JP2008079036A - Image processing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processing apparatus capable of suppressing productivity deterioration to an image with lower compression ratio while avoiding image quality deterioration as far as possible. <P>SOLUTION: The image data input from a scanner part 11 are concurrently compressed by a first compression/expansion unit 13 of lossless compression system and a second compression/expansion unit 14 of non-lossless compression system, after that, compression ratio of lossless compression is compared with a predetermined threshold, and when the compression ratio of the lossless compression is below the threshold, the lossless-compressed image data are transferred from a first image memory 15 to a hard disk device 33 to be stored, and when the compression ratio of the lossless compression exceeds the threshold, the non-lossless-compressed image data are transmitted to the hard disk device 33 to be stored. The threshold and the specified compression ratio are made below a boundary value that data transfer relative to storage/reading of the compressed image data to the hard disk device 33 is not in time for input/output speed of the non-lossless-compressed image data at the scanner part 11 and a printer part 22. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image processing apparatus that internally compresses and stores input / output image data, and more particularly to an image processing apparatus having a plurality of compression methods.

  In recent years, in an image processing apparatus such as a digital copying machine, the speed of data, resolution, and color have increased, and the amount of data handled has increased dramatically. For this reason, when storing image data, there is a method for compressing and storing the compressed image data, and transferring and storing the compressed image data from a semiconductor memory to a storage device such as a hard disk device and a relatively low bit unit price. Generally adopted.

  The compression methods are roughly classified into a lossless compression method and an irreversible compression method. The lossless compression method has no deterioration in image quality, but depending on the image content, the compression rate is low, and in some cases the compression rate exceeds 1, The amount of data may be larger than the original image. On the other hand, the lossy compression method can increase the compression rate, but the image quality is degraded accordingly. Thus, the compression rate and image quality degradation when image data is compressed vary depending on the compression method and the image content.

  Therefore, a technology that prepares multiple compressors to compress with different compression methods and selects the optimal compression method according to the remaining capacity of the memory or preferentially selects the compression method with the smallest compression rate Has been proposed (see, for example, Patent Document 1). In addition, in order to obtain a plurality of image files with different compression methods without causing a decrease in throughput, the first compressor based on the lossless compression method and the second compressor based on the lossy compression method are operated simultaneously in parallel. A digital still camera or the like has also been proposed (see Patent Document 2).

  Also, by dividing the image into areas such as text, halftone dots, and photographs, or by dividing the area by obtaining a histogram of the number of gradations, switching the compression method according to the image contents of each area for each area, the compression rate There are also technologies to achieve both image quality and image quality.

JP 2003-37739 A JP 2003-10951 A

  In an image processing apparatus such as a digital copying machine that transfers compressed image data to a hard disk device and stores it, there is a demand for reducing the degradation of image quality as much as possible rather than making the compression rate the highest priority. However, if a reversible compression method without image quality degradation is always employed, in the case of photographic images, the amount of data after compression increases, and the time required to transfer the compressed image data between the semiconductor memory and the hard disk device However, this transfer is not in time for image reading by the scanner unit and print output by the printer unit, resulting in a problem that productivity of the entire image processing apparatus is lowered.

  On the other hand, the method of distinguishing areas such as characters, halftone dots, and photographs in an image and switching the compression method for each area requires processing such as combining the individually expanded areas into a single image even during expansion. As a result, the price of the equipment will rise due to the significant addition of hardware.

  The present invention is intended to solve the above-described problem, and an object of the present invention is to provide an image processing apparatus that can suppress a decrease in productivity for an image with a low compression rate while avoiding image quality degradation as much as possible. It is said.

  The gist of the present invention for achieving the object lies in the inventions of the following items.

[1] Input means for inputting image data;
A first compression / decompression unit that compresses and decompresses image data using a first compression method;
A second compression / decompression unit that compresses and decompresses image data using a second compression method;
First storage means for temporarily storing image data compressed or expanded by the first compression / decompression unit or the second compression / decompression unit;
A second storage means;
Transfer means for transferring data between the first storage means and the second storage means;
Output means for printing out the image data expanded by the first compression / decompression unit or the second compression / decompression unit;
The control means comprises: compressing the image data input from the input means in parallel by the first compression / decompression unit and the second compression / decompression unit; The compression rate of the compressed image data is compared with a predetermined threshold value. When the compression rate is equal to or lower than the threshold value, the image data compressed by the first compression / decompression unit is stored in the first storage by the transfer means. When the compression ratio is larger than the threshold value, the image data compressed by the second compression / decompression unit is transferred by the transfer unit to the first storage unit and transferred to the second storage unit. An image processing apparatus, wherein the image processing apparatus transfers the data from the storage means to the second storage means and stores it in the second storage means.

  In the above invention, the input image data is compressed in parallel by the first compression method and the second compression method, and the image data compressed by each compression method is temporarily stored in the first storage means. When the compression rate of the first compression method is less than or equal to a predetermined threshold value, the image data compressed by the first compression method is transferred to the second storage means and stored, and the compression rate of the first compression method is the threshold value If the image data exceeds 1, the image data compressed by the second compression method is transferred to the second storage means and stored.

[2] input means for inputting image data;
A first compression / decompression unit that compresses and decompresses image data using a first compression method;
A second compression / decompression unit that compresses and decompresses image data using a second compression method;
First storage means for temporarily storing image data compressed or expanded by the first compression / decompression unit or the second compression / decompression unit;
A second storage means;
Transfer means for transferring data between the first storage means and the second storage means;
Output means for printing out the image data expanded by the first compression / decompression unit or the second compression / decompression unit;
And the control means compresses the image data input from the input means in parallel by the first compression / decompression unit and the second compression / decompression unit, and then uses the first compression / decompression unit. The compressed image data is compared with a predetermined threshold value. If the size of the compressed image data is smaller than the threshold value, the image data compressed by the first compression / decompression unit is transferred to the first transfer means by the transfer means. When the size of the compressed image data is larger than the threshold value, the image data compressed by the second compression / decompression device is transferred from the storage means to the second storage means and stored in the second storage means. An image processing apparatus, wherein the first storage unit transfers the data to the second storage unit and stores the second storage unit in the second storage unit.

  In the above invention, the input image data is compressed in parallel by the first compression method and the second compression method, and the image data compressed by each compression method is temporarily stored in the first storage means. If the size of the compressed image data compressed by the first compression method is smaller than a predetermined threshold value, the image data compressed by the first compression method is transferred to the second storage means and stored, and the first compression method If the size of the compressed image data compressed in step 2 is larger than the threshold value, the image data compressed by the second compression method is transferred to the second storage means and stored.

[3] The first compression method is a lossless compression method,
The image processing apparatus according to [1] or [2], wherein the second compression method is an irreversible compression method.

  In the above invention, when the compression rate in the lossless compression method is less than or equal to the threshold value, the image data compressed in the lossless compression method without image quality deterioration is transferred to the second storage means and stored, and the compression rate in the lossless compression method is If it is larger than the threshold value, the image data compressed by the irreversible compression method capable of reducing the compression rate although the image quality is deteriorated as compared with the reversible compression method is transferred to the second storage means and stored.

[4] The image data compressed by the first compression method is transferred and stored in a first area secured in advance in the second storage means,
The threshold value is one page at which the output unit prints out half the worst value of the data amount per unit time that can be transferred by the transfer unit between the first storage unit and the first area. The image processing apparatus according to [1], wherein the image processing apparatus is set to a value equal to or less than a value obtained by multiplying a data amount of image data by a value obtained by multiplying the number of prints per unit time by the output unit.

  In the above invention, the image data compressed by the first compression method is transferred and stored in the first area reserved in advance in the second storage means. Further, the threshold value is output as one half of the worst value of the amount of data that can be transferred between the first storage unit and the first area of the second storage unit by the transfer unit per unit time for the compressed image data. The value is set to a value equal to or less than the value obtained by multiplying the data amount of image data for one page to be printed out by means by the number of printed sheets per unit time.

  The value obtained by multiplying the data amount of image data for one page to be printed by the number of prints per unit time is the data amount of uncompressed image data processed per unit time when the output means performs continuous printing. It is. The amount of data after compressing the uncompressed image data corresponding to the amount of data is one half of the worst value of the amount of data that the transfer means can transfer between the first storage area and the first area per unit time. In the following case, the data transfer between the first storage means and the second storage means is in time for the print output, and does not cause a decrease in productivity. Therefore, such a compression rate is set as a threshold value.

  Note that the worst value of the amount of data that can be transferred is halved during the printing output from the first storage means to the first area (writing) and in the opposite direction (reading). By doing. The first area may be a part or all of the storage area of the second storage means.

  For example, when the second storage device is a hard disk device, the amount of data that can be transferred per unit time (data transfer speed) varies depending on whether the reserved area is closer to the inner or outer periphery of the disk. In addition, when the transfer path is a bus, the transfer path also varies depending on the congestion status of the bus and the priority of bus use. Therefore, the threshold value is based on the worst value of transfer between the first area in which the image data compressed by the first compression method is stored and the first storage area (the minimum value of the amount of data that can be transferred per unit time). Is set.

[5] The image processing apparatus according to any one of [1 to [4], wherein the second compression method is an irreversible compression method that compresses image data at a specified compression rate.

  In the above invention, when the compression is performed by the second compression method, the compression is performed at the designated compression rate without changing the compression rate depending on the image content. If the specified compression rate is set to a compression rate that does not cause a decrease in productivity, when image data compressed by the second compression method is selected as a transfer target, the productivity caused by the transfer is reduced. A decrease can be avoided.

[6] The image processing apparatus according to [5], wherein the specified compression rate is smaller than the threshold value.

  In the above invention, when the compression rate in the first compression method is larger than the threshold value, the image data (image data compressed in the second compression method) compressed at the specified compression rate smaller than the threshold value is stored in the second storage. It is transferred to the means and stored.

[7] The image data compressed by the second compression method is transferred and stored in a second area secured in advance in the second storage means,
The specified compression rate is printed out by the output unit at one half of the worst value of the data amount per unit time that can be transferred by the transfer unit between the first storage unit and the second area. The image processing apparatus according to [5], wherein the image processing apparatus is set to a value equal to or less than a value obtained by multiplying a data amount of image data for one page to be multiplied by the number of printed sheets per unit time by the output unit.

  In the above invention, the image data compressed by the second compression method is transferred to and stored in the second area secured in advance in the second storage means. The designated compression rate is a half of the worst value of the amount of data that can be transferred between the first storage means and the second area of the second storage means in unit time by the transfer means for the compressed image data. The value is set to a value obtained by dividing the data amount of one page of image data to be printed out by the output means by the value obtained by multiplying the number of prints per unit time.

  By setting the designated compression rate to such a value, when the compression rate in the first compression method is larger than the threshold value, the image data compressed in the second compression method is stored in the second area of the second storage unit. Since the transfer is always in time for the print output, the transfer between the first storage means and the second storage means does not reduce the productivity of the print output.

[8] Transfer and store the image data compressed by the first compression method and the image data compressed by the second compression method in the same area secured in advance in the second storage means. The image processing device according to any one of [1] to [7].

[9] The data compressed by the first compression method is transferred to and stored in a first area secured in advance in the second storage means, and the image data compressed by the second compression method is The image processing apparatus according to any one of [1] to [7], wherein the image processing apparatus transfers and stores in a second area different from the first area, which is secured in advance in a second storage unit.

[10] The image processing apparatus according to any one of [1] to [9], wherein the first storage unit is a semiconductor memory, and the second storage unit is a hard disk device.

  According to the image processing apparatus of the present invention, the input image data is compressed in parallel by the first compression method and the second compression method, and the image data compressed by each compression method is stored in the first memory. If the compression rate in the first compression method or the size of the image data after compression is equal to or less than a predetermined threshold value, the image data compressed in the first compression method is preferentially stored in the second means. Since the data is transferred to the storage means and stored, for example, if the first compression method is a lossless compression method without image quality deterioration and the second compression method is an irreversible compression method with a high compression rate, image quality deterioration due to compression will be reduced. While avoiding as much as possible, even in the case of an image with a low compression rate by the first compression method, it is avoided that the data transfer between the first storage unit and the second storage unit is not in time for the print output and the productivity is lowered. be able to.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a schematic configuration of an image processing apparatus 10 according to the first embodiment of the present invention. The image processing apparatus 10 is configured as a digital copying machine having a copy function that acquires image data obtained by optically reading a document, forms an image on the recording paper, and prints out the image data. .

  The image processing apparatus 10 includes a scanner unit 11 as an input unit that optically reads a document, a scanner image processing circuit 12 that performs various types of image processing on image data obtained by reading the document with the scanner unit 11, and A first compression / decompression unit 13 that compresses and decompresses image data by the first compression method, a second compression / decompression unit 14 that compresses and decompresses image data by the second compression method, and a first compression / decompression unit 13 A first image memory 15 for temporarily storing the image data compressed or expanded by the second image memory 16 and a second image memory 16 for temporarily storing the image data compressed or expanded by the second compression / decompression unit 14. A first memory / compression decompression controller 17 to which the first compression / decompression device 13 and the first image memory 15 are connected, and a second compression / decompression device 14 and a second image memory 16. And a second memory / decompression controller 18 connected to the bottom.

  Furthermore, the image processing apparatus 10 forms an image on a recording sheet based on the image data from the printer image processing circuit 21 and the image data from the printer image processing circuit 21 that performs various image processing for print output on the image data. And a printer unit 22 as output means for printing out.

  Further, the image processing apparatus 10 includes a system bus 31 configured by a PCI (Peripheral Component Interconnect) bus or the like. The system bus 31 includes a CPU (Central Processing Unit) 32 that functions as a control unit that controls the operation of the image processing apparatus 10 and a hard disk device 33 (denoted as HDD in the figure) as a second storage unit. The HDD-I / F (Hard Disk Drive-Interface) 34, the NIC / printer controller 35, the first memory / compression / decompression controller 17 and the second memory / compression / decompression controller 18 connected under the control are connected. ing.

  The NIC / print controller 35 has a function of a network controller (NIC: Network Interface Card), is connected to a LAN (Local Area Network) 2 and the like, and exchanges data with the outside. The NIC / print controller 35 has a function of receiving print data composed of character codes or the like from an external terminal (not shown) via the LAN 2 and developing the print data into image data (image data). The function as an input means of image data is fulfilled similarly to the above.

  The CPU 32 is further connected to a host bus 36 different from the system bus 31. A memory 37 such as a flash memory storing various programs executed by the CPU 32 and a RAM (Random Access Memory) serving as a work memory of the CPU 32 is connected to the host bus 36. The scanner image processing circuit 12 and the printer image processing circuit 21 are connected to the CPU 32 via the host bus 36, and receive various operation settings including settings relating to image processing from the CPU 32.

  Although not shown in FIG. 1, the scanner unit 11 has a light source that irradiates the document, a line image sensor that reads the document for one line in the width direction, and a reading position in units of lines is moved in the length direction of the document. It includes a moving mechanism, an optical component such as a lens and a mirror that guides reflected light from the original to a line image sensor and forms an image. The line image sensor is composed of a CCD (Charge Coupled Device). Further, an A / D converter that converts an analog image signal output from the line image sensor into digital image data is provided. The scanner unit 11 further includes an automatic document feeder (not shown) for sequentially reading a plurality of documents.

  The scanner system image processing circuit 12 is a spatial filter for performing seeding correction / luminance density conversion, image delay FIFO (First-In First-Out), area discrimination, magnification conversion, density γ conversion, inclination correction / error. A circuit for performing image processing such as diffusion is provided. The output of the scanner image processing circuit 12 is input to both the first memory / compression / decompression controller 17 and the second memory / compression / decompression controller 18. Depending on the setting, the scanner system image processing circuit 12 can also output the image data without performing image processing.

  The first compression / decompression unit 13 compresses / decompresses image data by a reversible compression method as a first compression method. The second compression / decompression unit 14 compresses / decompresses image data by a lossy compression method as a second compression method. The second compression / decompression unit 14 performs irreversible compression at a designated compression rate. For example, JPEG (Joint Photographic Experts Group) 2000 is an irreversible compression method that can specify the compression rate.

  The lossless compression method is a compression method in which there is no deterioration in image quality due to compression / expansion, and the original image can be completely restored at the time of expansion. The compression rate varies depending on the image content. Depending on the image content, the compression rate may exceed “1”, and the amount of data after compression may increase from before compression. On the other hand, the irreversible compression method is a compression method capable of increasing (decreasing) the compression rate, although the original image cannot be completely restored when decompressed. The higher the compression rate, the more image quality degradation.

  As shown in FIG. 4, the relationship between the level of the compression rate and the size of the compression rate is as follows: “The compression rate is high (the image data size after compression is small) and the compression rate is small”. It is a relationship.

  The first image memory 15 and the second image memory 16 are semiconductor memories that function as first storage means. The first memory / compression / decompression controller 17 manages the exchange of data among the scanner image processing circuit 12, the first compression / decompression device 13, the first image memory 15, the system bus 31, and the printer image processing circuit 21. It has a function to control. Specifically, a function for inputting image data output from the scanner image processing circuit 12, an address signal, a timing signal, and the like are given to the first image memory 15 to write and read data to and from the first image memory 15. A function to control, a function to transfer data to and from the first compression / decompression unit 13, a function to transfer data between the first image memory 15 and the hard disk device 33 via the HDD-I / F 34, It fulfills the function of outputting the image data stored in the first image memory 15 to the printer image processing circuit 21.

  The second memory / compression / decompression controller 18 is a first memory / compression / decompression controller for the second compression / decompression unit 14 and the second image memory 16 instead of the first compression / decompression unit 13 and the first image memory 15. Performs the same function as 17. The first memory / compression / decompression controller 17 and the second memory / compression / decompression controller 18 are configured by a semiconductor integrated circuit such as an ASIC (Application Specific Integrated Circuit).

  The printer-type image processing circuit 21 has a selector 21a for switching between input of image data from the first memory / compression / decompression controller 17 and image data from the second memory / compression / decompression controller 18, and the selector 21a. And a circuit for performing image processing such as cell averaging, resolution conversion, printer γ conversion, minute scaling, and screen processing on the input image data. The CPU 32 performs switching setting for the selector 21a through the host bus 36, and the selector 21a switches the input destination of the image data according to the setting. Image data output from the printer image processing circuit 21 is input to the printer unit 22 and printed out. Depending on the setting, the printer system image processing circuit 21 can also output to the printer unit 22 without performing image processing on the image data input through the selector 21a.

  The printer unit 22 forms an image corresponding to the image data input from the printer image processing circuit 21 on a recording sheet by an electrophotographic process and outputs the image. It is configured as a so-called laser printer having a drum, a charging device, a laser unit, a developing device, a transfer separation device, a cleaning device, and a fixing device. Instead of an LED printer that irradiates a photosensitive drum with an LED (Light Emitting Diode) instead of a laser beam, other types of printers may be used.

  Next, the flow of operations from input to output of image data will be described.

  FIG. 2 shows a data flow of a portion related to compression / decompression in the operation from input to output of image data. The operation is performed in units of pages. As shown in FIG. 2, the first image memory 15 and the second image memory 16 are divided into compression relay areas 15a and 16a, regeneration relay areas 15b and 16b, and page memories 15c and 16c, respectively. Prior to the operation, the CPU 32 performs a setting for instructing the processing contents to the first memory / compression / decompression controller 17 and the second memory / compression / decompression controller 18, and the first memory / compression / decompression controller 17 and the second memory / compression controller 17. The memory / compression / decompression controller 18 operates according to the setting. For example, the designation of the compression ratio X in the second compression / decompression unit 14, the number of lines constituting an image of one page, the number of pixels constituting the line, the number of gradations, storage address information of image data, and the like are set. .

  Image data is input from the scanner unit 11 or the NIC / print controller 35. The input image data is sequentially input to both the first memory / compression / decompression controller 17 and the second memory / compression / decompression controller 18. The first memory / compression / decompression controller 17 sequentially transfers the input image data to the first compression / decompression unit 13, and the first compression / decompression unit 13 compresses the image data by the first compression method (reversible compression method). The first memory / compression / decompression controller 17 sequentially receives the compressed image data from the first compression / decompression unit 13 and sequentially stores them in the compression relay area 15a of the first image memory 15 (P1a in FIG. 2).

  The second memory / compression / decompression controller 18 sequentially transfers the input image data to the second compression / decompression unit 14, and the second compression / decompression unit 14 transfers the image data to the second compression method (irreversible compression with a designated compression ratio X). Method). The second memory / compression / decompression controller 18 sequentially receives the compressed image data from the second compression / decompression unit 14, and sequentially stores them in the compression relay area 16a of the second image memory 16 (P1b in FIG. 2). The above operations P1a and P1b are executed in parallel, and accordingly, the compression by the lossless compression method by the first compression / decompression unit 13 and the compression by the irreversible compression method by the second compression / decompression unit 14 are executed in parallel. .

  When the operation P1a is performed, the first memory / compression / decompression controller 17 counts the data amount of the compressed image data, and the first compression / decompression unit 13 and the second compression / decompression unit 14 serve for one page. When the compression operation is completed, the CPU 32 acquires the data amount of the image data (image data for one page after compression) compressed by the first compression / decompression unit 13 from the first memory / compression / decompression controller 17. The end of the compression process is notified to the CPU 32 by an interrupt signal, for example. The CPU 32 recognizes the data amount of the image data before compression of the page from information such as the number of lines of the page compressed this time, the number of pixels of one line, the number of gradations, and the like, and the first memory / compression is performed with the data amount. The compression rate R in the first compression / decompression unit 13 is obtained by dividing the data amount after compression acquired from the expansion controller 17.

  Then, the compression rate R is compared with a predetermined threshold value Y. When the compression rate R is equal to or less than the threshold value Y, the image data compressed by the first compression / decompression unit 13 by the lossless compression method is stored in the first image memory 15. Is sent to the first memory / compression / decompression controller 17 from the compression relay area 15a to the designated area of the hard disk device 33 for storage. The first memory / compression / decompression controller 17 transfers the compressed image data stored in the compression relay area 15a to the hard disk device 33 according to an instruction from the CPU 32, and the hard disk device 33 transfers the transferred image data to the designated area. (P2a).

  On the other hand, if the compression ratio R exceeds the threshold Y, the image data compressed by the second compression / decompression unit 14 is transferred from the compression relay area 16a of the second image memory 16 to the designated area of the hard disk device 33 and stored. Is output to the second memory / compression / decompression controller 18. The second memory / compression / decompression controller 18 transfers the compressed image data stored in the compression relay area 16a to the hard disk device 33 in accordance with an instruction from the CPU 32, and the hard disk device 33 transmits the transferred image data to the designated area. (P2b).

  When inputting image data of a plurality of pages, the above-described series of operations is repeated, and the image data compressed by either the first or second compression / decompression device 13 or 14 of each page is sequentially stored in the hard disk device 33. Stored in When the compressed image data is transferred to the hard disk device 33 and stored, information indicating the compression method is added to the header information. Further, after the transfer of the image data to the hard disk device 33 is completed, the respective image data is deleted from the compression relay areas 15a and 16a.

  At the time of print output based on the image data stored in the hard disk device 33, the CPU 32 recognizes the compression method of the compressed image data from the header information, and performs the following operation according to the recognized compression method. The memory / compression / decompression controller 17, the second memory / compression / decompression controller 18, the printer image processing circuit 21, and the like are instructed to execute the following processing.

  When the image data to be printed is compressed by the first compression method (reversible compression method), the image data is transferred from the hard disk device 33 to the reproduction relay area 15b of the first image memory 15 (P3a in FIG. 2). ), The image data decompressed by the first compression / decompression unit 13 is output to the printer image processing circuit 21 via the first memory / compression decompression controller 17 (P4a).

  When image editing such as rotation or overlay is performed, the decompressed image data is temporarily stored in the page memory 15c, and image editing is performed. Thereafter, the first memory / compression decompression controller 17 is transferred from the page memory 15c. Then, the image data is output to the printer image processing circuit 21 (P5a). The printer image processing circuit 21 selects and inputs the image data from the first memory / compression / decompression controller 17 with the selector 21a. The input image data is subjected to print output image processing and then printed out by the printer unit 22.

  When the image data to be printed is compressed by the second compression method (lossy compression method), the image data is transferred from the hard disk device 33 to the reproduction relay area 16b of the second image memory 16 (see FIG. 2). Then, the image data expanded by the second compression / decompression device 14 is output from the second memory / compression / decompression controller 18 to the printer image processing circuit 21 (P4b).

  When there is image editing such as rotation or overlay, the decompressed image data is temporarily stored in the page memory 16c and image editing is performed, and then the page memory 16c passes through the second memory / compression / decompression controller 18. Image data is output to the printer image processing circuit 21 (P5b). The printer image processing circuit 21 selects and inputs the image data from the second memory / compression / decompression controller 18 with the selector 21a. The image data is subjected to image processing for print output and then printed out by the printer unit 22.

  Note that the data transfer rate between the first image memory 15 or the second image memory 16 and the hard disk device 33 (P2a, P2b, P3a, P3b in FIG. 2) depends on the first memory / compression / decompression controller 17 and the second Among the processing speed of the memory / compression / decompression controller 18, the speed of the system bus 31, the speed of the HDD-I / F 34 (SATA: Serial ATA (Advanced Technology Attachment)), the internal transfer speed of the hard disk device 33, etc. Is limited by

  Next, a method for setting the threshold value Y and the specified compression rate X will be described.

  The threshold value Y and the designated compression ratio X are simply obtained from the equation Y = X ≦ (A / 2) / (B × C / 60) (1). Here, A is the amount of data that can be transferred per second (data transfer) between the first image memory 15 or the second image memory 16 and an area reserved in advance in the hard disk device 33 for storing compressed image data. (Speed) is the worst value, B is the data amount of image data for one page printed out by the printer unit 22, and C is the number of prints per minute by the printer unit 22. Note that the worst-case data transfer speed A is halved during printing output from the first image memory 15 or the second image memory 16 to the hard disk device 33 and vice versa. Is transferred (read).

  Incidentally, the data transfer speed between the first image memory 15 or the second image memory 16 and the hard disk device 33 differs depending on whether the access position in the hard disk device 33 is the inner peripheral portion or the outer peripheral portion of the hard disk. FIG. 3 shows an example of the relationship between the data transfer rate and the access position on the hard disk when sequential writing to the hard disk device is performed. In the figure, the horizontal axis indicates LBA (Logical Block Addressing), and the smaller the LBA value, the more the access position is located on the outer periphery side of the disk. As can be seen from FIG. 3, the data transfer rate is faster toward the outer periphery of the disk, and the data transfer rate decreases as it approaches the inner periphery.

  When the hard disk device 33 is partitioned into a system area for storing data on the system side and a compressed image area for storing compressed image data, the position where the compressed image area is secured is the outer peripheral portion of the disk. The closer to, the higher the data transfer rate A in the above equation (1). The worst value is determined based on the data transfer rate to the sector located at the innermost periphery in the partition secured as the compressed image area. For example, in the hard disk device having the characteristics shown in FIG. 3, when the area E from LBA “1” to “36 × 1000000” is secured as the compressed image area, the worst value of the data transfer rate is 50 MB / It becomes about s (MegaByte / Sec).

When the compressed image area is secured in the partition including the outermost peripheral sector of the hard disk device 33,
A = the worst value [MB / s] of the sequential read / write speed to the partition having the outermost peripheral sector of the hard disk device 33,
B = data amount of uncompressed image data [MB] = number of pixels in the main scanning direction × number of pixels in the sub-scanning direction × number of bits per pixel,
C = maximum output speed of the image processing apparatus 10 [number of copies / minute],
Threshold value Y and designated compression rate X can be set as The number of bits per pixel depends on the number of gradations. For example, 256 bits is 8 bits. The actual threshold value Y and the specified compression rate X are set to values that are smaller by a certain margin than the value of (A / 2) / (B × C / 60).

  A more specific example will be described.

  When the image processing apparatus 10 outputs 120 A4-size images of 1 pixel per bit with a resolution of 1200 dpi (Dot Per Inch) per minute, the partition of the outermost peripheral sector of the hard disk device 33 is set in advance as a compressed image area. It is assumed that the worst value of the sequential read / write speed in this area is 30 MB / s.

  At this time, in the equation (1), A is 30 [MB / s], B is 18 [MB], C is 120 [number of copies / minute], and the threshold Y and the specified compression rate X are expressed by the equation (1). Assuming that the maximum value of the range that can be taken in is, threshold Y = specified compression ratio X = (30/2) / (18 × 120/60) = about 0.417. In the case of an image in which the compression ratio when the first compression / decompression unit 13 compresses by the lossless compression method exceeds the threshold Y (41.7%), the compressed image area secured in the first image memory 15 and the hard disk device 33, and The data transfer speed during the period may not be in time for print output, and productivity may be reduced. Therefore, if the designated compression rate X for compression by the irreversible compression method by the second compression / decompression unit 14 is set to 41.7% or less, the compression rate in the first compression / decompression unit 13 becomes the threshold value Y ( 41.7%), the image data compressed by the second compressor / decompressor 14 is adopted and transferred to the hard disk device 33 to be stored, thereby avoiding a decrease in productivity due to the transfer. it can.

  It is desirable to secure a certain margin for setting the actual threshold value Y and the specified compression ratio X in consideration of the rotation waiting time of the hard disk device 33, the priority and overhead associated with the use of the system bus 31, and the like. For example, when the margin is 10%, the threshold Y and the specified compression rate X may be 37.5% with respect to 41.7% without the margin. Further, the threshold Y and the designated compression rate X do not need to be set to the same value, and the compression rate X of the lossy compression method is preferably Y ≧ X in order to have a margin.

  As described above, in the image processing apparatus 10 according to the present embodiment, the threshold Y and the designated compression rate X are set, and the compression rate in the lossless compression method by the first compression / decompression unit 13 is equal to or less than the threshold Y. The image data compressed by the lossless compression method is transferred to the hard disk device and stored, and when the compression rate by the lossless compression method exceeds the threshold value Y, the second compression / decompression unit 14 uses the compression rate X equal to or lower than the threshold value Y. The reversibly compressed image data is transferred to the hard disk device and stored. In this way, image data that is compressed using the lossless compression method as much as possible to avoid image degradation, and is compressed by inputting images that contain many of the disadvantages of the lossless compression method, such as photographs and halftone dots. When the rate is deteriorated, it is possible to avoid a decrease in productivity of the image processing apparatus 10 due to a delay in transfer to the hard disk device 33 by adopting image data compressed by the lossy compression method.

  In the above example, a compressed image area (first area) secured in advance in the hard disk device 33 for storing image data compressed by the first compression / decompression unit 13 using the first compression method (reversible compression method); Without distinguishing from the compressed image area (second area) reserved in advance in the hard disk device 33 in order to store the image data compressed by the second compression / decompression device 14 by the second compression method (lossy compression method), Although these are the same area, the first area and the second area may be set as separate areas (partitions).

  In this case, the sequential read / write speed J of the partition secured as the first area is measured, and this value J is substituted into A in the equation (1), and the threshold Y is Y ≦ (J / 2) / (B × C / 60). Further, the sequential read / write speed K of the partition secured as the second area is measured, and this value K is substituted into A in the equation (1), and the designated compression ratio X is X ≦ (K / 2) / ( B × C / 60).

  Thus, by securing the first area and the second area in separate areas and individually setting the threshold value Y and the designated compression ratio X based on the worst value of the data transfer speed in each area, a plurality of It is possible to cope with a case where a request for storing compressed image data in a different partition is made for each compression method by adopting a hard disk device having a partition structure or by using a plurality of hard disk devices.

  A specific example when the first area and the second area are set as separate areas (partitions) is shown. When the image processing apparatus 10 outputs 120 A4-size images of 1 pixel and 1 bit per minute at a resolution of 1200 dpi, a partition that can secure a data transfer speed J of 30 MB / s at the worst value is obtained by the lossless compression method. A second area for storing image data compressed in an irreversible compression scheme in a first area for storing compressed image data and a partition that can secure a data transfer rate K of 20 MB / s at the worst value. Secure in the area. In this case, the threshold Y = (J / 2) / (B × C / 60) = (30/2) / (18 × 120/60) = about 0.417, the designated compression ratio X = (K / 2) / (B × C / 60) = (20/2) / (18 × 120/60) = about 0.278.

  Therefore, when the compression rate of the image data in the lossless compression method by the first compression / decompression unit 13 is 41.7% (threshold Y) or less, the losslessly compressed image data is transferred to the hard disk device 33, and the first compression / decompression is performed. When the compression rate of the image data in the lossless compression method by the device 13 exceeds 41.7%, the hard disk device stores the image data irreversibly compressed by the second compression / decompression device 14 with the compression rate X of 27.8% or less. 33.

  Further, in this case, the threshold Y and the designated compression rate X are individually determined in accordance with the worst data transfer speed in each of the secured first area and second area, so that the relationship of Y ≧ X does not necessarily exist.

  Conversely, when it is desired to make the lossy-compressed image as high as possible, the specified compression ratio X ≧ threshold Y may be satisfied. For example, the second area for storing the image data compressed by the irreversible compression method in the partition that can secure the data transfer rate of 30 MB / s at the worst value by switching the positions for securing the first area and the second area. When a partition that can be secured in the area and can secure a data transfer rate of 20 MB / s at the worst value is secured in the first area for storing image data compressed by the lossless compression method, the threshold value Y = 0.278 is designated. The compression ratio X is about 0.417.

  Next, a second embodiment will be described.

  In the first embodiment, the compression rate is compared with the threshold value, but in the second embodiment, the size (data amount) of the compressed image data is compared with the threshold value. Is the same as in the first embodiment.

  Specifically, when the compression operation for one page is completed by the first compression / decompression unit 13 and the second compression / decompression unit 14, the CPU 32 displays the image data (one page after compression) compressed by the first compression / decompression unit 13. Data amount (compressed image data size) V is obtained from the first memory / compression / decompression controller 17, and the data amount V is compared with a predetermined threshold Y ′. If the size V of the compressed image data is smaller than the threshold Y ′, the image data compressed by the first compression / decompression unit 13 by the lossless compression method is transferred from the compression relay area 15a of the first image memory 15 to the hard disk device 33. Transfer it to the specified area and store it.

  On the other hand, when the size V of the image data compressed by the first compression / decompression unit 13 is larger than the threshold Y ′, the image data compressed by the second compression / decompression unit 14 is transferred from the compression relay area 16a of the second image memory 16 to the hard disk. The data is transferred to the designated area of the device 33 and stored.

At this time, the threshold Y ′ of the image size for not reducing productivity is
Y ′ = (A / 2) × (C / 60): determined by the formula (2) Here, as in the case of equation (1), A is the worst value of the data transfer speed, and C is the number of printed sheets per minute by the printer unit 22.

  As a specific example, when A is 50 MB / S (MegaByte / Sec) and C is 120 ppm (Paper / minute), the threshold Y ′ of the image data size for preventing the productivity from dropping is Y ′ = (50 /2)/(120/60)=12.5 MB. In the case of a low-speed machine with a small number of copy output sheets (ppm), for example, when A is 50 MB / S and C is 30 ppm, the threshold Y ′ of the image data size for preventing the productivity from dropping is Y '= (50/2) / (30/60) = 50 MB.

  As described above, even when comparing the post-compression image data size V with the threshold value Y ′, the same effect as in the first embodiment for comparing the compression rates can be obtained. Further, the calculation for obtaining the compression rate from the data size becomes unnecessary, and the processing load corresponding to that is reduced.

  The embodiment of the present invention has been described with reference to the drawings. However, the specific configuration is not limited to that shown in the embodiment, and there are changes and additions within the scope of the present invention. Are also included in the present invention.

  For example, in the embodiment, the CPU 32 is configured to perform the function as the control unit. However, the first memory / compression / decompression controller 17 and the second memory / compression / decompression controller 18 may be part or all of the functions of the control unit. It may be configured to perform the following functions.

  In the embodiment, the first image memory 15 and the second image memory 16 are separate memories, but a single memory element may be used. In addition to the first memory / compression / decompression controller 17 and the second memory / compression / decompression controller 18, the HDD-I / F 34 may be configured so that the transfer means functions partially. For example, the HDD-I / F 34 performs data transfer between the HDD-I / F 34 and the first memory / compression / decompression controller 17 or the second memory / compression / decompression controller 18, and the first memory / compression / decompression controller 17 and the second memory / compression / decompression controller 18 may be configured to perform data transfer between itself and the first image memory 15 or the second image memory 16.

  In addition, the hard disk device 33 is preferably used by setting a partition so as to separate the system area and the compressed image area, but the hard disk device 33 may be used without setting the partition. Further, the second storage means is not limited to the hard disk device. The second storage means is preferably a large capacity storage device.

  In the embodiment, the first compression method is the reversible compression method and the second compression method is the irreversible compression method, but both may be irreversible compression methods. For example, the lossy compression method that does not specify the compression rate may be the first compression method, and the lossy compression method that specifies the compression rate may be the second compression method.

  Further, in the embodiment, the operation of printing out while inputting image data such as a copy operation has been described as an example. However, the operation by the image processing apparatus 10 is not limited to this, and the hard disk device 33 is input and compressed to compress the image. The input operation for transferring to and storing the image data and the output operation for reading the compressed image data stored from the hard disk device 33, decompressing it, and printing it out may be performed at different timings. In this case, the threshold Y and the value of the specified compression rate X may be set based on Y = X ≦ A / (B × C / 60) for one of the input operation and the output operation.

  In addition, in the embodiment, the actual compression rate is compared with the threshold Y for each page, but the compression method may be selected by comparing the compression rate with the threshold for a plurality of pages. Conversely, one page may be divided into a plurality of blocks, and the compression method may be selected in units of blocks. Similarly, when comparing the size of the image data after compression and the threshold value Y ′, the compression method may be selected by comparing the threshold value with a plurality of pages or blocks.

1 is a block diagram illustrating a configuration of an image processing apparatus 10 according to an embodiment of the present invention. It is explanatory drawing which shows the data flow of the part relevant to compression and expansion | extension in the operation | movement from the input of an image data to an output which the image processing apparatus concerning embodiment of this invention performs. It is explanatory drawing which shows an example of the relationship between the data transfer speed at the time of sequential writing to a hard-disk apparatus, and the access position (LBA) on a hard disk. It is explanatory drawing which shows the relationship between the level of a compression rate, and the numerical value of a compression rate.

Explanation of symbols

2 ... LAN
DESCRIPTION OF SYMBOLS 10 ... Image processing apparatus 11 ... Scanner part 11a ... Line image sensor 11b ... A / D converter 12 ... Scanner system image processing circuit 13 ... 1st compression / decompression device 14 ... 2nd compression / decompression device 15 ... 1st image memory 15a ... Compression relay area 15b ... Reproduction relay area 15c ... Page memory 16 ... Second image memory 16a ... Compression relay area 16b ... Reproduction relay area 16c ... Page memory 17 ... First memory / compression decompression controller 18 ... Second memory / compression Decompression controller 21 ... Printer image processing circuit 21a ... Selector 22 ... Printer unit 31 ... System bus 32 ... CPU
33 ... Hard disk device 34 ... HDD-I / F
35 ... NIC / printer controller 36 ... Host bus 37 ... Memory

Claims (10)

Input means for inputting image data;
A first compression / decompression unit that compresses and decompresses image data using a first compression method;
A second compression / decompression unit that compresses and decompresses image data using a second compression method;
First storage means for temporarily storing image data compressed or expanded by the first compression / decompression unit or the second compression / decompression unit;
A second storage means;
Transfer means for transferring data between the first storage means and the second storage means;
Output means for printing out the image data expanded by the first compression / decompression unit or the second compression / decompression unit;
And the control means compresses the image data input from the input means in parallel by the first compression / decompression unit and the second compression / decompression unit, and then uses the first compression / decompression unit. The compression rate of the compressed image data is compared with a predetermined threshold value. When the compression rate is equal to or lower than the threshold value, the image data compressed by the first compression / decompression unit is stored in the first storage by the transfer means. When the compression ratio is larger than the threshold value, the image data compressed by the second compression / decompression unit is transferred by the transfer means to the first storage means and transferred to the second storage means. An image processing apparatus, wherein the image processing apparatus transfers the data from the storage means to the second storage means and stores it in the second storage means. Input means for inputting image data;
A first compression / decompression unit that compresses and decompresses image data using a first compression method;
A second compression / decompression unit that compresses and decompresses image data using a second compression method;
First storage means for temporarily storing image data compressed or expanded by the first compression / decompression unit or the second compression / decompression unit;
A second storage means;
Transfer means for transferring data between the first storage means and the second storage means;
Output means for printing out the image data expanded by the first compression / decompression unit or the second compression / decompression unit;
And the control means compresses the image data input from the input means in parallel by the first compression / decompression unit and the second compression / decompression unit, and then uses the first compression / decompression unit. The compressed image data is compared with a predetermined threshold value. If the size of the compressed image data is smaller than the threshold value, the image data compressed by the first compression / decompression unit is transferred to the first transfer means by the transfer means. When the size of the compressed image data is larger than the threshold value, the image data compressed by the second compression / decompression device is transferred from the storage means to the second storage means and stored in the second storage means. An image processing apparatus, wherein the first storage unit transfers the data to the second storage unit and stores the second storage unit in the second storage unit. The first compression method is a lossless compression method,
The image processing apparatus according to claim 1, wherein the second compression method is an irreversible compression method. The image data compressed by the first compression method is transferred and stored in a first area secured in advance in the second storage means,
The threshold value is one page at which the output unit prints out half the worst value of the data amount per unit time that can be transferred by the transfer unit between the first storage unit and the first area. 2. The image processing apparatus according to claim 1, wherein the image processing apparatus is set to a value equal to or less than a value obtained by multiplying a data amount of image data by a value obtained by multiplying the number of prints per unit time by the output unit. The image processing apparatus according to claim 1, wherein the second compression method is a lossy compression method that compresses image data at a specified compression rate. The image processing apparatus according to claim 5, wherein the designated compression rate is smaller than the threshold value. The image data compressed by the second compression method is transferred and stored in a second area secured in advance in the second storage means,
The specified compression rate is printed out by the output unit at one half of the worst value of the data amount per unit time that can be transferred by the transfer unit between the first storage unit and the second area. The image processing apparatus according to claim 5, wherein the image processing apparatus is set to a value equal to or less than a value obtained by multiplying a data amount of image data for one page to be multiplied by the number of printed sheets per unit time by the output unit. The image data compressed by the first compression method and the image data compressed by the second compression method are transferred and stored in the same area secured in advance in the second storage means. The image processing apparatus according to claim 1. The data compressed by the first compression method is transferred and stored in a first area secured in advance in the second storage means, and the image data compressed by the second compression method is stored in the second storage The image processing apparatus according to claim 1, wherein the image processing apparatus transfers and stores in a second area different from the first area, which is secured in advance by the means. The image processing apparatus according to claim 1, wherein the first storage unit is a semiconductor memory, and the second storage unit is a hard disk device.

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