JP4345055B2 - Image processing apparatus and method, and printer system - Google Patents

Description

  The present invention relates to a technique for performing image processing in parallel using a plurality of processors.

  Generally, in a laser printer system, a print object described in PDL (page description language) is developed into a print image by a RIP (raster image processor), and sequentially sent to a print engine for each scan line (raster) for printing. Execute.

  At this time, if all the print images are developed and stored for one page, a very large memory area is required. Therefore, it is common to divide one page into bands composed of a plurality of scanning lines and develop a print image in that unit.

In order to perform such band-by-band expansion processing at high speed, a configuration has been proposed in which each band is assigned to each of a plurality of processors and the expansion processing is performed in parallel (Patent Document 1).
JP 2003-51019 A

  When the RIP is provided in the host device, the developed print image needs to be transmitted to the printer side. In this case, since the print image has a large amount of data, it is usual to adopt a framework in which compression processing is performed before transmission by the host device and decompression is performed on the printer side.

  Here, when the host device or the printer includes a plurality of processors, a configuration in which each band is assigned to each of the plurality of processors and compression processing or decompression processing is performed in parallel as in Patent Document 1 can be considered.

  However, in such a method of parallelizing in units of bands, data of individual scanning lines (individual bands) is not parallelized. Therefore, there remains a problem that the time required for obtaining the processing result for the first one scanning line (one band) is the same as when processing is performed by a single processor. In other words, despite the parallelization by a plurality of processors, no advantage is obtained with respect to the rise until the actual printing is executed.

  In addition, in the case of the method of parallelization in units of bands, in order to improve the throughput, a memory area for storing the processing results for the number of processors so that each processor can execute processing in parallel for the band allocated to itself. Is required. Therefore, if the number of processors is increased to increase the degree of parallelism, there arises a problem that the memory area necessary for processing increases accordingly.

  As a result of studying the above problem, the inventors of the present application have determined that the plurality of processors in each of the partial areas when the individual scan lines are divided into a plurality of partial areas for at least one scan line constituting the image. It came to be thought that the said objective can be achieved by assigning at least one of them and performing image processing in parallel.

  Here, not only when image processing is executed by a single processor, but also when parallelization is performed by a plurality of processors as described above, the following problems may occur in image processing of individual processors. .

  That is, when performing image processing in the past, memory access is often based on byte-by-byte access, so each pixel is represented by 1 byte (or m bytes), and if N pixels, N bytes ( In general, the image processing is performed on byte-unit data such as N × m bytes).

  For example, when there is an image of 18 pixels having gradation values as shown in FIG. 15A, according to the conventional configuration, image processing is performed on 18-byte data as shown in FIG. 15B. Will be done. Under such a conventional configuration, even if each pixel of the image is expressed with a bit length of less than 1 byte, the image processing is performed after the pixel is raised to 1 byte. However, there arises a problem that a large number of memory areas are required for executing image processing. In addition, although the raised portion (the remaining 7 bits in the case of a 1-bit pixel) is originally unnecessary data (unused bits), it is treated as data to be calculated in processing. There is also a problem that processing time increases due to the calculation of originally unnecessary data.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-described problems, improve memory efficiency when executing image processing, and reduce processing time.

  The inventors of the present application have studied various configurations in order to achieve the above object, and as a result, the gradation data for each pixel is not expressed in bytes and image processing is performed, but the gradation data for a plurality of pixels is continuously displayed. Thus, it has been considered that the above problem can be solved by generating the arranged data string (bit string) and performing image processing on the generated data string in byte units.

  Here, image compression processing / image expansion processing is specifically assumed as the image processing. In this case, a data sequence of a plurality of pixels packed in byte units becomes an object of image compression, and thus results in an image expansion. Therefore, in order to finally use individual pixel data, a packed image is used. It is necessary to individually extract (unpack) the data of each pixel from the decompression result.

  For example, when the bit length of each pixel is a constant value, the data of each pixel can be extracted by extracting the data having the constant bit length in order from the beginning of the decompression result.

  On the other hand, even when each pixel is configured to take any one of a plurality of types of bit lengths, if the image decompression processing is performed by a single processor, a table (hereinafter referred to as a bit length array) , Referred to as “bit information table”), the data of each pixel can be extracted by extracting the data of the bit length described in the table in order from the beginning of the decompression result.

  However, as described above, when at least one of a plurality of processors is assigned to each partial area and image decompression processing is performed in parallel, the start position of each partial area and the start position of a periodic pattern of bit lengths are not necessarily included. Therefore, there is a problem that each processor cannot obtain a correct bit length of each pixel (cannot be appropriately unpacked) by applying a periodic pattern in order from the top of its own partial area.

  Therefore, an object of the present invention is to provide a framework that can be appropriately unpacked when assigning at least one of a plurality of processors to each of the partial areas and performing image expansion processing in parallel.

  The image processing apparatus according to the present invention arranges data of each pixel when the bit length of each pixel of the scan line is L1 to LN for at least one scan line constituting the image (L1 +... + LN) Image processing of the scanning line is performed at least for a long data string.

  According to the configuration of the present invention, compared to the conventional configuration in which image processing is performed after the gradation data of each pixel of the image is increased in units of bytes, the capacity of the memory area necessary for execution of the image processing, the calculation target, and the like. Therefore, it is possible to efficiently execute image processing.

  An image processing apparatus of the present invention is an image processing apparatus that performs image processing in parallel using a plurality of processors, and for each of at least one scanning line constituting an image, each scanning line is divided into a plurality of partial regions. Control means for assigning at least one of the plurality of processors to each of the partial areas and performing image processing in parallel, wherein the control means includes a bit of each pixel of the partial area corresponding to a certain processor. When the lengths are L1 to LN, respectively, the processor performs control so that image processing of the partial region is performed at least for a data string of (L1 +... + LN) length in which the data of the respective pixels are arranged. It is characterized by.

  Preferably, in the image, an arrangement of bit lengths of each pixel forms a periodic pattern, and a boundary of the partial region coincides with at least one of the boundaries of the periodic pattern. In this case, there is provided means for storing the periodic pattern, and the control means applies the periodic pattern to the (L1 +... + LN) length data string to obtain the bit length of each pixel, and The information may be extracted.

  According to such a configuration, the start position of each partial region and the start position of the periodic pattern are always matched, and pixels are stored in the data string with a bit length that matches the periodic pattern from the beginning. Therefore, for any partial region, gradation data of each pixel can be extracted if bit length data is extracted in the order of the periodic pattern from the top of the data string.

  Preferably, at least one of the bit lengths L1 to LN of each pixel is different from other bit lengths.

  Preferably, the image processing is image compression processing or image expansion processing.

  A printer control apparatus according to the present invention is a printer control apparatus having a function of performing image processing in parallel using a plurality of processors, and for each of at least one scan line constituting an image, each scan line is divided into a plurality of partial areas. Control means for assigning at least one of the plurality of processors to each of the partial areas, performing image compression processing in parallel, and transmitting compressed data corresponding to the partial areas to the printer device And when the bit length of each pixel of the partial area corresponding to a certain processor is L1 to LN, the control means arranges the data of each pixel (L1 +... + LN) length Control is performed so as to perform image compression processing of the partial area at least for the data string.

  The printer device of the present invention is a printer device having a function of performing image processing in parallel using a plurality of processors, and comprises a storage means for storing a periodic pattern for specifying the arrangement of bit lengths of each pixel, and an image For each of the at least one scan line, when each scan line is divided into a plurality of partial areas, the compressed partial data corresponding to each of the partial areas is received from the host device, and the compressed partial data is received from the plurality of processors. Control means for allocating at least one of them and performing image decompression processing in parallel. The control means, when the bit length of each pixel of the partial area corresponding to a certain processor is L1 to LN, respectively, At least a data string of (L1 +... + LN) length in which the data of each pixel output as a result of the image decompression process is arranged. As elephant, by applying the periodic pattern obtains the bit length of each pixel, and extracts the information for each pixel.

  The printer system according to the present invention includes a host device and a printer device configured to be communicable with the host device, and each of the host device and the printer device performs image processing in parallel using a plurality of processors. A host system having a function, wherein at least one scanning line constituting an image, the host device divides each scanning line into a plurality of partial areas, and each of the partial areas includes a plurality of processors. First control means for performing image compression processing in parallel by assigning at least one, and transmitting compressed data corresponding to each partial area (hereinafter referred to as “compressed partial data”) to a printer device; When the bit length of each pixel of the partial area corresponding to a certain processor is L1 to LN, The processor controls to perform the image compression processing of the partial area for at least a data string of (L1 +... + LN) length in which the data of each pixel is arranged, and the printer device arranges the bit length of each pixel. Storage means for storing a periodic pattern for identifying the compressed partial data corresponding to each of the partial areas when the individual scanning lines are divided into a plurality of partial areas for at least one scanning line constituting the image. Second control means for receiving at least one of a plurality of processors from the host device and performing image decompression processing in parallel by assigning at least one of the plurality of processors to the compressed partial data, wherein the second control means is a partial area corresponding to a certain processor. When the bit length of each pixel is L1 to LN, the data of each pixel output as a result of the image expansion processing by the processor is displayed. The bit length of each pixel is obtained by applying the periodic pattern to at least a data string of (L1 +... + LN) length in which data is arranged, and information for each pixel is extracted.

  According to the image processing method of the present invention, when the bit length of each pixel of the scan line is L1 to LN for at least one scan line constituting the image, the data of each pixel is arranged (L1 +... + LN) Image processing of the scanning line is performed at least for a long data string.

  The image processing method of the present invention can be implemented by a computer, and a computer program therefor can be installed or loaded on the computer through various media such as a CD-ROM, a magnetic disk, a semiconductor memory, and a communication network. . It also includes the case where a computer program is recorded and distributed on a printer card or printer option board.

  According to the present invention, it is possible to improve memory efficiency and reduce processing time when executing image processing. In addition, it is possible to provide a framework that can be appropriately unpacked when assigning at least one of a plurality of processors to each partial region and performing image decompression processing in parallel.

(First embodiment)
FIG. 1 is a block diagram showing a hardware configuration of a printer system 1 according to an embodiment of the present invention. As shown in FIG. 1, the printer system 1 may be any of a host device 10 and a communication network (LAN, Internet, dedicated line, packet communication network, a combination thereof, etc., and includes both wired and wireless. ), A printer device (image forming device) 20 configured to be communicable with the host device 10.

  The host device 10 includes hardware such as a main CPU, a parallel processing unit 15 including parallel processors 11 to 14, a ROM, a RAM, a user interface, and a communication interface. In the present embodiment, the parallel processing unit 15 includes four processors 11 to 14, but the number of processors can be any number greater than or equal to 2 (for example, 8) depending on the design.

  The host device 10 includes a printer driver unit 16 as a normal control function necessary for causing the printer device 20 to execute printing.

  The printer driver unit 16 has the same functional configuration as that of a normal printer driver, and is described in a predetermined printer control language such as a postscript in response to a print request from an application program operating on the host device 10, for example. RIP means for generating a raster image based on data to be printed, image processing means for creating a print image by performing predetermined image processing (halftone processing, etc.) on the raster image, and the like.

  However, as will be described later, the printer driver unit 16 of the present embodiment performs a pack process for generating a data string in which gradation data of each pixel is continuously arranged for each scanning line constituting the print image. And a compression control means 17 for executing image compression processing in parallel using the parallel processing unit 15 and a transfer means 18 for transferring the compression processing result by the parallel processing unit 15 to the printer device 20. This is different from the conventional configuration (see FIG. 2).

  Each of these means is functionally realized by the main CPU executing a program stored in a ROM or RAM in the host device 10 or an external storage medium.

  The printer device 20 includes a power mechanism unit and a printer controller 26.

  The power mechanism unit includes a paper feed mechanism that supplies paper into the printer, a print engine that performs printing, and a paper discharge mechanism that discharges paper outside the printer. As the print engine, for example, a serial printer that prints in units of characters, such as an inkjet printer or a thermal transfer printer, a line printer that prints in units of lines, a page printer that prints in units of pages, and the like are used. it can.

  The printer controller 26 includes a main CPU, a parallel processing unit 25 including processors 21 to 24, a ROM, a RAM, a user interface, a communication interface, and the like. In the present embodiment, the parallel processing unit 25 includes four processors 21 to 24. However, the number of processors can be any number of 2 or more (e.g., 8) depending on the design. In addition, the power mechanism unit may include an independent CPU. In this case, the CPU of the power mechanism unit communicates with the main CPU of the information processing unit via a predetermined communication path to control the print engine. Thus, a printing operation is performed.

  The printer controller 26 has the same functional configuration as a printer controller in a normal printer. For example, the printer controller 26 receives a command or data from the host device 10 and stores it in a reception buffer, and controls the power mechanism unit to execute printing. The engine control means etc. to be provided are provided.

  However, as will be described later, the printer controller 26 according to the present embodiment uses the storage unit 27 that stores the bit information table and the parallel processing unit 25 to perform decompression that performs decompression processing in parallel on individual scanning lines. The control means 28, the unpacking means 29 for extracting data for each pixel from the decompressed data, and the transfer means 30 for transferring the print image obtained as a result of the decompression / unpacking process to the print engine in the order used for printing. Is different from the conventional configuration (see FIG. 2).

  Each of these means is realized by the main CPU executing a program stored in a ROM or RAM in the printer device 20, an external storage medium, or the like.

  Hereinafter, the printing process in the printer system 1 will be described with reference to a flowchart and an explanatory diagram shown in FIG. In addition, each process (including the partial process to which the code | symbol is not provided) can be arbitrarily changed in order within the range which does not produce contradiction in the processing content, or can be performed in parallel.

(Processing in the host device 10)
When the printer driver unit 16 receives a print request from an application program operating on the outside or the host device 10, the printer driver unit 16 transmits a print instruction command to the printer device 20 (printer controller 26), and also to the RIP unit or the like. To start the process.

  When the RIP unit receives an instruction to start processing, the RIP unit generates a raster image based on print target data described in a predetermined printer control language such as a postscript received from the application program. If the print target data can be received in the form of a raster image from an application program or the like, the processing by the RIP unit can be omitted.

  The image processing means performs predetermined image processing (halftone processing or the like) on the generated raster image, generates a print image, and stores it in a predetermined area of the RAM.

  Here, the halftone process employed in the present embodiment will be described.

  In this embodiment, a screen table and a table (hereinafter referred to as “gradation conversion table”) that stores a plurality of correspondence relationships between input gradation values on a raster image and output gradation values on a print image are used. Halftone processing.

  An example of the screen table is shown in FIG. In this example, reference numbers 1 to 9 (identifiers) are assigned in a 9 × 9 size matrix, and each reference number uniquely identifies each correspondence stored in the gradation conversion table. Note that reference numbers may be assigned without duplication depending on the design, and screen tables having other shapes and sizes may be used.

  An example of the gradation conversion table is shown in FIG. In the example shown in the figure, there are three types of correspondence relationships in which the bit length (number of expression bits) of the output gradation value is 3 bits, 2 bits, and 1 bit, respectively. The bit length is 3 bits, 2 bits for reference numbers 3-7, and 1 bit for reference numbers 8-9.

  As can be seen from the figure, the bit length is uniquely determined when the correspondence (reference number) is determined, and the correspondence (reference number) is uniquely determined by the element position in the screen table, so the bit length is the element in the screen table. It can be considered that it is determined according to the position. FIG. 3B shows a table in which bit lengths are associated with element positions in the screen table. Such a table corresponds to the bit information table described above.

  In this halftone process, one pixel on the raster image is converted into 9 × 9 pixels on the print image by applying a screen table to each pixel of the raster image. At this time, each gradation value of 9 × 9 pixels on the print image is obtained by using a gradation conversion table in which the gradation value of one pixel on the raster image is specified according to the position in the screen table. Each is determined by converting to a gradation value having a predetermined bit length. Therefore, in the print image obtained in this way, the arrangement of bit lengths forms a periodic pattern using the screen table (that is, the bit information table) as a basic pattern.

  When halftone processing is performed in this way and a print image is generated, the compression control means 17 performs parallel compression processing as follows. Note that the following processing may be executed sequentially when one or more scan lines are generated for the print image.

  First, the compression control means 17 selects lines in the main scanning direction (hereinafter simply referred to as “scanning lines”) constituting the generated print image in the order of the sub-scanning direction (FIG. 5: Step S100). The main scanning direction and the sub-scanning direction are determined based on scanning in the printer device 20.

  Next, the compression control means 17 divides the selected scanning line into a plurality of partial areas (FIG. 5: S101). At this time, the compression control unit 17 adds dummy pixels to the print image as necessary so that the boundary of the partial area matches at least one of the boundaries of the periodic pattern specified by the bit information table. (I.e., after padding) (see FIG. 6).

  A specific padding method will be described. For example, if the number of processors is P, the number of pixels in one scanning line of the print image is M, and the horizontal size of the bit information table is Q, the number of dummy pixels X to be added by padding is determined as follows.

if {M mod (P × Q) = 0}
then X = 0
else X = P * Q- (M mod (P * Q))
Then, X dummy pixels are added to the end of the scanning line, and then divided into equal P partial areas. Note that a pixel (dummy pixel) to be added by padding can be removed later if it is stored even if it is stored. However, here, a 1-bit dummy is added at the end of the scanning line. It is assumed that as many pixels as necessary are added. When padding is performed in this way, the number of pixels in each partial area is always a multiple of the horizontal size Q of the bit information table, so that the boundary of the partial area coincides with at least one of the boundaries of the periodic pattern.

  Hereinafter, the partial area divided in this way is referred to as a “channel”, and channel numbers are added in order of arrangement in the scanning line to identify each channel (see FIG. 7).

  Note that step S101 can be omitted if channels are defined in common for all scanning lines.

  Next, the compression controller 17 generates, for each partial data of the selected scanning line, a data string in which gradation data of each pixel in the partial data is continuously arranged (a pack process is performed). (FIG. 5: Step S102). That is, when the number of pixels in the partial data is N and the bit length of each pixel is L1 to LN, a data string (hereinafter referred to as “L1 +. A data string including at least “pack partial data” is generated and stored in a predetermined area of the RAM.

  For example, there is an image of 18 pixels having gradation values as shown in FIG. 15A, and the bit length of each pixel is (L1,..., L18) = (1, 1, 2, 2, 2, 2, 2, 3, 3, 1, 2, 2, 2, 2, 2, 3, 3), the compression control means 17 uses nine pixels as shown in FIG. A 5-byte data string including at least pack part data of 36 bits in length is generated by arranging gradation data (1 + 1 + 2 + 2 + 2 + 2 + 2 + 2 + 3 + 3 + 1 + 1 + 2 + 2 + 2 + 2 + 2 + 2 + 3 + 3). In the pack part data generated in this way, gradation data of a plurality of pixels is continuously stored (buried) in one byte except for the last byte, and each pixel is stored in units of bytes as in the past. However, there is no unused bit that has been generated when handling data by raising it.

  Next, the compression control means 17 assigns at least one of the processors 11 to 14 to each of the plurality of channels (FIG. 5: Step S103). Specifically, a combination of a channel and a processor is fixedly assigned, such as a processor 11 for channel 1 and a processor 12 for channel 2.

  Next, the compression control means 17 determines whether or not the allocated processor can process new data. If the allocated data can be processed, the compression control means 17 passes the head position of the corresponding packed partial data to the allocated processor, and An instruction to read the partial data is given (FIG. 5: Step S104).

  Here, the case where the processor can process new data is a case where the processor can newly write the next processing result. As a determination method, for example, when an output buffer writable by each of the processors 11 to 14 has a capacity corresponding to the processing result of one partial data, whether or not new writing can be performed depending on whether or not the processing result has been transferred. Therefore, a configuration can be considered in which a transfer end flag indicating whether or not the processing result has been transferred for each processor is prepared, and whether or not the processor can process new data based on the flag.

  Next, when there is an unselected scan line among the scan lines constituting the generated print image, the compression control unit 17 returns to Step S100 (FIG. 5: Step S105).

  When each of the processors 11 to 14 of the parallel processing unit 15 receives the head position and the read instruction of the pack partial data from the compression control means 17 (FIG. 8: Step S200: YES), it is based on the head position from a predetermined area of the RAM. Pack part data is read (FIG. 8: step S201).

  Then, a predetermined compression process is performed on the read packed partial data to generate compressed partial data (FIG. 8: step S202), and the compressed partial data is written in its own output buffer (FIG. 8: step S203). ). As the predetermined compression processing, various conventional compression algorithms can be adopted depending on the design. For example, if the print image is binary data, JBIG (Joint Bi-level Image Experts Group). It is conceivable to adopt an algorithm.

  The transfer means 18 cyclically selects a processor corresponding to the channel in the order of channel arrangement (FIG. 9: step S300).

  Next, the transfer means 18 completes the compression process of the pack part data in the selected processor and the printer device 20 (printer controller 26) can receive the compressed part data (FIG. 9: Step S301: YES), the compressed partial data is transferred from the output buffer of the processor to the printer device 20 (printer controller 26) (FIG. 9: Step S302). At this time, predetermined boundary information is added and transferred at the end (or first) of the compressed partial data so that the boundary of the compressed partial data can be detected.

  Next, when the transfer of the compressed partial data is completed, the transfer unit 18 turns on the transfer end flag for each processor of the processor (FIG. 9: step S303). The per-processor transfer end flag of the processor is returned to OFF when the compression control means 17 gives a read instruction to the processor.

  Next, the transfer means 18 returns to step S300 when not all the compressed partial data has been transferred for the generated print image (FIG. 9: step S304).

  According to such a configuration, the compression processing is performed in parallel for each channel constituting one scan line (that is, for each partial data), so the compression processing time for each scan line is shortened. be able to. In particular, since the compression processing time for the first scan line is shortened, the compression processing for the first scan line is completed after the compression processing for the print image is started, and the processing result is the printer device 20 (printer controller 26). It is possible to shorten the time until the data is transferred to (), and it is possible to realize a compression process (and thus a print process) that starts quickly.

  In addition, for each partial data, after generating a data string in which gradation data of a plurality of pixels are continuously arranged (that is, after packing), compression processing is performed on the data string. Therefore, compared to the conventional configuration that performs image processing after increasing the gradation data of each pixel of the image in units of bytes, the amount of memory area required for executing image processing and the amount of data to be calculated are suppressed. Thus, the compression process can be executed efficiently.

(Processing in the printer device 20)
When the command received by the receiving means is a print instruction command, the printer controller 26 controls the power mechanism unit by the engine control means to prepare for printing, and instructs the expansion control means 28 and the like to start processing. To do.

  When receiving the instruction to start processing, the decompression control means 28 assigns at least one of the processors 21 to 24 to the compressed partial data (channel) to be read next from the data reception buffer (FIG. 10: S400). ).

  Specifically, a combination of a channel and a processor is fixedly assigned, such as a processor 21 for the compressed partial data of channel 1 and a processor 22 for the compressed partial data of channel 2.

  Here, it is desirable to configure the data reception buffer as a FIFO type buffer (or by a FIFO type memory) on the RAM, for example. In this case, as described above, since the transfer means 18 of the host device 10 is configured to transfer the compressed partial data to the printer device 20 (printer controller 26) in the order of the channels, the compressed portion data in the data reception buffer is transferred. Writing / reading is also the order of channels. Therefore, the decompression control means 27 can specify which channel the compressed partial data to be read out next corresponds to, and can assign a fixed combination of processor and channel.

  Next, the decompression control means 28 determines whether or not the allocated processor can process new data, and if possible, instructs the reading of the compressed partial data from the data reception buffer (FIG. 10: step S401). ).

  Here, for example, when the output buffer writable by each of the processors 21 to 24 has a capacity corresponding to one partial data, the above determination can be made based on the transfer end flag in the same manner as the compression control means 17.

  Next, when there is compressed partial data that has not been decompressed, the decompression control means 28 returns to step S400 (FIG. 10: step S402).

  When each processor 21 to 24 of the parallel processing unit 25 receives an instruction to read compressed partial data from the decompression control means 27 (FIG. 11: step S500: YES), the compressed partial data at the read position of the data reception buffer is read ( FIG. 11: Step S501). Each processor can identify the read start / end position of the compressed partial data by detecting the boundary information added to the compressed partial data.

  Next, each of the processors 21 to 24 executes a predetermined decompression process on the read compressed partial data to generate corresponding packed partial data (FIG. 11: step S502), and the packed partial data is stored in the processor itself. (FIG. 11: Step S503). The decompression process needs to employ the decompression process corresponding to the compression algorithm employed in the parallel processing unit 15 of the host device 10.

  The unpacking means 29 selects scanning lines in the order of the sub-scanning direction in order to unpack the data in the order used for printing (FIG. 12: step S600).

  Next, the unpacking unit 29 selects channels for the selected scanning line in the order used for printing, that is, in the order of arrangement (FIG. 12: step S601).

  Next, the unpacking means 29 determines whether or not the packed partial data is stored in an expanded state in the output buffer of the processor corresponding to the selected channel (FIG. 12: step S602). When it is determined that the data is stored, the pack partial data is read (FIG. 12: step S603).

  Here, since the read packed portion data is packed with gradation data of pixels having different bit lengths, in order to extract the gradation data of each pixel from the packed portion data. It is necessary to know the separation of gradation data for each pixel. In the present embodiment, the printer controller 26 includes a bit information table storage unit 27 that stores a bit information table specified by the halftone process performed in the host device 10. By referring to the storage unit 27, the pixel information is stored. It is configured so that the separation of the gradation data for each can be grasped.

  The unpacking means 29 refers to the bit information table storage means 27 and acquires a periodic pattern (bit length arrangement pattern) corresponding to the selected scanning line (FIG. 12: step S604). For example, if the vertical size of the bit information table is P, the periodic pattern of the Qth scan line is an array of bit lengths of the (QmodP) line of the bit information table.

  Then, based on the acquired periodic pattern, gradation data of each pixel included in the pack partial data is extracted (FIG. 12: Step S605). However, it is not necessary to extract gradation data for dummy pixels added by padding. For example, if a 1-bit dummy pixel is added to the end of the scanning line, the value of the number of dummy pixels X is received from the host device 10 and the extraction is completed with the X bits remaining for the pack portion data of the final channel. .

  Here, as described above, in the compression control processing performed in the host device 10, the channel boundary is divided so as to coincide with at least one of the boundary of the periodic pattern specified by the bit information table, and then each of them is divided. The partial data of the channel is packed to generate packed partial data. In this case, the start position of each channel and the start position of the periodic pattern of the bit length are always matched, and the packed partial data is packed with pixels with the bit length that matches the periodic pattern from the beginning. Therefore, if the unpacking means 29 extracts bit length data in the order of the periodic pattern corresponding to the selected scanning line from the head of the packed portion data for any channel, it is included in the packed portion data. The gradation data of each pixel can be extracted.

  FIG. 14 is a diagram showing a state of unpacking. For example, when the pack portion data is a data string as shown in FIG. 14A and the periodic pattern has a value as shown in FIG. 14B, the gradation data of each pixel is shown in FIG. As shown in FIG. 14 (d), it is extracted from the packed portion data in the order of 1 bit, 1 bit, 2 bits, 2 bits, 2 bits, 2 bits, 2 bits, 3 bits, 3 bits,. The value shown in is obtained.

  Next, if the printing engine is a type that can print by area gradation, for example, the unpacking means 29 is arranged for each pixel included in the packed portion data for each dot based on the extracted gradation data of the pixel. The area ratio data (= the gradation value of the pixel / the maximum gradation value of the bit length of the pixel) is obtained and stored in, for example, a FIFO type transfer buffer realized on the RAM in the order of arrangement of the pixels (FIG. 12: Step S606).

  Next, after extracting the gradation data of all the pixels for the selected channel, the unpack unit 29 turns on the transfer end flag of the processor corresponding to the selected channel (FIG. 12: step S607). The transfer end flag of each processor is returned to OFF when the decompression control means 28 gives a read instruction to the processor.

  Next, if there is an unselected channel for the selected scanning line, the unpacking unit 29 returns to S601 (FIG. 12: step S608), and if not, if there is an unselected scanning line, The process returns to S600 to select the scan line (FIG. 12: step S609).

  The transfer means 30 determines whether or not data for one scan line is stored in the transfer buffer (FIG. 13: step S700), and when it is determined that the data is stored, the data for one scan line is stored. The data is read out and transferred to the print engine (FIG. 13: Step S701). Since the partial data is stored in the FIFO type transfer buffer in the order used for printing by the unpack unit 29, the transfer unit 30 prints in the order used for printing if it is read from the transfer buffer in order and transferred. Can be transferred to the engine.

  According to this configuration, since the decompression process is executed in parallel for each channel constituting one scan line (that is, for each compressed partial data), the decompression process time for each scan line is shortened. can do.

  In particular, since the decompression time of the first scan line is shortened, the decompression process is completed for the first scan line after the decompression process of the compressed print image is started, and the processing result is transferred to the print engine. It is possible to shorten the time until the image is processed, and it is possible to realize a decompression process (and thus a print process) that starts quickly.

  Furthermore, when the partial data for one scanning line is prepared in the output buffer of each processor, it is transferred to the printing engine, and when the transfer is completed, the next line is expanded, that is, synchronized in units of scanning lines. Since the decompression process and the transfer process are performed, if there is a memory area with a capacity of at least one scan line as a memory area for storing partial data as a decompression process result (specifically, each processor has If the capacity of the output buffer is equal to or larger than the memory capacity for one scanning line / the number of processors), it is possible to improve the throughput by parallelization.

  In other words, when one processor is assigned to one scan line (or one band) and processed in parallel as in the prior art, the number of scan lines is the same as the number of processors as the memory area for storing the decompression processing result. If there is no memory area for the number of bands (or the number of bands), the effect of parallelization according to the number of processors cannot be obtained, whereas one processor is assigned to one partial data for parallel processing as in this embodiment. In this case, it is sufficient that each processor has a memory area corresponding to partial data, and it is not necessary to prepare a memory area for one scanning line for each processor. Even when only a small number of memory areas can be used, the effect of parallelization according to the number of processors can be obtained. It can be.

  For example, by parallelizing decompression processing, (expansion processing time of one scan line) ≈MAX {expansion processing time of compressed partial data of each processor}, by providing an appropriate number of processors, Elongation processing time) <(time required for printing one scanning line in the print engine), and in real time even for a laser printer or the like that needs to continuously supply the print data for each line to the engine at a constant speed Can respond.

  Furthermore, each processor can start the decompression process for the next compressed partial data when the packed partial data, which is the result of its decompression process, is unpacked and transferred to the transfer buffer. It is possible to execute the decompression process in parallel with the transfer process to the engine.

  Further, in the above configuration, since the data string (that is, the pack portion data) in which the gradation data of a plurality of pixels are continuously arranged is an output target of the decompression process, the gradation data of each pixel of the image is in byte units. Compared to the conventional configuration in which the expansion result is output in a raised state, the capacity of the memory area necessary for executing the image processing and the amount of data to be calculated can be suppressed, and the expansion processing can be executed efficiently.

(Other)
The present invention is not limited to the above-described embodiment, and can be variously modified and applied. For example, the present invention can be applied to other than the compression / decompression process other than the printer system.

  Further, for example, in the above embodiment, when at least one scanning line constituting an image is divided into a plurality of partial areas, at least one of the plurality of processors is provided in each of the partial areas. Although the configuration in which the image processing is performed in parallel has been described, the present invention is not limited to such a configuration, and the parallel processing is not premised, and at least one scanning line constituting the image is set for each of the scanning lines. When the bit length of each pixel is L1 to LN, the scanning line image processing is performed at least for a data string of (L1 +... + LN) length in which the data of each pixel is arranged. You can also.

  For example, in the above-described embodiment, the printer device 20 includes the parallel processing unit 25 and the printer controller 26. However, the present invention is not necessarily limited to such a configuration. For example, the parallel processing unit 25 and the printer controller 26 may be configured as external devices that can be connected to the printer device 20. Furthermore, the parallel processing unit 25 and the printer controller 26 may be configured as devices that can be connected to the host device 10 according to a standard such as a PCI bus. When the parallel processing unit 25 is connected to the host device 10, the functions of the printer controller 26 may be realized by the main CPU or the like of the host device 10.

  For example, in the above-described embodiment, halftone processing for converting one pixel on the raster image into 9 × 9 pixels on the print image has been described. For example, one pixel on the raster image is converted to one pixel on the print image. A halftone process such as a type to perform may be employed.

  For example, in the above-described embodiment, the configuration in which one scan line is equally divided into partial areas according to the number of processors has been described. However, for example, the size of the partial area to be allocated is changed according to the processor specifications and the like. It is not necessary to divide. Further, the number of divisions (number of channels) of the partial area is not necessarily equal to the number of processors.

  Further, for example, in the above-described embodiment, the configuration in which the combination of the channel and the processor is fixedly described has been described. However, for example, a processor that has finished processing may be allocated to the next channel. In this case, the correspondence between the processor and the channel may be different for each scan line. Note that not only the processors of the parallel processing units 15 and 25 but also the main CPU may be assigned channels to execute parallel processing.

  Further, for example, in the above embodiment, the configuration in which the processors 11 to 14 read partial data from the RAM has been described. However, for example, the host device 10 transfers means for transferring partial data from the RAM to the processors 11 to 14 (for example, DMA transfer means). ), The compression control means may instruct the means. In this case, the processors 11 to 14 execute processing upon receiving the transfer from the means. Similarly, for example, when the printer device 20 includes means for transferring compressed partial data from the data reception buffer to the processors 21 to 24 (for example, DMA transfer means), the decompression control means may instruct the means. The processors 21 to 24 execute processing in response to the transfer from the means.

  Further, for example, in the above embodiment, the case where the output buffers writable by each of the processors 11 to 14 (processors 21 to 24) has a capacity corresponding to the processing result of one partial data has been described. It may be possible to write to an output buffer that is larger than the capacity. In this case, each processor can perform compression processing (decompression processing) one after another as long as the capacity of the output buffer permits. In addition to the configuration provided in the parallel processing unit, the output buffer of each processor may be configured using a part of the RAM of the host device 10 or the printer device 20.

  Further, for example, in the above-described embodiment, the configuration in which the parallel processing is performed for all the scan lines of the print image has been described. However, if the present invention is applied to at least one scan line constituting the print image, the compression processing time for the scan line is determined. / An effect of shortening the extension processing time can be obtained.

  Further, for example, in the above embodiment, the configuration in which the transfer unit 18 sequentially transfers the compressed partial data to the printer device 20 has been described. . At this time, for example, the compressed partial data may be stored once in the RAM and then transferred.

  Further, for example, in the above-described embodiment, the configuration in which the transfer unit 18 transfers the channel in the order of the channels has been described, but the configuration in which the channel identification information is added to the compressed partial data and transferred to transfer in a different order. It can also be. In this case, the expansion control means 27 can determine the processor to be assigned based on the identification information.

  Further, for example, in the above-described embodiment, a configuration has been described in which the transfer unit 30 transfers data to the print engine when data for one scan line is prepared. However, depending on the type of print engine, data for one scan line is described. Alternatively, the data may be transferred to the print engine without waiting for the data to be aligned or when the data for a plurality of scanning lines (for example, data for one band) is prepared.

  Further, for example, in the above embodiment, on the premise of the configuration in which compression / decompression processing is performed in parallel for each scanning line for each scanning line, the boundary matching condition (the channel boundary matches with at least one of the boundary of the periodic pattern) However, the present invention is not necessarily limited to such a configuration. For example, a plurality of scanning lines may be combined to form a band, and compression / expansion processing may be performed in parallel for each band in units of channels. In this case, boundary matching conditions (band boundary is a periodic pattern) in the sub-scanning direction may be used. It is possible to consider a configuration in which band division is performed so as to satisfy a condition that it matches at least one of the boundaries.

1 is a block diagram illustrating a hardware configuration of a printer system according to an embodiment of the present invention. 2 is a block diagram showing a functional configuration diagram of a printer driver means 16 and a printer controller 26. FIG. It is a figure for demonstrating a screen table and a bit information table. It is a figure for demonstrating a gradation conversion table. 4 is a flowchart showing processing contents of a compression control means 17; It is a figure for demonstrating a mode that it divides | segments into a partial area | region by performing padding. It is a figure for demonstrating a channel. 3 is a flowchart showing processing contents in a parallel processing unit 15. 4 is a flowchart showing processing contents of a transfer means 18; 5 is a flowchart showing the processing contents of the expansion control means 28. 4 is a flowchart showing processing contents in a parallel processing unit 25. It is a flowchart which shows the processing content of the unpack means 29. FIG. 4 is a flowchart showing processing contents in a transfer means 30. It is a figure for demonstrating a mode that it unpacks. It is a figure for demonstrating a mode that pixel data is stored in a conventional structure and this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Printer system, 10 Host apparatus, 11-14 Processor for parallel processing, 15 Parallel processing unit, 16 Printer driver means, 17 Compression control means, 18 Transfer means, 20 Printer apparatus, 21-24 Processor for parallel processing, 25 Parallel processing Unit, 26 printer controller, 27 bit information table storage means, 28 decompression control means, 29 unpack means, 30 transfer means

Claims (1)

A host apparatus and a printer apparatus configured to be communicable with the host apparatus, and each of the host apparatus and the printer apparatus performs image processing in parallel using a plurality of processors that execute memory access in units of bytes. A printer system having a function of performing
The host device
Image processing means for converting the gradation data of each pixel of the image into gradation data having a bit pattern having a periodic pattern by performing halftone processing using a gradation conversion table;
For at least one scanning line constituting the image , padding is performed so that the boundary of each partial area coincides with at least one of the boundaries of the periodic pattern, and then divided into a plurality of partial areas. a compression control section for controlling the image compression processing in the row Migihitsuji in parallel by assigning at least one of the plurality of processors,
Transfer means for transmitting compressed data corresponding to each partial area (hereinafter referred to as “compressed partial data”) to the printer device in the arrangement order of the partial areas in the scanning line ;
The compression control means includes
The bit length of the gradation data after being converted by the image processing means of each pixel in the partial region corresponding to a certain processor is at least one of L1 to LN (at least one of L1 to LN is different from other bit lengths) ) , A (L1 +... + LN) -length data sequence in which the gradation data converted by the image processing means are arranged is generated, and the processor sets the generated data sequence as the target. Control to perform partial area image compression,
The printer device
Storage means for storing the cycle pattern,
An elongate control means for the compressed partial data received from the host device is controlled to perform image decompression processing in parallel by assigning at least one of the compressed partial data to a plurality of processors,
An unpacking unit that obtains the bit length of each pixel by applying the periodic pattern to the data string after the image decompression process, and obtains the gradation data of each pixel in the partial region corresponding to the compressed partial data;
A printer system comprising: a print engine that performs printing based on the gradation data acquired by the unpacking unit .

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