fixing device 22 and is discharged to the discharge tray 24 by the discharge roller 23.

  The control of each part in the color printer 100 described above is performed by the electrical / control device 26.

  FIG. 2 is a block diagram illustrating an exemplary configuration of the transmission / control apparatus 26. The transmission / control apparatus 26 includes a control unit 750, a main memory 751, an image processing unit 752, and a panel control unit 753.

  The control unit 750 includes a CPU 701, a CPU I / F 702, a memory arbiter (ARB) 703, a memory controller 704, a DMAC (Direct Memory Access Controller) 705, a bus controller 706, and a communication controller 707. The CPU 701 is connected to the memory arbiter 703 via the CPU I / F 702, the bus 734 is connected via the bus controller 706, and the main memory 751 is connected via the memory controller 704. The memory controller 704 controls access to the main memory 751. Further, a DMAC 705, a communication controller 707, and a ROM (Read Only Memory) 731 are connected to the memory arbiter 703. The memory arbiter 703 arbitrates access to the main memory 751 by the CPU 701, DMAC 705, communication controller 707, and bus 734.

  The CPU 701 accesses the ROM 731 via the CPU I / F 702 and the memory arbiter 703, reads and executes a program stored in advance in the ROM 731, and controls the overall operation of the color printer 100. The ROM 731 stores font information such as characters in advance in addition to various programs executed by the CPU 701.

  The communication controller 707 controls communication performed via the network 761. For example, PDL (Page Description Language) data output from the computer 760 is received by the communication controller 707 via the network 761. The communication controller 707 transfers the received PDL data to the main memory 751 via the memory arbiter 703 and the memory controller 704.

  Note that the network 761 may perform communication within a predetermined range such as a LAN (Local Area Network), or may be capable of communicating over a wider range than the Internet. The network 761 is not limited to wired communication but may be wireless communication, or serial communication such as USB (Universal Serial Bus) or IEEE (Institute Electrical and Electronics Engineers) 1394.

  The main memory 751 has a CMYKA band data storage area 751A and a page code storage area 751B. The CMYKA band data storage area 751A stores CMYK version band data and attribute A band data. Further, the page code storage area 751B stores a page code obtained by encoding the band data of each version of CMYK into the band data of the attribute A and coding in pixel units.

  Although not shown, the main memory 751 further has a PDL data storage area for storing PDL (Page Description Language) data supplied from the computer 760, for example.

  For example, the CPU 701 performs drawing based on the PDL data supplied from the computer 760 to generate multi-value band data for each of the CMYK versions and also generate attribute A band data. The generated multi-value band data of each CMYK version and the band data of attribute A are stored in the CMYKA band data storage area 751A of the main memory 751 via the memory arbiter 4.

  The bus controller 706 arbitrates access to the bus 734 by each unit connected to the bus 734. A control unit 750 is connected to the bus 734, and an image processing unit 752 and a panel control unit 753 are connected.

  The panel control unit 753 is made of, for example, an ASIC (Application Specific Integrated Circuit), and includes a bus I / F 729 and a panel control unit 730. An operation panel 737 provided with various operators and display elements is connected to the panel control unit 730. The panel control unit 730 communicates with the control unit 750 via the bus I / F 729 and the bus 734, and transmits a control signal corresponding to a user operation performed on the operation panel 737 to the control unit 750, or by the CPU 701. Based on the display control signal generated and transmitted from the control unit 750, the display element provided in the operation panel 737 is driven.

  The image processing unit 752 is made of, for example, an ASIC, and performs image processing of an image to be printed by the C plate printer engine 738, the M plate printer engine 739, the Y plate printer engine 740, and the K plate printer engine 741.

  In the image processing unit 752, the bus arbiter 708 is connected to the C + A version code DMAC 713, the M + A version code DMAC 714, the Y + A version code DMAC 715, the K + A version code DMAC 716, the CMYK version image DMAC 709, the attribute DMAC 710, and the CMYK + A version code DMAC 712. The communication with the bus 734 of each unit is arbitrated.

  The CMYK image DMAC 709 is a band of one of the C, M, Y, and K plates (referred to as the C plate) from the CMYKA band data storage area 751A of the main memory 2 via the bus 734 and the control unit 750. Data is read and transferred to the CMYK + A encoding unit 711. Similarly, the attribute DMAC 710 reads the band data of attribute A from the CMYKA band data storage area 751A of the main memory 751 via the bus 734 and the control unit 750, and transfers it to the CMYK + A encoding unit 711.

  The CMYK + A encoding unit 711 encodes, for example, the band data of the C version transferred from the CMYK version image DMAC 709 and the band data of the attribute A transferred from the attribute DMAC 710 according to a method to be described later to form one code string. Generate. This code generated by the CMYK + A encoding unit 711 is stored in the page code storage area 751B of the main memory 751 by the CMYK + A version code DMAC 712 via the bus 734 and the control unit 750.

  In the following description, a code generated from the C version band data and the attribute A band data is referred to as a C + A version band code. Similarly, the band data of the M, Y, and K plates are also referred to as the M + A plate band code, the Y + A plate band code, and the K + A plate band code, respectively. In the following, in order to avoid complications, the processing for each of the C plate, the M plate, the Y plate, and the K plate will be described as a representative of the processing of the C plate unless otherwise specified.

  The C + A version code DMAC 713 reads the C + A version band code from the page code storage area 751 </ b> B of the main memory 751 via the bus 734 and the control unit 750, and transfers it to the C + A decoding unit 717. The C + A decoding unit 717 decodes the C plane image data and the attribute value from the transferred C + A plane band code by a method described later, and supplies the decoded data to the C plane gradation processing unit 721. The C plane gradation processing unit 721 performs gradation processing on the C plane image data based on the supplied C plane image data and attribute values, and supplies the processed data to the C plane engine controller 725. The C plane engine controller 725 controls the C plane printer engine 738 based on the supplied C plane image data.

  For the M + A version band code, the Y + A version band code, and the K + A version band code, the same processing as that of the C + A version band code is performed. That is, the M + A version code DMAC 714 reads the M + A version band code from the page code storage area 751 B of the main memory 751 and transfers it to the M + A decoding unit 718. The M + A decoding unit 718 decodes the M plate image data and the attribute value from the transferred M + A plate band code, and supplies the decoded image data to the M plate gradation processing unit 722. The M plate gradation processing unit 722 performs gradation processing on the M plate image data based on the supplied M plate image data and attribute values, and supplies the processed image data to the M plate engine controller 726. The M plane engine controller 726 controls the M plane printer engine 739 based on the supplied M plane image data.

  The Y + A version code DMAC 715 reads the Y + A version band code from the page code storage area 751B of the main memory 751 and transfers it to the Y + A decoding unit 719. The Y + A decoding unit 719 decodes the Y plane image data and attribute values from the transferred Y + A plane band code, and supplies the decoded data to the Y plane gradation processing unit 723. The Y plane gradation processing unit 723 performs gradation processing on the Y plane image data based on the supplied Y plane image data and attribute values, and supplies the processed data to the Y plane engine controller 727. The Y plane engine controller 727 controls the Y plane printer engine 740 based on the supplied Y plane image data.

  The K + A version code DMAC 716 reads the K + A version band code from the page code storage area 751B of the main memory 751 and transfers it to the K + A decoding unit 720. The K + A decoding unit 720 decodes the K plate image data and the attribute value from the transferred K + A plate band code, and supplies the decoded data to the K plate gradation processing unit 724. The K plate gradation processing unit 724 performs gradation processing on the K plate image data based on the supplied K plate image data and attribute values, and supplies the processed data to the K plate engine controller 728. The K plate engine controller 728 controls the K plate printer engine 741 based on the supplied K plate image data.

  FIG. 3 shows an exemplary format of the CMYKA band data storage area 751A in the main memory 751. As illustrated in FIG. 3-1, the CMYKA band data storage area 751A has a plane configuration for each of the C, M, Y, and K plates, and 8 bits are allocated to each pixel. It is done. That is, the CMYK band data is a multi-value plane image in which each pixel has a bit depth of 8 bits.

  As shown in FIG. 3-2, the attribute A uses 2 bits out of 8 bits, and attribute information indicating attributes common to the C, M, Y, and K plates is displayed for each pixel. Stored in association. In the example of FIG. 3B, a 2-bit value (referred to as an attribute value) indicating attribute information is “00”, indicating that the corresponding pixel has a background attribute. Similarly, the attribute values “01”, “10”, and “11” indicate that the corresponding pixels have a graphics attribute, a character attribute, and a photo attribute, respectively.

  The CMYK image and attribute information of each CMYK plate will be described more specifically with reference to FIG. FIG. 4A illustrates an example of a CMYK image based on CMYK image data. In this example, the CMYK image is a mixture of photographic images, characters, and graphics images. FIG. 4B illustrates an area having the attribute of a photographic image in the CMYK image illustrated in FIG. FIG. 4C illustrates an area having character attributes in the CMYK image illustrated in FIG. FIG. 4-4 illustrates an area having graphics image attributes in the CMYK image illustrated in FIG. 4-5 conceptually shows an example of attribute information corresponding to the CMYK image of FIG. 4-1. The attribute information is set, for example, exclusively for the areas based on the attributes exemplified in FIGS. 4-2 to 4-4.

<Outline of image processing applicable to this embodiment>
FIG. 5 is a flowchart of an example schematically illustrating image processing in the color printer 100 having the above-described configuration. FIG. 6 shows an example of a data flow related to the encoding process in the flowchart of FIG. Similarly, FIG. 7 shows an example of a data flow related to the decoding and printing processing in the flowchart of FIG.

  For example, PDL data generated by the computer 760 is received by the communication controller 707 via the network 761 and stored in a PDL data storage area (not shown) of the main memory 751 (step S1). The CPU 701 reads PDL data from the PDL data storage area of the main memory 751, analyzes the PDL (step S2), and draws CMYK plates and attribute A band images in units of planes based on the analysis result (step S3). .

  The drawn CMYKA band data based on the drawn CMYK plates and the band image of attribute A is transferred to the memory controller 704 via the memory arbiter 703 in the next step S4, and controlled by the memory controller 704, the CMYK band of the main memory 751. It is stored in the data storage area 751A (path A in FIG. 6). As described above, the CMYKA band data includes multi-value plane image data in which each pixel has a bit depth of 8 bits, and attribute information corresponding to each pixel using 2 bits out of 8 bits.

  The CMYK version image DMAC 709 reads the CMYK band data from the CMYKA band data storage area 751A via the bus 734, and transfers the data to the CMYK + A encoding unit 711 (path B in FIG. 6). Although details will be described later, the CMYK version image DMAC 709 reads one version of band data (C version in the example of FIG. 6) from the CMYKA band data storage area 751A and transfers it to the CMYKA encoding unit 11. Further, the attribute DMAC 710 reads the band data of attribute A from the CMYKA band data storage area 751A via the bus 734, and transfers it to the CMYKA encoding unit 11 (path C in FIG. 6). The CMYK + A encoding unit 711 encodes the transferred CMYK band data and attribute A band data according to the encoding method of the present invention (step S5).

  Code data obtained by encoding the CMYK band data and the attribute A band data is supplied to the main memory 751 via the bus 734 in the next step S6, and is controlled by the memory controller 704 in the page code storage area 751B. Stored for each version (path D in FIG. 6).

  Hereinafter, the C version data will be described for the decryption process. For each of the M, Y, and K data, the same processing as the C data described below is sequentially performed following the processing for the C data.

  The C + A version code DMAC 713 reads the C + A version band code from the page code storage area 751B via the bus 734, and transfers it to the C + A decoding unit 717 (path E in FIG. 7). The C + A decoding unit 717 decodes the transferred C + A plane band code into C plane image data and attribute values, and transfers them to the C plane gradation processing unit 721 according to the path F in FIG. 7 (step S7). The C plate gradation processing unit 721 performs gradation processing on the C plate image data based on the C plate image data and the attribute value transferred from the C + A decoding unit 717 (step S8). The gradation-processed C plane image data is supplied to the C plane engine controller 725 along the path G in FIG. 7 (step S9). The C plate printer engine 738 performs printing based on the C plate image data supplied through the path H.

  As described above, the encoding of the band data stored in the CMYKA band data storage area 751A is performed while incorporating the band data of the attribute A for each version of CMYK. This point will be described with reference to the flowchart of FIG. First, in step S10, the CPU 701 draws CMYK band data and attribute A band data in units of planes. The drawn CMYK band data and attribute A band data are stored in the CMYK band data storage area 751A of the main memory 751.

  In the next step S <b> 11, the CMYK plane image DMAC 709 reads the C plane band data and the attribute A band data from the CMYKA band data storage area 751 </ b> A and transfers them to the CMYK + A encoding unit 711. The CMYK + A encoding unit 711 encodes the transferred C band data and attribute A band data. The C + A version band code obtained by encoding the C version band data and the attribute A band data is stored in the page code storage area 751B of the main memory 751.

  Thereafter, in steps S12 to S14, the band data of M plate to K plate and the band data of attribute A are encoded in the same manner. That is, in step S12, the M plane band data and the attribute A band data are read from the CMYKA band data storage area 751A by the CMYK plane image DMAC 709, transferred to the CMYK + A encoding unit 711, and encoded. The M + A version band code obtained by encoding the M version band data and the attribute A band data is stored in the page code storage area 751B of the main memory 751.

  Similarly, in the next step S13, the Y plane band data and the attribute A band data are read from the CMYKA band data storage area 751A by the CMYK plane image DMAC 709, transferred to the CMYK + A encoding unit 711, and encoded. The The Y + A version band code obtained by encoding the Y version band data and the attribute A band data is stored in the page code storage area 751B of the main memory 751.

  Further, in the next step S14, the band data of the K plate and the band data of the attribute A are read from the CMYKA band data storage area 751A by the CMYK plate image DMAC 709, transferred to the CMYK + A encoding unit 711, and encoded. . The K + A version band code obtained by encoding the K version band data and the attribute A band data is stored in the page code storage area 751B of the main memory 751.

  FIG. 9 is a flowchart showing an example of decoding and printing processing for one plate (C plate in this example). In step S20, the C + A version code DMAC 713 reads one C + A version band code from the page code storage area 751B in synchronization with the C version printer engine 738, and transfers it to the C + A decoding unit 717. In the next step S21, the C + A decoding unit 717 decodes the C + A version band code transferred from the C + A version code DMAC 713 to obtain C version image data and attribute values in units of pixels. The C plane image data and attribute values are transferred to the C plane gradation processing unit 721.

  The C plate gradation processing unit 721 performs predetermined gradation processing on the C plate image data transferred from the C + A decoding unit 717. At this time, the C plane gradation processing unit 721 switches gradation processing according to the attribute value transferred from the C + A decoding unit 717 together with the C plane image data. The C plane image data subjected to gradation processing by the C plane gradation processing unit 721 is supplied to the C plane engine controller 725. The C plate engine controller 725 controls the C plate printer engine 738 according to the supplied C plate image data to print the C plate (step S23).

  In the next step S24, it is determined whether or not the processing for one band of the C plate has been completed. If it is determined that the processing has not been completed, the process returns to step S20, and the same processing is performed for the next code. The process is repeated. On the other hand, if it is determined in step S24 that the processing for one band of the C plate has been completed, a series of processing is ended, and the processing of the next plate (for example, the M plate) is performed in the same manner as in the case of the C plate. It starts at the timing of

  In this way, in the decoding process, one code is read, the plate image data and the attribute value are decoded, and transferred to the gradation processing device.

<Outline of Encoding Processing According to Embodiment of the Present Invention>
FIG. 10 is a functional block diagram illustrating an example of the operation of the CMYK + A encoding unit 711 according to the embodiment of the present invention. The image reading processing unit 200 reads CMYK band data from the CMYKA band data storage area 751A of the main memory 751. The reading of the CMYK band data by the image reading processing unit 200 is performed in units of pixels for each scan line for each of the CMYK plates. The image reading processing unit 200 transfers the read band data to the line memory control processing unit 201.

  The line memory control processing unit 201 stores the band data transferred from the image reading processing unit 200 in the line memory 202. The line memory 202 can store band data for at least two lines, stores the data supplied this time, and holds the data for one line stored immediately before. To be controlled.

  For example, the line memory 202 has first and second areas each capable of storing pixels for one line. For example, the line memory control processing unit 201 sets the line so that the pixel data for which encoding has been completed is switched between the first and second areas every time encoding of pixel data for one line is completed. Controls access to the memory 202.

  The line memory control processing unit 201 reads out pixel data of a pixel to be encoded (hereinafter referred to as a target pixel) and pixel data of three pixels around the target pixel from the line memory 202. Here, the three neighboring pixels from which pixel data is read from the line memory 202 are scanned with respect to the immediately preceding pixel a in the scan order of the target pixel and the current line to which the target pixel belongs, as illustrated in FIG. The pixel b located immediately above the pixel of interest and the pixel c just before in the scan order of the pixel of interest in the immediately preceding previous line (the line immediately above the line to which the pixel of interest belongs).

  Pixel data of the surrounding three pixels a, b, and c of the pixel of interest read from the line memory 202 is transferred to the prediction processing unit 203. The pixel data of the target pixel read from the line memory 202 is transferred to the prediction error processing unit 204.

The prediction processing unit 203 calculates a predicted value P by plane prediction according to the following formula (1) based on the pixel values of the peripheral pixels transferred from the line memory control processing unit 201, and predicts the pixel value of the target pixel. Data indicating the calculated predicted value P is transferred to the prediction error processing unit 204.
P = a + b-c (1)

  The prediction error processing unit 204 is based on the data indicating the prediction value P transferred from the prediction processing unit 203 and the pixel data of the target pixel transferred from the line memory control processing unit 201, and the predicted value for the pixel value of the target pixel A prediction error value that is an error of P is obtained. The prediction error data indicating the prediction error value is transferred to the run length generation processing unit 205 together with the pixel data indicating the pixel value of the target pixel.

  On the other hand, the attribute read processing unit 206 reads the attribute A band data (hereinafter referred to as attribute data) from the CMYKA band data storage area 751 A of the main memory 751 and transfers it to the attribute change detection processing unit 207. The reading of attribute data by the attribute reading processing unit 206 is performed in synchronism with the reading of CMYK band data by the image reading processing unit 200 described above in units of pixels.

  The attribute change detection processing unit 207 detects a change in the attribute value indicated in the attribute data transferred from the attribute read processing unit 206. When a change in the attribute value is detected, the attribute change detection processing unit 207 transfers attribute data indicating the attribute value after the change to the run length generation processing unit 205.

  The run length generation processing unit 205 generates a run length based on the prediction error data transferred from the prediction error processing unit 204 and the attribute data transferred from the attribute change detection processing unit 207. More specifically, when the prediction error value indicated by the prediction error data is “0”, the run length generation processing unit 205 increases the run length value by 1 to increase the length of the prediction error value to “0”. The run length value is generated by counting. On the other hand, when the prediction error value is other than “0”, the run length generation processing unit 205 converts the prediction error data indicating the prediction error value and the run length data indicating the run length value into a pixel indicating the pixel value of the target pixel. The data is transferred to the code format generation processing unit 208 together with the data.

  In addition, the run length generation processing unit 205 executes the run when there is a change in the attribute value even when the prediction error value is “0”, that is, when the attribute data is transferred from the attribute change detection processing unit 207. Stop length generation. Then, the attribute data, the prediction error data indicating the prediction error value, and the run length data indicating the run length value are transferred to the code format generation processing unit 208 together with the pixel data indicating the pixel value of the target pixel.

  The code format generation processing unit 208 performs encoding based on the run length data, prediction error data, attribute data, and pixel data of the target pixel transferred from the run length generation processing unit 205 to generate code data. The generated code data is transferred to the code writing unit 209.

  More specifically, the code format generation processing unit 208 encodes the run length value indicated by the run length data transferred from the run length generation processing unit 205 according to the format of the run length code described later with reference to FIG. To do. Also, if the prediction error value indicated by the prediction error data transferred from the run length generation processing unit 205 is a value within a predetermined range, encoding is performed according to the format of a prediction error code described later with reference to FIG. If the prediction error value is outside the predetermined range, the pixel value of the corresponding pixel is used as a code. Furthermore, when the attribute value changes, that is, when the attribute data is transferred from the run length generation processing unit 205, the attribute value indicated by the attribute data is encoded according to the attribute code format described later with reference to FIG. Turn into.

  Note that after the run length value is encoded by the code format generation processing unit 208, the run length value is initialized by the run length generation processing unit 205.

  The code format generation processing unit 208 transfers the generated code data to the code writing unit 209. The code writing unit 209 writes the transferred code data in the page code storage area 751B of the main memory 751.

<Code format>
FIG. 12 shows an exemplary format of a code generated by the code format generation processing unit 208. In the present embodiment, the prediction error value, the run length value, and the attribute value are Huffman-coded to generate a prediction error code, a run length code, and an attribute code, and the pixel value when the prediction error value is outside the predetermined range. A PASS code using the code itself as a code is generated. The PASS code is generated when the prediction error value is Huffman encoded and the code length exceeds the code length applied to the prediction error value.

  FIG. 12A illustrates an example of the code format of the prediction error code, the attribute code, and the PASS code. Each code includes a header for identifying each of the codes and a numerical value portion in which a numerical value that is a main body of the code is stored.

  The prediction error value is Huffman encoded so that the greater the value, the lower the frequency. At this time, the prediction error values are classified according to ranges set in stages, and encoding is performed so that different code lengths are assigned to the respective ranges. The classified ranges are identified by error headers using predetermined bits (3 bits in the present embodiment) from the top of the code. A prediction error value encoded as a numerical part is added to the error header to generate one prediction error code.

In the present embodiment, for example, a range of 6 is set for the prediction error value Pe as follows.
Prediction error range # 1: Pe = 1, Pe = −1
Prediction error range # 2: Pe = -3, Pe = -2, Pe = 2, Pe = 3
Prediction error range # 3: −7 ≦ Pe ≦ −4, 4 ≦ Pe ≦ 7
Prediction error range # 4: −15 ≦ Pe ≦ −8, 8 ≦ Pe ≦ 15
Prediction error range # 5: −31 ≦ Pe ≦ −16, 16 ≦ Pe ≦ 31
Prediction error range # 6: −63 ≦ Pe ≦ −32, 32 ≦ Pe ≦ 63

Further, the group identification bits and the bit lengths of the additional bits of each group are set as follows, for example.
Prediction error range # 1: error header = “000”, added code length = 1 bit prediction error range # 2: error header = “001”, added code length = 2 bit prediction error range # 3: error header = “010”, added code length = 3-bit prediction error range # 4: error header = “011”, added code length = 4-bit prediction error range # 5: error header = “100”, added Code length = 5 bits prediction error range # 6: error header = “101”, added code length = 6 bits

  For example, the value “110” is used as a header (referred to as a PASS header), and the PASS code is generated by adding pixel data itself having a bit depth of 8 bits as a numerical value part to the PASS header.

  For example, the value “111” is used as the header (referred to as the attribute header), and the attribute code is generated by encoding the attribute value into a code having a code length of 2 bits and adding it as a numerical part to the attribute header. Is done.

  FIG. 12-2 illustrates a code format of an example of the run length code in which the run length value is encoded. In the present embodiment, the run length value is Huffman encoded so that a shorter code length is assigned as the value is smaller, a run length value is 1 and a 1 bit code length is assigned, and the run length value is encoded into a code “0”. The

  Hereinafter, as illustrated in FIG. 12B, when the run length value is 2, a code length of 2 bits is assigned and encoded to a code “10”. When the run length value is 3 to 5, a 4-bit code length is assigned and encoded to codes “1100”, “1101”, and “1110”, respectively.

  When the run length value is 6 or more, encoding is performed in a format in which a numerical value part having a predetermined code length is connected after a code “1111” having a code length of 4 bits. As shown in the lower part of FIG. 12-2, the numerical value part is composed of one or a plurality of frames having a code length of 4 bits including a 1-bit frame header at the head, for example. The code indicating the run length value is divided every 3 bits, and the 3 bits excluding the header of each frame are packed so that the above-mentioned code “1111” side is the MSB. In the example of FIG. 12B, the maximum number of frames is limited to 7, and the run length value can be expressed up to 1048576. If the run length value is 5, the frame can be omitted.

  The frame header indicates whether or not the next frame follows a certain frame. For example, a frame header value “0” indicates that there is a next frame, and a frame header value “1” indicates that the frame ends.

  FIG. 13 shows a configuration example of the above-described prediction error code, PASS code, attribute code, and run-length code. As illustrated in FIG. 13A, a prediction error code and a run-length code constitute one code. The PASS code and the run length code constitute one code. On the other hand, the attribute code is configured as a single code.

  As illustrated in FIG. 13B, the entire code data is configured by sequentially arranging the codes in the order in which the codes are encoded. Each code is a code composed of a prediction error code and a run-length code by reading the head 3-bit header, or a code composed of a PASS code and a run-length code, or It is possible to determine whether the code is composed of the attribute code alone.

<Details of encoding process>
FIG. 14 is a flowchart illustrating an example of encoding processing according to the present embodiment, which is performed by the CMYKA encoding unit 11. Prior to the processing of the flowchart of FIG. 14, it is assumed that the run length value is set to 1 which is an initial value in advance.

First, in step S30, the value of the initialization flag is set to 1. Next, in step S31, the image reading unit 200 reads one pixel to be processed (target pixel G _DATA ) from the CMYKA band data storage area 751A of the main memory 751. The read target pixel G _DATA is written in an area of the line memory 202 in which pixel data of the current line, which is a line to be encoded, is stored under the control of the line memory control processing unit 201 (step S32).

In the next step S <b> 33, the prediction processing unit 203 _reads out pixel data of the three neighboring pixels a, b, and c (see FIG. 11) of the target pixel G _DATA from the line memory 202. Then, using the pixel values of these pixels a, b and c, the pixel value of the target pixel G _DATA is predicted by plane prediction according to the above-described equation (1), and the plane prediction value is obtained. In the next step S34, the prediction by the error processing unit 204, from the pixel value of the target pixel G _DATA, and plane prediction value is subtracted determined in step S33, the error of the plane prediction value for the target pixel G _DATA (prediction error value ) Is required. Then, the process proceeds to step S35.

In step S35, the attribute reading unit 206, the CMYKA band data storage area 751A of the main memory 751, the attribute data corresponding to the target pixel G _DATA is read out.

In the next step S36, the run length generation processing unit 205 determines whether or not the _target pixel G _DATA satisfies at least one of the following conditions (1) to (3).
(1) The prediction error value obtained in step S34 is a value other than zero.
(2) The attribute value indicated by the attribute data read in step S35 is different from the attribute value obtained in the previous process.
(3) The target pixel G _DATA is the last pixel of the line.

If it is determined that the target pixel G _DATA does not satisfy any of the above conditions (1) to (3), the process proceeds to step S37. In other words, this is a case where the prediction error value is 0, the corresponding attribute value is the same as the attribute value obtained in the previous processing, and is not the last pixel of the current line. In step S37, the run length value is increased by one. Then, the process returns to step S31, and the process is repeated with the next pixel in the scan order as the new target pixel _GDATA .

On the other hand, in step S36 described above, attention pixel G _DATA is if it is determined that meets any one of the above (1) to (3), the process proceeds to step S38. In step S38, it is determined whether or not the value of the initialization flag is 1. If it is determined that the number is 1, the process proceeds to step S40. On the other hand, if it is determined that the initialization flag is not 1, the process proceeds to step S39.

  In step S39, the code format generation processing unit 208 encodes the run length value according to the code format described with reference to FIG. 12-2 to generate a run length code. Then, the process proceeds to step S40, and the value of the initialization flag is set to 0.

The process proceeds to step S41, whether the attribute values corresponding to the pixel of interest G _DATA is different from the attribute values corresponding to the previous pixel is determined. If it is determined that the attribute value corresponding to the target pixel G _DATA is the same as the attribute value corresponding to the previous pixel, the process proceeds to step S45.

  In step S405, it is determined whether the prediction error value is not zero. If it is determined that the prediction error value is 0, the process proceeds to step S51. On the other hand, if it is determined that the prediction error value is not 0, the process proceeds to step S46.

  In step S46, it is determined whether or not the prediction error value is outside a predetermined range. More specifically, in step S46, it is determined whether or not the value is outside the prediction error range shown in FIG. 12A, that is, outside the range of −63 to 63.

  If the prediction error value is within the predetermined range, that is, if the prediction error value is −63 or more and 63 or less, the process proceeds to step S47. In step S47, the run length generation processing unit 205 determines which range of the range # 1 to # 6 shown in FIG. 12A the prediction error value belongs to, and encodes the prediction error header based on the determination result. I do. When the prediction error header is encoded, the process proceeds to step S48, where the prediction error value is encoded according to the code format described with reference to FIG. Generated. Then, the process proceeds to step S51.

On the other hand, if it is determined in step S46 that the prediction error value is outside the predetermined range, that is, the prediction error value is less than −63 or greater than 63, the process proceeds to step S49. In step S49, the run-length generation processing unit 205 encodes the PASS header according to the code format described with reference to FIG. When the PASS header is encoded, the process proceeds to step S50, and the pixel data of the pixel of interest G _DATA itself is added as a code to the PASS header to generate a PASS code. Then, the process proceeds to step S51.

In step S51, it is determined whether or not the _target pixel _GDATA is the last pixel of the current line. If it is determined that the target pixel G _DATA is not the final pixel of the current line, the process proceeds to step S52, the run length value is set to 1, and the initial value is reset. Then, the process returns to step S31, and the process is repeated with the next pixel in the scan order as the new target pixel _GDATA .

On the other hand, if it is determined in step S51 that the target pixel _GDATA is the last pixel of the current line, the process proceeds to step S53. In step S53, the line memory control processing unit 201 switches the writing area of the line memory 202. That is, the current line to which the _target pixel G _DATA belongs is held as it is in one area of the line memory 202 as an encoded previous line, and the other area of the line memory 202 is stored as pixel data of the line to be encoded next Is an area in which is stored. Then, the process proceeds to step S54 to determine whether or not the process has been completed for all lines. If it is determined that the processing has been completed, a series of encoding processing is ended.

On the other hand, if it is determined in step S54 that the process has not been completed for all lines, the process returns to step S31, and the process is repeated with the first pixel of the next line as the target pixel _GDATA .

If it is determined in step S41 described above that the attribute value corresponding to the target pixel _GDATA is different from the attribute value corresponding to the previous pixel, the process proceeds to step S42.

  In step S42, the run length generation processing unit 205 encodes the attribute header according to the code format described with reference to FIG. When the attribute header is encoded, the process proceeds to step S43, where the attribute value is encoded in accordance with the code format described with reference to FIG. 12A, and is added to the attribute header to generate the attribute code.

  When the attribute code is generated in step S43, the process proceeds to step S44, and it is determined whether or not the prediction error value obtained in step S34 is a value other than zero. If it is determined that the prediction error value is a value other than 0, the process proceeds to step S46 described above. On the other hand, if it is determined that the prediction error value is 0, the process proceeds to step S49 described above.

  An example of the encoding process according to the embodiment of the present invention will be described more specifically with reference to FIG. FIG. 15A illustrates a more specific example of each value when encoding is performed according to the flowchart of FIG. 14 described above, in units of pixels. FIG. 15B schematically illustrates an example of code data (code string) generated by encoding the pixel and attribute data illustrated in FIG. 15A according to the flowchart of FIG. 14 described above.

  FIG. 15A shows an example in which the C version band data is encoded. In the C version band data and attribute data, the pixel of number # 0 is the first pixel, and the encoding process is performed from the left side to the right side of the figure. The codes are appropriately encoded in the order of the attribute value, the prediction error value, the PASS value, and the run length value, as exemplified by the vertical direction in FIG.

  In the example of FIG. 15, in the C version band data, the pixel values of the number # 2, number # 7, number # 10, number # 12, and number # 15 are changed with respect to the immediately preceding pixel. And In addition, it is assumed that the attribute values of the pixels of number # 2, number # 7, number # 10, and number # 15 have changed with respect to the immediately preceding pixel.

When the target pixel G _DATA is the first pixel of the line (pixel # 0), it is assumed that the prediction error value is 0 and that the attribute value has just changed, and the attribute value and the pixel value The initial value of (PASS value) is given. That is, it is determined in step S38 that the initialization flag is 1, and the initialization flag is set to 0 in step S40 without encoding the run length value. Thereafter, the initialization flag does not change from 0. Then, in step S41, it is determined that the attribute value of the previous pixel is different from the attribute value of the _target pixel GDATA, and an attribute code 600 is generated in step S42 and step S43. Since the prediction error value is 0, the process proceeds to step S49 based on the determination in step S44, and a PASS code 601 is generated in steps S49 and S50.

Since the target pixel G _DATA is not the last pixel of the line, the process proceeds to step S52 based on the determination in step S51, the run length value is reset to 1, and the next pixel (pixel # 1) is the target pixel G _DATA. The process from step S31 is performed. Since the attribute value of the pixel of number # 1 is the same as that of number # 0, the process proceeds to step S37 based on the determination in step S36, 1 is added to the run length value to set the value to 2, and the next pixel ( Pixel # 2) is the target pixel _GDATA .

  Since the pixel of number # 2 has a different attribute value from the previous pixel of number # 1, the process proceeds to step S38 based on the determination in step S36. Since the encoding flag is 0, the process proceeds to step S39 according to the determination in step S38, the run length value “2” is encoded, and the run length code 602 is generated.

  Since the pixel # 2 has an attribute value different from that of the previous pixel # 1, the attribute code 603 is generated in steps S42 and S43 by the determination in step S41, and the prediction error value is not 0. Since the value is in the range of −63 to 63, the prediction error code 604 is generated in steps S47 and S48 based on the determinations in steps S44 and S45.

In step S52, the run length value is reset to 1, the process returns to step S31, and the next pixel (pixel # 3) is set as the target pixel _GDATA . From the pixel # 2 to the pixel # 6, the attribute value does not change and the prediction error value is 0. Further, since the pixel is not the last pixel of the line, the process proceeds to step S37 according to the determination in step S36. After the transition, 1 is added to the run length value sequentially. The run length value at the time when the pixel # 6 is processed is 5.

When the processing of the pixel # 6 is completed, the pixel # 7 is set as the target pixel _GDATA . Since the pixel of number # 7 has a different attribute value from the previous pixel of number # 6, the process of step S36 proceeds to step S38. Since the encoding flag is 0, the process proceeds to step S39 based on the determination in step S38, the run length value “5” is encoded, and the run length code 605 is generated.

  Since the pixel # 7 has an attribute value different from that of the previous pixel # 6, the attribute code 606 is generated in steps S42 and S43 by the determination in step S41, and the prediction error value is not 0. Since the value is in the range of −63 to 63, the prediction error code 607 is generated in steps S47 and S48 based on the determinations in steps S44 and S45.

In step S52, the run length value is reset to 1, the process returns to step S31, and the next pixel (pixel # 8) is set as the target pixel _GDATA . From the pixel # 7 to the pixel # 9, the attribute value does not change and the prediction error value is 0. Further, since the pixel is not the last pixel of the line, the process proceeds to step S37 according to the determination in step S36. After the transition, 1 is added to the run length value sequentially. The run length value at the time when the pixel # 9 is processed is 3.

When the processing of the pixel # 9 is completed, the pixel # 10 is set as the target pixel _GDATA . Since the pixel of number # 10 has a different attribute value from the previous pixel of number # 9, the process proceeds to step S38 based on the determination in step S36. Since the encoding flag is 0, the process proceeds to step S39 according to the determination in step S38, the run length value “3” is encoded, and the run length code 608 is generated.

  Since the pixel # 10 has an attribute value different from that of the previous pixel # 9, the attribute code 609 is generated in steps S42 and S43 by the determination in step S41, and the prediction error value is not 0. Since the value is outside the range of −63 to 63, the PASS code 610 is generated using the pixel value itself of the pixel of number # 10 in step S49 and step S50 by the determination in step S44 and step S45.

In step S52, the run length value is reset to 1, the process returns to step S31, and the next pixel (the pixel of number # 11) is set as the target pixel _GDATA . Since the attribute value of the pixel of number # 11 is the same as that of number # 10, the process proceeds to step S37 according to the determination in step S36, and 1 is added to the run length value to set the value to 2, and the next pixel ( Pixel # 12) is the target pixel _GDATA .

  The pixel of number # 12 is the same as the pixel of number # 10 with the previous attribute value. On the other hand, since the prediction error value of the pixel # 12 is not 0, the process proceeds to step S38 based on the determination in step S36. Since the initialization flag is 0, the process proceeds to step S39 based on the determination in step S38, the run length value “2” is encoded, and the run length code 611 is generated.

  Since the pixel with the number # 12 has the same attribute value as the pixel with the number # 10, the process proceeds to step S45 based on the determination in step S41. The prediction error code 612 is generated in step S47 and step S48 because the prediction error value of the pixel of number # 12 is not 0 and is a value in the range of −63 to 63.

  Thereafter, the processing is repeated according to the flowchart of FIG. 14, and a run-length code 613, an attribute code 614, a prediction error code 615, and a run-length code 616 are sequentially generated to form code data.

  Another example of the encoding process according to the embodiment of the present invention will be described with reference to FIG. Here, a case will be described in which the attribute value changes while the state where the prediction error value is 0 continues.

  The example of FIG. 16 is an example of the M version corresponding to the C version band data shown in FIG. 15 described above, and has the same attribute data as the example of FIG. In the pixels # 10 and # 15, the attribute values have changed with respect to the immediately preceding pixel. In the example of FIG. 16, the pixel values of the pixels of number # 2, number # 4, number # 12, and number # 15 change with respect to the immediately preceding pixel, but prediction by the prediction process is appropriate. The prediction error value is 0 from pixel # 2 to pixel # 14.

  Similarly to the example described with reference to FIG. 15, a case will be described in which processing is completed up to the pixel of number # 6 and processing of the next pixel (pixel of number # 7) is performed. At this time, the run length value is 5 by the addition from pixel # 2 to pixel # 6.

  Since the pixel of number # 7 has a different attribute value from the previous pixel of number # 6, the process proceeds to step S38 based on the determination in step S36. Since the encoding flag is 0, the process proceeds to step S39 according to the determination in step S38, the run length value “5” is encoded, and the run length code 620 is generated.

  Since the pixel # 10 has an attribute value different from that of the previous pixel # 6, the attribute code 621 is generated in steps S42 and S43 based on the determination in step S41.

  Further, since the prediction error value of the pixel of number # 10 is 0, the PASS code 622 is generated using the pixel value itself of the pixel of number # 10 in steps S49 and S50 by the determination in step S44. Since the pixel of number # 10 is not the final pixel of the line, the process proceeds to step S52 based on the determination in step S51, and the run length value is reset to 1.

  In this way, even when the prediction error value is 0, the run-length value is initialized with the change in the attribute value, so that the pixel value of the pixel whose attribute value has changed is encoded as the PASS code at the change point of the attribute value. Must be included in the data. By doing so, it is possible to generate pixel data based on the pixel value and the run length value obtained by decoding the PASS code and the run length code, respectively, at the time of decoding.

<Encoding device>
FIG. 17 is a block diagram illustrating an exemplary configuration of the CMYK + A encoding unit 711 according to the present embodiment. The bus arbiter I / F 320 is an interface to the bus arbiter 708. The bus arbiter I / F 320 communicates with the bus arbiter 708 via the CMYK version image DMAC 709, the attribute DMAC 710, and the CMYKA code DMAC 12, thereby performing a write / read request to the main memory 751 via the bus 734, data read / write, and the like. .

  The band image reading unit 300 transmits a memory address to the bus arbiter I / F 320 based on the address information generated by the band data address generation unit 301. The bus arbiter I / F 320 transmits this memory address to the bus arbiter 708 via the CMYK version image DMAC 709, and reads the CMYK band data from the CMYKA band data storage area 751A of the main memory 751 for each version of CMYK via the bus 734. The band image reading unit 300 transfers the read band data to the line memory control unit 302.

  A first line memory 303 and a second line memory 304 are connected to the line memory control unit 302. The first line memory 303 and the second line memory 304 may be different areas of the same memory. The line memory control unit 302 assigns one of the first line memory 303 and the second line memory 304 as a memory for storing an encoded line, and assigns the other as a memory for storing a reference line. When the encoding of the encoding line is completed, the memory allocation is switched.

  The line memory control unit 302 assigns the pixel data supplied from the band image reading unit 300 as a memory for storing an encoded line among the first line memory 303 and the second line memory 304 (for example, To the first line memory 303). At the same time, this pixel data is transferred to the prediction processing unit 305 as pixel data of the target pixel by the line memory control unit 302. In addition, the line memory control unit 302 reads out pixel data of the three neighboring pixels a, b, and c of the target pixel from the first line memory 303 and the second line memory 304 and transfers them to the prediction processing unit 305.

  The prediction processing unit 305 uses the pixel data of the pixels a, b, and c transferred from the line memory control unit 302 to predict the pixel value of the pixel of interest by plane prediction according to the above equation (1). Data indicating the planar predicted value of the target pixel is transferred to the prediction error processing unit 306 together with the pixel data of the target pixel. The prediction error processing unit 306 obtains an error with respect to the pixel value of the pixel data of the target pixel of the target pixel of the plane predicted value transferred from the prediction processing unit 305, and sends it to the run length generation processing unit 310 together with the pixel data of the target pixel as prediction error data. Forward.

  The band attribute reading unit 307 transmits a memory address to the bus arbiter I / F 320 based on the address information generated by the band attribute address generation unit 308. The bus arbiter I / F 320 transmits this memory address to the bus arbiter 708 via the attribute DMAC 710, and reads the band data (attribute data) of the attribute A from the CMYKA band data storage area 751A of the main memory 751 via the bus 734. The band attribute reading unit 307 transfers the read attribute data to the attribute change detection processing unit 309.

  The attribute change detection processing unit 309 detects a change in the attribute value indicated in the attribute data transferred from the band attribute reading unit 307. When a change in the attribute value is detected, the attribute change detection processing unit 309 transfers attribute data indicating the attribute value after the change to the run length generation processing unit 310.

  The run length generation processing unit 310 generates a run length based on the prediction error data transferred from the prediction error processing unit 306 and the attribute data transferred from the attribute change detection processing unit 309. More specifically, when the prediction error value indicated by the prediction error data is “0”, the run length generation processing unit 310 increases the run length value by 1 and sets the length of the prediction error value to “0”. The run length value is generated by counting. On the other hand, when the prediction error value is other than “0”, the run length generation processing unit 310 converts the prediction error data indicating the prediction error value and the run length data indicating the run length value into a pixel indicating the pixel value of the target pixel. The data is transferred to the code format generation processing unit 311 together with the data.

  Also, the run length generation processing unit 310 executes the run when the attribute value has changed even when the prediction error value is “0”, that is, when the attribute data is transferred from the attribute change detection processing unit 309. Stop length generation. Then, the attribute data, the prediction error data indicating the prediction error value, and the run length data indicating the run length value are transferred to the code format generation processing unit 311 together with the pixel data indicating the pixel value of the target pixel.

  The code format generation processing unit 311 has been described with reference to FIGS. 12A and 12B based on the run length data, the prediction error data, the attribute data, and the pixel data of the target pixel transferred from the run length generation processing unit 310. Thus, encoding is performed to generate code data. The generated code data is transferred to the code writing unit 312.

  That is, the code format generation processing unit 311 encodes the run length value indicated by the run length data transferred from the run length generation processing unit 310 to generate a run length code. If the prediction error value indicated by the prediction error data transferred from the run length generation processing unit 310 is a value within a predetermined range, the prediction error header and the prediction error value are encoded to generate a prediction error code. If the prediction error value is a value outside the predetermined range, the PASS header is encoded and the PASS code is generated using the pixel value of the target pixel as the code. Furthermore, when the attribute value changes and attribute data is transferred from the run length generation processing unit 310, the attribute header is encoded to generate an attribute code.

  Note that after the run length value is encoded by the code format generation processing unit 311, the run length value is initialized by the run length generation processing unit 310.

  The code format generation processing unit 311 transfers each generated code to the band code writing unit 312. The band code writing unit 312 is an address for writing each code data transferred from the code format generation processing unit 311 to the page code storage area 751B of the main memory 751 based on the address information generated by the band code address generation unit 313. Is generated. The generated address is transferred from the band code writing unit 312 to the bus arbiter I / F 320 together with the code data transferred from the code format generation processing unit 311. The bus arbiter I / F 320 requests the bus I / F 34 to write each code data to the page code storage area 751B of the main memory 751 based on the address transferred from the band code writing unit 312.

<Outline of decryption processing>
FIG. 18 is a functional block diagram illustrating an example of the operation of the C + A decoding unit 717 according to the embodiment of the present invention. Note that the M + A decoding unit 718, the Y + A decoding unit 19 and the K + A decoding unit 720 can be realized with the same configuration as the C + A decoding unit 717, and therefore, here, the C + A decoding unit 717 will be representatively described.

  In the C + A decoding unit 717, the code reading unit 400 reads the C + A version band code data from the page code storage area 751B of the main memory 751 and transfers it to the code format analysis unit 401. Based on the header of the transferred code data, the code format analysis unit 401 analyzes whether the code data is an attribute code, a prediction error code, or a PASS code. If the code data is an attribute code, the attribute value is decoded based on the code format described with reference to FIG. 12A and transferred to the attribute value generation processing unit 407 as attribute data.

  On the other hand, if the transferred code data is a prediction error code or a PASS code, the code format analysis unit 401 decodes the prediction error value or the pixel value based on the code format described with reference to FIG. Then, the decoded prediction error value or pixel value is transferred to the error processing unit 403 together with the prediction code header or the PASS header as prediction error data or pixel data.

  Furthermore, when the transferred code data is a prediction error code or a PASS code, the code format analysis unit 401 extracts a run-length code arranged after the prediction error code or the PASS code. Then, the run-length code is decoded into the run-length value based on the code format described with reference to FIG. 12-2, and the decoded run-length value is used as run-length data in the run-length processing unit 402 and the attribute value generation processing unit 407. Forward.

  In the error processing unit 403, the pixel value generation processing unit 414 determines whether the header transferred from the code format analysis unit 401 is a prediction error header or a PASS header. If it is determined that the header is a PASS header, since the data transferred from the code format analysis unit 401 together with the header is pixel data itself, the pixel data is transferred to the line memory control processing unit 404.

  On the other hand, if it is determined that the header transferred from the code format analysis unit 401 is a prediction error header, the prediction processing unit 413 reads the periphery 3 of the target pixel read from the line memory 405 by the line memory control processing unit 404. Based on the pixel data of the decoded pixels a, b, and c, the pixel value of the target pixel to be decoded is predicted by plane prediction. The pixel value generation processing unit 414 adds the prediction error value based on the prediction error data transferred from the code format analysis unit 401 and the prediction value predicted by the prediction processing unit 620 to generate the pixel value of the target pixel. . Pixel data based on the generated pixel value is transferred to the line memory control processing unit 404.

  In the run length processing unit 402, the prediction processing unit 410 is based on the pixel data of the decoded pixels a, b, and c of the surrounding three pixels of the pixel of interest supplied from the line memory control processing unit 404. Similarly to the unit 413, the pixel value of the target pixel is predicted, and the predicted value is transferred to the pixel value generation processing unit 411. The pixel value generation processing unit 411 generates a pixel value based on the prediction value transferred from the prediction processing unit 410. The generated pixel data of the pixel value is output by the length indicated by the run length value based on the run length data transferred from the code format analysis unit 401 under the control of the run length processing control unit 412. The pixel data output from the run length processing unit 402 is transferred to the line memory control processing unit 404.

  The line memory control processing unit 404 writes the pixel data transferred from the run length processing unit 402 and the error processing unit 403 to the line memory 405 and outputs from the C + A decoding unit 717 via the image output unit 406.

  Note that the line memory 405 can store pixel data for two lines, a current line that is being decoded and a previous line that has just been decoded. The line memory control processing unit 404 controls reading / writing of pixel data with respect to the line memory 405. For example, the line memory control processing unit 604 reads the peripheral three pixels a, b, and c of the target pixel from the line memory 405 and supplies them to the error processing unit 402 and the run length processing unit 403 described above.

  The attribute value generation processing unit 407 outputs the attribute data transferred from the code format analysis unit 401 by the length indicated by the run length value based on the run length data transferred from the code format analysis unit 401. The attribute data output from the attribute value generation processing unit 407 is output from the C + A decoding unit 717 via the attribute output unit 408. Here, the output of the attribute data is performed in synchronism with the output of the pixel data from the image output unit 406 described above in units of pixels.

<Details of decryption processing>
FIG. 19 is a flowchart illustrating an example of a decoding process performed on the code data encoded by the encoding process according to the present embodiment, which is performed by the C + A decoding unit 717. Note that the processing in the M + A decoding unit 718, the Y + A decoding unit 719, and the K + A decoding unit 720 is the same as the processing in the C + A decoding unit 717. Therefore, the processing in the C + A decoding unit 717 represents the decoding processing of each version of CMYK. I will explain.

  In step S60, the code reading unit 400 reads the C + A version band code from the page code storage area 751B of the main memory 751. The code format analysis unit 401 reads and analyzes the header of the first 3 bits of the C + A version band code read by the code reading unit 400, and determines whether the code is a prediction error code, a PASS code, or an attribute code. (Step S61 and Step S65).

  That is, the code format analysis unit 401 first determines in step S61 whether the header is a prediction error header. If it is determined that the header is not a prediction error header, the process proceeds to step S65 to determine whether the header is a PASS header. If it is determined that the header is not a PASS header, the code is determined to be an attribute code because the header is an attribute header. In this case, the process proceeds to step S67, the numerical part following the header is read, and the attribute value is obtained according to the code format described with reference to FIG. If the attribute value is obtained in step S67, the process proceeds to step S77 described later.

If the code format analysis unit 401 determines in step S61 that the header is a prediction error header, the code is determined to be a prediction error code, and the process proceeds to step S62. Then, the numerical part following the header is read, and the prediction error value is obtained according to the code format described with reference to FIG. In the next step S63, based on the pixel values of the surrounding three pixels a, b, and c of the target pixel G _DATA to be decoded, read from the line memory 405 by the prediction processing unit 413 in the error processing unit 403. The pixel value of the target pixel G _DATA is predicted by plane prediction according to the equation (1).

In the next step S64, the pixel value generation processing unit 414 adds the prediction error value obtained in step S62 and the prediction value obtained in step S63 to generate the pixel value of the target pixel _GDATA . Then, the process proceeds to step S68.

On the other hand, if it is determined in step S61 described above that the header is not a prediction error header and it is determined in next step S65 that the header is a PASS header, the code is determined to be a PASS code, and the process proceeds to step S66. . In step S66, the numerical value portion following the header is read, and the pixel value is extracted from the PASS code in accordance with the code format described with reference to FIG. 12A, and this is set as the pixel value of the _target pixel _GDATA . Then, the process proceeds to step S68.

  In step S <b> 68, a run length code arranged subsequent to the prediction error code or the PASS code determined in the determination process in step S <b> 61 or the determination process in step S <b> 65 is read into the code format analysis unit 401. In the next step S68, the run-length code is decoded into the run-length value according to the code format described with reference to FIG.

In the next step S70, the pixel value of the _target pixel GDATA obtained in step S64 or step S66 described above is written in the area of the current line in the line memory 405. The pixel value of the _target pixel G _DATA is output by the image output unit 406 in the next step S71. In step S71, the attribute value obtained in the previous processing in step S67 and held in the attribute output unit 408 is also output in synchronization with the pixel value of the _target pixel _GDATA .

  When the pixel value and the attribute value are output in step S71, the process proceeds to step S72, and it is determined whether or not the run length value obtained in step S69 is 1. If it is determined that the run length value is 1, the process proceeds to step S77 described later.

On the other hand, if it is determined that the run length value is not 1, the process proceeds to step S73. In step S73, the prediction processing unit 410 in the run length processing unit 402 reads out from the line memory 405, based on the pixel values of the three surrounding pixels a, b, and c of the target pixel to be decoded (the above formula ( According to 1), the pixel value of the target pixel is predicted by plane prediction. The predicted value obtained by this prediction is used as the pixel value of the target pixel G _DATA .

The pixel value of the _target pixel G _DATA obtained in step S73 is written in the current line area of the line memory 405 in the next step S74. The pixel value of the _target pixel G _DATA is output by the image output unit 406 in the next step S75. In step S75, the attribute value obtained in the previous process in step S67 and held in the attribute output unit 408 is also output in synchronization with the pixel value of the _target pixel _GDATA .

  In the next step S76, it is determined whether or not the processing in steps S73 to S75 has been repeated by the number of times obtained by subtracting 1 from the run length value obtained in step S69. If it is determined that the process has not been performed the number of times obtained by subtracting 1 from the run length value, the process returns to step S73.

On the other hand, if it is determined in step S76 that the process has been performed the number of times obtained by subtracting 1 from the run length value, the process proceeds to step S77. In step S77, it is determined whether or not the target pixel G _DATA, that is, the pixel output immediately before is the last pixel of the line. If it is determined that the pixel is the last pixel, the process proceeds to step S78, and the area of the previous line and the area of the current line are switched in the line memory 405. For example, the current line to which the pixel output immediately before belongs is held as it is in the one area of the line memory 405 as a decoded previous line, and the other area of the line memory 405 is stored in the pixel of the current line next. Area. Then, the process proceeds to step S79.

  In step S79, it is determined whether or not processing has been completed for all pixels. If it is determined that the process has been completed, a series of decoding processes are completed. On the other hand, if it is determined in step S79 that the process has not been completed for all pixels, the process returns to step S60, and the process for the next code is performed.

<Decoding device>
FIG. 20 is a block diagram illustrating a configuration example of the C + A decoding unit 717 according to the embodiment of the present invention. Note that the M + A decoding unit 718, the Y + A decoding unit 19 and the K + A decoding unit 720 can be realized with the same configuration as the C + A decoding unit 717, and therefore, here, the C + A decoding unit 717 will be representatively described.

  The bus arbiter I / F 500 is an interface to the bus arbiter 708. The bus arbiter I / F 500 communicates with the bus arbiter 708 via the C + A version code DMAC 713, thereby reading data from the main memory 751 and reading data from the main memory 751 via the bus 734.

  The band code reading unit 501 transmits a memory address to the bus arbiter I / F 500 based on the address information generated by the band code address generation unit 502. The bus arbiter I / F 500 transmits this memory address to the bus arbiter 708 via the C + A version code DMAC 713 and reads the C + A version band code from the page code storage area 751B of the main memory 751 via the bus 734. The band code reading unit 501 transfers the read C + A version code data to the code format analysis unit 503.

  Based on the header of the transferred code data, the code format analysis unit 503 analyzes whether the code data is an attribute code, a prediction error code, or a PASS code. If the code data is an attribute code, the attribute value is decoded based on the code format described with reference to FIG. 12A and transferred to the attribute value generation processing unit 510 as attribute data.

  On the other hand, if the transferred code data is a prediction error code or a PASS code, the code format analysis unit 503 decodes the prediction error value or the pixel value based on the code format described with reference to FIG. Then, the decoded prediction error value or pixel value is transferred to the error processing unit 505 together with the prediction error header or the PASS header as prediction error data or pixel data.

  Furthermore, when the transferred code data is a prediction error code or a PASS code, the code format analysis unit 503 extracts a run-length code from the prediction error code or the PASS code. Then, the run-length code is decoded into the run-length value based on the code format described with reference to FIG. 12-2, and the decoded run-length value is used as run-length data in the run-length processing unit 504 and the attribute value generation processing unit 510. Forward.

  In the error processing unit 505, the prediction processing unit 530 reads out the three neighboring pixels a, b, and c of the pixel of interest read from the first line memory 507 and the second line memory 508 by the line memory control unit 7506, respectively. Based on the pixel data, the pixel value of the target pixel to be decoded is predicted by plane prediction. Predicted value data indicating the predicted value is transferred to the pixel value generation processing unit 531.

  The pixel value generation processing unit 531 determines whether the header transferred from the code format analysis unit 503 is a prediction error header or a PASS header. If it is determined that the header is a PASS header, since the data transferred from the code format analysis unit 401 together with the header is pixel data itself, the pixel data is transferred to the line memory control processing unit 506.

  On the other hand, when the pixel value generation processing unit 531 determines that the header transferred from the code format analysis unit 503 is a prediction error header, the pixel value generation processing unit 531 indicates the prediction value indicated by the prediction value data transferred from the prediction processing unit 530 and the code format. The prediction error value based on the prediction error data transferred from the analysis unit 503 is added to generate a pixel value of the target pixel. Pixel data based on the generated pixel value is transferred to the line memory control processing unit 506.

  In the run-length processing unit 504, the prediction processing unit 510, the prediction processing unit 530, and the peripheral 3 of the target pixel read from the first line memory 507 and the second line memory 508 by the line memory control unit 7506, respectively. Based on the pixel data of the pixels a, b, and c, the pixel value of the target pixel is predicted in the same manner as the prediction processing unit 530 described above. Predicted value data indicating the predicted value is transferred to the pixel value generation processing unit 521.

  The pixel value generation processing unit 521 generates a pixel value based on the prediction value data transferred from the prediction processing unit 620. The pixel data of the generated pixel value is output by the length indicated by the run length value based on the run length data transferred from the code format analysis unit 503 under the control of the run length pixel value generation control processing unit 522. The pixel data output from the run length processing unit 504 is transferred to the line memory control processing unit 506.

  The line memory control processing unit 506 stores the pixel data transferred from the run length processing unit 504 and the error processing unit 505 and stores the data of the current line in the first line memory 507 and the second line memory 508. Are transferred to the image processing unit I / F 509.

  Note that the first line memory 507 and the second line memory 508 connected to the line memory control processing unit 506 may be different areas of the same memory. The line memory control unit 7506 assigns one of the first line memory 507 and the second line memory 508 as a memory for storing the current line, and assigns the other as a memory for storing the previous line. When the encoding of the encoding line is completed, the memory allocation is switched.

  The attribute value generation processing unit 510 sequentially outputs the attribute data transferred from the code format analysis unit 503 by the length indicated by the run length value by the run length data transferred from the code format analysis unit 503. The attribute data output from the attribute generation processing unit 510 is transferred to the image processing unit I / F 509.

  The image processing unit I / F 509 outputs the pixel data transferred from the line memory control unit 7506 and the attribute data transferred from the attribute value generation processing unit 510 in synchronization with each other, and outputs them to the C plane gradation processing unit 721. Forward.

<Effect>
As described above, in the present invention, when image data and attribute data are encoded by run-length encoding, the run-length value of the image data is terminated at the change point of the attribute data, and the attribute is assigned to the change point. The sign of the data is incorporated. Therefore, the image data and the attribute data can be encoded into one code, the image data and the attribute data can be decoded by one decoding device, and the waste of bus transfer at the time of printing can be eliminated. It is.

  In addition, since the encoding of the image data and the encoding of the attribute data are performed integrally, the image data and the attribute data can be encoded with one encoding device, and the device scale can be reduced. .

  Furthermore, as shown in FIGS. 15 and 16 described above, it is not necessary to have run-length codes for attribute data and image data, respectively, and the amount of codes can be reduced.

<Other embodiments>
In the above description, the CMYK + A encoding unit 711 and the C + A decoding unit 717 (and the M + A decoding unit 718, the Y + A decoding unit 719, and the K + A decoding unit 720 (hereinafter, represented by the C + A decoding unit 717) according to the embodiment of the present invention). However, the present invention is not limited to this example. That is, the CMYK + A encoding unit 711 and the C + A decoding unit 717 in the image processing apparatus applicable to the embodiment of the present invention can be realized as programs that operate on a CPU (not shown) incorporated in the image processing apparatus. It is.

  In this case, the program executed as the CMYK + A encoding unit 711 on the CPU is, for example, each functional unit (image reading unit 200, line memory control processing unit 201, prediction process) of the CMYK + A encoding unit 711 described with reference to FIG. Unit 203, prediction error processing unit 204, run length generation processing unit 205, attribute reading processing unit 206, attribute change detection processing unit 207, code format generation processing unit 4208, and code writing unit 209). Similarly, the program executed as the C + A decoding unit 717 on the CPU is the functional units of the C + A decoding unit 717 described with reference to FIG. 18 (code reading unit 400, code format analysis unit 401, run length processing unit 402, The module configuration includes a prediction error processing unit 403, a line memory control processing unit 404, an image output unit 406, an attribute value generation processing unit 407, and an attribute output unit 408).

  These programs are recorded in a computer-readable recording medium such as a CD (Compact Disk), a flexible disk (FD), and a DVD (Digital Versatile Disk) in a format that can be installed or executed. The The program is not limited to this, and the program may be stored in advance in a ROM (not shown) connected to the CPU. Furthermore, the program may be stored on a computer connected to a network such as the Internet and provided by being downloaded via the network. The program may be configured to be provided or distributed via a network such as the Internet.

  As actual hardware, the CPU loads, for example, each unit described above onto a main storage device (not shown) by reading and executing a program that functions as the encoding unit 204 or the decoding unit 205 from the recording medium described above, for example. Is done. For example, in the case of a program that executes the CMYK + A encoding unit 711, the image reading unit 200, the line memory control processing unit 201, the prediction processing unit 203, the prediction error processing unit 204, the run length generation processing unit 205, and the attribute reading processing unit 206. The attribute change detection processing unit 207, the code format generation processing unit 4208, and the code writing unit 209 are generated on the main storage device.

1 CPU
3 Memory Arbiter 4 Memory Controller 6 Bus Controller 8 Bus Arbiter 711 CMYK + A Encoding Unit 17 C + A Decoding Unit 7
18 M + A decoding unit 7
19 Y + A decoding unit 7
20 K + A decoding unit 7
51 Main Memory 51A CMYKA Band Data Area 51B Page Code Storage Area 200 Image Reading Processing Unit 201 Line Memory Control Processing Unit 202 Line Memory 203 Prediction Processing Unit 204 Prediction Error Processing Unit 205 Run Length Generation Processing Unit 206 Attribute Reading Processing Unit 207 Attribute Change Detection processing unit 208 Code format generation processing unit 400 Code reading unit 401 Code format analysis unit 402 Run length processing unit 403 Error processing unit 404 Line memory control processing unit 405 Line memory 407 Attribute value generation processing unit

Japanese Patent No. 3750367 JP 2001-169120 A JP 2002-152518 A Japanese Patent Laid-Open No. 11-185024 JP 2005-309865 A Japanese Patent No. 3676078

Claims (11)

An image processing apparatus that encodes pixel data and attribute data corresponding to the pixel data,
Run length generating means for generating a run length based on pixel data;
Encoding means for encoding the run length generated by the run length generation means and the attribute data;
Detecting means for detecting a change in attribute data corresponding to the pixel data;
The encoding means includes
When a change in the attribute data is detected by the detection means, the run length generated by the run length generation means is encoded and the run length is initialized, and the attribute data after the change is An image processing apparatus that outputs the indicated code and the encoded run length as one code string. A prediction means for predicting a pixel value based on pixel data of a target pixel;
Prediction error calculation means for calculating an error of the prediction value obtained by predicting the pixel value of the target pixel by the prediction means with respect to the pixel value of the target pixel;
The run length generating means includes:
The image processing apparatus according to claim 1, wherein the run length in which the error calculated by the prediction error calculation unit is zero is generated. The encoding means includes
When the change of the attribute data is detected by the detection means and the error calculated by the prediction error means is 0, a code indicating the pixel value itself by the pixel data corresponding to the attribute data is The image processing apparatus according to claim 2, further outputting the code string. The encoding means includes
The image processing apparatus according to claim 1, wherein the run-length encoding is performed using Huffman encoding.
An image processing method for encoding pixel data and attribute data corresponding to the pixel data,
A run length generating step for generating a run length based on the pixel data;
An encoding step for encoding the run length generated by the run length generation step and the attribute data;
Detecting a change in attribute data corresponding to the pixel data,
The encoding step includes:
When a change in the attribute data is detected in the detection step, the run length generated in the run length generation step is encoded and the run length is initialized, and the attribute data after the change is An image processing method characterized by outputting the indicated code and the encoded run length in one code string.   A program for causing a computer to function as the image processing apparatus according to any one of claims 1 to 4. Decodes code data including a run length generated based on pixel data and encoded in accordance with a change in attribute data corresponding to the pixel data and a code string including the code indicating the attribute data after the change. An image processing apparatus that
Code processing means for obtaining the pixel data, the run length, and the attribute data, respectively, based on the code data;
Pixel data output means for outputting the pixel data obtained by the code processing means for the length indicated by the run length obtained by the code processing means;
And attribute data output means for outputting the attribute data obtained by the code processing means in synchronization with the pixel data output means for the length indicated by the run length obtained by the code processing means. A featured image processing apparatus. The code data further includes a code indicating an error with respect to the target pixel of a predicted value obtained by predicting the pixel value of the target pixel based on the encoded pixel value;
The run length is a value indicating a length where the error is 0,
Storage means for accumulatively storing the decoded pixel data;
Prediction means for predicting a pixel value of a pixel to be decoded based on the decoded pixel data stored in the storage means;
The code processing means further determines the error based on the code data,
When the run length is a value other than 1, the pixel data is obtained using the prediction value predicted by the prediction means as a pixel value,
The image processing apparatus according to claim 7, wherein when the run length is 1, the pixel data is obtained by adding a prediction value predicted by the prediction unit and the error. The code data further includes a code indicating the pixel value itself of the target pixel,
9. The image processing apparatus according to claim 7, wherein when the code indicating the pixel value itself is obtained from the code data, the code processing unit obtains the pixel data based on the pixel value. . Decodes code data including a run length generated based on pixel data and encoded in accordance with a change in attribute data corresponding to the pixel data and a code string including the code indicating the attribute data after the change. An image processing method for
A code processing step for determining the pixel data, the run length, and the attribute data based on the code data;
A pixel data output step for outputting the pixel data obtained by the code processing means for the length indicated by the run length obtained by the code processing step;
Attribute data output for outputting the attribute data obtained by the code processing step in synchronization with the output of the pixel data by the pixel data output step by the length indicated by the run length obtained by the code processing step. And an image processing method.   A program for causing a computer to function as the image processing apparatus according to any one of claims 7 to 9.

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