JP2005128875A - Storage device, image forming device and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain quick data transfer at a fixed speed by using a storage device having a plurality of storage areas whose data reading speeds are different. <P>SOLUTION: A CPU 201 assigns a storage area whose reading speed is the highest from the dead area of a storage medium 211 having storage areas whose data reading speeds are different to inputted image data. The CPU 201 calculates the threshold of a data compression rate satisfying the data transfer speed requested by an output part 209 from the reading speed of the assigned storage area and the data transfer speed. The CPU 201 compares the compression rate of the image data compressed by a reversible compressing part 2041 with the threshold. When the compression rate of the compressed image data is less than the threshold, an irreversible compressing part 2042 compresses the input image data at the compression rate which is not less than the threshold. The image data compressed at the compression rate which is not less than the threshold are stored in the assigned storage area. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a storage device for storing a large amount of data.

  In recent years, digital multi-function peripherals having a copy function, a printer function, and the like have been provided with an electronic sort function capable of electronically sorting and printing a document consisting of a plurality of pages. For example, the electronic sort function repeatedly reads all pages of a document to be copied, temporarily stores the data in a storage medium, and then reads and prints the stored data in page order. Thereby, a plurality of copies can be output by one image reading. In print output, document data described in a page description language is transmitted to a digital multifunction peripheral via a network, and is converted into bitmap data in the digital multifunction peripheral, and all pages are stored in a storage medium in the same manner as described above. By storing, the same electronic sort is realized.

  In order to realize electronic sorting, it is necessary to temporarily store data of all pages of a document in a storage medium as described above. As a storage medium having a high data transfer speed, there is a semiconductor memory. However, in order to store a large number of pages of image data in a digital multi-function peripheral, a capacity of several gigabytes is required, and such a large-capacity semiconductor memory is expensive and difficult to adopt. Therefore, a rotary storage medium represented by a hard disk device is widely used as a medium that is relatively inexpensive and can store a large amount of data. However, when these rotary storage media are used, the cost problem is solved, but the problem remains in terms of data transfer speed. In the hard disk device, a zone bit recording method is used for the purpose of increasing the capacity. In the zone bit recording system, the disk surface is divided into a plurality of concentric zones as shown in FIG. Each zone is divided into a plurality of sectors, and the outer zone has a larger number of sectors. The write capacity per sector is the same. As a result, the outer zone has a larger storage capacity. Therefore, the data writing / reading speed becomes higher in the outer zone. If two pieces of data with the same data amount are stored in the outer peripheral part and the inner peripheral part, the data stored in the outer peripheral part has a faster reading speed even though the data amount is the same. Become.

  In an image forming apparatus that performs printing using data stored on a hard disk, it is necessary to transfer data from the hard disk to the print output unit at a constant speed in accordance with the printing speed. However, when data is stored across a plurality of zones as described above, the data stored in the inner peripheral portion has a lower reading speed than the outer peripheral portion, and as a result, printing cannot be performed at a constant speed. Occurs.

Various techniques have been proposed for the purpose of preventing such inconvenience and performing high-speed data transfer at a constant speed (for example, Patent Documents 1 and 2).
In the technique described in Patent Document 1, when image data is stored in a storage medium having a plurality of storage areas with different writing / reading speeds, the storage position is determined according to the purpose of use of the image data. Specifically, data that needs to be transferred at a constant speed and at a high speed, such as a document that is subject to electronic sorting, is stored on the outer periphery where the transfer speed is relatively high, and other data is transferred at a transfer speed. Is stored in a relatively low speed inner periphery. In this way, high-speed data transfer is achieved at a constant speed.
In the technique described in Patent Document 2, a printer includes a plurality of storage devices having different data transfer rates. The lower limit value of the data compression rate required for each storage device is determined by the relationship between the printing processing speed of the printer and the data transfer speed. After the image data is compressed by a predetermined compression method, a storage device whose compression rate exceeds the lower limit value is selected, and the compressed data is stored in the storage device.
JP 2000-32243 A JP-A-9-193488

However, in the technique described in Patent Document 1, since a storage area that can be used is limited when high-speed data transfer is necessary at a constant speed, the area is expanded when it is desired to increase the area to be used. Work is necessary and lacks convenience. The technique described in Patent Document 2 uses a plurality of storage devices, which increases the cost.
The present invention has been made under the background described above, and is a technology capable of performing high-speed data transfer at a constant speed using a storage device having a plurality of storage areas with different data reading speeds. The purpose is to provide.

  In order to solve the above-described problem, the present invention provides a storage unit having a plurality of storage areas with different data reading speeds, an output unit that outputs an image based on image data read from the storage unit, An allocation unit that allocates the storage area having the fastest reading speed among the free areas of the storage unit to the input image data, the reading speed of the storage area allocated by the allocation unit, and the output unit A threshold value calculation means for obtaining a threshold value of a data compression rate satisfying the data transfer speed from the data transfer speed, a compression means for compressing image data, a compression rate of the image data compressed by the compression means, and the threshold value calculation means The comparison means for comparing the threshold value obtained by the above and the compression rate of the image data compressed by the compression means is less than the threshold value A recompression unit that compresses the input image data at a compression rate equal to or higher than the threshold value, and image data that has been compressed at a compression rate equal to or higher than the threshold value by the compression unit or the recompression unit is allocated by the allocation unit. And a storage device for storing in the storage area.

  Further, the present invention provides an assigning means for allocating a storage area having the fastest reading speed among the free areas of the storage unit having a plurality of storage areas having different data reading speeds to the input image data. Data satisfying the data transfer speed from the read speed of the storage area allocated by the allocating means and the data transfer speed requested by the output section that outputs an image based on the image data read from the storage section A threshold value calculating means for obtaining a threshold value of the compression ratio, a compressing means for compressing the image data, a comparing means for comparing the compression ratio of the image data compressed by the compressing means with the threshold value obtained by the threshold value calculating means, When the compression rate of the image data compressed by the compression unit is less than the threshold, the input image data is Re-compression means for compressing at a compression rate equal to or higher than the threshold value, and storage means for storing the image data compressed at the compression rate equal to or higher than the threshold value by the compression means or the re-compression means in the storage area allocated by the allocation means Provide a program to function as

  According to the present invention, the assigning means assigns the storage area having the fastest reading speed among the free areas of the storage unit having a plurality of storage areas having different data reading speeds to the input image data. The threshold value calculation means uses the data read speed of the storage area assigned by the assignment means and the data transfer speed required by the output section that outputs an image based on the image data read from the storage section. A threshold value of the data compression rate that satisfies the transfer rate is obtained. The comparison unit compares the compression rate of the image data compressed by the compression unit with the threshold value obtained by the threshold value calculation unit. When the compression rate of the image data compressed by the compression unit is less than the threshold value, the recompression unit compresses the input image data at a compression rate equal to or higher than the threshold value. A storage unit stores the image data compressed by the compression unit or the recompression unit at a compression rate equal to or higher than the threshold in the storage area allocated by the allocation unit.

  According to the present invention, data is stored in order from the outer periphery of the hard disk, and image data is stored by performing data compression according to the reading speed of each area so as to satisfy the required transfer rate of the output unit. It is possible to transfer a large amount of image data at a high speed and at a constant speed. Further, it is possible to store data while satisfying the transfer rate required by the output unit without limiting the storage area.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Here, a description will be given using an example of a copying machine provided with a storage device according to the present invention.
[First Embodiment]
[Constitution]
FIG. 2 is a diagram illustrating a hardware configuration of the copying machine 2 including the storage device 20. A CPU (Central Processing Unit) 201 controls the entire storage device 20. The input unit 207 includes a feeder, takes in a document original placed on the feeder one page at a time, reads the image, and generates image data. The image data input from the input unit 207 is compressed by the lossless compression unit 2041 of the compression unit 204 and temporarily stored in the system memory 202. When compression of a predetermined amount (for example, one page) of image data is completed, the storage medium control unit 210 transfers the image data to the storage medium 211 in accordance with an instruction from the CPU 201. The storage medium 211 is a hard disk device. The storage position of the image data in the storage medium 211 is stored in advance in the management table 2061 and is controlled according to the notification from the management unit 206.
The output unit 209 prints an image by an electrophotographic method based on the image data. When the output unit 209 outputs an image, the storage medium control unit 210 reads the designated image data from the storage medium 211 in accordance with an instruction from the CPU 201 and transfers it to the system memory 202. The image data transferred to the system memory 202 is transferred to the expansion unit 208, and is sequentially expanded and sent to the output unit 209.

The storage medium 211 is a hard disk device and includes a plurality of disks 30. As shown in FIG. 3, the recording surface of the disk 30 is concentrically divided by a zone bit recording method. Here, an example in which the number of divisions is three will be described, but the number of divisions is not limited to three. As shown in FIG. 4, the data reading speed is 20 MB / sec or more in the area A, 15 MB / sec or more in the area B, and 10 MB / sec or more in the area C.
The data transfer request speed in FIG. 4 will be described. In an apparatus such as a copying machine or a printer, the output unit needs to receive data at a constant speed, and the speed is determined by the performance of the output unit. When this speed cannot be satisfied, the output unit needs to temporarily stop the output or reduce the output speed, resulting in a decrease in output efficiency. Here, it is assumed that a data transfer rate of δMB / sec or more is required.

  The management unit 206 calculates the compression rate threshold value of each area from the data transfer request speed requested by the output unit 209 and the read speed of each area of the storage medium 211, and stores it in the management table 2061. The compression rate is defined as the amount of data before compression divided by the amount of data after compression. For example, if the data amount before compression is 100 MB and the data amount after compression is 50 MB, the compression rate in this case is 2.0. The amount of image data before compression is determined by the size of the image. For example, when an A4-size color image is scanned at 300 bpi (bit per inch) and the colorimetric values are quantized at 24 bits, the data amount of one line (one column of pixels in the short side direction) is about 7000 bytes.

  The compression rate threshold is a minimum compression rate that enables the output unit 209 to print an image at a predetermined speed without stopping printing or reducing the printing speed. That is, when image data compressed at a compression rate higher than the threshold value is stored in the storage unit, the image data of the next page can be read and prepared for printing while the output unit 209 performs printing. . The threshold value of the compression rate is obtained by dividing the data transfer request speed of the output unit 209 by the read speed of the area. For example, if the data transfer request rate is 40 MB / sec and the read rate is 20 MB / sec, the compression rate threshold in this case is 2.0.

In creating the management table 2061, it is necessary to know the data reading speed of each area. However, the data reading speed may be measured in advance, or a measuring unit is provided in the storage device. The data reading speed may be measured when the storage device is activated. FIG. 4 is a diagram showing an example of the management table 2061 created in this way.
Next, the management unit of the data compression rate will be described. As shown in FIG. 6, the amount of image data representing a document is managed in three units: line, page, and job. A line is a series of pixels for one column, and a page is represented by image data of a plurality of lines. A job is an entire document.

  The data compression rate is managed in line units. The reason is described below. When the compression rate of the image data is viewed for each line, generally, the compression rate varies as shown in FIG. At this time, if the compression rate of a certain line is less than the threshold value, the arrival of data to be output is delayed, so the output unit 209 is forced to pause when outputting the line. Therefore, in the present invention, in order to enable output at a constant speed, the compression rate is compared with a threshold value for each line, and if it is less than the threshold value, recompression described later is performed.

  In this embodiment, a reversible compression method without image quality deterioration is used as the compression method used for the first compression. For example, JBIG (Joint Bi-lebel Image experts Group) can be used as the lossless compression method. In addition, when a compression rate equal to or higher than the threshold cannot be obtained by the first compression, recompression is performed using an irreversible compression method that can obtain a higher compression rate than the lossless compression method. As the lossy compression method, for example, JPEG (Joint Photographic Coding Expert Group) can be used. However, the compression method is not limited to the above example, and other methods that can obtain an equivalent compression rate may be used.

[Operation]
The operation of the storage device having the above configuration will be described using an example of a copying machine including the storage device. FIG. 5 is a flowchart showing the operation of the storage device. It is assumed that the copying machine is turned on.
First, the management unit 206 of the storage device notifies the storage medium control unit 210 which position in the storage medium 211 the image data is stored (step S501). The storage position is determined by the management unit 206 searching for an area with the fastest reading speed among the vacant areas at that time.

Next, one page of the document is read by the input unit 207, and image data representing the read page is generated (step S502).
The generated image data is sent to the lossless compression unit 2041 line by line, and is compressed line by line using a predetermined compression parameter (step S503).
The compressed data is stored in the system memory 202 in units of lines (step S504).

Here, the CPU 201 determines whether or not all the lines included in the page have been input (step S505), and if there are any uninput lines, the process returns to step S502 to input the lines.
If all lines have been input, the compression rate is determined (step S506). Here, the CPU 201 extracts the compression rate threshold value of the designated storage location from the management table 2061 and compares the compression rate of each line stored in the system memory 202 with the threshold value. If the compression rate of all lines on the page is equal to or greater than the threshold (step S506: YES), the image data of the page is stored in the designated storage position (step S507).

  On the other hand, if there is a line for which a compression ratio equal to or higher than the threshold is not obtained in step S506 (step S506: NO), recompression is performed. First, the CPU 201 reads out image data stored in the system memory 202 and sends this image data to the decompression unit 208. The image data sent to the decompression unit 208 is decompressed (step S508) and transferred to the buffer memory 205 (step S509). The management unit 206 sets a compression parameter in the irreversible compression unit 2042 so that a compression rate equal to or higher than the threshold can be obtained (step S510).

Next, the image data stored in the buffer memory 205 is sent to the irreversible compression unit 2042 and recompressed by the irreversible compression method (step S503).
After the recompressed image data is transferred to the system memory 202 (step S504) and the comparison between the compression rate and the threshold (step S506) is performed. The data is stored in the designated storage location of the storage medium 211 (step S507). The CPU 201 performs this series of processing on all pages.

  FIG. 8A is a list showing a state when the image data of all pages included in one job has been stored in the storage medium 211. FIG. 8B shows the storage position of each page. The entire job has n + 5 pages, and the image data is compressed from the area A where the reading speed is the fastest to be compressed to be equal to or higher than a compression rate threshold defined in the area. Here, not all pages can be stored in the area A alone, and therefore data is also stored in the area B after the n + 2nd page. Since the reading speed of the area B is slower than that of the area A, the threshold value β of the compression rate of the stored data is higher than the threshold value α of the area A (β> α). As a result, as shown in the column of guaranteed transfer rate, data transfer at a transfer rate δMB / sec requested by the output unit 209 is possible for all pages.

As described above, according to the present invention, image data is stored in order from the outer periphery of the hard disk, and is subjected to data compression in accordance with the reading speed of each area so as to satisfy the required transfer rate of the output unit. Therefore, large-capacity image data can be transferred at a high speed and at a constant speed. Further, it is possible to store data while satisfying the transfer rate required by the output unit without limiting the storage area.
Further, by managing the compression rate for each column of pixels, it is possible to prevent the printing speed from being lowered by the line. Since an irreversible compression method is used for recompression, recompression can be performed at a compression rate that exceeds the compression rate in the first compression (reversible compression). At the time of recompression, since the image data subjected to lossless compression is expanded and used, there is no need to hold the image data before compression.

[Second Embodiment]
In the first embodiment described above, the management unit 206 and the irreversible compression unit 2042 are configured by hardware as shown in FIG. 2, but the storage device 90 in the second embodiment of the present invention is programmed by the CPU 901. Are configured to function as a management unit and an irreversible compression unit. FIG. 9 is a diagram illustrating a hardware configuration of the copying machine 9 including the storage device 90 configured as described above. Here, the management table is stored in the management table area 910 of the system memory 902. Further, the system memory 902 is provided with a recompression area 911. The decompressed image data is held in the recompression area 911, and the CPU 901 performs recompression by the irreversible compression method.

FIG. 10 is a flowchart showing the operation of the storage device 90 configured as described above. Steps common to FIG. 5 are given the same reference numerals. The difference from the flow shown in FIG. 5 is processing (steps S1008 to S1010) when it is determined that the compression rate is less than the threshold. The image data that needs to be recompressed is decompressed by the CPU 901 and stored again in the recompression area 911 in the system memory 902 (S1008). The CPU 901 sets a compression parameter for compressing the image data by the irreversible compression method (step S1009), and compresses the image data (S1010). The compressed data is stored again in the system memory 902, and the CPU 901 determines whether or not the compression rate is equal to or greater than a predetermined threshold (step S506). If it is equal to or greater than the threshold (step S506: YES), the image data is stored in the storage medium 907.
According to the above configuration, when updating / changing the management table and the irreversible compression method, it is only necessary to replace the program, so there is no need to modify the hardware.

[Third Embodiment]
In the third embodiment of the present invention, the storage device 90 in the second embodiment is configured such that the user can specify the compression method. For example, as shown in FIG. 11, a fixed compression method mode and a variable compression method mode are provided, and a screen that prompts the user to designate one is displayed on the display panel of the copying machine. The variable compression mode is a mode described in the above embodiment, and is a mode in which image data is first compressed by a lossless compression method and recompressed by an irreversible compression method when the compression rate is less than a threshold value. is there. On the other hand, the fixed compression method mode is a mode in which the lossy compression method is used for both the initial compression and the recompression. The reason for using the lossy compression method is as follows. In the above embodiment, when the compression rate by the lossless compression method is less than the threshold, recompression is performed by the lossy compression method. In this case, a page compressed by the lossless compression method and a page compressed by the lossy compression method are mixed in one job. In the case of a job composed of a natural image such as a photograph, a subtle difference in image quality occurs due to different compression methods for each page. Since the lossy compression method has a higher compression ratio than the lossless compression method, the image quality of the image compressed by the lossy compression method is lower than that of the lossless compression method. And compress all pages using a lossy compression method.

When compression is performed in the fixed compression mode, the contents written in the management table are as shown in FIG. When the area used for storing the image data extends over a plurality of areas, the highest threshold value among them is applied. In the case of only the area A, the compression ratio threshold value α of the area A is applied. The threshold value β of the region B is applied when the region A and the region B are extended, and the threshold value γ of the region C is applied when the region A is extended to the region C. Here, α <β <γ.
FIG. 13 is a flowchart showing the operation of the storage device configured to be able to select the variable compression mode and the fixed compression mode. Steps common to those in FIG. 10 are denoted by the same reference numerals. First, the CPU 901 displays the screen shown in FIG. 11 on the display panel of the copier 9 (step S1301). When an instruction for specifying a mode is input by the user, the CPU 901 determines which mode is specified by the input instruction (step S1302).

When the variable compression method mode is designated (step S1302: YES), the processing after step S501 is performed. On the other hand, when the fixed compression mode is designated (step S1302: NO), the processing after step S1303 is performed.
First, the CPU 901 designates an area for storing image data (step S1303), and sets a compression parameter for the lossy compression method (step S1304). When image data is input (step S1305), the image data is transferred to the system memory 902 (step S1306). The CPU 901 compresses the image data transferred to the system memory 902 by an irreversible compression method (step S1307). Then, the compression rate of the compressed image data is compared with a threshold value (step S1308), and if the compression rate is equal to or higher than the threshold value (step S1308: YES), it is stored in the storage medium 907 (step S507). If the compression rate is less than the threshold (step S1308: NO), the process returns to step S1304, the compression parameters are reset so that a higher compression rate can be obtained, and the processing from step S1305 is performed.
According to said structure, it can prevent that the difference in the image quality between pages resulting from the difference in a compression system arises.

[Modification]
The present invention is not limited to the form described above, and can be implemented in various forms. For example, the embodiment described above can be modified as follows.
The compression rate of the image data may be managed in units of pages instead of units of lines.
A lossless compression method may be used for both initial compression and recompression of image data. In this case, the lossless compression method at the time of re-compression may be a method that can obtain a higher compression rate than the lossless compression method in the first compression, or a higher compression than the first compression by changing the compression parameter. You may make it get a rate.

The image data before compression may be retained after the first compression, and the image data before compression may be used instead of decompressing the image data compressed by the first compression at the time of recompression. .
In the above-described embodiment, an example of a storage device in which the storage unit is a hard disk device has been described, but the storage unit may be a storage device such as a semiconductor memory. The storage device according to the present invention may be used in an image forming apparatus other than a copying machine, such as a printer.

It is a figure which shows the recording surface of a hard disk. 2 is a diagram illustrating a hardware configuration of a copying machine 2 including a storage device 20. FIG. It is a figure which shows the recording surface of a hard disk. It is a figure which shows the example of a management table. 4 is a flowchart showing the operation of the storage device 20. FIG. It is a figure which shows the unit showing the data amount of image data. It is a figure which shows the dispersion | variation in the compression rate for every line. It is a list showing a state when image data is stored in a storage medium. It is a figure showing the storage position of the image data of each page. 2 is a diagram showing a hardware configuration of a copying machine 9 provided with a storage device 90. FIG. It is a flowchart which shows operation | movement of the memory | storage device 90 in 2nd Embodiment. It is a figure which shows the example of a display of the display panel of the copying machine 9 in 3rd Embodiment. It is a figure which shows the content written in the management table in fixed compression system mode. It is a flowchart which shows operation | movement of the memory | storage device 90 in 3rd Embodiment.

Explanation of symbols

201 ... CPU, 202 ... system memory, 203 ... bus control unit, 204 ... compression unit, 2041 ... reversible compression unit, 2042 ... irreversible compression unit, 205 ... buffer memory, 206 ... management unit, 207 ... input unit, 208 ... Decompression unit, 209... Output unit, 210... Storage medium control unit, 211.

Claims (7)

A storage unit having a plurality of storage areas with different data reading speeds;
An output unit that outputs an image based on the image data read from the storage unit;
An allocating means for allocating a storage area with the fastest reading speed from the free area of the storage unit to the input image data;
Threshold calculation means for obtaining a threshold value of a data compression rate that satisfies the data transfer speed from the read speed of the storage area allocated by the allocation means and the data transfer speed requested by the output unit;
Compression means for compressing image data;
A comparison means for comparing the compression ratio of the image data compressed by the compression means with the threshold value obtained by the threshold value calculation means;
Recompression means for compressing the input image data at a compression ratio equal to or higher than the threshold when the compression ratio of the image data compressed by the compression means is less than the threshold;
A storage unit configured to store the image data compressed by the compression unit or the recompression unit at a compression ratio equal to or higher than the threshold in a storage area allocated by the allocation unit. The comparison means compares the compression rate and the threshold value for each column of pixel values constituting the image data,
The re-compression unit compresses the input image data of the page at a compression rate equal to or higher than the threshold when there is a column of pixels whose compression rate is less than the threshold. The storage device described in 1. The compression means compresses data by a reversible compression method,
The storage device according to claim 1, wherein the recompression unit compresses data by a lossy compression method. Having decompression means for decompressing the image data compressed by the lossless compression method;
The recompressing unit decompresses the image data using the decompressing unit when the compression rate of the image data compressed by the compressing unit does not meet the threshold value, and the decompressed image data exceeds the threshold value. The storage device according to claim 1, wherein compression is performed at a compression rate.   The storage device according to claim 1, wherein the storage unit is a hard disk device.   An image forming apparatus comprising the storage device according to claim 1. Computer equipment,
An assigning means for allocating a storage area with the fastest reading speed among the free areas of the storage unit having a plurality of storage areas with different data reading speeds to the input image data;
Data satisfying the data transfer speed from the read speed of the storage area allocated by the allocating means and the data transfer speed requested by the output section that outputs an image based on the image data read from the storage section A threshold value calculating means for obtaining a threshold value of the compression rate;
Compression means for compressing image data;
A comparison means for comparing the compression ratio of the image data compressed by the compression means with the threshold value obtained by the threshold value calculation means;
Recompression means for compressing the input image data at a compression ratio equal to or higher than the threshold when the compression ratio of the image data compressed by the compression means is less than the threshold;
A program for functioning as storage means for storing image data compressed by the compression means or the recompression means at a compression rate equal to or higher than the threshold in a storage area allocated by the allocation means.

Images