JP4474487B2 - Image processing apparatus and image processing method - Google Patents

Description

  The present invention relates to an image processing apparatus and an image processing method for performing drawing with a rasterize function in band units.

  Conventionally, as this type of image processing apparatus, there is an apparatus called a so-called page printer such as a laser beam printer. In these apparatuses, raster data for one page is held on a raster memory to perform image processing. Raster data as such an image processing apparatus handles not only text but also all kinds of images from simple figures to images such as photographs.

  In addition, these image processing apparatuses have recently improved in resolution. For example, in order to generate one page of A4 size at a resolution of 600 dpi, a memory of 4 MBytes is required. In addition, the resolution tends to increase more and more, and the gradation represented by 2 gradations (1 bit) per pixel has been changed from 16 gradations (4 bits) to 256 gradations (8 bits). Increasingly, more and more raster memory is required. In addition, recently, there are many cases where colors are handled, and in the case of a YMCK space compared to monochrome, an additional four planes are required, and the memory size has become enormous.

  In order to suppress an increase in cost due to such an increase in memory, various memory saving technologies have been proposed. For example, instead of storing one page of raster data on the raster memory, a method of suppressing the amount of raster memory by encoding raster data for each band on the raster memory has been used.

  However, when the above method is used, depending on the decoding method, there is a case where the decoded data needs to be temporarily stored in a buffer before video transfer to the printer engine. In order to output data to the engine without causing data underflow, this decoding method performs parallel processing of decoding the next band to another buffer while transferring video from the buffer to the printer engine. It is necessary to do. In other words, two work buffers are required, and an extra memory is required compared to a decoding method that does not require a work buffer at all, and the memory area for storing encoded data is reduced. There was a point.

  The present invention has been made to solve the above-described problems of the prior art. The object of the present invention is to perform image transfer processing with a constant work buffer even if the decoding method is different, and to physically store the memory. An object of the present invention is to provide a high-quality image processing apparatus and image processing method without increasing the number of images.

In order to achieve the above object, in the image processing apparatus according to the present invention,
A printer engine;
Real-time decoding means for converting the video data into a video signal while decoding the band encoded data without going through the memory, and transferring the video signal to the printer engine;
Non-real time decoding means for decoding the band encoded data and storing it in the first area of the work memory, converting the data stored in the second area of the work memory into a video signal, and transferring it to the printer engine;
When using the real-time decoding means, the band height is set to a first height, and when using the non-real-time decoding means, the band height is set to a second height which is half of the first height. And a setting means.

  According to the present invention, it is possible to perform image transfer processing with a constant work buffer even if the decoding methods are different, and to provide a high-quality image processing apparatus and image processing method without physically increasing the memory. It has become possible.

1 is a schematic diagram showing an internal structure of an image processing apparatus as an embodiment of the present invention. 2 is a block diagram illustrating an internal configuration of a printer control unit of the image processing apparatus. FIG. 4 is a flowchart illustrating a flow of an entire page generation process in the image processing apparatus. It is a flowchart which shows the flow of the encoding system selection process in an image processing apparatus. It is a flowchart which shows the flow of the investigation process of the decoding system in an image processing apparatus. It is a flowchart which shows the flow of the band height setting process in an image processing apparatus. It is a flowchart which shows the flow of the production | generation process of the encoding page in an image processing apparatus. It is a flowchart which shows the flow of the decoding / transfer process in an image processing apparatus. It is a flowchart which shows the flow of the real-time decoding process in an image processing apparatus. It is a flowchart which shows the flow of the non-real-time decoding process in an image processing apparatus. It is a flowchart which shows the flow of 2 band parallel processing in an image processing device. It is a block diagram explaining 2 band parallel processing in an image processing device. It is a block diagram explaining 2 band parallel processing in an image processing device. It is a block diagram explaining the image processing technique used as the premise of this invention. It is a block diagram explaining the image processing technique as embodiment of this invention. It is a block diagram explaining the image processing technique as embodiment of this invention.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the relative arrangement, numerical formulas, numerical values, and the like of the components described in this embodiment are not intended to limit the scope of the present invention only to those unless otherwise specified.

(One embodiment)
[Constitution]
FIG. 1 is a cross-sectional view showing the internal structure of a laser beam printer (hereinafter abbreviated as LBP) as an embodiment of the present invention. The LBP can register a character pattern or a fixed form (form data) from a data source (not shown). In the figure, reference numeral 1000 denotes an LBP main body, which inputs and stores character information (character code), form information, macro instructions, etc. supplied from an externally connected host computer, and corresponding characters according to the information. A pattern, a form pattern, and the like are generated, and an image is formed on a recording sheet that is a recording medium. Reference numeral 1012 denotes an operation panel on which switches for operation and an LED display are arranged. Reference numeral 1001 denotes a printer control unit that controls the entire LBP 1000 and analyzes character information supplied from a host computer. The control unit 1001 mainly converts character information into a video signal having a corresponding character pattern and outputs the video signal to the laser driver 1002. The laser driver 1002 is a circuit for driving the semiconductor laser 1003, and switches on and off the laser light 1004 emitted from the semiconductor laser 1003 in accordance with the input video signal. A laser 1004 is swung left and right by a rotary polygon mirror 1005 and scans on the electrostatic drum 1006. Thereby, an electrostatic latent image of a character pattern is formed on the electrostatic drum 1006. This latent image is developed by the developing unit 1007 around the electrostatic drum 1006 and then transferred to the recording paper. A cut sheet is used as the recording paper. The cut sheet recording paper is stored in a paper cassette 1008 mounted on the LBP 1000 and is taken into the apparatus by the paper feed roller 1009 and the transport rollers 1010 and 1011, and is stored in the electrostatic drum 1006. Supplied.

  FIG. 2 is a block diagram showing an internal configuration of the control unit 1001 provided in the LBP 1000. As shown in FIG.

  Reference numeral 2001 denotes an external device such as a host computer, 2003 denotes an address data bus, 2004 denotes a host I / F including a buffer unit, 2005 denotes a CPU for controlling a control unit, and 2006 denotes a program for performing controller control and the like. ROM, 2007 is DMA controlled by CPU, 2008 is a panel unit, 2009 is an I / F circuit including an output buffer unit for storing data to be sent to the 2011 engine, and 2010 is RAM. ing.

[Prerequisite processing technology]
The image processing technique which is the premise of the present invention will be described using the block diagram of FIG.

  First, the control unit 1001 of the printer 1000 inputs image data described in a page description language (PDL) generated by the external device 2001 to the host I / F 2004.

  Next, according to the band encoding processing program stored in the ROM 2006, the CPU 2005 functions as the band encoded expression generation unit 1401, and the band encoded expression information obtained by dividing the page description language input from the external device 2001 into bands. And stored in the band encoding area 1402 secured in the RAM 2010. Here, the band coded expression information refers to drawing objects such as "bitmap", "run length", "trapezoid", "box", and "fast boundary coded bitmap" divided into band units and the background. A generic term for patterns and drawing logic when drawing them in raster memory. The details of the band coded expression information are disclosed in Japanese Patent Laid-Open No. 6-87251.

  Next, the band coded expression information is rendered in band units using a renderer 1404 and stored in the band raster area 1403.

  When the rendered raster data is developed in the band raster area, the first band is sent to the engine 2011 via the transfer unit 1405 and output. While the raster data of the band is being output, the raster data of the next band is developed in another band raster area 1403. By alternately developing and transferring to the band raster area in this way, the printer engine can output without causing data underflow. Further, at the same time as performing the transfer (printing) operation, a band coded representation of the next page is generated.

  However, there are many complex drawing objects in the image data, and the band encoding area 1402 becomes full, and all drawing objects may not be stored as band encoded expression information. For example, even if a single band area in the band encoding area is taken, all of the objects to be drawn in the band may not be stored. In this case, since all the drawing objects do not exist in the band encoding area 1402, if raster development is performed in the band raster area 1403 as described above, a drawing object that cannot be output is generated.

[Characteristic processing technology]
In order to solve the above problem, the encoded representation is rendered once, and is encoded again with an encoding method having a high compression ratio so that all the image information fits in the band encoding region. At this time, the following page generation processing is performed by the control unit 1001.

  FIG. 3 is a flowchart showing the entire page generation process.

  In step S301, image data is input to the host I / F unit 2004 from an external device 2001 such as a host computer. Here, the image data input from the host I / F unit 2004 is not a full raster image format of a print image, but is compact data such as a page description language (PDL) that specifies only an object on the page and the position of the object. The format is preferably, but other image data formats may be used.

  In step S302, the printing mode of the input data is analyzed and the encoding method is selected. Next, in step S303, the decoding method corresponding to the encoding is checked, and in step S304, the band height (width) corresponding to the decoding method is set. Here, when the decoding method is a non-real-time decoding method, the band height is set to half that of the real-time decoding method.

  Here, the real-time decoding method is defined as a method that allows video transfer without temporarily storing the decoded data in the work buffer when video transfer is performed to the printer engine after decoding. A band is a generic term for data obtained by dividing data for one page into several strips having the same size, and the height of each divided strip is defined as a band height.

  In steps S305 to S307, page generation / transfer processing is performed based on the band height set in step S304.

  FIG. 15 shows page generation / transfer processing when the decoding processing is performed by the real-time decoding method as a result of the investigation in step S303.

  The input PDL is converted into a band encoded representation by the band encoded representation generation unit 1401 and stored in the band encoded area 1402. If all the image information cannot be stored in the band coding area secured in advance, the image is rendered for each band by the renderer 1404 and stored in the band raster area 1403. The band raster area is an area where bitmap data for one band can be stored. Here, the band raster area 1403 and the band encoding area 1401 are shown separately, but both are areas on the RAM 2010. If the band raster area 1403 is large, the band encoding area 1401 is compressed. . This is the same in FIG.

  The bitmap data stored in the band raster area 1403 is encoded by the method selected in S302 in the CPU 2005 functioning as the encoding unit 1501. The encoded data is stored in the compression band area 1503. The band encoding areas 1402 for the bands stored in the compressed band area 1503 are sequentially released. When encoded data for one page is stored in the compressed band area 1503, the decoding unit 1502 decodes the data for each band, and sequentially transfers the decoded bitmap data to the printer engine via the transfer unit 1405.

  FIG. 16 shows the page generation / transfer process when the decoding process is performed by the non-real-time decoding method as a result of the investigation in step S303.

  The input PDL is converted into a band encoded representation by the band encoded representation generation unit 1401 and stored in the band encoded area 1402. At this time, the band height is set to the height set in step S303, that is, half the height of the real-time decoding method.

  If all the image information cannot be stored in the band coding area secured in advance, the image is rendered for each band by the renderer 1404 and stored in the band raster area 1403. The band raster area is an area where bitmap data for one band can be stored.

  The bitmap data stored in the band raster area 1403 is encoded by the method selected in S302 in the CPU 2005 functioning as the encoding unit 1501. The encoded data is stored in the compression band area 1503.

  When encoded data for one page is stored in the compressed band area 1503, the decoding unit 1502 next decodes the data for each band and develops the band raster 1403. In order to transfer bitmap data to the printer engine without interruption in the middle, two band rasters are required. While rasterizing the bitmap data on the band raster for one band, the band raster for another band. To sequentially transfer the bitmap data to the printer engine. In other words, two band rasters are used as a double buffer for parallel processing, but the band height is set to half in advance, so that the necessary band raster is required compared to when performing decoding using the real-time decoding method. The area does not increase and other memory areas are not compressed.

  Below, each process of step S302-S304 and S306-S307 is demonstrated.

[Choose encoding method]
FIG. 4 is a flowchart showing in detail the encoding method selection process.

  In step S401, the mode is investigated. In this case, it is assumed that the data to be printed is divided into modes such as a color mode, a monochrome mode, and an image mode. Of course, the color mode can be selected only for a color printer. If the mode is an image in the mode investigation in step S401, the encoding method 1 is selected in step S402, and the encoding method is determined to be the encoding method 1 in step S405.

  Similarly, if the mode is color in the mode check in step S401, the encoding method 2 is selected in step S403, and the encoding method is determined to be the encoding method 2 in step S405. Further, if the mode is monochrome in the mode check in step S401, the encoding method 3 is selected in step S404, and the encoding method is determined to be the encoding method 3 in step S405.

  However, when the conditions of the image mode and the color mode or the monochrome mode overlap, it is assumed that the image mode has a mode selection priority over the other modes. When the determination of the encoding method for each mode is completed, the encoding method selection process ends in step S406.

[Investigation of decryption method]
FIG. 5 is a flowchart showing details of the investigation process of the decoding method.

  In step S501, the encoding method selected in step S302 of FIG. 3 is acquired. In step S502, it is investigated whether a real-time decoding system exists as a decoding system for the encoding system acquired in step S501.

  If it is determined in step S502 that a real-time decoding method exists, the decoding method is set to real-time decoding in step S503. On the contrary, if it is determined in step S502 that real-time decoding does not exist, the decoding method is set to a non-real-time decoding method. When the decoding method is set, the process ends.

[Band height setting]
FIG. 6 is a flowchart showing in detail the band height setting process.

  Usually, the band height is determined by the relative relationship to the area for storing data for one page, and the larger the height, the smaller the boundary raster between the bands, and the smaller the overlapping data. It is known for its high efficiency. Here, it is assumed that the band height is determined to be “H”.

  The band height (H) determined in step S601 is acquired.

  In step S602, the decoding method investigated in step S303 in FIG. 3 is acquired.

  In step S603, if the decoding method acquired in step S602 is non-real time decoding, the process proceeds to step S604, and the band height is set to half (1 / 2H). Conversely, if the decoding method acquired in step S602 is real-time decoding, the process proceeds to step S605, and the band height is set as it is (H).

  Then, the processing system for setting the band height ends.

[Encoding process]
When the image information cannot be stored in the band encoding area in the band encoded representation, the encoded page is generated by performing the processing as shown in FIG.

  FIG. 7 is a flowchart showing in detail the encoded page generation process.

In step S701, work memory is allocated. The work memory here is a band raster area for storing the decoded bitmap data, and the amount of memory having the same size as the band generated in proportion to the band height determined in step S304 of FIG. It is. In step S702, “n” indicating the number of bands is initialized to zero. "N" is
0 <= n <= n_max
* However, n_max is the maximum band number and is an integer.
An integer that satisfies In step S703, it is checked whether “n” indicating the current band number exceeds “n_max”. If “n_max” is exceeded, it is determined that all the bands have been processed, and the processing system is ended in step S708. If the current band number “n” does not exceed “n_max” in step S703, the process proceeds to step S704.

  In step S704, the band coded representation of step S305 in FIG. 3 is rendered on the work memory acquired in step S701.

  Next, in step S705, the bitmap data rendered in step S704 is encoded into the work memory acquired in step S701 using the encoding method selected in step S302 of FIG.

  In step S706, the encoded data is stored in the compressed band area 1503.

  In step S707, the current band number “n” is advanced to the next band (n = n + 1).

  Returning to step S603 again, the above processing is repeated until the last band is reached, and the encoded page generation processing is terminated.

[Decryption / transfer processing]
FIG. 8 is a flowchart showing details of the decoding / transfer processing.

  In step S801, it is checked whether the encoding method selected in the decoding method check in step S303 in FIG. 3 is a real time decoding method or a non-real time decoding method. If it is a real-time decoding method, the process proceeds to step S803 and a real-time decoding process is performed. If it is a band decoding system, the process proceeds to step S802 and the band decoding process is performed.

  FIG. 9 is a flowchart for explaining the real-time decoding process in detail.

In step S901, a real-time decoding method is selected as the decoding method. In step S802, the current band number “n” is initialized to zero. "N" is
0 <= n <= n_max
* However, n_max is the maximum band number and is an integer.
An integer that satisfies In step S903, it is checked whether or not the current band number “n” exceeds “n_max”. If so, it is determined that the decoding for all the bands has been completed, the process proceeds to step S906, and the real-time encoding process is terminated. Conversely, if the current band number “n” does not exceed “n_max” in step S903, the process proceeds to step S904.

  In step S904, the encoded data of the “n” band is decoded, converted into a video signal, transferred to the printer engine, and the band is decoded and transferred.

  In step S905, the current band number “n” is advanced to the next band “n = n + 1”.

  Then, the process returns to step S903, and the process is performed up to the last band in the same manner as the above process, the real-time decoding process ends, and the decoding / transfer process ends.

  On the other hand, if the decoding method is a non-real time decoding method in step S801 in FIG. Details of the non-real-time decoding process will be described with reference to the flowchart of FIG.

  In step S1001, the non-real time decoding method is selected as the decoding method. Next, band processing is performed in step S1002. A detailed description of the band processing will be given using the flowchart of FIG.

  In step S1101, work memory for two bands is acquired. This is twice the size of the work memory acquired in step S701 in FIG. 7, but is the same size as the size of the work memory acquired at the time of real-time decoding (1 / 2H × 2). In other words, since the band height is halved, there is no difference in the size of the work memory itself in both real-time decoding and non-real-time decoding. The respective work memories are called work memory 1 and work memory 2.

  First, in step S1102, the encoded data of the 0th band is decoded and stored in the work memory 1.

  In step S1103, the current number “n” is initialized to 1.

"N" is
1 <= n <= n_max
* However, n_max is the maximum band number and is an integer.
An integer that satisfies

  In step S1104, it is checked whether or not the current band number “n” exceeds the final band “n_max”. If not, the process proceeds to step S1105.

  In step S1105, the "n-1" band is converted from the work memory 1 into a video signal, transferred to the printer engine, and the "n-1" band is decoded and transferred. Initially, this corresponds to the 0th band decoded in step S1102. In parallel with this process, the “n” band is decoded and the decoded data is stored in the work memory 1. First, the encoded data of the first band is decoded and stored.

  In step S1106, the current band number “n” is advanced to the next band number (n = n + 1).

  A schematic representation of these processes is shown in FIGS.

  First, the decoded data of the “n” band already decoded in the work memory 1 of FIG. 12 is converted into a video signal and transferred to the printer engine. Meanwhile, the encoded data of the “n + 1” band is decoded and stored in the work memory 2.

  Next, proceeding to FIG. 13, the data decoded in the work memory 1 in FIG. 12 is similarly converted into a video signal and transferred to the printer engine. In the meantime, the video signal has already been converted into the video signal and the “n” band data is no longer necessary, so the work memory 1 is decoded in the “n + 2” band.

  The processes of FIGS. 12 and 13 are continued until the final band.

  In this process, it is assumed that the decoding to another work memory always ends before the video transfer from one work memory to the printer engine is completed.

  Next, returning to step S1104, the above processing is continued until the final band.

  When the process reaches step S1104 up to the last band, the decoding / transfer process is terminated.

(Other embodiments)
In the above embodiment, only three types of image, color, and monochrome are dealt with for mode selection. However, other modes may be used.

  The above embodiment deals with the case where three types of encoding methods are used, but any number of types of encoding methods may be used.

  Although the above embodiment deals with the case where the processing is performed for two bands in the band processing, the case where there are two or more bands may be used.

  The above embodiment has dealt with the case where work memory is allocated at the time of encoding and decoding, but it may be a case where a certain area is prepared.

  The above embodiment deals with the case where the number of bands is two or more. However, the number of bands may be less than two.

  In the above embodiment, in the mode selection, when the conditions of the image mode and the color mode or the monochrome mode are overlapped, the image mode is preferentially treated as the mode selection item. .

  Note that the present invention can be applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, and a printer), and a device (for example, a copying machine and a facsimile device) including a single device. You may apply to.

  Another object of the present invention is to supply a storage medium (or recording medium) in which a program code of software that realizes the functions of the above-described embodiments is recorded to a system or apparatus, and the computer (or CPU or CPU) of the system or apparatus. Needless to say, this can also be achieved by the MPU) reading and executing the program code stored in the storage medium. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention. Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an operating system (OS) running on the computer based on the instruction of the program code. It goes without saying that a case where the function of the above-described embodiment is realized by performing part or all of the actual processing and the processing is included.

  Furthermore, after the program code read from the storage medium is written into a memory provided in a function expansion card inserted into the computer or a function expansion unit connected to the computer, the function is determined based on the instruction of the program code. It goes without saying that the CPU or the like provided in the expansion card or the function expansion unit performs part or all of the actual processing and the functions of the above-described embodiments are realized by the processing.

  When the present invention is applied to the storage medium, the storage medium stores program codes corresponding to the flowcharts described above (particularly, shown in FIGS. 3 and 6).

  According to the present invention, it is possible to perform image transfer processing with a constant work buffer even if the decoding methods are different, and to provide a high-quality image processing apparatus and image processing method without physically increasing the memory. became.

Claims (2)

A printer engine;
Real-time decoding means for converting the video data into a video signal while decoding the band encoded data without going through the memory, and transferring the video signal to the printer engine;
Non-real time decoding means for decoding the band encoded data and storing it in the first area of the work memory, converting the data stored in the second area of the work memory into a video signal, and transferring it to the printer engine;
When using the real-time decoding means, the band height is set to a first height, and when using the non-real-time decoding means, the band height is set to a second height which is half of the first height. And an image processing apparatus. A printer engine, real-time decoding means for converting the band encoded data to a video signal while decoding the band encoded data without going through the memory, and transferring to the printer engine; and the band encoded data is decoded and stored in the first area of the work memory. And an image processing method executed by an image processing apparatus having non-real time decoding means for converting data stored in the second area of the work memory into a video signal and transferring it to the printer engine,
When using the real-time decoding means, the band height is set to a first height, and when using the non-real-time decoding means, the band height is set to a second height which is half of the first height. An image processing method.

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