JP2000022909A - Image data encoding and decoding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image data encoding and decoding device which can store more images. SOLUTION: This device is equipped with an image process part which inputs document images, page by page, in the form of 4-bit digital image data and decomposes the 4-bit digital image data into four bit plane images, encoding parts 72a to 72d which compresses the decomposed bit plane images, hard disks 73a to 73d which store codes of the compressed bit plane images, an input signal switching part 71 which switches the correspondence between the codes by the bit plane images and the hard disks 73a to 73d storing them, a decoding part which expands and reproduces the codes by the bit plane images stored on the hard disks 73a to 73d, a main control part which integrates the reproduced bit plane images into 4-bit image data, and an output signal switching part which switches the correspondence between the four integrated bit plane images and bit positions of the generated 4-bit image data. Consequently, the codes by the bit planes can be stored equally on the hard disks 73a to 73d.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to encoding image data in an image forming apparatus such as a digital copying machine,
The present invention relates to an image data encoding / decoding device that decodes decoded data, and more particularly to an image data encoding / decoding device suitable for a digital image forming device that implements an electronic sorting function.

[0002]

2. Description of the Related Art In an image forming apparatus such as a digital copying machine, an operation of storing image information of an original in an internal storage device in the reading order, reading all the originals, and outputting the image data stored therein in the reading order. Is provided with a so-called electronic sort function that realizes sorting of copy output by repeating a desired number of copies. Such a copying machine with an electronic sort function has the advantages that a document is read only once and a mechanical part for sorting is not required, as compared with a conventional copying machine that performs mechanical sorting. As an image storage device that stores image data,
Generally, a large-capacity storage medium such as a hard disk is used. However, in recent years, the image input / output speed of a copying machine has become extremely high. If images are stored directly on one hard disk, the speed of the hard disk becomes a bottleneck, and the performance of the speed of the copying machine during electronic sorting is reduced. Therefore, a method has been proposed in which one hard disk is assigned to each bit plane of multi-valued image data and input / output is performed.

The conventional system will be described with reference to FIGS. 11 to 13 taking a case of multi-valued 4 bits as an example. FIG.
1 is a diagram for explaining a conventional example in which multi-valued bits are allocated to a plurality of hard disks, FIG. 12 is a diagram for explaining the relationship between upper and lower bits of image data and a code amount in the related art, and FIG. FIG. 10 is a diagram for explaining an example of each code assigned to each hard disk in the related art.

Conventionally, as shown in FIG. 11, bit 0 which is the least significant bit of 4-bit data is assigned to the first hard disk, bit 1 of the lower bit is assigned to the second hard disk, and bit 0 which is the upper bit. Bit 3 is allocated to the third hard disk, bit 4 which is also the most significant bit is allocated to the fourth hard disk, and so on. In this case, although not shown, in order to accumulate a large number of documents on each of the first to fourth hard disks, an encoding / decoding unit is provided in front of the input / output of the hard disk, and an encoding / decoding unit is provided for each bit plane. It is effective to encode using a binary image compression algorithm such as MMR or QM-coder and reduce the amount of data to store.

[0005] However, when compression is performed for each bit plane, as shown in FIG. 12A, an image of an upper bit plane having a high correlation between pixels has a good compression rate and a small code amount. As shown in (1), there is a problem that the correlation between pixels becomes less as the lower bits become smaller, so that compression cannot be performed and the code amount increases. For this reason, considering the case where the capacity of the four hard disks is set to be the same and codes are stored by the allocation shown in FIG. 11, the code amount is “the code amount stored in the fourth hard disk” <“the third hard disk”. The amount of code stored in the first hard disk <the amount of code stored in the second hard disk <the amount of code stored in the first hard disk holds.

Here, as shown in FIG. 13, four images (images 0 to 3) are compressed for each bit plane as described above, and are stored in the first to fourth hard disks.
That is, bit 0 of images 0 to 3 is stored in the first hard disk.
The second hard disk has the code of bit 1 of images 0 to 3, the third hard disk has the code of bit 2 of images 0 to 3, and the fourth hard disk has images 0 to 3.
Consider storing the 3 bit 3 code. In FIG. 13, the amount of code amount is indicated by the height in the vertical direction, and the length of the arrow indicates the capacity of the hard disk. When codes are accumulated as shown in FIG. 13, since there is a relation of the code amount as described above, when the first hard disk runs out of space, as shown in FIG. Is likely to still have free space. However, since the lowest-order bit plane image cannot be stored, the image data cannot be encoded and stored any more.

To solve such a problem, as shown in, for example, Japanese Patent Application Laid-Open No. Hei 6-31371, the upper bit plane is coded by the MMR method having a relatively low coding compression rate, and the lower bit plane is coded. It has been proposed to avoid the above problem by encoding the plane using a QM coder method having a higher encoding compression rate than the MMR method.

[0008]

However, in the method disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 6-311371,
Since an encoding method with a high compression ratio cannot be used for the upper bits, the efficiency of code accumulation of the upper bits is not good.
Further, simply using a coding scheme with a high compression rate cannot make the compression rate almost the same as the compression rate of the least significant bit.

The present invention has been made in view of such a situation of the prior art, and has as its object to store codes in an equal amount on each hard disk and to store a larger number of images. It is another object of the present invention to provide an image data encoding / decoding device which can perform the following.

[0010]

In order to achieve the above object, the first means comprises: image input means for inputting a document image as n-bit digital image data one page at a time; Bit plane image generating means for decomposing as a single bit plane image, n encoding means for compressing the bit plane image decomposed by the bit plane image generating means, and bit plane image compressed by the encoding means N code accumulating means for storing the code of each bit plane image; first signal switching means for switching the correspondence between the code for each bit plane image and the n code accumulating means for accumulating the code; N decoding means for expanding and reproducing the code for each bit plane image stored in the code storage means, and reproducing by this decoding means Bit plane image integration means for integrating each of the obtained bit plane images into n-bit image data, and a second unit for switching a correspondence between the integrated n bit plane images and the bit positions of the generated n-bit image data. And two signal switching means.

The second means is an image data management means for assigning a number to each page of the image data input by the image input means and managing the image data, and the image data management means. It is characterized by further comprising a signal switching control means for controlling the first signal switching means and the second signal switching means with reference to the number of each of the obtained images and for switching the correspondence.

Further, a third means is the first means, wherein a free capacity comparing means for comparing the size of the free capacity of the n code accumulating means and a comparison result of the free capacity comparing means. It is characterized by further comprising a signal switching control means for controlling the first signal switching means and the second signal switching means and for switching the correspondence.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a functional block diagram showing an entire configuration of a copying machine according to an embodiment of the present invention, FIG. 2 is a diagram for explaining in detail the configuration of an image storage unit in FIG. 1, and FIG.
FIG. 4 is a diagram showing an address management table corresponding to each hard disk in the memory of the main control unit in FIG. 1, and FIG.
FIG. 6 is a table showing an example in which the setting of the signal switching unit in FIG. 1 is switched by the lower bit of the image number, FIG. 6 is a diagram for explaining an example of each code assigned to each hard disk in FIG. 2, and FIG. FIG. 3 is a diagram for describing a configuration of a decoding unit in one image storage unit.

In FIG. 1, the digital copier comprises a main control unit 1 and image forming elements 3, 4, 5, 6, 7, and 8 connected to the main control unit 1 via a bus. Is configured. The main control unit 1 includes a CPU, a ROM, a RAM, and the like, and controls the entire copying apparatus. An operation unit 2 connected to the main control unit 1 via a bus performs various operations and settings of the copying apparatus. The main control unit 1 is also connected to the automatic document feeder 3, scanner 4, A / D converter 5, image processing unit 6, image storage unit 7, and recording unit 8, which are the image forming elements, via a bus. . The automatic document feeder 3
When using this, if you set multiple originals,
Documents are transported one by one to the platen of the scanner 4, and the scanner 4
Make the originals readable one by one. The scanner 4 reads an original, and an image data signal from the scanner 4 is sent to an A / D conversion unit 5, where the image data signal is converted to an A / D signal.
Convert to a bit digital signal.

The image processing section 6 performs image processing such as scaling and density adjustment, and outputs a document read from the recording section 8 as a copy. The image storage unit 7 is configured by a storage device such as a memory or a hard disk. The image storage unit 7 can temporarily store the image data from the image processing unit 6, read it out, and output it as a copy from the recording unit 8. The image storage unit 7 includes an encoding unit that compresses image data and stores it as a code in order to reduce the amount of storage, and a decoding unit that expands the encoded data and returns it to image data. The image storage unit 7
At the time of the sorting operation, after storing the originals of all pages, the image data is transferred to the recording unit in the order of input, thereby copying and outputting all the pages, and these operations are repeated for the required number of copies. In FIG. 1, a solid line indicates transfer of a control signal, and a double line indicates transfer of an image data signal.

Next, the image storage unit 7, which is a feature of the present invention, will be described in more detail. The image storage unit 7 encodes and stores 4-bit image data for each bit plane. As shown in FIG. 2, an input signal switching unit 71 to which each bit plane is input, and an encoding unit for each bit plane. First to fourth encoding units 72a, 72b, 72
c, 72d and these four first to fourth encoding units 7
It has four first to fourth hard disks 73a, 73b, 73c, 73d connected to 2a to 72d, respectively. The input signal switching unit 71 selects which bit plane is input to which encoding unit.
The combinations of the settings are four types of settings 1 to 4 shown in FIG. 3, and each bit plane is connected to a different encoding unit for each setting.

Codes stored in the first to fourth hard disks 73a to 73d from the first to fourth encoding units 72a to 72d are stored in a memory (not shown) provided in the main control unit 1 as shown in FIG. 4) Hard disk 73 in each
a-73d, and has an address management table corresponding to each of the image numbers (images 0, 1, 2,...) in the order of the input images.
・). That is, the write start addresses (A10, A11...) In the hard disk of the table storing the codes for each image number are stored in the memory. Further, referring to the lower two bits of the image number, the setting of the signal switching unit 71 is changed for each image as shown in FIG.

As described above, by switching the hard disk of the storage destination of the code of each bit plane every time one image is stored, each code which has been allocated as shown in FIG. In the embodiment, the distribution is performed as shown in FIG. That is, in the image 0, the code of the bit 0 is
3a, the code of bit 1 is the second hard disk 73b
The code of bit 2 is allocated to the third hard disk 73c, and the code of bit 3 is allocated to the fourth hard disk 73d. In the next image 1, the code of bit 0 is on the fourth hard disk 73d, the code of bit 1 is on the first hard disk 73a, the code of bit 2 is on the second hard disk 73b, and the code of bit 3 is on the third hard disk 73c. It is distributed to. Hereinafter, for image 2, the code of bit 0 is stored in the third hard disk 73c, the code of bit 1 is stored in the fourth hard disk 73d,
Is assigned to the first hard disk 73a, the code of bit 3 is assigned to the second hard disk 73b, and for image 3, the code of bit 0 is assigned to the second hard disk 73b.
The code of bit 1 is allocated to the third hard disk 73c, the code of bit 2 is allocated to the fourth hard disk 73d, and the code of bit 3 is allocated to the first hard disk 73a.
Thereby, the first to fourth hard disks 73 a to 73 a
d can secure substantially equal empty areas, and it becomes possible to add a new image code to these empty areas.

The code data thus accumulated is shown in FIG.
Are decoded by the decoding unit of the image storage unit 7 and returned to the bit plane image. The decoding unit returns the first to fourth decoding units 74a to 74d connected to the first to fourth hard disks 73a to 73d and the codes decoded by the first to fourth decoding units 74a to 74d to the bit plane. And an output signal switching unit 75. The first to fourth hard disks 73a to 73d are
The main controller 1 refers to the start addresses in the first to fourth hard disks 73a to 73d for each image number and performs reading from the first to fourth hard disks 73a to 73d. The output signal switching unit 75 includes the main control unit 1
The connection to each bit position is switched according to FIG. 5 by referring to the lower bits of the image number.

As described above, in the present embodiment, the multi-level image data is encoded for each bit plane by electronic sorting, and the code for each bit plane is stored in a separate hard disk, and each bit plane is stored for each image. Changed the hard disk to be used. As a result, compared with the case where the bit plane is fixed, codes can be stored evenly in each hard disk, and a larger number of images can be stored.

The above-mentioned switching between the bit plane and the hard disk is performed by the lower two bits of the image number. However, this switching may be performed by the size of the free area of the hard disk. That is, as shown in FIG. 8, the first image, that is, the code of the image 0 is assigned to each of the first to fourth hard disks 73a to 73a for each bit plane.
73d. As a result, it is expected that the free space of the first hard disk 73a in which the code of bit 0 is accumulated becomes the smallest, and that the compression ratio is expected to increase next. The main control unit 1 switches the setting of the input signal switching unit 71 to the setting 4 in FIG. 5 so that the code is stored in the first hard disk 73a. In this way, the setting is switched according to FIG. 9 so that the code of the most significant bit 3 is assigned to the hard disk having the least available space. According to this method, when the second image is stored in the first to fourth hard disks 73a to 73d, as shown in FIG.
The codes are stored in the first to fourth hard disks 73a to 73d. When the next image is to be stored, the free space in the second hard disk 73b is reduced, so the input signal switching unit 75 sets the setting 3 according to FIG.

On the other hand, when an image is decoded and taken out from the first to fourth hard disks 73a to 73d, the start address of the address management table shown in FIG. 4 is set for each of the first to fourth hard disks 73a to 73d. Compare. When the hard disk having the highest start address stores the image to be read, the empty area is found to be the smallest. Therefore, according to FIG. 9, if the output signal switching unit 75 in FIG. It can be returned to the original bit plane position.

As described above, in the method of storing the codes for each bit plane on a separate hard disk, switching is performed so that the codes of the uppermost bit plane are stored in the hard disk having a small free space for each image. Compared with the case where the plane is fixed, the same amount of codes can be stored in each hard disk, and a larger number of images can be stored.

[0025]

As is apparent from the above description, according to the first aspect of the present invention, the code storage means for storing the code of each bit plane is sequentially switched for each image. An equal amount of codes can be stored in the means. This makes it possible to store a larger number of images.

According to the second aspect of the present invention, a number is assigned to each page of image data and managed, and signal switching is controlled while referring to the number of each image. Can manage. Also, the correspondence between the code for each bit plane image and the n code accumulation means for accumulating the same is switched, and the correspondence between the n bit plane images to be integrated and the bit positions of the generated n-bit image data. Can be appropriately switched.

According to the third aspect of the present invention, the size of the free space of the code storage means is compared, and the code of the most significant bit plane is stored in the code storage means having a small free area for each image. , It is possible to store an equal amount of codes in each code storage unit as compared with the case where the bit plane is fixed. This makes it possible to store a larger number of images.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of an embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration of an image storage unit in FIG. 1;

FIG. 3 is a diagram illustrating an example of setting of a combination of each encoding unit and a bit plane in FIG. 2;

FIG. 4 is a diagram showing an example of an address management table corresponding to each hard disk in a memory of a main control unit in FIG. 1;

FIG. 5 is a diagram illustrating an example of a case where the setting of a signal switching unit in FIG. 1 is switched by a lower bit of an image number.

FIG. 6 is a diagram showing an example of each code assigned to each hard disk in FIG. 2;

FIG. 7 is a diagram illustrating a configuration of a decoding unit in the image storage unit of FIG. 1;

FIG. 8 is a diagram showing another method of switching the correspondence between each bit plane and a hard disk.

FIG. 9 is a diagram showing a setting of switching between a hard disk and a signal in the system of FIG. 8;

FIG. 10 is a diagram illustrating a storage state of codes when a second image is stored in the method of FIG. 8;

FIG. 11 is a diagram showing a conventional example in which multi-valued bits are assigned to a plurality of hard disks.

FIG. 12 is a diagram showing a relationship between upper and lower bits of image data and a code amount in the related art.

FIG. 13 is a diagram showing an example of each code assigned to each hard disk in the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main control part 2 Operation part 4 Scanner 5 A / D conversion part 6 Image processing part 7 Image storage part 8 Recording part 71 Input signal switching part 72a, 72b, 72c, 72d Encoding part 73a, 73b, 73c, 73d Hard disk 74a , 73b, 73c, 74d Decoding section 75 Output signal switching section

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 5B047 AA01 AB02 EA10 EB01 5B057 AA11 BA02 CA02 CA08 CA12 CA16 CB02 CB08 CB12 CB16 CC01 CG01 CH12 5B065 BA01 CA30 CC01 CS04 5C073 AA02 AA06 BA06 BB02 BC02 CE01

Claims (3)

[Claims] An image input unit for inputting a document image as n-bit digital image data one page at a time; a bit-plane image generating unit for decomposing the n-bit digital image data into n bit-plane images; N encoding means for compressing the bit plane image decomposed by the bit plane image generating means; n code accumulating means for storing the code of the bit plane image compressed by the encoding means; First signal switching means for switching the correspondence between a code for each plane image and n code storage means for storing the code, and a code for each bit plane image stored in the n code storage means. N decoding means for decompressing and reproducing, and n-bit image data for each bit plane image reproduced by the decoding means And a second signal switching unit that switches a correspondence between the n bit plane images to be integrated and a bit position of the generated n-bit image data. Characteristic image data encoding / decoding device. 2. An image data management means for assigning and managing a number for each page of image data input by said image input means, and referring to the number of each image assigned by said image data management means, 2. The image data encoding / decoding apparatus according to claim 1, further comprising: a signal switching control unit that controls the first signal switching unit and the second signal switching unit and switches the correspondence. 3. A free capacity comparing means for comparing the size of free capacity of the n code accumulating means, and the first signal switching means and the second signal based on a comparison result of the free capacity comparing means. Control the switching means,
2. The image data encoding / decoding apparatus according to claim 1, further comprising: signal switching control means for switching the correspondence.