Patent Publication Number: US-8976376-B2

Title: Printing control apparatus, printing system, recording medium having recorded thereon printing control program, and printing control method

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a printing control apparatus and, more particularly, to a printing control apparatus, a printing system, a recording medium having recorded thereon a printing control program, and a printing control method performing a rasterizing process. 
     2. Description of Background Art 
     A printing system is generally made up of a printing control apparatus and a printer. The printing control apparatus receives manuscript data from an external Personal Computer (PC). The manuscript data is data generated by editing parts to be used in each page and laying them out, and described in Page Description Language (PDL). The printing control apparatus performs a rasterizing process (hereinafter, described as an “RIP process”) by an Raster Image Processor (RIP) on the received manuscript data to generate printing output data. The printing output data includes data obtained by the RIP process (hereinafter, called “RIP-processed data”), and synthesis information used for synthesizing the RIP-processed data in the printer. The printing output data is transmitted to the printer. The printer outputs a printed matter based on the received printing output data. In the printing industry, to achieve reduction in print cost, an increase in speed of processes performed by a printing system (hereinafter, called a “printing process”) as described above is in demand. 
     Japanese Patent Application Laid-Open Publication No. 2011-67993 discloses an image processing apparatus performing the RIP process by a plurality of RIP processing units in parallel. The image processing apparatus corresponds to the above-described printing control apparatus. Hereinafter, the RIP process performed in parallel will be called a “parallel RIP process”. By such a parallel RIP process, the speed of the RIP process can be increased. To the plurality of RIP processing units, a cache memory is connected. In the cache memory, RIP-processed data obtained by the RIP process in the RIP processing units is cached. Consequently, with respect to a reuse part as a part which is repeatedly used in a plurality of pages, its RIP-processed data is cached for the first time, and the cached RIP-processed data is used for the second time on. In such a manner, the speed of the RIP process can be further increased. RIP-processed data of each part is transmitted to a printer for each page in which the part is used. The parallel RIP process is disclosed also in United States Patent Application Publication No. 2004/95596 and Japanese Patent Application Laid-Open Publication No. 2006-39719. The RIP process using a cache is disclosed also in Japanese Patent Application Laid-Open Publication No. 2009-71352. 
     In the technique disclosed in Japanese Patent Application Laid-Open Publication No. 2011-67993 and the like, however, even RIP-processed data corresponding to a reuse part is transmitted from a printing control apparatus to a printer for each page used. Consequently, in the case where a reuse part exists, although the speed of the RIP process can be increased, the speed of the entire printing process cannot be sufficiently increased. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a printing control apparatus, a printing system, a recording medium having recorded thereon a printing control program, and a printing control method realizing higher speed of entire printing process. 
     To achieve the above-described object, the present invention has the following features. 
     One aspect of the present invention relates to a printing control apparatus for obtaining output data in a print output form from manuscript data expressed in a page description language and made up of a plurality of pages, and transmitting the output data to an external printer, the apparatus comprising: 
     an output processing unit for converting the manuscript data assigned to the output data and transmitting the output data to the printer; and 
     a first storage unit for storing at least a reuse part obtained by converting reuse part data indicative of a part reused in the manuscript data and an identifier corresponding to the reuse part, in the output data, 
     wherein the output processing unit reads a reuse part to be transmitted to the printer and an identifier corresponding to the reuse part from the first storage unit, and 
     omits transmission of a reuse part corresponding to the same identifier as that corresponding to the reuse part already transmitted to the printer. 
     With such a configuration, in a printing control apparatus in which at least a reuse part in output data is stored in a first storage unit, an identifier corresponding to a reuse part is stored in the first storage unit. Transmission of a reuse part corresponding to the same identifier as that corresponding to a reuse part already transmitted to the printer in the reuse part read from the first storing unit is omitted. Consequently, the speed of the output data transmitting process becomes higher. Accordingly, the speed of the entire printing process can be made higher. 
     In such an apparatus, preferably, one or more output processing units are further provided. 
     With such a configuration, by using a plurality of output processing units, the speed of the process of converting the manuscript data to output data can be increased. Consequently, the speed of the entire printing process can be further increased. 
     Preferably, the apparatus further includes a reuse information obtaining unit for obtaining information regarding reuse of a part in the manuscript data. 
     With such a configuration, whether each part in manuscript data is a reused part or not is known from reuse information. For example, using the reuse information, an identifier can be assigned to a reuse part in output data. 
     In such an apparatus, preferably, the manuscript data includes information regarding reuse of apart in the manuscript data. 
     Also with such a configuration, by reuse information, whether each part in manuscript data is a reused part or not can be known. For example, using the reuse information, an identifier can be assigned to a reuse part in output data. 
     In such an apparatus, preferably, each of the output processing units assigns the identifier to the reuse part based on the information regarding reuse of a part in the manuscript data. 
     With such a configuration, in each output unit, using the reuse information, an identifier can be assigned to a reuse part in output data. 
     Preferably, the apparatus further includes an output control unit for obtaining an identifier read from the first storage unit by each output processing unit from the output processing unit and, when the identifier is an identifier corresponding to a reuse part already transmitted to the printer, controlling an output processing unit having obtained the identifier so as not to transmit the reuse part corresponding to the identifier to the printer. 
     With such a configuration, by determining whether an identifier read by an output processing unit is an identifier corresponding to a reuse part already transmitted to the printer or not by the output control unit, an advantage similar to the above-described configuration can be obtained. 
     In such an apparatus, preferably, the output processing units are configured to mutually refer to identifiers read from the first storage unit, and each output processing unit determines whether or not the identifier read from the first storage unit is an identifier corresponding to a reuse part already transmitted to the printer. 
     With such a configuration, by determining whether or not an identifier read from an output processing unit is an identifier corresponding to a reuse part already transmitted to the printer by an output processing unit, an advantage similar to that of the above-described configuration can be obtained. 
     In such an apparatus, preferably, the first storage unit also stores a part of the output data, the part being obtained by converting part data indicative of a part used only once in the manuscript data. 
     With such a configuration, a part obtained by converting part data indicative of apart used only once in manuscript data, in output data is also stored in the first storing unit. Consequently, in the case where output data has to retransmitted to the printer such as the case where, for example, deficiency, disappearance, or the like of output data occurs in the printer, it is sufficient to retransmit output data stored in the second storing unit so that a process of converting manuscript data to output data does not have to be performed again. Thus, the speed of the entire printing process in the case where retransmission of output data is necessary can be increased. 
     Another aspect of the present invention relates to a printing system having a printing control apparatus according to the above aspect of the invention, and the printer. 
     In such an apparatus, preferably, the printer includes: 
     a second storage unit for storing output data received from each of output processing units; and 
     a printing unit for reading the output data stored in the second storage unit and executing printing. 
     With such a configuration, a reuse part of output data transmitted only once is stored in the second storing unit, so that the reuse part can be certainly reused in the printer. 
     In such an apparatus, preferably, the printing control apparatus transmits synthesis information regarding synthesis of each of parts of the output data in each page to the printing unit, and 
     the printing unit synthesizes the parts of the output data stored in the second storage unit page by page based on the received synthesis information. 
     With such a configuration, by synthesizing parts of output data page by page using synthesis information, a printed matter expressing a synthesis state of the parts of the output data can be output. 
     Still another aspect of the present invention relates to a computer-readable recording medium having recorded thereon a printing control program, when executed using a memory by a CPU of a computer for obtaining output data in a print output form from manuscript data expressed in a page description language and made up of a plurality of pages and transmitting the output data to an external printer, causing the CPU to perform: 
     an output processing step of converting the manuscript data assigned to the output data and transmitting the output data to the printer; and 
     a storage step of storing at least a reuse part obtained by converting reuse part data indicative of a part reused in the manuscript data and an identifier corresponding to the reuse part in the output data into a storage unit, 
     wherein in the output processing step, 
     a reuse part to be transmitted to the printer and an identifier corresponding to the reuse part are read from the storage unit, and 
     transmission of a reuse part corresponding to the same identifier as that corresponding to a reuse part already transmitted to the printer is omitted. 
     In such a recording medium, preferably, the printing control program causes the CPU to further perform one or more output processing steps. 
     In such a recording medium, preferably, the printing control program causes the CPU to further perform a reuse information obtaining step of obtaining information regarding reuse of a part in the manuscript data. 
     In such a recording medium, preferably, the manuscript data includes information regarding reuse of a part in the manuscript data. 
     In such a recording medium, preferably, in each of the output processing steps, the identifier is assigned to the reuse part based on information regarding reuse of a part in the manuscript data. 
     In such a recording medium, preferably, the printing control program causes the CPU to further perform an output control step of obtaining an identifier read from the storage unit in an output processing step and, when the identifier is an identifier corresponding to a reuse part already transmitted to the printer, controlling the output processing step so as not to transmit the reuse part corresponding to the identifier to the printer. 
     In such a recording medium, preferably, the output processing steps are configured to mutually refer to identifiers read from the storage unit, and 
     in each output processing step, whether or not the identifier read from the storage unit is an identifier corresponding to a reuse part already transmitted to the printer is determined. 
     In such a recording medium, preferably, in the storage step, a part of the output data is also stored, the part being obtained by converting part data indicative of a part that is used only once in the manuscript data. 
     Yet another aspect of the present invention relates to a printing control method of obtaining output data in a print output form from manuscript data expressed in a page description language and made up of a plurality of pages and transmitting the output data to an external printer, the method comprising: 
     an output processing step of converting the manuscript data assigned to the output data and transmitting the output data to the printer; and 
     a storage step of storing at least a reuse part obtained by converting reuse part data indicative of a part reused in the manuscript data and an identifier corresponding to the reuse part in the output data into a storage unit, 
     wherein in the output processing step, 
     a reuse part to be transmitted to the printer and an identifier corresponding to the reuse part are read from the storage unit, and 
     transmission of a reuse part corresponding to the same identifier as that corresponding to a reuse part already transmitted to the printer is omitted. 
     These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram illustrating an overall configuration of a printing system according to an embodiment of the present invention and apparatuses related to the system; 
         FIG. 2  is a diagram illustrating a hardware configuration of a printing control apparatus in the embodiment; 
         FIG. 3  is a block diagram illustrating a functional configuration of a main part of the printing control apparatus in the embodiment; 
         FIG. 4  is a block diagram illustrating a functional configuration of a main part of a printer in the embodiment; 
         FIG. 5  is a flowchart illustrating an example of the procedure of cache process of RIP-processed data and identifiers in the embodiment; 
         FIG. 6  is a diagram for explaining the cache process of RIP-processed data and identifiers in the embodiment; 
         FIG. 7  is a flowchart illustrating an example of the procedure of process of transmitting RIP-processed data in the embodiment; 
         FIG. 8  is a diagram for explaining the process of transmitting RIP-processed data in the embodiment; 
         FIG. 9  is a flowchart illustrating an example of the procedure of printed matter generating process in the embodiment; 
         FIG. 10  is a block diagram illustrating a functional configuration of a main part of a printing control apparatus in a first modification of the embodiment; 
         FIG. 11  is a diagram for explaining the cache process of RIP-processed data and identifiers in the first modification; 
         FIG. 12  is a block diagram illustrating a functional configuration of a main part of a printing control apparatus in a second modification of the embodiment; 
         FIG. 13  is a diagram for explaining a cache process of RIP-processed data and identifiers in a third modification of the embodiment; 
         FIG. 14  is a flowchart illustrating an example of the procedure of cache process of RIP-processed data and identifiers in the third modification; and 
         FIG. 15  is a diagram for explaining a process of transmitting RIP-processed data in the third modification. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     &lt;1. Overall Configuration&gt; 
       FIG. 1  is a block diagram illustrating an overall configuration of a printing system according to an embodiment of the present invention and apparatuses related to the system. The printing system  1  according to the embodiment performs variable printing as a mode of on-demand printing. In the variable printing, a printed matter which varies by a record unit including one or more pages is output. That is, manuscript data received by a printing control apparatus in the variable printing (hereinafter, called “variable manuscript data”) is made up of a plurality of records. For example, one record corresponds to a printed matter (such as a record, an invoice, or a direct mail) related to one customer. In such variable printing, a part or all of parts used may vary among pages. On the other hand, reuse parts can be used among pages. 
     The printing system  1  has a printing control apparatus  10  and a printer  20 . The printing control apparatus  10  and the printer  20  are connected to each other via a communication line. To the printing control apparatus  10 , a plurality of editing apparatuses  2  are connected via a network  3 . The network  3  may be the Internet or an Local Area Network (LAN). The printing control apparatus  10  and the editing apparatus  2  may be connected to each other not necessarily by the network  3  but by a communication line or the like. 
     The editing apparatus  2  is typically a PC. The editing apparatus  2  is used for generating variable manuscript data. The variable manuscript data is generated by editing parts to be used in each page and laying them out. The editing process is performed by using, for example, Desk Top Publishing (DTP) software. The variable manuscript data is data described in the PDL. As the PDL, for example, PostScript (a registered trademark of Adobe Systems Incorporated) is used. The variable manuscript data generated by each of the editing apparatuses  2  is transmitted to the printing control apparatus  10  via the network  3 . Although the plurality of editing apparatuses  2  are connected to the network  3  in  FIG. 1 , the number of editing apparatuses  2  may be one. 
     The printing control apparatus  10  performs the RIP process and the like on the variable manuscript data received via the network  3  to generate printing output data. The printing output data includes RIP-processed data as output data and synthesis information used for synthesizing the RIP-processed data. The variable manuscript data to be processed in the printing control apparatus  10  is obtained by integrating variable manuscript data transmitted from the plurality of editing apparatuses  2 . The printing output data generated by the printing control apparatus  10  is transmitted to the printer  20  via the communication line. 
     The printer  20  outputs a printed matter based on the printing output data received via the communication line. The printer  20  is, for example, an ink jet printer. Although one printer  20  is connected to the printing control apparatus  10  in  FIG. 1 , the present invention is not limited to the configuration. A plurality of printers  20  may be connected to the printing control apparatus  10 . 
     &lt;2. Configuration of Printing Control Apparatus&gt; 
       FIG. 2  is a diagram illustrating a hardware configuration of the printing control apparatus  10  in the embodiment. As illustrated in  FIG. 2 , the printing control apparatus  10  has a body  11 , an auxiliary storage apparatus  12 , a disk drive  13 , a display apparatus  14 , a keyboard  15 , a mouse  16 , and the like. The body  11  includes a CPU  111 , a memory  112 , a first disk interface unit  113 , a second disk interface unit  114 , a display control unit  115 , an input interface unit  116 , a network interface unit  117 , and an output interface unit  118 . The CPU  111 , the memory  112 , the first disk interface unit  113 , the second disk interface unit  114 , the display control unit  115 , the input interface unit  116 , the network interface unit  117 , and the output interface unit  118  are connected to one another via a system bus. The auxiliary storage apparatus  12  is connected to the first disk interface unit  113 . The disk drive  13  is connected to the second disk interface unit  114 . The display apparatus  14  is connected to the display control unit  115 . The keyboard  15  and the mouse  16  are connected to the input interface unit  116 . The network  3  is connected to the network interface unit  117 . The printer  20  is connected to the output interface unit  118  via the communication line. The auxiliary storage apparatus  12  is a magnetic disk drive or the like. To the disk drive  13 , a computer-readable recording medium such as a CD-ROM  40  is inserted. To the disk drive  13 , not only the CD-ROM  40  but also a CD-R/RW or the like can be inserted as described later. The display apparatus  14  is a liquid crystal display or the like. The display apparatus  14  is used for displaying information desired by an operator. The keyboard  15  and the mouse  16  are used to enter an instruction to the printing control apparatus  10  by an operator. 
     In the auxiliary storage apparatus  12 , a program  30  for the printing control process in the embodiment (hereinafter, called “printing control program”) is stored. The CPU  111  controls the entire printing control apparatus  10 . The CPU  111  realizes various functions of the printing control apparatus  10  by executing the printing control program  30  stored in the auxiliary storage apparatus  12 , in the memory  112 . The memory  112  includes an Random Access Memory (RAM) and an Read Only Memory (ROM). The memory  112  functions as a work area in which the CPU  111  executes the printing control program  30  stored in the auxiliary storage apparatus  12 . The printing control program  30  is provided by, for example, being stored in the CD-ROM  40  or the like. That is, the user purchases the CD-ROM  40  or the like as a recording medium of the printing control program  30 , inserts it into the disk drive  13 , reads the printing control program  30  from the CD-ROM  40 , and installs the program into the auxiliary storage apparatus  12 . Alternatively, the printing control program  30  transmitted via the network  3  can be received and installed into the auxiliary storage apparatus  12 . 
       FIG. 3  is a block diagram illustrating a functional configuration of a main part of the printing control apparatus  10  in the embodiment. As illustrated in  FIG. 3 , the printing control apparatus  10  has a reuse information obtaining unit  51 , a data control unit  52 , first to fourth RIP processing units  61  to  64  as a plurality of output processing units, and first to fourth cache units  71  to  74  as first storage units. The reuse information obtaining unit  51 , the data control unit  52 , the first to fourth RIP processing units  61  to  64 , and the first to fourth cache units  71  to  74  are realized as a result of executing the printing control program  30  by the CPU  111  in the memory  112 . In the embodiment, a parallel RIP process is executed using the first to fourth RIP processing units  61  to  64 . The first to fourth cache units  71  to  74  correspond to the first to fourth RIP processing units  61  to  64 , respectively. Each cache unit is realized when a part of the storage region of the memory  112  is assigned to an RIP processing unit corresponding to the cache unit. In the embodiment, the configuration that the printing control apparatus  10  has four RIP processing units (first to fourth RIP processing units  61  to  64 ) will be described. It is, however, sufficient that the number of RIP processing units is plural (similarly, it is sufficient that the number of cache units is plural). 
     The variable manuscript data includes two kinds of parts. One of the parts is a part whose content varies among records (hereinafter, called a “variable part”). The other part is a part which is used a plurality of times in variable manuscript data, that is, reused (hereinafter, called a “reuse part”). 
     The reuse information obtaining unit  51  obtains information related to reuse of parts (hereinafter, called “reuse information”) from variable manuscript data. The reuse part information includes, for example, the number of reuse times of each part. From the number of reuse times of each part, reuse parts in the variable manuscript data are known and variable parts in the variable manuscript data are also known. Detection of a reuse part may be performed together with known preflight check. The reuse information obtaining unit  51  transmits the obtained reuse information to the data control unit  52 . 
     The data control unit  52  assigns variable manuscript data to each of the RIP processing units. For example, the data control unit  52  transmits the variable manuscript data page by page in order of a first RIP processing unit  61 , a second RIP processing unit  62 , a third RIP processing unit  63 , a fourth RIP processing unit  64 , the first RIP processing unit  61 , . . . . Hereinafter, variable manuscript data of one page will be described as “page data”. In the case where a reuse part is used in page data to be transmitted, the data control unit  52  transmits information indicative of the reuse part in the received reuse information together with the page data. The data control unit  52  controls transmission of printing output data from each of the RIP processing units to the printer  20 . That is, the data control unit  52  functions as an output control unit. 
     Each of the RIP processing units performs the RIP process on each of parts in received page data to generate RIP-processed data obtained by performing the RIP process on data indicative of a variable part (hereinafter, called “variable part data”) in the page data (hereinafter, called “RIP-processed variable part data”) and to generate RIP-processed data obtained by performing the RIP process on data indicative of a reuse part (hereinafter, called “reuse part data”) in the page data (hereinafter, called “RIP-processed reuse part data”). In the embodiment, the RIP-processed data corresponds to output data. The RIP-processed reuse part data corresponds to a reuse part in output data. 
     To RIP-processed reuse part data, an RIP processing unit assigns an identifier unique to the RIP-processed reuse part data based on received reuse information. The data form of an identifier is not limited and various forms such as a serial number and  16 -bit data can be employed. Assignment of an identifier to RIP-processed reuse part data may be performed by the data control unit  52  based on reuse information. 
     An RIP processing unit obtains synthesis information to be used for synthesizing RIP-processed data in the printer  20  from received page data. Alternatively, the data control unit  52  may obtain synthesis information from variable manuscript data. 
     An RIP processing unit caches RIP-processed variable part data, RIP-processed reuse part data, and an identifier corresponding to the RIP-processed reuse part data into a corresponding cache unit. Hereinafter, various RIP-processed data and/or identifiers cached in the cache unit will be collectively called “cache data”. Each RIP processing unit may cache synthesis information in a corresponding cache unit. 
     An RIP processing unit reads cache data from a cache unit in accordance with control of the data control unit  52  and transmits synthesis information and RIP-processed data included in the cache data as printing output data to the printer  20 . The RIP-processed data and the synthesis information may be transmitted at different timings to the printer  20 . In the case where the data control unit  52  obtains synthesis information from variable manuscript data, the synthesis information may be transmitted from the data control unit  52  to the printer  20 . Synthesis information can be transmitted to the printer  20  in various transmitting methods. 
     In the embodiment, in the case where a variable part is used, RIP-processed variable part data corresponding to the variable part is certainly transmitted. On the other hand, in the case where a reuse part is used, RIP-processed reuse part data corresponding to the reuse part is transmitted only when variable manuscript data is used for the first time in all of pages, and is not transmitted when the data is used for the second time and subsequent times. The details of the process of transmitting RIP-processed data in printing output data will be described later. 
     &lt;3. Configuration of Printer&gt; 
       FIG. 4  is a block diagram illustrating a functional configuration of a main part of the printer  20  in the embodiment. As illustrated in  FIG. 4 , the printer  20  has a printing unit  21  and a storage unit  22  as a second storage unit. The printing unit  21  includes a control unit  211  and a printing execution unit  212 . The configuration of such a printer  20  is disclosed in, for example, Japanese Patent Application Laid-Open Publication No. 2002-287934. 
     The control unit  211  receives printing output data and stores it into the storage unit  22 . It is sufficient to store at least RIP-processed data in the storage unit  22 , and synthesis information may not be stored. The control unit  211  reads synthesis information and RIP-processed data necessary for synthesis from the storage unit  22  and transmits them to the printing execution unit  212 . The printing execution unit  212  synthesizes RIP-processed data based on the synthesis information and outputs a printed matter of one page. In the case where the number of kinds of RIP-processed data is only one, without performing synthesis of RIP-processed data, a printed matter is output. 
     &lt;4. Cache Process&gt; 
       FIG. 5  is a flowchart illustrating an example of the procedure of cache process of RIP-processed data and identifiers in the embodiment. The cache process shown in  FIG. 5  is performed by an RIP processing unit. As will be described later, a part of the cache process may be performed by the data control unit  52 . The cache process may be performed on the page unit basis or every RIP-processed data. 
     First, whether RIP-processed data obtained by the RIP process is RIP-processed reuse part data or not is determined (step S 10 ). In the case where the RIP-processed data obtained by the RIP process is RIP-processed reuse part data, the program advances to step S 11 . In the case where the RIP-processed data obtained by the RIP process is not RIP-processed reuse part data, that is, is RIP-processed variable part data, the RIP-processed variable part data is cached in a corresponding cache unit (step S 12 ). After step S 12 , the cache process is finished. 
     In step S 11 , whether the RIP-processed reuse part data is already cached in a corresponding cache unit or not is determined. In the case where the RIP-processed reuse part data is already cached, caching of the RIP-processed reuse part data is not performed, and the cache process is finished. In the case where the RIP-processed reuse part data is not cached yet, the RIP-processed reuse part data is cached together with a corresponding identifier (step S 13 ). After step S 13 , the cache process is finished. Whether RIP-processed reuse part data is cached or not may be determined by an RIP processing unit or the data control unit  52 . The determination is made, for example, based on an identifier corresponding to RIP-processed reuse part data. 
       FIG. 6  is a diagram for explaining the cache process of RIP-processed data and identifiers in the embodiment. In the example illustrated in  FIG. 6 , it is assumed that one reuse part and one variable part are used in each page, and caching of RIP-processed reuse part data to each of cache units is the first time. 
     The first RIP processing unit  61  receives first page data  91  and performs the RIP process on it, thereby generating RIP-processed reuse part data  101  and first RIP-processed variable part data  102   a.  The first RIP processing unit  61  caches the RIP-processed reuse part data  101 , the first RIP-processed variable part data  102   a,  and an identifier  103  corresponding to the RIP-processed reuse part data  101  in the first cache unit  71 . 
     The second RIP processing unit  62  receives second page data  92  and performs the RIP process on it, thereby generating the RIP-processed reuse part data  101  and second RIP-processed variable part data  102   b.  The second RIP processing unit  62  caches the RIP-processed reuse part data  101 , the second RIP-processed variable part data  102   b,  and the identifier  103  corresponding to the RIP-processed reuse part data  101  in the second cache unit  72 . 
     The third RIP processing unit  63  receives third page data  93  and performs the RIP process on it, thereby generating the RIP-processed reuse part data  101  and third RIP-processed variable part data  102   c.  The third RIP processing unit  63  caches the RIP-processed reuse part data  101 , the third RIP-processed variable part data  102   c,  and the identifier  103  corresponding to the RIP-processed reuse part data  101  in the third cache unit  73 . 
     The fourth RIP processing unit  64  receives fourth page data  94  and performs the RIP process on it, thereby generating the RIP-processed reuse part data  101  and fourth RIP-processed variable part data  102   d.  The fourth RIP processing unit  64  caches the RIP-processed reuse part data  101 , the fourth RIP-processed variable part data  102   d,  and the identifier  103  corresponding to the RIP-processed reuse part data  101  in the fourth cache unit  74 . 
     &lt;5. RIP-Processed Data Transmitting Process&gt; 
       FIG. 7  is a flowchart illustrating an example of the procedure of process of transmitting RIP-processed data in the embodiment. Since a method of transmitting synthesis information in printing output data is not limited as described above, it is not described here. The procedure of process of transmitting RIP-processed data shown in  FIG. 7  is performed in each RIP processing unit. First, cache data is read and transmitted to an RIP processing unit (step S 21 ). The cache data read here corresponds to page data of one page. 
     Next, in the RIP processing unit, the read cache data is analyzed. Concretely, whether the RIP-processed data is RIP-processed reuse part data or not is determined (step S 22 ). The determination is performed, for example, based on the presence/absence of an identifier. In the case where the RIP-processed data is RIP-processed reuse part data, the program advances to step S 23 . In the case where the RIP-processed data is not RIP-processed reuse part data, that is, is RIP-processed variable part data, the RIP-processed variable part data is transmitted to the printer  20  (step S 24 ). After step S 24 , the program advances to step S 27 . 
     In step S 23 , a determination is made as to whether or not an identifier corresponding to RIP-processed reuse part data is the same as the identifier corresponding to the RIP-processed reuse part data, which is already transmitted to the printer  20  (hereinafter, called “transmitted identifier”). Hereinafter, determination of whether an identifier is a transmitted identifier or not in step S 23  will be described as “identifier determination”. In the case where an identifier corresponding to RIP-processed reuse part data is a transmitted identifier, the RIP-processed reuse part data is not transmitted to the printer  20  (step S 25 ). In the case where an identifier corresponding to RIP-processed reuse part data is not a transmitted identifier, the RIP-processed reuse part data is transmitted to the printer  20  (step S 26 ). After steps S 25  and S 26 , the program advances to step S 27 . 
     In step S 27 , whether analysis on all of the RIP-processed data in the cache data is finished or not is determined. In the case where it is finished, the RIP-processed data transmitting process is finished. In the case where it is not finished, the program returns to step S 22 . 
     The identifier determination is performed by, for example, the data control unit  52  or an RIP processing unit. First, the case where the identifier determination is performed by the data control unit  52  will be described. In the case where cache data read from a corresponding cache unit includes an identifier, an RIP processing unit transmits the identifier to the data control unit  52 . The data control unit  52  performs the identifier determination by determining whether or not the received identifier is the same as the transmitted identifier, in other words, the identifier already received from the first to fourth RIP processing units  61  to  64 . The data control unit  52  can store an identifier received from an RIP processing unit to, for example, a predetermined storage table or the like. By referring to an identifier received in the past using such a storage table, the data control unit  52  can determine whether the received identifier is the same as that already received from the first to fourth RIP processing units  61  to  64  or not. The method of determining whether a received identifier is the same as that already received from the first to fourth RIP processing units  61  to  64  or not is not limited to the example described above, but various other methods can be employed. In the case where the received identifier is a transmitted identifier, the data control unit  52  does not give an instruction to transmit RIP-processed reuse part data corresponding to the identifier to the printer  20 , or gives an instruction not to transmit RIP-processed reuse part data corresponding to the identifier to the printer  20 , to the RIP processing unit as the transmitter. In the case where the received identifier is not a transmitted identifier, the data control unit  52  instructs an RIP processing unit as the transmitter to transmit RIP-processed reuse part data corresponding to the identifier to the printer  20 . 
     Next, the case where the identifier determination is performed by an RIP processing unit will be described. In the case where cache data read from a corresponding cache unit includes an identifier, an RIP processing unit performs the identifier determination by determining whether or not the identifier is the same as the transmitted identifier, in other words, the identifier already read by any of the first to fourth RIP processing units  61  to  64 . Each of the RIP processing units has, for example, a predetermined storage table and can store an identifier which is read from a corresponding cache unit into the storage table. The first to fourth RIP processing units  61  to  64  can mutually refer to identifiers which were read in the past by using the storage tables. By referring to the storage tables in the first to fourth RIP processing units  61  to  64 , each of the RIP processing units can determine whether an identifier read from a corresponding cache unit is the same as that already read by any of the first to fourth RIP processing units  61  to  64  or not. The method of determining whether an identifier read from a corresponding cache unit is the same as that already read by any of the first to fourth RIP processing units  61  to  64  or not is not limited to the example described above, but various other methods can be employed. 
     Although description has been given on assumption that an actor performing the identifier determination is the data control unit  52  or an RIP processing unit, the present invention is not limited to the case. It is sufficient that the identifier determination can be performed in the printing control apparatus  10 . 
       FIG. 8  is a diagram for explaining the process of transmitting RIP-processed data in the embodiment. In the embodiment, the process of transmitting RIP-processed data is performed in order of the first RIP processing unit  61 , the second RIP processing unit  62 , the third RIP processing unit  63 , the fourth RIP processing unit  64 , the first RIP processing unit  61 , . . . . As illustrated in  FIG. 8 , in each cache unit, cache data similar to that in the example shown in  FIG. 6  is cached. In description of  FIG. 8 , it is assumed that the identifier determination is performed by the data control unit  52 . 
     At a timing when RIP-processed data corresponding to a printed matter  201  of the first page is to be transmitted, the first RIP processing unit  61  reads the RIP-processed reuse part data  101 , the identifier  103  corresponding to the data  101 , and the first RIP-processed variable part data  102   a  cached in the first cache unit  71 . The first RIP processing unit  61  transmits the read identifier  103  to the data control unit  52 . It is assumed that the number of times that the data control unit  52  receives the identifier  103  from any of the first to fourth RIP processing units  61  to  64  is one at this time. That is, the identifier  103  read by the first RIP processing unit  61  is not a transmitted identifier. Consequently, the data control unit  52  instructs the first RIP processing unit  61  to transmit the RIP-processed reuse part data  101  to the printer  20 . The first RIP processing unit  61  transmits the first RIP-processed variable part data  102   a  to the printer  20  automatically without an instruction of the data control unit  52  or simultaneously with the RIP-processed reuse part data  101 . In such a manner, the first RIP processing unit  61  transmits, as RIP-processed data, both of the RIP-processed reuse part data  101  and the first RIP-processed variable part data  102   a  to the printer  20 . 
     At a timing when RIP-processed data corresponding to a printed matter  202  of the second page is to be transmitted, the second RIP processing unit  62  reads the RIP-processed reuse part data  101 , the identifier  103  corresponding to the data  101 , and the second RIP-processed variable part data  102   b  cached in the second cache unit  72 . The second RIP processing unit  62  transmits the read identifier  103  to the data control unit  52 . At this time, the identifier  103  has already been transmitted from the first RIP processing unit  61  to the data control unit  52 . Consequently, the number of times that the data control unit  52  receives the identifier  103  from any of the first to fourth RIP processing units  61  to  64  is the second time. That is, the identifier  103  read by the second RIP processing unit  62  is a transmitted identifier. Therefore, the data control unit  52  does not give an instruction to transmit the RIP-processed reuse part data  101  to the printer  20  or gives an instruction not to transmit the RIP-processed reuse part data  101  to the printer  20 , to the second RIP processing unit  62 . The second RIP processing unit  62  transmits the second RIP-processed variable part data  102   b  to the printer  20  automatically without an instruction of the data control unit  52  or by an instruction of the data control unit  52 . In such a manner, the second RIP processing unit  62  transmits, as RIP-processed data, only the second RIP-processed variable part data  102   b  to the printer  20 . In a manner similar to the second RIP processing unit  62 , the third and fourth RIP processing units  63  and  64  transmit third and fourth RIP-processed variable part data  102   c  and  102   d  to the printer  20 . 
     &lt;6. Printed Matter Generating Process&gt; 
       FIG. 9  is a flowchart illustrating an example of the procedure of processes for generating a printed matter (hereinafter, called “printed matter generating process”) in the printer  20  in the embodiment. First, printing output data corresponding to a printed matter of each page received by the control unit  211  is stored in the storage unit  22  (step S 31 ). Therefore, even if the RIP-processed reuse part data is transmitted only once as described above, the RIP-processed reuse part data can be used in each page at the time of synthesizing the RIP-processed data. 
     Next, by the control unit  211 , synthesis information and RIP-processed data necessary for synthesis is read from the storage unit  22  (step S 32 ). The RIP-processed data necessary for synthesis is determined by synthesis information. The synthesis information and the read RIP-processed data are transmitted to the printing execution unit  212 . 
     By the printing execution unit  212 , the RIP-processed data is synthesized based on the synthesis information, and a printed matter of one page expressing the synthesis state of the RIP-processed data is output (step S 33 ). 
     In the example shown in  FIG. 8 , the control unit  211  receives, as printing output data corresponding to the printed matter  201  of the first page, the synthesis information of the first page, the RIP-processed reuse part data  101 , and the first RIP-processed variable part data  102   a,  and stores them to the storage unit  22 . After that, the control unit  211  reads the synthesis information of the first page, the RIP-processed reuse part data  101  and the first RIP-processed variable part data  102   a  necessary for synthesis from the storage unit  22 , and transmits them to the printing execution unit  212 . The printing execution unit  212  synthesizes the RIP-processed reuse part data  101  and the first RIP-processed variable part data  102   a  based on the synthesis information of the first page, and outputs the printed matter  201  of the first page expressing a state where the data is synthesized. 
     The control unit  211  receives, as printing output data corresponding to the printed matter  202  of the second page, the synthesis information of the second page and the second RIP-processed variable part data  102   b,  and stores them to the storage unit  22 . The printing output data does not include the RIP-processed reuse part data  101 . After that, the control unit  211  reads the synthesis information of the second page, the RIP-processed reuse part data  101  and the second RIP-processed variable part data  102   b  necessary for synthesis from the storage unit  22 , and transmits them to the printing execution unit  212 . The printing execution unit  212  synthesizes the RIP-processed reuse part data  101  and the second RIP-processed variable part data  102   b  based on the synthesis information of the second page, and outputs the printed matter  202  of the second page expressing a state where the data is synthesized. Printed matters  203  and  204  of the third and fourth pages are output by a procedure similar to that of the printed matter  202  of the second page. 
     &lt;7. Advantages&gt; 
     According to the embodiment, in the printing control apparatus which caches RIP-processed data, an identifier corresponding to RIP-processed reuse part data is cached. Since identifier determination using the identifier is performed, RIP-processed reuse part data of the same kind is transmitted to the printer  20  only at the time of use for the first time. Consequently, the speed of the printing output data transmitting process becomes higher than that of the conventional case. The speed of the entire printing process can be made higher than that of the conventional case. 
     In the embodiment, a parallel RIP process is performed. As compared with the case of performing the RIP process using one RIP processing unit, the speed of the RIP process can be increased. Accordingly, the speed of the entire printing process can be further increased. 
     In the embodiment, RIP-processed data is cached in a cache unit. Consequently, in the case where RIP-processed data has to be retransmitted to the printer  20  such as a case where, for example, deficiency, disappearance, or the like of RIP-processed data occurs in the printer  20 , it is sufficient to retransmit RIP-processed data cached in a cache unit. It is unnecessary to perform the RIP process again. Thus, the speed of the entire printing process in the case where retransmission of RIP-processed data is necessary can be increased. 
     &lt;8. First Modification&gt; 
       FIG. 10  is a block diagram illustrating a functional configuration of a main part of the printing control apparatus  10  in a first modification of the embodiment. In the modification, as illustrated in  FIG. 10 , a common cache unit  75  which is commonly used for the first to fourth RIP processing units  61  to  64  is provided in place of the first to fourth cache units  71  to  74 . The common cache unit  75  is realized by assigning a part of the storage region of the memory  112  commonly to the first to fourth RIP processing units  61  to  64 . 
       FIG. 11  is a diagram for explaining the cache process of RIP-processed data and identifiers in the modification. In the modification, the first to fourth RIP processing units  61  to  64  use the common cache unit  75  for caching, so that it is sufficient to cache RIP-processed reuse part data of one kind and an identifier corresponding to the data once by any of the first to fourth RIP processing units  61  to  64 . For example, as illustrated in  FIG. 11 , it is sufficient that only the first RIP processing unit  61  caches the RIP-processed reuse part data  101  and the identifier  103  corresponding to the data in the common cache unit  75 , and the second to fourth RIP processing units  62  to  64  do not have to perform similar caching. Consequently, as compared with the foregoing embodiment, the efficiency of the cache process can be increased. 
     &lt;9. Second Modification&gt; 
       FIG. 12  is a block diagram illustrating a functional configuration of a main part of the printing control apparatus  10  in a second modification of the embodiment. In the modification, as illustrated in  FIG. 12 , the reuse information obtaining unit  51  is not provided. On the other hand, variable manuscript data in the modification preliminarily includes reuse information in the embodiment. In the modification, by using reuse information included in variable manuscript data, an advantage similar to that of the embodiment can be obtained. 
     &lt;10. Third Modification&gt; 
       FIG. 13  is a diagram for explaining a cache process of RIP-processed data and identifiers in a third modification of the embodiment. In the modification, as illustrated in  FIG. 13 , a unique identifier is assigned to not only RIP-processed reuse part data but also RIP-processed variable part data. An identifier assigning method is similar to that of the foregoing embodiment. 
     The first RIP processing unit  61  also caches an identifier  104   a  (hereinafter, called “first variable identifier”) corresponding to the first RIP-processed variable part data  102   a  into the first cache unit  71 . The second RIP processing unit  62  also caches an identifier  104   b  (hereinafter, called “second variable identifier”) corresponding to the second RIP-processed variable part data  102   b  into the second cache unit  72 . The third RIP processing unit  63  also caches an identifier  104   c  (hereinafter, called “third variable identifier”) corresponding to the third RIP-processed variable part data  102   c  into the third cache unit  73 . The fourth RIP processing unit  64  also caches an identifier  104   d  (hereinafter, called “fourth variable identifier”) corresponding to the fourth RIP-processed variable part data  102   d  into the fourth cache unit  74 . 
       FIG. 14  is a flowchart illustrating an example of the procedure of cache process of RIP-processed data and identifiers in the modification. In the modification, as illustrated in  FIG. 14 , step S 22  of determining whether RIP-processed data is RIP-processed reuse part data or not and step S 24  of transmitting RIP-processed data to the printer  20  in the case where the RIP-processed data is RIP-processed variable part data are not provided. Since none of identifiers corresponding to RIP-processed variable part data in the modification are transmitted identifiers, all of the identifiers are always transmitted to the printer  20  in a manner similar to the embodiment (steps S 23  and S 26 ).  FIG. 15  is a diagram for explaining a process of transmitting RIP-processed data in the modification. In the modification, as illustrated in  FIG. 15 , since none of the first to fourth variable identifiers  104   a  to  104   d  are transmitted identifiers, they are transmitted to the printer  20 . 
     In the modification, in a mode of assigning an identifier without discriminating RIP-processed reuse part data and RIP-processed variable part data, an advantage similar to that of the foregoing embodiment can be obtained. 
     &lt;11. Others&gt; 
     Although it has been described that the first to fourth cache units  71  to  74  are realized by the memory  112  in the embodiment and the common cache unit  75  is realized by the memory  112  in the first modification of the embodiment, the invention is not limited to the configurations. The first to fourth cache units  71  to  74  and the common cache unit  75  may be realized by the auxiliary storage apparatus  12  or the like. 
     Although it has been described that the parallel RIP process is performed in the foregoing embodiment and the modifications, the invention is not limited to the parallel RIP process. An RIP process may be performed by using one RIP processing unit. In this case, only one cache unit is provided. Also in such a mode, the speed of the printing output data transmitting process can be increased more than the conventional case. 
     Although variable printing has been described as an example in the foregoing embodiment and the modifications, the invention is not limited to the variable printing. The present invention is not limited to the variable printing but can be applied to any printing in which RIP-processed data is transmitted part by part from a printing control apparatus to a printer and a part of the same kind is used a plurality of times. The present invention has been described specifically above and the above description is illustrative in all of aspects and is not restrictive. It is to be understood that a number of other changes or modifications are possible without departing from the scope of the present invention. 
     From the above, the present invention can provide the printing control apparatus, the printing system, the recording medium having recorded thereon the printing control program, and the printing control method realizing higher speed of the entire printing process. 
     This application claims priority based on Japanese Patent Application No. 2012-75808 filed on Mar. 29, 2012, and entitled “Printing control apparatus, Printing System, Printing Control Program, and Printing Control Method”, which is incorporated herein by reference in its entirety.