JPH11215381A - Coder and recoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coder and a decoder by which coding and decoding processing is conducted at a high-speed accurately as well as at a very high efficiency. SOLUTION: An image area division means 201 divides a received image into small block areas. An area image information storage means 202 stores image information of the divided small block areas, a similar image selection means 203 selects a small block area similar to a noted small block area. A similar image discrimination means 204 discriminates whether or not an image is identical to the image of the noted small block area and valid or not. Based on the discrimination result, an image matching coding means 205, a similarity prediction coding means 206 and a prediction coding means 207 encode efficiently the noted small block area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an encoding apparatus used for encoding processing for compressing data to be transmitted and received,
And a decoding device, which is particularly suitable for compressing binary image data, and which can be applied not only to black-and-white image data processing but also to monochrome (mono-color) image data processing. And a decoding device.

[0002]

2. Description of the Related Art In recent years, most documents used in offices have been created by personal computers and word processors, and documents handwritten have almost disappeared.

[0003] Most of documents prepared by personal computers and word processors are composed of character and ruled line information, and almost no documents include photographs.

[0004] These images usually have a certain degree of regularity in character size, character shape, character spacing, character arrangement, and the like. On the other hand, an image such as a handwritten character or a photograph does not have the above-described features.

On the other hand, in a device such as a facsimile or a digital copier which handles an image as electronic information, an input image is optically scanned by a scanner or the like and converted into electronic information.

The amount of electronic information at the time of performing this conversion depends on the resolution and the size of the image, and increases as the resolution and the size of the image increase. Usually, the converted electronic information is often temporarily stored in a storage area, and therefore, the larger the amount of information, the larger the required storage area.

In particular, in recent years, the resolution has tended to be improved, and the memory or disk capacity required for storing those images has also increased, and there has been a problem that an increase in cost cannot be avoided.

One of the methods for solving this problem is a method for efficiently encoding an image. Representative examples of image coding include the MH, MR, and MMR methods used in facsimile and the like. Since these methods encode an image in raster units regardless of the type of the image, it can be applied to any type of image.

The above-described image coding method will be further described below. The image coding methods are roughly classified into binary image and multi-value image. The former includes MH, MR, and MMR coding methods, which are standard facsimile coding methods. Recently, an encoding method using an arithmetic code has attracted attention, and there is an encoding method called QM-Coder.
This QM-Coder is based on ITU-T (International Telecommunicat
ion Union-Telecommunication Standardization Secto
r, International Telegraph and Telephone Advisory Committee and ISO (International O
rganization for Stadardization (International Organization for Standardization)).

On the other hand, the latter has a discrete cosine transform (hereinafter referred to as DCT), which has been studied as a standard method by ITU-T and ISO.
There is an ADCT (Adaptive Cosine Transform) method (called the JPEG method) that uses image data, and a method that converts image information into frequency information and then encodes the information.

Therefore, according to the image processing apparatus provided with the conventional encoding device, it is possible to perform such conventional encoding, compress the amount of information, and reduce the memory and the like.

[0012]

However, in the above-described conventional encoding apparatus, it is possible to efficiently encode a character image, but not to an image such as a photograph or a handwritten character. Encoding is not performed with a satisfactory degree of efficiency.

Further, even when a character image is encoded, it is impossible to obtain a very high encoding efficiency because the encoding is performed simply as an image without using information such as the properties of the character. There is a problem that there is.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has been made in consideration of the above circumstances.
It is an object of the present invention to provide an encoding device and a decoding device capable of performing a decoding process.

[0015]

According to the first aspect of the present invention,
Image area dividing means for dividing input image information into block areas in units of characters or figures; area image information storing means for storing a plurality of block area image information input from the image area dividing means; The block area input from the area dividing unit is set as a target block area, and a plurality of block areas stored in the area image information storage unit are set as reference block areas, and the image information of the target block area and the image information of the reference block area are compared. A similar image selecting means for comparing and selecting and extracting image information of a reference block area similar to the image information of the target block area; and the image information of the reference block area selected by the similar image selecting means is the target block area. When the image information is the same as that of the reference block area, the target block area is determined to be the same area. When the image information of the target block region is not the same as the image information of the target block region, the target block region is determined to be a similar region, and the image information of the reference block region is not the same as or similar to the image region of the target block region. Similar image determining means for determining the target block area as a non-similar area; and image information of the reference block area stored in the area image information storing means. Image coincidence encoding means for encoding the image data of the target block area determined to be the similar area with the image information of the corresponding reference block area stored in the area image information storage means and the target block. Similar prediction encoding means for predicting and encoding based on the image information of the area, and an image of the target block area determined to be the dissimilar area Information, predictive coding means for predicting and coding based on the image information of the block area of interest, and coding results output from the image coincidence coding means, the similar prediction coding means and the prediction coding means. And code information creating means for creating code information based on the information.

Therefore, according to the present invention, when encoding image information, the image information is divided into small block regions such as characters and figures, and the divided small block regions are stored while storing the information. For each piece of information of the small block area, an image of a similar small block area similar to the image of the small block area of interest is selected from among the small block area images that appeared before, and the selected similar small block area is selected. If the image of the target small block region is the same as the image of the target small block region, encoding is performed using the region information of the similar small block region. Otherwise, the selected similar small block region is replaced with the code of the target small block region. After determining whether or not the area is an effective similar small block area that is effective for image formation, if it is effective, the image of the target small block area is compared with the image of the similar small block area and the target small block area. Perform coding by predicting from the image, and if not effective, perform predictive coding on the image of the small block area of interest without using the image of the similar small block area, thereby performing coding very efficiently Can be.

According to a second aspect of the present invention, in the first aspect of the present invention, the area image information storage means stores a storage sequence representing the size and position information of the block area.

Therefore, according to the present invention, the effect of the first aspect of the present invention can be obtained, and a method of saving the image itself can be considered when saving the image of the small block area. There is a problem that the size of the image becomes large. Therefore, if the image information is the same or substantially the same as that of the small block area that has already appeared, by referring to the image information of the small block area that has already appeared, the position and size of the small block area can be obtained. You can refer to the actual image simply by specifying only. If these are added to an index to form a storage sequence, it is possible to refer to the target image only by referring to the index.

According to a third aspect of the present invention, in the second aspect of the present invention, the image coincidence encoding means includes an index and a position information of a storage sequence representing image information of the target block area determined as the same area. The similarity predictive encoding means predicts and encodes based on the image information and the index and position information of the storage sequence representing the image information of the block area of interest determined as the similar area, The predictive encoding unit performs encoding based on the size and position information of the target block area determined as the dissimilar area and the image information.

Therefore, according to the present invention, the effect of the invention described in claim 2 can be obtained, and encoding of an image in units of small block areas can be achieved by encoding a small block area which always appears at the time of encoding. There is an advantage that it is not necessary to perform encoding in order and an advantage that only an arbitrary small block area can be extracted and decoded at the time of decoding. When encoding a small block area, it is efficient to encode only the index of an image that has already appeared, and if there is a similar image, predictive encoding is performed using a similar image. For example, the coding efficiency is improved.

Therefore, taking advantage of these advantages, the image coincidence encoding means encodes an index representing an image of a similar similar small block area, thereby achieving highly efficient encoding.
The similarity prediction coding means encodes a small block area of interest using an index representing an image of a similar similar small block area and an image of a small block area of interest to generate a code, thereby enabling highly efficient coding. become.

According to a fourth aspect of the present invention, in the third aspect of the present invention, the image coincidence encoding unit, the similar prediction encoding unit, and the prediction encoding unit determine a position of the target block area ahead of the target block area. The position information of the target block area is encoded based on a difference between the information and the position information of the target block area.

Therefore, according to the present invention, the operation of the invention described in claim 3 can be obtained, and character images created by a personal computer or a word processor often have regularity in arrangement and intervals of characters. The smaller the absolute value of the code amount of the position information, the higher the efficiency. Therefore, if the position information of the small block area near the small block area of interest is used, the absolute value required for the position information can be reduced, and highly efficient encoding can be performed.

According to a fifth aspect of the present invention, in the third or fourth aspect of the present invention, the image coincidence encoding unit, the similar prediction encoding unit, and the prediction encoding unit include a target block ahead of the target block area. The position information of the block area of interest is encoded based on a difference between the distances between the nearest ends of the area and the block area of interest.

Therefore, according to the present invention, the effect of the invention described in claim 3 or 4 can be obtained, and the smaller the absolute value of the code amount of the position information is, the higher the efficiency becomes. When the position information of the small block area is used, the absolute value required for the position information can be reduced by using the information between the closest grid points, and highly efficient encoding can be performed. .

According to a sixth aspect of the present invention, in the first aspect of the present invention, the image coincidence encoding unit, the similar prediction encoding unit, and the prediction encoding unit are any one of the encoding units. In addition to adding first identification information indicating whether or not encoding has been performed, the code information creating unit adds second identification information indicating the end of the code information.

Therefore, according to the present invention, the effect of the invention described in any one of the first to fifth aspects can be obtained, and the image information can be reproduced without error on the decoding side by adding identification information to each code. become. Further, the processing on the decoding side can be easily determined based on the identification information, so that the processing speed can be improved.

According to a seventh aspect of the present invention, in the first aspect of the present invention, the similar image selecting means selects and extracts a reference block area having the same size as the target block area. It is characterized by doing.

Therefore, according to the present invention, the effect of the invention described in any one of the first to sixth aspects can be obtained, and when a similar image is searched in the encoding device, there are many images to be searched. In such a case, there is a problem that the processing becomes slow. However, since the similar image selection unit searches only the image that matches the size of the attention area, the search can be performed quickly with a simple configuration.

According to an eighth aspect of the present invention, in the first aspect of the present invention, the similar image selecting means compares the image information of the target block area with the image information of the reference block area. The determination is made based on the number of image data mismatches of pixels constituting each piece of image information.

Therefore, according to the present invention, the operation of the invention described in any one of the first to seventh aspects is obtained, and the similar image determining means determines the image of the small block area of interest and the selected similar small block area. The number of inconsistent pixels between the image and the image is counted, and based on the number, it is determined whether or not the pixel is the same, and whether or not the image is valid. Can be.

According to a ninth aspect of the present invention, there is provided an identification means for identifying the same area, a similar area and a dissimilar area based on input code information, a reproduction area storage means for storing image information of a block area, An image coincidence decoding unit that instructs to output image information of a block area stored in the reproduction area storage unit when the identification unit identifies the same region; and a case where the identification unit identifies the similar region. Similar prediction decoding means for predictively decoding based on image information of a block area stored in the reproduction area storage means, creating image information of another block area and storing the image information in the reproduction area storage means, Predictive decoding means for predicting and decoding the code information when it is identified as a dissimilar area, creating image information of the block area and storing the image information in the reproduction area storage means; Characterized in that it comprises a reproduction image combining means for generating image information of the entire basis of the image information stored in the storage block area range storage means.

Therefore, according to the present invention, when index information is encoded, the original image is reproduced from the index information, and when the image is encoded using the image of the similar small block area, Reproduces an image by using an image of a similar small block area, and reproduces an image without using an image of a similar small block area if the code is encoded without using the image of the similar small block area Then, since each reproduced image can be finally combined to form an entire image, it is possible to reproduce an image without error from a highly efficient code generated by each of the encoding means. Can be.

[0034]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an encoding apparatus according to the present invention,
An embodiment of a decoding device will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing a configuration of an embodiment in which an encoding device and a decoding device according to the present invention are applied to a facsimile.

As shown in FIG. 1, in the facsimile, first, an image reading unit 101 reads a document using a CCD image sensor or the like on a transmission side, and then, an image processing unit 102 converts transmission data into appropriate data. Finally, the encoding unit 103 performs encoding and sends out the generated code to the transmission path.

On the other hand, when an image is reproduced on the receiving side, the encoded data is decoded by the decoding unit 104 and the image processing unit 1
At 05, a hard copy is obtained by performing image processing suitable for the output device and outputting it to the image output unit 106 such as a plotter.

Examples of processing performed by the image processing units 102 and 105 include resolution conversion and size conversion for binary images, and color (color component) conversion for multivalued images including colors. Examples include resolution conversion and size conversion. Examples of the encoding method used in the encoding unit 103 and the decoding unit 104 include the MH, MR, MMR method used in the conventional facsimile and the JBIG method using the arithmetic code for binary images. There is a JPEG method using adaptive discrete cosine transform for multivalued images.

Next, the encoding section 103 shown in FIG. 1 will be described in more detail with reference to FIG. In FIG.
FIG. 2 shows a block diagram of a configuration of an encoding unit 103 shown in FIG. FIG. 2 also shows a block diagram of a configuration of an embodiment of the encoding device according to the present invention.

The coding unit 103 includes an image area dividing unit 201 for dividing image information into small block areas in units of characters, figures, and the like, and an area image information storing unit for storing image information of divided images. A similar image selecting unit 203 for selectively extracting an image of a small block region similar to the image of the small block of interest from among the small block region images that have previously appeared and stored in the region image information storing unit 202; Whether or not the image of the selected and extracted similar small block area is the same as the image of the small block area of interest,
If not the same, the similar image determining unit 204 that determines whether or not the small block region is effective as a similar small block region, and the image of the small block region when the similar image determining unit 204 determines that they are the same. , Using the image information of the similar small block region, and a similar prediction encoding unit 206 that predicts and codes the image of the small block region of interest from the image of the similar small block region. A predictive coding unit 207 that performs predictive coding of the image of the small block region of interest without using an image of the similar small block region, an image matching coding unit 205, a similar predictive coding unit 206, and a predictive coding unit 207 based on the three encoding results output from each of the 207s.

Next, the operation of the encoding unit shown in FIG. 2 will be described below. First, image information (image) input for encoding is input to the image area dividing means 201,
It is divided into units such as characters and figures. The divided image information is input to the area image information storage unit 202, and the image of the divided small block area is stored. Subsequently, the similar image selecting unit 203 selectively extracts a small block region similar to the image of the target small block region based on the image information stored in the region image information storing unit 202.

When the similar small block area is selectively extracted,
Subsequently, the similar image determining unit 204 determines whether the image of the similar small block region selected by the similar image selecting unit 203 is the same as the image of the small block region of interest or encodes the small block region of interest. Is determined to be an effective similar small block area. If the selected image of the similar small block area is the same as the image of the small block area of interest, the image matching encoding unit 205 performs encoding using the image information of the similar small block area.

If it is determined that the selected image of the similar small block area is valid as the similar image of the image of the small block area of interest, the similar prediction encoding means 206 outputs the image information of the image of the similar small block area, Then, prediction is performed using the image of the similar small block region, and the image of the target small block region is encoded. If it is determined that the selected image of the similar small block region is not valid as the similar image of the image of the small block region of interest, the prediction encoding unit 207 predicts the image using a normal method that does not use the image of the similar small block region. And encode the image of the small block area of interest.
The above is the basic operation.

Next, the operation of the individual members shown in FIG. 2 will be described in more detail below. First, information on the small block area divided by the image area dividing means 201 is stored in the area image information storage means 202. As this information, a method of storing the position information and the size of the image of the small block area is considered. Can be This is because the amount of information can be reduced as compared with the case where an actual image is stored. In addition, it is conceivable that the information to be stored is managed by adding an index. According to this, the area image can be referred to only by knowing the index number, which is very efficient.

Next, although various methods can be considered as the determination method performed by the similar image determination means 204, a method of simply determining from the number of mismatched pixels between the image of the small block region that has appeared before and the image of the small block region of interest. Can be considered. This method can be realized with a very simple configuration, and can speed up the processing. As a determination example, if there is no mismatching pixel, it is determined that they are the same, and if the number of mismatching pixels is smaller than a predetermined number or ratio, it is determined that the similar image is valid,
Otherwise, there is a method of determining that the similar image is invalid.

Further, as to how to encode the image of the small block area of interest, the following method may be used. The method described below is a method of determining the encoding of the image of the small block area of interest using two thresholds Th and Th0.

An example of the encoding process in the encoding device according to the present invention will be described in detail with reference to FIG. FIG. 9 shows a flowchart of an example of the encoding process of the encoding device according to the present invention. However, when describing FIG. 9, description will be made using terms that are different from terms used in the present specification and the drawings and are generally used by those skilled in the art. Therefore, in FIG. 9, the “pattern of interest” refers to the “small block region of interest” in the terms of the present specification and the drawings, and “coincidence encoding” refers to the image shown in FIG. 2. Refers to encoding by the coincidence encoding means 205,
“Pattern reference encoding” refers to encoding by the similar prediction encoding unit 206 shown in FIG. 2, and “pattern encoding” refers to encoding by the prediction encoding unit 207 shown in FIG. Further, “pattern registration” means storage in the area image information storage unit 202 shown in FIG.

The encoding shown in FIG. 9 is a flow of encoding by lossy (so-called irreversible transformation). In this case, in step S91, the degree of coincidence of the pattern of interest is determined.
3 and performs match coding, and Th0> match degree ≧ Th
If so, the process proceeds to step S95 to perform pattern reference encoding. If the degree of coincidence <Th, the process proceeds to step S97 to perform pattern encoding.

After the pattern reference encoding in step S95 and the pattern encoding in step S97, the flow shifts to step S99 to execute pattern registration. Here, Th is a threshold value of the degree of coincidence, and Th is
0 is a threshold value of the coincidence coding.

As is clear from the flowchart shown in FIG. 9, the control of the image quality and the coding efficiency in the coding apparatus according to the present invention can be controlled by both Th and Th0 parameters.

The degree of coincidence is EX-OR between the pattern of interest and the selected matching (selection) pattern (for example, an image of a small block area that has appeared before).
More specifically, a value calculated by the following equation is used in the processing. Matching degree = (number of pixels matching the selected pattern) / (total number of pixels of the pattern of interest). Note that Th0 (Th0> Th) is determined by simulation.

Next, the encoding operation of the image coincidence encoding unit 205, the similar prediction encoding unit 206, and the prediction encoding unit 207 shown in FIG. 2 will be described in further detail. The image coincidence encoding unit 205 encodes a code obtained by encoding the index of the storage sequence stored in the region image information storage unit 202 representing the image of the similar similar small block region and the position information at which the target small block region is located. create.

The similarity prediction encoding means 206 stores the area image information storing means 20 representing the image of the similar similar small block area.
A code that encodes the image of the small block area of interest is created using the index of the storage column stored in 2, the position information of the position of the small block area of interest, and the image of the similar small block area.

The predictive coding means 207 calculates the size of the small block area of interest and the position information where the small block area of interest is located,
Then, a code is generated by encoding the image of the small block area of interest.

It is preferable to provide identification information at the beginning of each code string in order to identify that the code is coded by the above three coding means. This identification information is transmitted to the image coincidence encoding unit 205 and the similar prediction encoding unit 2
In order to indicate which one of the code sequence 06 and the predictive coding unit 207 has been coded, each coding unit adds it to the beginning of each code string. Further, the code information creating unit 208 adds identification information indicating the end of the code information composed of the code string encoded by each encoding unit. As the identification information, there are four types including the identification information indicating the end of the code in addition to the three modes, so that at least two bits are sufficient. Of course, if this identification information is also encoded, the amount of information is reduced.

In addition to the position information, rather than simply coding the position from the base point (for example, the upper left of the paper), the position information of the small block area coded immediately before the target small block area and the focus It is conceivable to encode the difference from the position information indicating the position of the small block area. This method has the advantage that the absolute value required as the position information is reduced, so that the encoded information is also reduced.

Further, in order to reduce this absolute value,
It is conceivable that the difference information from the closest grid point is encoded as position information, in which case the absolute value is further reduced and the encoding efficiency is improved. In this case, FIG.
This will be described with reference to FIG. FIG. 6 shows a conceptual diagram when efficiently encoding position information.

As shown in FIG. 6, as the position information, a set of grid points represented by offset and having the shortest distance between the grid points included in the small block area is selected.

Next, the above-described image coincidence encoding means 205,
Similar prediction encoding means 206 and prediction encoding means 207
A conceptual diagram in the case where the information encoded according to the above is a code transmitted by the code information creating means 208 will be described with reference to FIG. FIG. 5 shows a conceptual diagram of codes encoded by the above three encoding means.

Next, the similar image selecting means 2 shown in FIG.
03 will be described. As a method for selecting a similar small block area similar to the image of the small block area of interest, a method of searching only those having the same size as the small block area of interest can be considered. According to this, the processing time required for the search can be reduced, and the processing speed can be improved.

Next, an example of an encoding method actually applied by the three encoding means will be described with reference to FIGS.
This will be described below with reference to FIG. FIG. 7 is a block diagram of a configuration of a coding unit that performs the arithmetic coding method, and FIG. 8 is a conceptual diagram of coding by the arithmetic coding method.

As shown in FIG. 7, in the arithmetic coding method, in the coding, input image data is encoded by a pixel to be encoded by a part called a prediction information creation unit (also referred to as a template) 701 and surrounding pixels. Predicted data in which Markov separation of an information source is performed according to the situation with pixels is generated, and encoding is performed based on the predicted data while an arithmetic coding unit 702 dynamically evaluates the predicted data. Here, “Markov separation” has the same meaning as “state of Markov source”, and is called a state of Markov source.

In decoding, the input code data is decoded by performing Markov separation of the information source according to the situation of the pixels already decoded by the same prediction information creating unit 704 as the pixels at the time of coding and the surrounding pixels. The prediction data of the data to be created is created, and the arithmetic decoding unit 7
At 03, decoding is performed while dynamically evaluating the prediction data.

The arithmetic coding method generally has higher coding efficiency than the conventional run-length coding method (MH, MR). The encoding method is based on a corresponding section on the number line of [0, 1] (binary decimal [0.0... 0, 0.1.
[1]) is divided into unequal lengths according to the occurrence probabilities of the respective symbols, the target symbol sequence is assigned to the corresponding sub-interval, and is included in the interval obtained by repeating the division recursively. The coordinates of the point to be expressed are represented as binary decimal numbers that can be distinguished from at least other sections, and used as codes.

Here, referring to FIG.
The concept of arithmetic coding will be described with reference to 0100 'as an example. First, at the time of encoding the first symbol, the entire section is divided into A (0) and A (1) according to the ratio of the occurrence probabilities of the symbols '0' and '1', and the section A (0) is generated by the occurrence of '0'. Is selected. Next, when encoding the second symbol, A (0) is further divided by the occurrence probability ratio of both symbols in that state, and A (0) is defined as a section corresponding to the generated symbol sequence.
1) is selected.

Coding proceeds by repeating such division and selection processing. On the other hand, in the decoding, a process completely opposite to that of the encoding is performed, and the symbol is reproduced based on the binary decimal number indicated by the code. What is important here is the width of a number line when encoding a symbol. If the width of the number line does not match between the start of encoding and the start of decoding, the symbol cannot be accurately reproduced. That is. Normally, the width of this number line is set to 1 on the encoding side and the decoding side.

In the present invention, an image input by the above processing is encoded. Here, the encoding operation of the encoding device according to the present invention will be described with reference to FIG. FIG. 4 shows a flowchart of the encoding operation of the encoding device according to the present invention.

As shown in FIG. 4, first, the image area dividing means 201 divides an input image into small block areas (step S1). Next, step S
In 3, the similar image selecting means 203 selects a similar small block area similar to the target small block area to be coded.

Next, the similar image determining means 204 determines whether or not the image of the similar small block region is the same as the image of the target small block region (step S5). here,
If it is determined that the image is the same as the image of the small block area of interest (Yes), in step S7, the image matching encoding unit 205 performs encoding using the image of the similar small block area, and performs the operation. To end.

When it is determined in step S5 that the image is not the same as the image of the small block area of interest (No)
Next, it is determined whether or not the image of the similar small block region is effective for encoding the image of the small block region of interest (step S9).

If it is determined in step S9 that it is effective to encode the image of the small block area of interest (Yes), the similar prediction encoding unit 206 performs encoding using the similar image. And terminate the operation (step S11).

If it is determined in step S9 that the image of the small block area of interest is not effective for encoding (No), the predictive encoding means 207 executes encoding without using a similar image. Then, the operation ends (step S13).

Next, an embodiment of the decoding apparatus according to the present invention will be described with reference to FIG. FIG. 3 shows a block diagram of an embodiment of the decoding device according to the present invention.

As shown in FIG. 3, the configuration of this decoding device is to identify the type of coding of the input code information,
Identification means 306 to output to image coincidence decoding means 301, similarity prediction decoding means 302, or prediction decoding means 303
And a code that encodes the index of the storage sequence stored in the area image information storage unit 202 that represents the image of the similar small block area that matches the image of the small block area of interest, and decodes the code of the small block area of interest. An image matching decoding unit 301 for reproducing an image, a similar prediction decoding unit 302 for performing prediction and decoding based on an image of a small block area which has already been reproduced,
Predictive decoding means 303 for performing predictive decoding irrespective of an image of a small block area which has already been reproduced, and reproduction area storage means 30 for storing reproduction images reproduced by these three decoding means.
4 and a reproduced image combining means 305 for combining the reproduced images reproduced by these three decoding means to reproduce the entire image.

Next, the operation of the decoding apparatus shown in FIG. 3 will be described in detail. First, the identification means 306
Is the target code from the input code information, whether the index is coded, or is coded using the image of the similar small block region, or does not use the image of the similar small block region Identify whether or not it is encoded. If the index is coded, the original image is reproduced from the index information and output to the reproduction area storage unit 304.

In the case of a code coded using the image of the similar small block area, the image is reproduced using the image of the similar small block area that has appeared before and output to the reproduction area storage means 304. I do. In the case of a code encoded without using the image of the similar small block area, the image is reproduced without using the image of the similar small block area and output to the reproduction area storage unit 304. The reproduction area storage unit 304 stores the reproduced image for each small block area and outputs the image to the reproduction image combining unit 305 in order to create the entire image. The reproduced image combining means 305 finally combines the reproduced images to create an entire image, and outputs it as image information. To summarize the above, the identification unit 306 identifies the same area, a similar area, and a dissimilar area based on the input code information. Reproduction area storage means 3
Reference numeral 04 stores image information of the block area. When the identification unit 306 identifies the same area, the image matching decoding unit 301 instructs to output the image information of the block area stored in the reproduction area storage unit 304. When the identification unit 306 identifies a similar region, the similar prediction decoding unit 302 performs predictive decoding based on the image information of the block region stored in the reproduction region storage unit 304, and creates image information of another block region. Playback area storage means 3
04. The predictive decoding means 303
When 6 is identified as a dissimilar area, the code information is predictively decoded, and the image information of the block area is created and stored in the reproduction area storage unit 304. The reproduced image combining means 305 creates the entire image information based on the image information of the block area stored in the reproduced area storage means 304.

Therefore, according to the encoding apparatus and the decoding apparatus of the above embodiment, when encoding is performed on the small block area divided by the image area dividing means 201, the small block area previously appeared Considering the correspondence relationship, if the image of the small block area of interest is the same image as the small block area that appeared before, the image matching encoding unit 205 performs encoding, and If the similar small block area is effective when encoding the small block area of interest, the similar prediction encoding unit 206 executes the encoding, and the similar small block area that has appeared earlier encodes the small block area of interest. If it is not effective at the time of encoding, since the predictive encoding means 207 performs the encoding, the encoding of the image composed of characters and the like can be performed very efficiently, and It is the same.

[0077]

As is apparent from the above description, according to the first aspect of the present invention, a character image created by a personal computer or a word processor has regularity such as character shape and size. If such information is used, character images can be coded with very high efficiency, so the image is divided into small blocks such as characters, and the image of the divided small block area is encoded. At the time of conversion, it is determined whether or not the same or similar one has already appeared in the small block area, and if it is the same, encoding is performed using the information of the previously appeared small block area. And if it is similar, the encoding is performed using the image of the similar small block area; otherwise, normal prediction encoding is performed, so that encoding that can be encoded with extremely high efficiency It is possible to provide a location.

According to the second aspect of the present invention, when an image of a small block area is stored, a method of storing the image itself can be considered, but in this case, the size of the storage area becomes large. There is. Therefore, if the size and position of the small block area that has already appeared are stored, the image of the actual small block area can be referred to, and these can be used as indexed storage columns. For example, it is possible to refer to the target image only by referring to the index. Therefore, the region image information storage means stores a storage sequence storing only the size and the position information of the region. An encoding device that can be avoided can be provided.

According to the third aspect of the present invention, encoding an image in units of small block areas does not necessarily require encoding in the order of small block areas that appear during encoding. There is an advantage that it is also good, and there is an advantage that it is possible to extract and decode only an arbitrary small block area at the time of decoding, and when encoding a small block area, if an image that has already appeared is encoded only its index It is efficient, and if there is a similar image, the encoding efficiency is improved by performing predictive encoding using an image of a similar small block area. Therefore, in the present invention, by utilizing these advantages, the image matching encoding means encodes an index representing an image of a similar similar small block area, thereby achieving highly efficient encoding. A code capable of performing high-efficiency coding by coding a target small block region using an index representing an image of a similar small block region and an image of the target small block region to generate a code. Device can be provided.

The invention according to claim 4 focuses on the fact that character images created by a personal computer or a word processor often have regularity in the arrangement and spacing of characters, and the code amount of position information is determined by its absolute value. Since the smaller the value is, the higher the efficiency is, it is possible to perform highly efficient encoding by reducing the absolute value required for the position information by using the position information of the small block area near the small block area of interest. Can be provided.

The invention according to claim 5 focuses on the fact that the smaller the absolute value of the code amount of the position information, the higher the efficiency, and utilizes the position information of the small block area near the small block area of interest. In this case, it is possible to provide an encoding device capable of performing highly efficient encoding by reducing the absolute value required for position information by using information between nearest lattice points. it can.

According to the present invention, the image information of the small block area of interest can be reproduced without error on the decoding side by adding identification information to each code, and the processing on the decoding side can be performed based on the identification information. Can be easily determined, so that an encoding device capable of improving the processing speed can be provided.

Further, according to the invention of claim 7, the similar image selecting means retrieves only the small block area that matches the size of the small block area of interest and selects it as a similar small block area, so that the configuration is simple. An encoding device capable of executing a search at high speed can be provided.

According to an eighth aspect of the present invention, the similar image determining means counts the number of inconsistent pixels between the target small block area and the selected similar small block area, and determines based on the number of pixels. , It is possible to provide an encoding device having a simple configuration and capable of executing the determination at high speed.

Further, according to the ninth aspect of the present invention, when the index information is encoded, the original image is reproduced from the index information and encoded using the image of the similar small block area. In the case where the image is reproduced using the image of the similar small block area, the image is reproduced without using the image of the similar small block area when the code is encoded without using the image of the similar small block area. To reproduce the image and finally combine the reproduced images to form the entire image, so that decoding can be performed without error based on highly efficient encoded codes. An apparatus can be provided.

Next, with reference to FIGS. 10 and 11, the coding performance of the coding apparatus according to the present invention and the conventional JBIG
Compare with the coding performance of -1. However, the following FIG.
0 and # 4 shown in FIG. 11 correspond to the image (Imag
This is a number representing the type of e), and the image # 4 represents an image with a large number of texts in horizontal writing. In addition, # 2 and # 8
Are handwritten images, # 3, # 5, # 6
May be an image in which tables and figures are mixed.

FIG. 10 shows the coding performance of the coding apparatus according to the present invention at the time of lossy (so-called irreversible transformation),
Table 1 shows the result of comparison with the encoding performance of the conventional JBIG-1.

Here, in Table 1 shown in FIG. 10, in the flowchart of FIG.
This shows the compression result when h = 85. In Table 1,
The column of new (t2) is the value of the encoding device according to the present invention, the integer value is the code amount (byte), and the ratio is JB.
The ratio with IG-1 is shown.

As apparent from Table 1 shown in FIG. 10, the resolution (resolution) is 400.
In [dpi], when Image is # 4, JBIG-1
Then, while the code amount is 99802 bytes,
In the encoding device according to the present invention, that is, new (t2), 4
8749 bytes. Therefore, JBIG-1
/New(t2)=2.05.

As can be seen from Table 1 shown in FIG. 10, in the encoding apparatus according to the present invention, an image such as # 4 having a large number of texts in a horizontal writing mode is more effective than JBIG-1. The coding efficiency is improved by 100%. Since the result of Table 1 shown in FIG. 10 is a result at the time of lossy,
Although there is a relationship with the reproduction image quality, it is clear that the value exceeds JBIG-1.

Next, the performance comparison at the time of lossless (so-called reversible conversion) will be described. FIG.
Table 2 shows a comparison result between the coding performance of the coding apparatus according to the present invention and the coding performance of the conventional JBIG-1 at the time of sless.

Here, Table 2 shown in FIG. 11 shows the compression result of the encoding apparatus according to the present invention.
In Table 2, the column of new is the value of the encoding device according to the present invention, the integer value is the code amount (byte), and the ratio is JB.
The ratio with IG-1 is shown.

As is apparent from Table 2 shown in FIG. 11, the resolution (resolution) is 400.
In [dpi], when Image is # 4, JBIG-1
Then, while the code amount is 99802 bytes,
In the encoding device according to the present invention, that is, in the new, 79707
byte. Therefore, JBIG-1 / new
= 1.25.

As is apparent from Table 2 shown in FIG. 11, the encoding apparatus according to the present invention uses the JBIG-1
It can be seen that it has the same or better performance at the time of the lossless as compared with. In particular, the coding efficiency is improved by about 25% as compared with JBIG-1 for a horizontally written text having a large number of texts such as # 4. Considering that JBIG-1 is a binary lossless coding scheme showing the highest efficiency at present, it can be said that the superiority of the coding apparatus according to the present invention is large.

[Brief description of the drawings]

FIG. 1 is a block diagram of a configuration of a facsimile provided with an embodiment of an encoding device and a decoding device according to the present invention.

FIG. 2 is a block diagram of a configuration of an embodiment of an encoding device according to the present invention.

FIG. 3 is a block diagram of a configuration of an embodiment of a decoding device according to the present invention.

FIG. 4 is a flowchart showing an operation of the encoding unit shown in FIG.

FIG. 5 is a conceptual diagram of a code transmitted by the encoding unit shown in FIG.

6 is a conceptual diagram when the encoding unit shown in FIG. 2 encodes position information.

7 is a block diagram of an operation unit that executes an arithmetic coding method performed by the coding unit illustrated in FIG. 2;

8 is a conceptual diagram of an arithmetic coding method by an operation unit of the arithmetic coding method shown in FIG. 7;

FIG. 9 is a flowchart of an example of encoding performed by the encoding device according to the present invention.

FIG. 10 is a table for explaining the performance of the encoding device according to the present invention.

FIG. 11 is a table for explaining the performance of the encoding device according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 Image reading part 102 Image processing part 103 Encoding part 104 Decoding part 105 Image processing part 106 Image output part 201 Image area division means 202 Area image information storage means 203 Similar image selection means 204 Similar image determination means 205 Image coincidence encoding means 206 Similar prediction coding means 207 Predictive coding means 208 Code information creation means 301 Image coincidence decoding means 302 Similar prediction decoding means 303 Prediction decoding means 304 Playback area storage means 305 Playback image combining means 306 Identification means 701 Prediction information creation unit 702 Arithmetic Encoding unit 703 Arithmetic decoding unit 704 Prediction information creation unit

Claims (9)

[Claims] 1. An image area dividing means for dividing input image information into block areas in units of characters or figures, and an area image information storing means for storing a plurality of image information of the block areas input from the image area dividing means. Means; a block area input from the image area dividing means as a target block area; and a plurality of block areas stored in the area image information storage means as reference block areas. Image information of a reference block area similar to the image information of the target block area, and image information of the reference block area selected by the similar image selection means. Is the same as the image information of the target block area, the target block area is determined to be the same area, and the reference block When the image information of the area is not the same as the image information of the target block area but is similar, the target block area is determined to be a similar area, and the image information of the reference block area is the same as the image information of the target block area. And if not similar, a similar image determining means for determining the target block area as a non-similar area; and image information of the target block area determined to be the same area as a corresponding reference stored in the area image information storing means. An image matching encoding unit that encodes using the image information of the block region; and an image of the corresponding reference block region stored in the region image information storage unit, the image information of the target block region determined to be the similar region. Predictive encoding means for predicting and encoding based on the information and the image information of the target block area, and a target block determined as the non-similar area. Prediction coding means for predicting and coding the image information of the block area based on the image information of the block area of interest; output from the image coincidence coding means, the similar prediction coding means, and the prediction coding means. And a code information creating means for creating code information based on the encoded result. 2. The encoding apparatus according to claim 1, wherein said area image information storage means stores a storage sequence indicating the size and position information of said block area. 3. The image coincidence encoding unit encodes using an index and a position information of a storage sequence representing image information of a block region of interest determined to be the same region, wherein the similar prediction encoding unit includes: Predicting and encoding based on the index, position information, and the image information of the storage sequence representing the image information of the target block area determined to be the similar area, and the predictive encoding unit is determined to be the non-similar area. 3. The coding apparatus according to claim 2, wherein coding is performed based on the size and position information of the noted block area and the image information. 4. The image coincidence encoding unit, the similar prediction encoding unit, and the prediction encoding unit, based on a difference between position information of the target block region ahead of the target block region and position information of the target block region. The encoding apparatus according to claim 3, wherein the position information of the block area of interest is encoded. 5. The image coincidence encoding unit, the similar prediction encoding unit, and the prediction encoding unit calculate a difference between the distances between the nearest end portions of the target block region and the target block region. The encoding device according to claim 3, wherein the position information of the target block area is encoded based on the position information. 6. The image coincidence encoding unit, the similar prediction encoding unit, and the prediction encoding unit add first identification information indicating which of the encoding units has encoded the image, and
The encoding device according to claim 1, wherein the code information creating unit adds second identification information indicating the end of the code information. 7. The encoding apparatus according to claim 1, wherein said similar image selecting means selects and extracts a reference block area having the same size as the target block area. . 8. The similar image selecting means compares the image information of the target block area with the image information of the reference block area, and makes a determination based on the number of mismatches of the image data of the pixels constituting each image information. 2. The method according to claim 1, wherein
8. The encoding device according to any one of claims 1 to 7. 9. An identification means for identifying the same area, a similar area and a dissimilar area based on input code information; a reproduction area storage means for storing image information of a block area; An image coincidence decoding unit that instructs to output image information of a block area stored in the reproduction area storage unit when the identification area is identified; and the reproduction area storage unit when the identification unit identifies the similar area. Predictive decoding based on the image information of a block area stored in the similar area, creating similar image information of another block area and storing the same in the reproduction area storage means; In this case, predictive decoding means for predictively decoding code information, creating image information of a block area, and storing the image information in the reproduction area storage means, and storing the image information in the reproduction area storage means. Decoding apparatus characterized by comprising a reproduction image combining means for generating image information of the entire basis of the image information of the block area.