JPH05110869A - Image storing method and device - Google Patents

Abstract

PURPOSE:To store the image information in a storing device by dividing and discriminating the image information and changing and coding the assignment of the gradation information and the resolution information in accordance with the characteristics. CONSTITUTION:A multiplexer MPX 61 selects the image information sent from a scanner to perform the reading and compresses the image data by a compressor 62. The compression divides the image information into blocks and discriminates the divided image information in accordance with the characteristics. When many bits of gradation information are assigned to one block, the assignment of the resolution information is minimized, and when the gradation is small assigned, the assignment of the resolution information is increased. Then, the resolution information becomes the number of bits corresponding to the number of picture elements in the block selected by a resolution information selector, and a resolution information coder codes the resolution information. Since it can be judged beforehand whether or not the image information of an original to be read by this can be stored in a storing device 65, the information can be easily stored in the device 65.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image communication function as a facsimile, a host computer or a personal computer, etc., in addition to a copying function for reading an image of a document and converting it into a digital signal and then recording the image. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image storage method and apparatus used in a digital copying machine or the like having multiple functions such as a function as a printer for outputting information, and particularly to a large-capacity memory such as a hard disk by compressing the information theoretical redundancy of image information. The present invention relates to an image storage method and apparatus for storing image information in a computer.

[0002]

2. Description of the Related Art In recent years, with the spread of personal computers and word processors, image information to be processed for copying in offices has become diversified and large in quantity.

Along with this, it is needless to say that even a copying machine for making a copy of a manuscript is required to further improve the image quality of a copied image. In addition to enlarging or reducing the image information of a document to copy it, various other functions are required.

As various functions required for this copying machine, for example, an electronic operation for electronically copying a plurality of originals in a state in which an arbitrary number of copies are sorted
tronic Recirculating Docu
ment Handler (hereinafter referred to as electronic RDH)
By copying the two or more sides of a large number of originals on one side of the recording paper and dividing the pages into two, the recording papers on which the images of the originals are copied are stacked at the center and folded in half. There is a bookbinding function that edits and copies an image of an original so that the original becomes a booklet in which the originals are arranged in order of pages.

Further, the functions required for the copying machine include an image communication function as a facsimile in addition to a copying function, and a function as a printer for outputting information from a host computer or a personal computer. ..

Conventionally, as a copying machine capable of realizing this kind of function, for example, there is the following so-called digital copying machine. That is, this digital copying machine
Manuscripts to be Automatic Document
By setting the document on the der (hereinafter referred to as ADF), the document is automatically conveyed by the ADF to the platen of the copying machine in sequence, the image of the document is read by the scanner, once converted into a digital signal, and stored. Then, the stored image information is read out, and the Image is read.
An image is recorded by Output Terminal (hereinafter referred to as IOT) to realize a document copy function.

In addition to the copying function as described above, the digital copying machine has an image communication function as a facsimile and a function as a printer for outputting information from a host computer or personal computer. There is. Therefore, this digital copier, in addition to the image information sent from the scanner, the image information from the facsimile sent via the telephone line, the information sent from the host computer or personal computer, Input is possible in parallel through the input interface and the multiplexer. Then, the image information from the facsimile and the information from the host computer or the personal computer input via the input interface are stored, the stored image information is read out, and the image is recorded by the IOT. ing.

In the above digital copying machine, when storing the image information of the original read by the scanner, the informational redundancy of the image information of the original is compressed so that more image information can be stored. An image storage device is used that stores image information in a state where the amount of information is reduced.

As shown in FIG. 15, this image storage device compresses image information read from a scanner 100 by a compressor 101 and then temporarily stores it in a large-capacity storage device 102 such as a hard disk.

At this time, the access time required to store the image information in the storage device 102 is 1 Mbyte / s.
ec, which is slower than the transfer speed of the image information sent from the compressor 101 to the storage device 102.
The image information compressed by 01 is directly stored in the storage device 1
02 can not be transferred and stored. Therefore, a page buffer 103 for temporarily storing image information in page units is provided between the compressor 101 and the storage device 102, and image information transferred from the compressor 101 is temporarily stored in page units in the page buffer 103. .. Then, in synchronization with the access speed of the storage device 102, the image information temporarily stored in the page buffer 103 is stored in the storage device 1.
It is designed to be transferred to 02 for storage.

After the storage of all the image information of the original document in the storage device 102, the image information of the original document stored in the storage device 102 is read page by page at a predetermined timing, and the read image information is read. The data is once written in the page buffer 103. Then, the page buffer 103
When the image information for one page is completed, the image information is sequentially decoded by the decompressor 104 and output to the IOT 105.

In the image storage device, the storage device 1 reduces the information amount of the image information by encoding the original image information in a compressed state by the compressor 101.
It will be stored in 02. An image information encoding system adopted in this image storage device is, for example, a so-called BLOCK as disclosed in Japanese Patent Laid-Open No. 56-69505.
Trunking Coding (hereinafter BTC
There is something called a method.

In this image coding method, the image information of a document read by a scanner and converted into a digital signal is divided into blocks of L × L pixels and coded as shown in FIG. Now, assuming that the density of each pixel in this block is a _ij , the average image density p0 of the entire block can be expressed as p0 = Σa _ij / L ² . Next, each pixel in the block is divided into a pixel having a density higher than the average image density p0 and a pixel having an average image density p0 or less,
If the average density and the number of pixels of the pixels having the average image density p0 or less are p1 and N1, p1 = Σa _ij / N1 (where Σ is taken for a _ij ≦ p0) and N1 = ΣΦ _ij can be expressed. If the average density and the number of pixels of pixels having a density higher than the average image density p0 are p2 and N2, then p2 = Σ
a _ij / N2 (where Σ is taken for a _ij > p0),
It can be expressed as N2 = ΣΦ _ij . Where Φ _ij is a
[Phi _ij = 0 when _ij ≦ p0, a _ij> when p0 [Phi _ij =
It is a variable that takes a value of 1.

Now, the integers m and n which are smaller than the number of pixels L ^{2 of the} entire block and the number of gradation levels of the density of each pixel.
To introduce. One of these integers m and n is an absolute value of the difference between the average image densities p1 and p2 | p1 −
This is a parameter for determining the magnitude of p2 |, and the other integer n is a parameter for determining the magnitude of the pixel numbers N1 and N2.

Then, | p1 -p2 | <m or n1 <n
Alternatively, when n2 <n, it is determined that the density distribution in the block is uniform, all the values of Φ _ij are set to 0, and the image of the entire block is represented by only the average image density p0. As a result, the image information in the block can be represented by Φ _ij, which has a value of 0 as the resolution information, and the average image density p0, as the gradation information.

On the other hand, when | p1-p2 | ≧ m and n1 ≧ n and n2 ≧ n, it is determined that the density distribution in the block is not uniform, Φ _ij is used as the resolution information, and the average density is used as the gradation information. p1 and p2 are used. In this case,
For pixels where Φ _ij is 0, that is, average image density p0 or less, p1 is used as gradation information, and for pixels where Φ _ij is 1, that is, density higher than average image density p0, p2 is used as gradation information. Corresponding to placing. As a result, the image information in the block is 0 for each pixel as resolution information.
Alternatively, it can be expressed by Φ _ij having a value of 1 and the average densities p1 and p2 as gradation information.

The image information in the block represented as described above is obtained by collecting the resolution information Φ _ij by several lines and encoding it by the existing binary encoding method, and the continuous length of blocks having the same information. Is encoded by the existing run-length encoding method to compress the document image information.

Of the parameters m and n in this image coding method, the parameter m has a role as a discriminant value for removing the isolated noise of the image, and
The parameter n has a role as a discriminant value for removing subtle fluctuations in the density in the block, and the larger the parameters m and n are, the more the image in the block is an averaged image. become.

In order to realize the electronic RDH function of copying a plurality of originals in an arbitrary number of copies by the image storage device adopting such an image encoding method, a plurality of documents read by the scanner 100 can be used. The image information of one original is compressed by the compressor 101 and sequentially stored in the storage device 102 via the page buffer 103. Then, the image information of a plurality of originals stored in the storage device 102 is sequentially read page by page, the decompressor 104 sequentially decodes the image information, and the IOT 105 sequentially records the image information of the plurality of originals in the order of pages. To do. By reading the image information of the original document from the storage device 102 and recording the image by the IOT 105 by the number of times corresponding to the number of copies of the original document, a plurality of original documents can be copied in an arbitrary number of copies. You can

[0020]

However, the above-mentioned prior art has the following problems. That is, in the image storage device, the image information of the document read by the scanner 100 is compressed by the compressor 101 by the image encoding method, and then the storage device 10 once.
The storage device 102 naturally has a finite storage capacity. Therefore, the electronic RDH
When realizing a function or the like, when a plurality of originals or the like are read and compressed and stored in the storage device 102 when the storage device 102 has a small storage capacity, the remaining capacity of the storage device 102 becomes zero during the process. May become.

In this case, the image information of the original cannot be stored in the storage device 102 any more, and a part of a series of originals to be read will be missing in page units. Therefore, the original reading operation by the scanner 100 must be suspended until the storage capacity of the storage device 102 becomes available, and the original reading operation must be restarted when the storage capacity of the storage device 102 becomes available. Then, when the reading operation of the original is restarted, it is necessary to reset the original whose reading operation was interrupted in the ADF again and read the original by designating the reading again. Depending on the remaining capacity of the device 102, there is a problem that the reading operation of the document becomes complicated.

Therefore, in order to solve the above problems, when the image information of a document is read by the scanner 100, the image information of the document to be read is stored in the storage device 1.
It suffices to be able to determine in advance whether or not the storage device 102 has a sufficient remaining capacity to be stored in the compressed state 02.

In this case, if the image storage device manages the remaining capacity of the storage device 102, the remaining capacity of the storage device 102 can be easily known. Further, if the size of the document is known, the information amount of the document before the compression processing can be automatically obtained from the resolution when the image of the document is read by the scanner 100.

On the other hand, the image information of the original is compressed by the compressor 1.
The amount of information after being compressed by 01 is different for each original because the image information of the original is compressed at a different compression rate for each original by the image encoding method, and the amount of information after compression of the original is calculated in advance. I can't know.

That is, in the case of the image coding system, the image information in the block is discriminated by the parameters m and n, and the image information in the block is determined by the resolution information Φ _ij and the gradation information p0, p1, p2. Representation and resolution information Φ _ij are grouped for several lines and existing 2
In addition to encoding by the value encoding method, continuous lengths of blocks having the same information are encoded by the existing run length encoding method. Therefore, the parameter m
The information amounts of the resolution information Φ _ij and the gradation information p0, p1, p2 for expressing the image information in the block are first different according to the characteristics of the image information in the block determined by n and n. Since Φ _ij is encoded by the existing binary encoding method and then by the run length encoding method, the information amount of the image information after encoding is
It varies depending on the content of each manuscript, and the amount of information after the manuscript is compressed cannot be known in advance.

Further, in the case of the image coding method, the pixels in the block can be expressed only by the three gradations of gradation information p0, p1 and p2, so that the block size is increased for the purpose of improving the coding efficiency. When L is made large, image information of a large area is expressed only by three gradations, and there is another problem that the image quality is significantly deteriorated.

Further, in the case of the image coding system,
Regardless of the characteristics of the image information, since the resolution information Φ _ij is evenly assigned to each pixel of all blocks, there is another problem that the amount of information is redundant by that amount. ..

As described above, in the case of the image storage device, the amount of information after the image information of the original document is compressed cannot be known in advance, so the image information of the original document to be read is compressed in the storage device 102. It is not possible to determine in advance whether or not the storage device 102 has a sufficient remaining capacity to be stored in the state. Therefore, it is impossible to solve the above-mentioned problem that the reading operation of the original becomes complicated. In addition, when the block size L is increased for the purpose of increasing the coding efficiency, the image quality is severely deteriorated, and there is another problem that the amount of information after compression is redundant.

In order to solve these problems, it is conceivable to change the basic design concept of the image storage device so that the image information of the original document is stored in the storage device 102 as it is without being compressed. .. In this case, the amount of information in the manuscript is
If the size and number of originals are known, the resolution when reading the image of the original by the scanner 100 is automatically known. Therefore, by comparing the information amount of the original with the remaining capacity of the storage device 102, the original to be read is read. It is possible to determine in advance whether or not the image information of can be stored in the storage device 102.

In this case, however, if the size of the original is A4 and the original is read at a resolution of 400 dpi, the information amount of the original is 2M per original.
It is a huge amount of bytes. Therefore, the storage device 1
02, the number of documents that can be stored in 02 is greatly reduced, and it becomes impossible to realize the electronic RDH function and the bookbinding function required for digital copying machines in a practical state. Occurs. On the other hand, when the storage capacity of the storage device 102 is set to be sufficiently large so that the image information of a large number of documents can be stored without being compressed, the storage device 102 naturally becomes very large and the cost is significantly increased. There is a new problem of causing ups.

Therefore, it is possible to determine in advance whether or not the image information of the document can be compressed and stored in the storage device, and the image information of the document to be read can be stored in the storage device 102 in a compressed state. To do this, either add a new process for measuring the compression ratio of the image information of the document before reading the document, or estimate the compression ratio of the document by statistical processing in advance, and calculate the average of the estimated document. It is also possible to use a compression ratio or the like.

That is, in the former case, the scanner 1
The prescan is performed prior to the regular reading operation of the document by 00, the compression rate of the image information of the document is measured in advance,
Using the measured compression ratio of the document, it is determined whether or not the storage device 102 has a sufficient remaining capacity to store the image information of the document to be read in the storage device 102 in a compressed state. It was done.

In the latter case, the compression rate of the original document is estimated in advance by statistical processing, and the information amount after compression of the original document is obtained by using the estimated average compression rate of the original document.
The storage device 10 has a sufficient remaining capacity to store the image information of the document to be read in the storage device 102 in a compressed state.
It is determined whether or not it is 2.

However, in the former case, the scanner 10
The prescan must be performed prior to the operation of reading the document by 0, and an extra sequence operation of prescan and its control are required. As a result, the control of the copying operation becomes complicated, and the number of copies that can be copied per unit time is reduced due to the need for the prescan and the calculation processing of the compression rate accompanying it. In order to prevent a decrease in the number of copies that can be copied in this unit time, back scanning may be assigned to pre-scan. However, in this case, since it is necessary to perform processing such as measurement of the compression ratio during back scanning, it is not possible to perform other image processing from a facsimile or the like during back scanning, and multiple image processing can be performed at the same time. Another problem is that it is no longer possible.

In the latter case, the average compression rate or the like statistically obtained is used as the compression rate of the original document, which is different from the actual compression rate of the original document read by the scanner 100. Even if a value obtained by adding a safety factor to the average compression rate is used, the storage device 102 determines that the amount of information after compression of the actually read original can be stored.
It is possible that there is more than the remaining capacity of. Then, in this case, the image information of the read original cannot be actually stored in the storage device 102, and the initial problem remains unsolved. This is because, if the gradation information of a document is processed by, for example, the error diffusion method, and if a halftone document such as a photo document happens to be present among a large number of text documents, the compression ratio of the document is easily averaged. Since the compression rate is much lower,
This is because the amount of information after compression increases.

Further, in both cases, since the above-mentioned image coding system is adopted, as already pointed out, when the block size L is increased for the purpose of improving the coding efficiency, the image quality is severely deteriorated, and The problem is that the amount of information after compression is redundant.

[0037]

Therefore, the present invention has been made in order to solve the above-mentioned problems of the prior art.
The purpose of this is to prevent the control of the copying operation from becoming complicated and to prevent the number of copies that can be copied per unit time from decreasing, without impairing the simultaneity of image processing. An object of the present invention is to provide an image storage method and device capable of determining in advance whether or not input image information can be stored in a storage device in a compressed state.

Another object of the present invention is to provide an image storage system and device which can facilitate file management in the storage device.

Further, another object of the present invention is to reduce the deterioration of the image quality even when the block size is increased in order to increase the coding efficiency when compressing the image information. An object of the present invention is to provide an image storage system and device capable of preventing the amount of information after compression from becoming redundant.

That is, the image storage method according to the present invention inputs image information, compresses the input image information, stores the compressed image information, and then reads the stored image information. In the image storage method of decompressing the image information, the image information is compressed by dividing the image information into blocks, discriminating the image information divided into the blocks according to the characteristics, and then determining the discriminated image information according to the characteristics. In accordance with the above, encoding is performed while changing the allocation of the gradation information and the resolution information, so that the information amount of the encoded image information becomes constant.

Further, the image storage device according to the present invention includes image input means for inputting image information, compression means for compressing the image information input by the image reading means, and image information compressed by the compression means. In an image storage device comprising a storage means for storing the image information and a decompression means for decompressing the image information read from the storage means, the compression means divides the image information into blocks and divides the blocks into blocks. Discriminating means for discriminating image information according to its characteristics, and image information discriminated by this discriminating means according to its characteristics, with the allocation of gradation information and resolution information changed, Are selected according to the discrimination result of the discriminating means, and a plurality of encoding means for encoding such that the number becomes constant, and image information encoded by these encoding means. It is configured to have a selection means.

The above-mentioned input image information is, for example, image information obtained by reading an image of an original with a scanner, but is not limited to this, and image information from a facsimile input via a telephone line. Alternatively, it may be information output from a host computer, a personal computer, or the like.

As the storage means, for example, a hard disk or the like is used, but the storage means is not limited to this, and a floppy disk or a semiconductor can be used as long as it can store image information in a compressed state. Other means such as a memory element may be used.

Further, the input image information is, for example, L
Although it is divided into blocks of × L pixels, the value of L is arbitrary, and the blocks do not necessarily have to be square, and may be divided into other shapes such as rectangles.

Further, the discrimination of the above-mentioned image information is carried out in accordance with the criterion as to whether or not the change in the density of the pixels in the block is large.

Furthermore, as the above-mentioned encoding means, for example, a plurality of encoders corresponding to a plurality of gradation numbers are used.

[0047]

In the image storage device according to the present invention, when the image information of the original is compressed by the compression means, the image information is divided into blocks, and the image information divided into the blocks is discriminated by the discrimination means according to the characteristics. In addition to discriminating, the image information discriminated by the discriminating means is coded into a plurality of codes so that the information amount of the image information becomes constant in a state in which the allocation of gradation information and resolution information is changed according to its characteristics. After being encoded by the means, the image information encoded by these encoding means is selected by the selecting means according to the discrimination result of the discriminating means.

[0048]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to illustrated embodiments.

FIG. 1 is an external perspective view showing a digital copying machine to which an embodiment of the image storage device according to the present invention is applied.

This digital copying machine is an electronic RDH that electronically performs not only normal copying of originals but also double-sided copying, single-sided multiplex copying, and copying of a plurality of originals sorted by an arbitrary number of copies. By copying multiple sheets of originals on both sides in a state where the pages are divided into two on each side of the recording paper, stacking the recording papers on which the images of the originals are copied, binding them in the center, and folding them in half A bookbinding function and the like are provided to edit and copy the image of the document so that the document becomes one booklet in which the pages are arranged in order of pages.

In addition to the copying function, the digital copying machine has an image communication function as a facsimile and a function as a printer for outputting information from a host computer or personal computer.

The digital copying machine 1 is roughly classified into an image input which reads an image of an original document, converts it into an electric signal, and performs basic processing such as zigzag correction on the image information converted into the electric signal and outputs the image information. Terminal
(Hereinafter referred to as IIT) 2 and the image information sent from this IIT 2 is stored, and after being subjected to secondary processing as necessary, the image is recorded and output.
eOutput Terminal (hereinafter referred to as IOT) 3 and C for controlling the operation of the IIT 2 and IOT 3
and an controller (hereinafter referred to as CONT) 4.

The CONT4 is a UserInterface (hereinafter, referred to as U
This UI 5 is provided with a keyboard 6 and a mouse 7 for the operator to specify the copying operation, or a display 8 for displaying the contents of the copying operation specified by the operator. ..

In this embodiment, the IIT2 automatically feeds the original document to the platen of the IIT2 on its upper part.
er (hereinafter referred to as ADF) 10. This A
The DF10 automatically flips the front and back of the original 10 and automatically
DualAu that can be transported to the 2nd platen
Of course, it may be a tomographic document feeder (hereinafter referred to as DADF).

As shown in FIG. 1, the ADF 10 has an I
It is built in a cover unit that covers the platen of the IT main unit so that it can be opened and closed. As shown in FIG. 2, the ADF 10 includes a document feed tray 12 that stores a large number of documents 11 and a feed belt 13 that feeds the documents 11 stored in the document feed tray 12 one by one. ,
A transport roll 16 that transports the document 11 delivered by the feed belt 13 to the platen 15 via the paper chute 14, and a transport that transports the document 11 transported by the transport roll 16 to the document setting position on the platen 15. When the image reading of the belt 17 and the original 11 placed on the platen 15 is completed, the discharge conveying rolls 18, 18 for discharging the original 6 sent by the conveying belt 17, and the discharged original 11 are discharged. It is composed of a document receiving tray 19 for accommodating.

Further, the ADF 10 includes a document size detecting means 50 for detecting the size of the document. As shown in FIG. 3, the document size detecting means 50 is provided with the ADF 1
It is composed of a plurality of reflection type optical sensors 51, 52, 53 arranged on the original feed tray 12 of No. 0. The optical sensors 51, 52, and 53 are the same size as the original 1
1 is arranged at a position where 1 passes, and the document feed tray 1
The size of the document 11 is detected based on the presence / absence of reflected light from the document 11 when the document 11 is set on the sheet 2.
Then, the output signals from the optical sensors 51, 52, and 53 are input to a CPU 71, which will be described later, so that the CPU 71 determines the size of the document 11.

The original 11 conveyed by the ADF 10 onto the platen 15 of the IIT main body is read by the scanner 20 of the IIT 2 as shown in FIG.
The scanner 20 includes a light source 21 that illuminates the document 11 placed on the platen 15, a reflection plate 22 that reflects the light emitted from the light source 21 toward the document 11, and a reflected light from the document 11. A plurality of mirrors 24, 25, 26 for guiding the image to the image sensor array 23 including a CCD or the like.
And a lens 27 for forming an image of the image light guided by the mirrors 24, 25 and 26 on the image sensor array 23. The light source 21, the mirrors 24, 25, 26, the image sensor array 23, and the like are integrally incorporated as a scanner 20 as shown in FIG. 2, and the scanner 20 is mounted on the platen 15 by a drive mechanism (not shown). The lower part can be reciprocated along the sub-scanning direction. And the scanner 20
While moving below the platen 15 in the sub-scanning direction,
The image of the document 11 placed on the platen 15 is read by the image sensor array 23.

The image information of the original 11 read by the image sensor array 23 of the scanner 20 is sent to a processor 28 and subjected to basic processing such as a zigzag correction as shown in FIG. Is output to.

The image information sent to this IOT3 is
As will be described later, the image storage device according to the present invention receives processing such as compression and storage. Then, the image information read out from the image storage device is read as shown in FIG.
It is converted into an optical signal by the OS unit 31, and scanning exposure is performed on the photosensitive belt 32.

As shown in FIG. 2, the ROS unit 31 includes one semiconductor laser 33, and a beam from the semiconductor laser 33 is reflected by a reflecting surface during a rotating operation to expose a photosensitive member over a predetermined scanning range. Belt 32
It is composed of a polygon mirror 34 that guides upward.

The ROS unit 31 scans the laser beam Bm emitted from the semiconductor laser 33, which oscillates in accordance with image information, by the polygon mirror 34 along the axial direction of the photoconductor belt 32, whereby the photoconductor belt 32 is scanned. An image corresponding to the image information is scanned and exposed on the image 32.

The photosensitive belt 32 has a primary charger 35.
After being uniformly charged in advance to a predetermined potential by the ROS unit 31, the image is scanned and exposed by the ROS unit 31 to form an electrostatic latent image on the surface thereof.

This electrostatic latent image is developed by the developing device 36 for developing with black toner to form a toner image.
After that, the toner image formed on the photosensitive belt 32 is
A plurality of paper feed cassettes 37 and 38 are arranged in the IOT body.
Recording paper 40 of a predetermined size supplied from any of
The transfer charger 41 charges the photoconductor belt 32
Transcribed from. Recording paper 4 on which this toner image is transferred
0 is the photoreceptor belt 32 due to the charging of the separation charger 42.
Then, the toner image is conveyed to the fixing device 43, and the toner image is fixed on the recording paper 40.

Further, the photosensitive belt 3 after the transfer process is completed.
The surface of No. 2 is cleaned by a cleaner 44 to remove residual toner, paper dust and the like, and the static eliminator 45 is charged to erase the residual charge, and prepares for the next image recording step.

The recording paper 40 on which the toner image is fixed as described above remains as it is in the normal copying mode in the discharge tray 4.
6 is discharged onto.

On the other hand, in the modes such as double-sided copying and single-sided multiplex copying, the recording paper 40 on which the toner image has been fixed is not discharged as it is, but is passed through the conveyance path 47 and the paper reversing mechanism 48 while double-sided copying or single-sided multiplex copying. In a mode such as copying, the recording paper 40 on which the toner image is fixed is not discharged as it is, and is conveyed through the conveyance path 47 and the paper reversing mechanism 48.
As it is or after being turned upside down, it is conveyed again to the transfer portion, and the transfer and fixing of a predetermined toner image is performed. After the transfer and fixing of such a predetermined image are repeated, the recording paper 40 is first discharged onto the discharge tray 46.

FIG. 5 is a block diagram showing an embodiment of the image storage apparatus according to the present invention applied to the digital copying machine configured as described above.

In the figure, reference numeral 60 is an input interface for inputting image information sent from the IIT2 scanner 20 and image information sent from a facsimile or a personal computer, and 61 is an image sent from the IIT2 scanner 20. A multiplexer (hereinafter referred to as MPX) that selects information or image information sent from a facsimile or personal computer.
Therefore, the MPX 61 is capable of time-divisionally selecting image information sent from the scanner 20 for reading an image, a facsimile, or a personal computer, and performing parallel image information selection processing. There is.

Further, 62 is a compressor for subjecting the image information sent from the MPX 61 to a predetermined compression process as will be described later, and 63 is a transfer speed of the image information compressed by the compressor 62. A speed conversion buffer, such as a FIFO, for temporarily storing image information sent via the speed conversion buffer 63, and synchronizes the storage device 65 such as a hard disk described later with the storage device. 65 is a page buffer for storing image information, 65 is a storage device such as a hard disk for storing image information sent from the page buffer 64, and 67 is for controlling the storage operation of the storage device 65. This is a disk controller.

Further, 68 is a FIFO for adjusting the transfer speed of the image information read from the storage device 65.
A speed conversion buffer consisting of, etc., 69 is a decompressor for decompressing the image information compressed and stored in the storage device 65 and converting it to the original image information, and 70 is a decompressor for the image information decompressed by the decompressor 69. An output interface 3 for outputting is an IOT for recording and outputting an image after subjecting the image information sent from the output interface 70 to secondary processing as required.

On the other hand, 71 is the MPX 60, the input interface 61, the compressor 62, and the speed conversion buffer 6
3, a CPU for controlling operations of the buffer memory 64, the speed conversion buffer 68, the decompressor 69, the output interface 70, the IOT 3, and the like.

Reference numeral 72 is a ROM that stores programs executed by the CPU 71, and 73 is a RAM that sequentially stores data necessary for image processing and the like.

FIG. 6 is a block diagram specifically showing the structure of the compressor.

In the figure, 75 is image information sent from the IIT 2, and this image information is divided into blocks of L × L pixels as shown in FIG. 7 by a known method. In this embodiment, 8 is adopted as the value of L, but it is not limited to this, and other values such as 2, 4, and 6 may be used. The shape of the block does not necessarily have to be a square, but may be a rectangle or the like.

Reference numeral 76 represents a block deciding device. This block deciding device 76 indicates whether the inputted image information 75 in block units is a block in which the density changes drastically or a block with a flat density gradient. The degree of existence is determined, and the determination result 77 is output to the distributor and the selector described later. The degree of whether the input image information 75 for each block is a block with a sharp change in density or a block with a flat density gradient is determined by calculating the variance σ of pixel density within the block. When the variance σ is large, it is determined that the concentration change is large, when the variance σ is small, it is determined that the concentration gradient is flat, and when it is in the middle, it is determined that the concentration distribution is intermediate. ..

However, the method of judging the block is
However, the present invention is not limited to this. For example, the pixel density value in a block is differentiated along the spatial axis, and both or one of the maximum value and the minimum value is detected, and determination may be made based on the size of this number. Good. Reference numeral 78 denotes a distributor, and this distributor 7
8 is a block decision result 77 of the block decision unit 76.
According to the above, the image information 75 of the input block is distributed to any of the 2-gradation BTC encoder to the m-gradation BTC encoder described below. 79 to 81 are gradation BTC
These gradation BTC encoders 79 to 8 are encoders.
There are m number of 1s from the 2-gradation BTC encoder to the m-gradation BTC encoder. In this embodiment, two gradation BT
In addition to the C encoder 79, a 4-gradation BTC encoder 80 and 1
Three encoders, a 6-gradation BTC encoder 81, are provided.

Then, the two-gradation BTC encoder 79
Performs the block approximation coding of 2 gradations, and the 4-gradation encoder 80 similarly performs the coding of 4 gradations and the 16-gradation encoder 8
1 is for encoding 16 gradations. in this way,
In the above-described embodiment, the number of gray scales when quantizing the pixels in the block is set to 2 or more so that the image quality degradation is small even when the coding block size L is made relatively large in order to improve the coding efficiency. It is expanding.

Further, reference numeral 82 is a selector, and this selector 82 is the two-gradation BTC encoder 79 to 16 gradation B.
The encoded image information 83 encoded by any of the TC encoders 81 is selected according to the block determination result 77 of the block determiner 76, and the encoded image information 84 is selected.
Is output as.

FIG. 8 is a block diagram showing the configuration of the gradation BTC encoder in more detail.

In the figure, reference numeral 86 is a quantization level calculator. This quantization level calculator 86 receives a quantization level and a quantization level when the block-unit image information 75 distributed by the distributor 78 is input. Is calculated. Specifically, as shown in FIG. 9, the maximum quantization level Q1 and the minimum quantization level Q2, Q4, or Q16 are determined for each number of gradations, and the interval between them is divided at equal intervals to perform linear quantization. The maximum quantization level Q1 is n in the order of increasing density from the maximum value max of the pixel density in the block.
The average value of the density values of pixels is used. Similarly, the minimum quantization level Q2 or Q4 or Q16 is the minimum density value m
The average value of the density values for n pixels is set in the order of increasing density from in. Here, when the number of pixels in the block is L ² and the number of gradations is 1, the value of the parameter n is n.
Is an integer value on the order of about n = L ² / l.

However, the method of determining the maximum quantization level and the minimum quantization level is not limited to the above method, and for example, the maximum density value max and the minimum density value min in the block may be used as they are. Further, the quantization is not limited to linear quantization at equal intervals between the maximum quantization level and the minimum quantization level, but may be nonlinear quantization.

Further, 87 is a gradation information encoder, and this gradation information encoder 87 encodes the quantization level 88 output from the quantization level calculator 86. Specifically, as shown in FIG. 9, the average value of the maximum quantization level and the minimum quantization level is La, the difference between the two is Lb, and these values La and Lb are encoded as gradation information. The signal 89 is output.

In this embodiment, the input image information 75
Is represented by 8 bits per pixel, the above values La and Lb are also represented by the same number of bits,
The encoded gradation information signal 89 has a total information amount of 16 bits.

However, the quantization level coding method is not limited to this, and the maximum quantization level Q1 and the minimum quantization level Q2 or Q4 or Q16 may be assigned as they are.

When the quantization level calculator 86 performs non-linear quantization, it is necessary to encode the way of changing the quantization step (difference between adjacent quantization levels) as gradation information. ..

Further, 90 is a quantizer, and this quantizer 90 quantizes the distributed image information 75 in accordance with the quantization level 88 quantized by the quantization level calculator 86. In this case, the quantization threshold is the average value of the corresponding quantization levels. For example, the threshold value between the quantization levels Q1 and Q2 is (Q
1 + Q2) / 2 and the threshold between the quantization levels Q2 and Q3 is (Q2 + Q3) / 2.

In this embodiment, the 2-gradation BTC encoder 7
Since the 9 to 16 gradation BTC encoder 81 quantizes to 2 gradations, 4 gradations, or 16 gradations, the quantized resolution information 91 is 1 for each pixel.
It is information of 2 bits, 2 bits, or 4 bits. That is, the resolution information 91 quantized in the 2-gradation BTC encoder 79 is 1 bit per pixel and 4 gradations B.
Resolution information 91 quantized in the TC encoder 80
Is a 2-bit per pixel, 16-gradation BTC encoder 8
The resolution information 91 quantized in 1 is 4 bits per pixel.

Further, reference numeral 92 is a resolution information selector, and this resolution information selector 92 corresponds to the resolution information 91 corresponding to the number of gradations quantized by the quantizer 90, from this resolution information 91. This is to remove visually redundant information and output necessary resolution information.

That is, as is generally known as the Weber's law, a slight gradation difference can be detected in an image area having a flat density gradient, but a slight gradation difference can be detected in an image area where the density changes drastically. There is a visual characteristic of the human eye that it is difficult to detect the difference.

Therefore, in this embodiment, in an image area with a flat density gradient, the number of gradations is increased and at the same time the resolution is lowered, and conversely, in an image area where the density changes drastically, the number of gradations is reduced and the resolution is increased simultaneously. It is set high.

By doing so, it is difficult to visually detect the deterioration of image quality due to encoding, and it is possible to avoid encoding redundant gradation information and resolution information, and it is possible to improve the encoding efficiency.

In this embodiment, in the case of encoding with two gradations, that is, in the image area where the density changes drastically, FIG.
As shown in FIG. 11, when resolution information of all 8 pixels × 8 pixels = 64 pixels is selected and coding is performed with 4 gradations, that is, in an image region where density changes are average, as shown in FIG. When the resolution information of 8 pixels × 8 pixels / 2 = 32 pixels is selected in a zigzag pattern and is encoded with 16 gradations, that is, in an image area with a flat density change, as shown in FIG. In the case of 8 pixels x 8 pixels, 8 pixels / 2 x 8 pixels / 2
The resolution information of 16 pixels is set so as to be selected in the shape of an orthogonal grid.

However, the method of selecting the resolution information is not limited to the above example, and, for example, in the case of 2-gradation encoding, 3
The resolution information of 2 pixels may be selected in a zigzag pattern.

It is important to note that when a large amount of gradation information is allocated to a certain block, the allocation of resolution information is reduced, and conversely, when a small amount of gradation information is allocated, a large amount of resolution information is allocated. It is to be. In addition, 93
Is a resolution information encoder, and this resolution information encoder 93 is for encoding the selected resolution information 94.

In this embodiment, the coding for suppressing the informational redundancy like the above-mentioned Huffman coding is not adopted, and the selected resolution information is directly coded in binary without coding. It is expressed and output as resolution information 95. Therefore, the information amount of the resolution information 95 is the number of bits corresponding to the number of pixels in the block selected by the resolution information selector 92.

In the compressor 62 configured as described above, the image information 75 in block units sent from the scanner 20 via the input interface 60 is encoded and compressed as follows.

That is, the image information 75 in block units.
Are input to the block determiner 76 and the distributor 78, respectively, as shown in FIG. The block determiner 76
Determines whether the input image information 75 in block units is a block with a sharp density change or a block with a flat density gradient.
To the distributor 78 and the selector 82.

Then, the distributor 78, in accordance with the block judgment result 77 from the block judgment unit 76, outputs the image information 75 of the input block to the 2-gradation BTC encoder 79.
To 16-gradation BTC encoder 81.
At this time, when it is determined by the block determination result 77 that the density change is significant, the image information 75 of the block is distributed to the 2-gradation BTC encoder 79, and the density change is a flat block. If it is determined that the image information 75 of the block is distributed to the 16-gradation BTC encoder 81, and if it is determined that the density change is an intermediate block, the image information 7 of the block is displayed.
5 is distributed to the 4-gradation BTC encoder 80.

Thereafter, the image information 75 of the block distributed to the 2-gradation BTC encoders 79 to 16-gradation BTC encoder 81 has a predetermined gradation number by the gradation BTC encoders 79-81. It is encoded into the signal 83.

The image information 75 of the block distributed to the 2-gradation BTC encoder 79 and the like is input to a quantization level calculator 86 as shown in FIG. Quantization level 8 according to information 75
8 is calculated.

Specifically, the quantization level calculator 86 of the 2-gradation BTC encoder 79 calculates the maximum quantization level Q1 and the minimum quantization level Q2. Also, 4 gradation BT
The quantization level calculator 86 of the C encoder 79 divides the maximum quantization level Q1 and the minimum quantization level Q4, and the maximum quantization level Q1 and the minimum quantization level Q4 into three equal quantization levels Q2. And the quantization level Q3.
Further, the quantization level calculator 86 of the 16-gradation BTC encoder 79 divides the maximum quantization level Q1 and the minimum quantization level Q16, and the maximum quantization level Q1 and the minimum quantization level Q16 into 15 equal parts. The calculated quantization levels Q2 to Q15 are calculated.

Next, the value of the quantization level 88 calculated by the quantization level calculator 86 is the gradation information encoder 87.
And is encoded by the gradation information encoder 87. Specifically, the average value of the maximum quantization level Q1 and the minimum quantization level Q2 or Q4 or Q16 is L
a and the difference between the two is Lb, and these values La are
And Lb are output as a signal 89 obtained by encoding gradation information. The gradation information 89 expresses each of the values La and Lb by 8 bits, and has a total information amount of 16 bits.

On the other hand, the image information 75 of the block distributed to the two-gradation BTC encoder 79 is also input to the quantizer 90, as shown in FIG.
The distributed image information 75 is quantized in accordance with the quantization level 88 quantized by the quantization level calculator 86. In this embodiment, since the 2-gradation BTC encoder 79 to 16-gradation BTC encoder 81 quantize into 2 gradations, 4 gradations, or 16 gradations, the quantized resolution The information 91 is 1 bi for each pixel.
The information is t, 2 bits, or 4 bits.

Then, the resolution information 91 quantized by the quantizer 90 is input to a resolution information selector 92, and the resolution information selector 92 determines the number of gradation levels quantized by the quantizer 90. Correspondingly, visually redundant information is removed from the resolution information 91, and necessary resolution information is output.

In this embodiment, in the case of encoding with two gradations, that is, in the image area where the density changes drastically, FIG.
As shown in FIG. 11, when resolution information of all 8 pixels × 8 pixels = 64 pixels is selected and coding is performed with 4 gradations, that is, in an image region where density changes are average, as shown in FIG. When the resolution information of 8 pixels × 8 pixels / 2 = 32 pixels is selected in a zigzag pattern and is encoded with 16 gradations, that is, in an image area with a flat density change, as shown in FIG. In the case of 8 pixels x 8 pixels, 8 pixels / 2 x 8 pixels / 2
= 16 pixels of resolution information is selected in the form of an orthogonal grid.

As a result, the information amount of the resolution information 94 selected and output by the resolution information selector 92 is:
The number of bits corresponds to the number of pixels in the block selected by the resolution information selector 92. That is, when encoding to two gradations, as shown in FIG.
In case of encoding with 4 gradations, it is shown in FIG.
As shown in (b), it becomes 32 bits, and when encoding with 16 gradations, as shown in FIG.
It becomes the resolution information 94 of t.

Therefore, the image information 83 encoded by the 2-gradation BTC encoder 79 to the 16-gradation BTC encoder 81 is the 8-bit gradation information 89 from the 2-gradation BTC encoder 79. × 2 = 16, resolution information 95 is 1b
The gradation information 89 is 8 bits from the encoded image information 96 of it × 64 = 64 and the 4-gradation BTC encoder 83.
The coded image information 83 of × 2 = 16 and resolution information 95 of 2 bits × 32 = 64 and the gradation information 89 of 8 bits × 2 = 16 and resolution information 95 from the 16 gradation BTC encoder 81. The coded image information 83 is 4 bits × 16 = 64.

The image information 83 coded by the 2-gradation BTC encoder 79 to 16-gradation BTC encoder 81 is determined by the block determiner 76 by the selector 82, as shown in FIG. Selected according to result 77,
The encoded image information 84 is output. that time,
The encoded image information 84 is output in a state where the gradation information and the resolution information are combined.

As described above, in the image coding method of this embodiment, the coded image information is always a signal having a constant information amount of 80 bits. Therefore, as shown in FIG. 12, it is possible to always assign a constant information amount of 80 bits to each block for encoding, regardless of the result of block determination. Then, if 2-bit block selection information is added to each block in order to identify which encoder has been selected at the time of decoding, the coding efficiency of this embodiment, that is, the compression rate, is 8 pixels × 8 pixels. × 8bit / (8
0 bit + 2 bit) = 6.244, which is always constant.

The image information encoded as described above is decoded by the decompressor 69 when being read from the storage device 65. The decoding performed by the decompressor 69 is performed as follows.

First, the decoding of the image information is performed in block units as well, but the encoders 79 to 8 shown in FIG. 6 are used according to the block selection information when encoding the image information.
Which of the encoders is selected for encoding is decoded, and the gradation information La and Lb and the resolution information shown in FIG. 9 are decoded.

In this embodiment, since coding such as Huffman coding is not adopted, a predetermined order and b
It suffices to sequentially read the gradation information and the resolution information, which are binary numbers arranged in it length. Next, using the read gradation information La and Lb, La + Lb / 2 to La-
Quantization level Q is divided up to Lb / 2 at equal intervals.
1, Q2, Q3 ... Q16 are calculated.

Then, the quantization level Q thus obtained
Image information is reproduced from 1, Q2, Q3 ... Q16 and the read resolution information. At this time, the 4-gradation encoder 80
If the resolution information is selectively missing in a zigzag pattern or a rectangular grid pattern as shown in FIG. The density of the missing pixel is reproduced by performing prediction or interpolation from the pixel density of. The encoded image is decoded by the above procedure.

With the above arrangement, the image storage device of the digital copying machine according to this embodiment stores and decodes image information associated with image copying operation and the like as follows. That is, when copying a document in the digital copying machine, the operator, as shown in FIG.
The original 11 to be copied is placed in the original feed tray 12 of the ADF 10.
When the copy operation is set on the upper side, what kind of copy operation is to be performed is designated by the keyboard 6 of the UI 5 and the start button is pressed to start the copy operation.

Then, the CPU 71 sends a signal to the ADF 10 to start feeding the first original 11 as shown in FIG. 13 (step 1). At that time, the CPU 71
Detects the size of the document 11 conveyed from the document feed tray 12 of the ADF 10 by the document size detection means 50 provided in the ADF 10 (step 2).

Next, the CPU 71 refers to (LUT) a table stored in advance in the RAM 73 based on the detected document size, compresses the image information of the document of the size by the compressor 65, and compresses it. The memory capacity m required to store the image information of the original document in the storage device 65 is calculated (step 3).

That is, in the image storing method adopted in this image storing apparatus, the compression rate of the image information of the original 11 is
It is always constant regardless of the type of manuscript, and its value is 6.24.
It is 4. Therefore, if the size of the manuscript 11 is detected, the information amount of the manuscript 11 itself is uniformly obtained from the value of the resolution when reading the manuscript. Therefore, from the information amount of the manuscript 11 itself and the value of the compression ratio, The memory capacity required to store the image information of the compressed original in the storage device 65 can be easily obtained. Now, when reading an A4 size document 11 at a resolution of 400 dpi as image information of 8 bits per pixel, the amount of information per document is about 15.5 Mby.
It becomes te. Therefore, the image information amount m after compression is 1
5.5 ÷ 6.244 = 2.48 Mbytes.

Thereafter, the CPU 71 causes the disk controller 67 to use the available space capacity M of the storage device 65.
(Step 4), it is determined whether or not the original 11 is the first original (step 5). If the manuscript 11 is the first manuscript, the value of Mj is set to 0 (step 6), and if the manuscript 11 is not the first manuscript, the value of mj is set to mj.
Is performed (step 7).

Then, it is judged whether the usable space capacity M of the storage device 65 is equal to or larger than the memory capacity m required to store the image information of the compressed original document in the storage device 65 (step 8). If the available space capacity M of the storage device 65 is less than the memory capacity m required to store the image information of the compressed document in the storage device 65, a scan stop command is issued (step 9). , Through the display 8 of the UI 5, the operator is notified that the original 11 cannot be read due to the lack of the available space capacity M of the storage device 65, and the available space capacity M of the storage device 65 has been compressed. Accumulation device 6 for image information of original
Until the memory capacity required to store 5 is m or more,
Wait for resumption (steps 10 and 11).

The CPU 71 causes the storage device 6 to store the image information of the original document compressed by the available space capacity M of the storage device 65.
When the memory capacity m required to store the image data in the storage medium 5 is equal to or larger than m, the scan start command is issued (step 12), and then the image information of the compressed document is stored in the storage device 65 from the available space capacity M of the storage device 65. The calculation for subtracting the memory capacity m required for storage is performed (step 13),
The scanning of the document 11 conveyed to the platen 15 by the ADF 10 is completed (step 14), and the document 11
Is discharged (step 15).

After that, the CPU 71 performs the above-described operation (steps 1 to 1) until the final manuscript 11 is reached (step 16).
14) is repeated, and when the discharge of the final document 11 is completed, the value Mp for securing the space capacity M of the storage device M is set to M.
Write j (step 17).

As described above, the CPU 71 controls the scanner 20.
Before the reading of the original 11, it is determined whether the image information of the original 11 read from the original 11 can be stored in the storage device 65 in a state of being compressed by the compressor 62, and the reading operation of the original 11 is executed. ..

Then, the image information of the read document 11 is input to the input interface 60 as shown in FIG.
And the MPX 61 to sequentially send the data to a compressor 62, and the compressor 62 receives a compression process with a constant compression rate. After that, the compressed image information of the document 11 is sequentially stored page by page in the storage device 65 via the speed conversion buffer 63 and the page buffer 64.

The image information of the original 11 stored in the storage device 65 is transferred to the decompressor 6 via the speed conversion buffer 68.
The data is sent to the digital camera 9, and the decompressor 69 receives the decompressing process which is the reverse of the compressing process and decodes it. The image information of the decrypted document 11 is output by the output interface 70.
Is output to the IOT 3 via the, and the predetermined image recording designated by the operator is performed by the IOT 3.

When the image recording in the IOT 3 is completed in this way, the CPU 71 confirms that the previous job has been completed (step 18), and the available space capacity of the storage device 65, as shown in FIG. The space capacity Mp reserved in the storage device 65 for executing the previous job is added to M (step 19), and the space capacity Mp of the storage device 65 used in the job is compressed by another job. It can be used for data storage.

As described above, the image storage method and apparatus according to this embodiment show the characteristics of the image information divided into blocks when the image information of the document 11 read by the scanner 20 is compressed by the compressor 62. The encoders 79 to 8 are determined according to the characteristics of the image information of this block.
It is configured to assign 1.

That is, when it is determined that the image information of the block is a block in which the density changes drastically, the encoder 79 for encoding with a small amount of gradation information and a large amount of resolution information is selected, On the contrary, when it is determined that the block has a flat density change, the encoder 81 that encodes with a large amount of gradation information and a small amount of resolution information is selected, and these encoders 79 are selected. ~ 81
The compression is performed so that the information amount of the image information after being encoded is always constant, that is, the compression rate of the image information of the document 11 is always constant. for that reason,
When the image information of the document 11 is read, if the size of the document 11 is known, the information amount of the image information after compressing the image information of the document 11 is automatically obtained.
It is possible to determine in advance whether or not the image information of the document 11 to be read can be stored in the storage device 65, based on the amount of image information and the remaining capacity of the storage device 65.

Therefore, the remaining capacity of the storage device 65 is insufficient during the reading of the document 11, the reading operation of the document 11 is interrupted, and the document 11 is set again in the ADF 10 when the remaining capacity of the storage device 65 is recovered. Thus, the complicated operation of restarting the reading operation of the document 11 is not necessary.
At this time, since prescanning for measuring the compression rate of the document 11 is not necessary, it is possible to prevent the control of the copying operation from becoming complicated and prevent the number of copies that can be copied per unit time from decreasing. it can.

The image information of the document 11 to be read is stored in the storage device 6 without measuring the compression rate of the document 11.
Since it is possible to judge in advance whether or not the data can be stored in No. 5, the simultaneity of image processing is not impaired.

Further, if the size of the manuscript 11 is known,
Since the information amount of the image information after compressing the image information of the document 11 is automatically obtained, the file management of the image information of the document 11 in the storage device 65 can be easily performed.

When compressing the image information of the manuscript 11,
Since the image information that requires gradation according to the characteristics of the image information is encoded by assigning a high gradation number such as 16 gradations, the encoding efficiency when compressing the image information is high. Even if the block size is increased in order to increase the image quality, the image quality does not deteriorate due to insufficient number of gradations.

Furthermore, when compressing the image information of the manuscript 11, instead of uniformly assigning high resolution information to all pixels in the block, the resolution information is increased or decreased according to the characteristics of the image information of the block. Since the information is compressed and allocated, it is possible to prevent the amount of information after compression from being unintentionally redundant.

FIG. 14 shows another embodiment of the present invention. The same parts as those in the above embodiment are designated by the same reference numerals. In this embodiment, an image input for each block is described. The information is not distributed to the encoders according to the characteristics thereof, but the image information input for each block is simultaneously encoded by a plurality of encoders 79 to 81, and encoded by the respective encoders 79 to 81. The selected image information is selected by the selector.

That is, the encoders 79 to 81 are constructed in the same manner as in the above-mentioned embodiment, and no block discriminator or distributor is provided. Then, the selector decodes the encoded image information by itself, compares it with the image information before encoding, selects the image information encoded in the state with the least distortion, and encodes the encoded information. Output as. At that time, as a measure of the distortion, a mean squared error may be used, or a cumulative value of absolute values of differences may be used.

In this embodiment, the block determiner and the distributor are unnecessary. The other structure and operation are the same as those of the above-mentioned embodiment, and the explanation thereof is omitted.

[0136]

The present invention has the above-described configuration and operation, and is capable of preliminarily determining whether or not the image information of the document to be read can be stored in the storage means and the apparatus thereof. Can be provided. Therefore, the remaining capacity of the storage means is insufficient during the reading of the original, the reading operation of the original is interrupted, and when the remaining capacity of the storage means is recovered, the original is set again and the reading operation of the original is restarted. No complicated operation is required. At this time, since prescanning for measuring the compression ratio of the original document is unnecessary, it is possible to prevent the control of the copying operation from becoming complicated and prevent the number of copies that can be copied per unit time from decreasing. .

Further, without measuring the compression rate of the original,
Since it is possible to determine in advance whether or not the image information of the document to be read can be stored in the storage unit, the simultaneity of image processing is not impaired.

Further, if the size of the document is known, the information amount of the image information after compression of the image information of the document is automatically obtained, so that the file management of the image information of the document in the storage means is easily performed. be able to.

Further, when compressing the image information of the original, since the image information requiring gradation according to the characteristics of the image information is encoded by assigning a high gradation number, the image information Even if the block size is increased in order to increase the coding efficiency when compressing the image, the image quality does not deteriorate due to insufficient number of gradations.

Furthermore, when compressing the image information of the document, instead of uniformly assigning high resolution information to all the pixels in the block, the resolution information is increased or decreased according to the characteristics of the image information of the block. Since the allocation is performed, it is possible to prevent the amount of information after compression from being unintentionally redundant.

[Brief description of drawings]

FIG. 1 is an external perspective view showing a digital copying machine to which an image storage device according to the present invention can be applied.

FIG. 2 is a configuration diagram of the digital copying machine.

FIG. 3 is a configuration diagram showing a scanner.

FIG. 4 is a block diagram showing IIT.

FIG. 5 is a block diagram showing an embodiment of an image storage device according to the present invention.

FIG. 6 is a block diagram showing a compressor.

FIG. 7 is an explanatory diagram showing a state in which an image signal is divided into blocks.

FIG. 8 is a block diagram showing an encoder.

FIG. 9 is an explanatory diagram showing a quantization state.

FIG. 10 is an explanatory diagram showing a quantization level calculation state.

FIG. 11 is an explanatory diagram showing a coding state.

FIG. 12 is a schematic diagram showing encoded image information.

FIG. 13 is a flowchart showing the operation of an embodiment of the image storage device according to the present invention.

FIG. 14 is a block diagram showing a main part of another embodiment of the image storage device according to the present invention.

FIG. 15 is a block diagram showing a conventional image storage device.

[Explanation of symbols]

Reference numeral 60 ... Input interface, 62 ... Compressor, 65 ... Storage device, 71 ... CPU 76 ... Block determiner, 78 ... Distributor, 79-81 ... Encoder, 82 ... Selector.

Claims (2)

[Claims] 1. An image storage method for inputting image information, compressing the input image information, storing the compressed image information, and then reading and expanding the stored image information, The compression of image information is performed by dividing the image information into blocks, discriminating the image information divided into the blocks according to their characteristics, and then dividing the discriminated image information according to the characteristics with gradation information and resolution. An image storage method characterized in that the information amount of the coded image information is made constant by encoding in a state where the allocation with information is changed. 2. An image input unit for inputting image information, a compression unit for compressing the image information input by the image reading unit, a storage unit for storing the image information compressed by the compression unit, and this storage. In an image storage device comprising a decompressing unit that decompresses the image information read from the unit, the compression unit divides the image information into blocks and discriminates the image information divided into the blocks according to their characteristics. Discriminating means and the image information discriminated by the discriminating means are coded so that the information amount of the image information becomes constant in a state in which the allocation of the gradation information and the resolution information is changed according to the characteristics thereof. A plurality of coding means and selection means for selecting the image information coded by these coding means according to the discrimination result of the discrimination means. Image storage device.