JP2006049994A - Arithmetic coding and decoding device of drawing information - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an arithmetic coding device of drawing information which can apply the same coding system without changing the reference pixel position of a template. <P>SOLUTION: The arithmetic coding device of the drawing information includes at least an aspect ratio changing means for changing a ratio of an inputting image in a horizontal direction to a vertical direction; a prediction pixel storage means for storing the predicted pixel of a pixel with an interest for every ambient pixel information, and outputting the predicted pixel corresponding to the ambient pixel information; a prediction probability storage means for storing the appearance probability of the predicted pixel for every ambient pixel information, and outputting the appearance probability of the prediction pixel corresponding to the ambient pixel information; and an arithmetic coding means for performing arithmetic coding based on the prediction pixel, the pixel with the interest, and the appearance probability of the prediction pixel. The aspect ratio of the input image is changed by utilizing the characteristic of the image to be inputted. The predicted pixel of the pixel with the interest is decided from the ambient pixel information of the pixel with the interest to the image after a change from the predicted pixel storage means. Simultaneously, the appearance probability is decided from the prediction probability storage means. The arithmetic coding of the pixel with the interest is performed based on the appearance probability of the predicted pixel. If necessary, the stored predicted pixel and the prediction probability are changed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image encoding arithmetic coding apparatus and an image decoding arithmetic decoding apparatus suitable for an image handling apparatus, particularly a digital copying machine, a facsimile machine, and a filing apparatus.

In recent years, in digital image processing devices such as digital copiers and facsimiles, the amount of information handled has increased due to the improvement in resolution and the increase in the amount of information per pixel, which inevitably increases the speed of data processing. ing. In addition to speeding up the data processing, it is important to speed up the processing itself. In addition, it is also important to reduce the time spent for transferring such large-volume data. In particular, the latter has become important in recent years, and one of the methods attracting attention is a method for reducing the amount of transferred data by efficiently compressing the data itself.
As well-known data compression methods, there are MH, MR, and MMR coding methods conventionally used in facsimiles. All of these can be encoded at a high compression rate in a text image, but there is a problem that compression is hardly possible in an image subjected to halftone processing such as a photographic image.
On the other hand, there is an entropy coding method typified by an arithmetic coding method as a coding method capable of efficiently compressing any image. Typical examples of arithmetic coding methods include the ITU-T, which determines the communication standard for facsimile, and the JBIG method, which is standardized by the ISO, the international standardization organization. Encoding is possible.
The arithmetic coding method employed in JBIG is called QM-Coder, and is a typical subtractive arithmetic coding method. The arithmetic encoding method predicts and encodes a pixel of interest, and the compression ratio is improved when the predictive mid ratio is high. On the other hand, if the predictive predictive value is bad, the compression ratio decreases.
The predictive predictive factor affects a predictor called a template in the arithmetic coding method, and is usually optimized by experiment based on a logical one. Since the template is determined by reflecting the property of the target image, it is necessary to change it when the property of the target image is changed. If this is not done, there is a problem that the compression rate is lowered.
The arithmetic coding system represented by QM-Coder adopted in the JBIG system performs coding by determining whether a pixel is a dominant symbol or a recessive symbol. At that time, the attention symbol (symbol: equivalent to a pixel in the case of an image) is predicted, and the appearance probability of the predicted symbol is used. These are adaptively changed (updated) based on statistical information while encoding, and are approximated to more accurate prediction symbols and appearance probabilities (like learning).
As a conventional technique related to arithmetic codes, for example, there is Patent Document 1 below.
JP-A-1-222576

An information string using surrounding pixel information called a template is used when the predicted symbol and the appearance probability are obtained. Since the template uses correlation of surrounding pixels, it is easily affected by image attributes, particularly resolution.
For example, when a template created for a 300 dpi image is applied to a 600 dpi image, the distance between pixels that can be referred to relatively changes, so that the expected performance cannot be achieved. This is particularly noticeable in high-resolution images. In order to solve this, it is conceivable to change the reference position of the surrounding pixels by changing the shape of the template. However, when the number of reference pixels is large, it leads to a problem that it becomes very complicated.
The present invention solves the above-described problem. The aspect ratio of an input image is changed using the characteristics of an input image, and the reference inter-pixel distance in one direction is set as the assumed inter-pixel distance (design) of the template. The first object is to provide an image information arithmetic coding apparatus to which the same coding method can be applied without changing the reference pixel position of the template.
It is a second object of the present invention to provide an image information arithmetic decoding device capable of accurately reproducing an original image from a code string encoded by the image information arithmetic encoding device.

In order to achieve the first object, according to the first aspect of the present invention, there is provided an aspect ratio changing means for changing a ratio between a horizontal direction and a vertical direction of an input image, and a predicted pixel of a target pixel for each surrounding pixel information. A prediction pixel storing means for storing and outputting a prediction pixel corresponding to the surrounding pixel information; a prediction probability for storing the appearance probability of the prediction pixel for each surrounding pixel information and outputting the appearance probability of the prediction pixel corresponding to the surrounding pixel information At least storage means and arithmetic coding means for performing arithmetic coding based on the appearance probability of the prediction pixel, the target pixel, and the prediction pixel, and using the characteristics of the input image, the aspect ratio changing means The aspect ratio of the input image is changed, the predicted pixel of the target pixel is determined from the surrounding pixel information of the target pixel with respect to the changed image by the predicted pixel storage unit, and the appearance probability of the predicted pixel is simultaneously determined by the prediction probability storage unit. Decide Wherein performs arithmetic coding of the pixel of interest based on the probability of occurrence of predicted pixels, and changes the prediction pixel and the prediction probability stored if required by the arithmetic coding unit.
According to the second aspect of the present invention, aspect ratio changing means for changing the ratio between the horizontal direction and the vertical direction of an input image, and surrounding pixels for extracting the surrounding pixel state of the target pixel in the image changed by the aspect ratio changing means An information determination unit; a prediction pixel storage unit that stores a prediction pixel of a target pixel for each surrounding pixel information determined by the surrounding pixel information determination unit; and outputs a prediction pixel corresponding to the surrounding pixel information; and the surrounding pixel information Prediction probability storage means for storing the appearance probability of the prediction pixel for each surrounding pixel information determined by the determination means, and outputting the appearance probability of the prediction pixel corresponding to the surrounding pixel information, and the prediction determined by the prediction pixel storage means Prediction pixel control means for changing and controlling the prediction pixel stored in the prediction pixel storage means based on the result of the pixel and the attention pixel; and the result of the prediction pixel and the attention pixel determined by the prediction pixel storage means. The prediction probability control means for changing and controlling the prediction probability stored in the prediction probability storage means, the prediction pixel determined by the prediction pixel storage means and the target pixel, and the appearance of the prediction pixel determined by the prediction probability storage means Arithmetic coding means for performing arithmetic coding based on the probability, and using the characteristics of the input image, the aspect ratio of the input image is changed by the aspect ratio changing means, and the predicted pixel storage means To determine the predicted pixel of the target pixel from the surrounding pixel information of the target pixel with respect to the image after the change, determine the appearance probability of the predicted pixel at the same time by the prediction probability storage unit, and determine the prediction pixel of the predicted pixel by the arithmetic encoding unit. The pixel of interest is arithmetically coded based on the appearance probability, and the stored prediction pixel and prediction probability are changed if necessary.
According to a third aspect of the present invention, in the picture information arithmetic coding apparatus according to the first or second aspect, the aspect ratio changing means increases the number of horizontal samples and decreases the number of vertical samples.
According to a fourth aspect of the present invention, in the arithmetic coding apparatus for image information according to the third aspect, the aspect ratio changing means actually inputs the resolution m (distance between reference pixels) assumed by the surrounding pixel information determining means and the actual input. The integer k closest to the ratio (n / m) to the resolution n is obtained, the horizontal number of samples is k times the original size, and the vertical number of samples is (1 / k) times. To do.
According to a fifth aspect of the present invention, in the arithmetic coding apparatus for picture information according to any one of the first to fourth aspects, an arithmetic coding apparatus for picture information in which information relating to the aspect ratio is inserted in the generated code is provided. Main features.

  In order to achieve the second object described above, the invention described in claim 6 provides image information for reproducing an image by decoding a code created by the image information arithmetic coding device described in claims 1 and 2. In the arithmetic decoding apparatus, surrounding pixel information determining means for extracting a surrounding pixel state of a decoding target pixel, and a predicted pixel of a target pixel is stored for each surrounding pixel information determined by the surrounding pixel information determining means, and surrounding pixel information Prediction pixel storage means for outputting a prediction pixel corresponding to, and the appearance probability of the prediction pixel for each surrounding pixel information determined by the surrounding pixel information determination means is stored, and the appearance probability of the prediction pixel corresponding to the surrounding pixel information is stored. The prediction probability storage means for outputting, the arithmetic decoding means for performing arithmetic decoding based on the appearance probability of the prediction pixel and the prediction pixel, the prediction pixel determined by the prediction pixel storage means and the decoded target pixel Original prediction pixel Prediction pixel control means for changing and controlling the prediction pixel stored in the memory means, and prediction probability storage means based on the result of the prediction pixel determined by the prediction pixel determination means and the decoded target pixel. Prediction probability control means for changing and controlling the prediction probability, and aspect ratio changing means for changing the ratio between the horizontal direction and the vertical direction of the input image and outputting the image, and from the surrounding pixel information of the decoding target pixel The prediction probability of the target pixel is predicted at the same time, and the appearance probability is obtained. When the aspect ratio is changed from the given code, the aspect ratio of the output image is changed and the image is reproduced. To do.

According to the present invention, the aspect ratio of the input image is changed using the characteristics of the input image so that the reference inter-pixel distance in one direction is the same as the assumed inter-pixel distance (design value) of the template. Therefore, the same encoding method can be applied without changing the reference pixel position of the template, and simple and highly efficient encoding is possible.
In addition, since the aspect ratio is changed by increasing the number of samples in the horizontal direction and decreasing the number of samples in the vertical direction, there is no need for complicated processing such as data rearrangement. (Design value) can be made the same, and simple and highly efficient encoding becomes possible.
In addition, the aspect ratio is changed from the assumed resolution of the template and the resolution of the image that is actually input. At that time, the number of horizontal samples is set to an integer multiple of the original number of samples, so no complicated processing is required. The reference inter-pixel distance can be made the same as the assumed inter-pixel distance (design value) of the template, and simple and highly efficient encoding becomes possible.
In addition, by inserting information about the aspect ratio (for example, the original resolution information and the changed resolution information, or the original aspect ratio and the changed aspect ratio, etc.) into the generated code, an error occurs on the decoding side. The image can be played without any problem.
In addition, the original image can be accurately reproduced from the code string encoded by the encoding apparatus of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a block diagram of a facsimile to which an image information arithmetic coding apparatus and an image information arithmetic decoding apparatus according to the present invention are applied.
On the transmission (encoding) side, the image reading unit 101 reads a document using a CCD image sensor or the like, and the subsequent image processing unit 102 performs processing to make transmission data appropriate data, and finally the encoding unit 103. The code generated by encoding is sent to the transmission line.
On the other hand, when the image is reproduced on the reception (decoding) side, the encoded data is decoded by the decoding unit 104, the image processing unit 105 performs image processing suitable for the output device, and the image is output to the image output unit 106 such as a plotter. To get a hard copy. 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, resolution conversion for multi-value images including colors. Size conversion etc. are mentioned.
Examples of encoding methods used in the encoding unit 103 and the decoding unit 104 include MH, MR, MMR methods used in facsimiles and JBIG methods using arithmetic codes for binary images. For multi-valued images, there are a JPEG method using adaptive discrete cosine transform and a JPEG2000 method using Wavelet transform.
FIG. 2 is a basic block diagram of QM-Coder which is one of arithmetic coding systems. QM-Coder is an arithmetic coding method adopted in the JBIG method.
The QM-Coder first creates surrounding pixel information of the pixel to be encoded by the template 201, and then determines the prediction probability of the target pixel from the surrounding pixel information created by the template 201 by the probability evaluator 202. Based on the prediction probability, the arithmetic encoder 203 performs arithmetic coding. Note that the probability evaluator 202 performs a process of updating the probability based on information from the arithmetic encoder 203 in order to make the prediction probability more accurate.

FIG. 3 is a block diagram of an image information arithmetic coding apparatus according to an embodiment of the present invention. The arithmetic coding apparatus for main image information extracts an aspect ratio change unit 301 that changes a ratio between a horizontal direction and a vertical direction of an input image, and a surrounding pixel state of a target pixel in the image changed by the aspect ratio change unit 301. A surrounding pixel information determining unit 302 and a prediction pixel storing unit 303 that stores a prediction pixel of a target pixel for each surrounding pixel information determined by the surrounding pixel information determination unit 302 and outputs a prediction pixel corresponding to the surrounding pixel information.
Further, the arithmetic coding apparatus for main image information stores the appearance probability of the predicted pixel for each piece of surrounding pixel information determined by the surrounding pixel information determination unit 302, and outputs the appearance probability of the predicted pixel corresponding to the surrounding pixel information. Prediction probability storage means 304, prediction pixel storage means 303, prediction pixel and attention pixel determined by prediction probability storage means 304, arithmetic coding means 305 for performing arithmetic coding based on the appearance probability of prediction pixels determined by prediction probability storage means 304. .
Also, the arithmetic coding device for main image information predicts a prediction pixel that changes and controls the prediction pixel stored in the prediction pixel storage unit 303 based on the result of the prediction pixel determined by the prediction pixel storage unit 303 and the target pixel. The control means 306 and the prediction probability control means 307 for changing and controlling the prediction probability stored in the prediction probability storage means 304 based on the result of the prediction pixel and the target pixel determined by the prediction pixel storage means 303 are provided.

Next, the operation will be described. First, the aspect ratio changing means 301 determines whether or not to change the aspect ratio of the input image using the characteristics of the input image. An example of determining whether or not to change is whether or not the input image is assumed for the template used by the surrounding pixel information determination unit 302. If the input image is not assumed, the aspect ratio is changed so as to be close to the assumed input image.
For a changed image (which may not be changed), the target pixel is input to the surrounding pixel information determination unit 302, and the surrounding pixel of the target pixel is determined based on the positional relationship between the stored surrounding pixel information and the target pixel. Information is determined. As an example of creation of surrounding pixel information, as shown in FIG. 4, there is a method in which the state of surrounding pixels represented by “◯” is used as information with respect to the target pixel represented by “×”.
When the surrounding pixel information is created, the prediction pixel value and the prediction appearance probability of the target pixel corresponding to the surrounding pixel information are subsequently derived from the prediction pixel storage unit 303 and the prediction probability storage unit 304, respectively. When the predicted pixel value, the predicted appearance probability, and the target pixel value are determined, they are input to the arithmetic encoding unit 305, and a code is generated and output by performing arithmetic encoding. When the encoding of the pixel of interest is completed, the prediction pixel control unit 306 and the prediction probability control unit 307 change the prediction pixel and the prediction probability if necessary.
As an example of the prediction pixel changing method, there is a method of changing the prediction pixel when a mismatch occurs between the prediction pixel and the target pixel a predetermined number of times or more. Similarly, as an example of a method of changing the predicted appearance probability, there is a method in which the predicted appearance probability is lowered when the predicted pixel and the target pixel do not match, and is increased otherwise.

Here, the arithmetic coding method will be briefly described. The arithmetic coding scheme generally has better coding efficiency than the conventional run length coding scheme (MH, MR). The encoding method uses the corresponding interval on the number line [0, 1] ([0.0... 0, 0.1... 1] in binary decimal) as the occurrence probability of each symbol. Accordingly, the coordinates of the points included in the section obtained by dividing the unequal length, assigning the target symbol series to the corresponding partial section, and repeating the division recursively are set as at least other sections. It is expressed as a binary decimal number that can be distinguished and used as it is.
Taking the symbol sequence '0100' as an example, the concept of arithmetic coding will be described with reference to FIG. First, when the first symbol is encoded, the entire interval is divided into A (0) and A (1) according to the ratio of the occurrence probability of the symbols “0” and “1”, and the interval A (0) is generated by the occurrence of “0”. Selected.
Next, when the second symbol is encoded, A (0) is further divided by the occurrence probability ratio of both symbols in that state, and A (01) is selected as a section corresponding to the generated symbol sequence. Encoding proceeds by repeating such division and selection processing. On the other hand, in the decoding process, a process completely opposite to the encoding process 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 the number line at the time of encoding the symbol, and if the width of this 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.

According to the first and second aspects of the present invention, even if the input image is not of the assumed characteristics for the template using the surrounding pixel information, the aspect ratio is changed to obtain the assumed input characteristics. Since they can be close to each other, encoding can be performed without reducing encoding efficiency. At this time, since only a simple operation of changing the aspect ratio is required, the processing is not complicated.
A method of changing the aspect ratio, but when the input image is line-sequential pixels, as in the invention shown in claim 3, the change is made to increase the number of horizontal samples and decrease the number of vertical samples. Then, the aspect ratio can be easily changed without requiring a work area for rearranging data (see FIG. 6).
Further, as in the invention described in claim 4, the integer k closest to the ratio (n / m) of the resolution m (reference pixel distance) assumed by the surrounding pixel information determination means and the resolution n actually input. The aspect ratio is calculated from the expected resolution of the template and the resolution of the actual input image by multiplying the number of horizontal samples by k times the original size and the number of vertical samples by (1 / k) times. When changing, the number of samples in the horizontal direction is an integer multiple of the original number of samples, so no complicated processing is required and the distance between the reference pixels in the vertical direction is the same as the assumed pixel distance (design value) of the template. Can do. Since the template uses the correlation of surrounding pixels, it is particularly susceptible to resolution.
As illustrated in FIG. 7, for example, pixels at positions a and b in a 300 dpi image correspond to pixels at positions (a + b) / 2 and (c + d) / 2 in a 600 dpi image. Therefore, the meaning of the b position possessed by the original template is lost. However, if the invention of claim 4 is applied, this problem can also be solved.
An example of the code output by the encoding device according to the invention described in the claims will be described with reference to the block diagram of FIG. In the code output by the encoding apparatus of the present invention, the identification information with the changed aspect ratio is inserted into an area representing the attribute of the image. Thereby, since the aspect ratio changed on the decoding side can be recognized, accurate image reproduction can be guaranteed. In the example, the identification code is inserted in the attribute information of the image, but it may be in the code information.

FIG. 9 is a block diagram of an image information arithmetic decoding apparatus according to an embodiment of the present invention. The arithmetic decoding device for main image information stores the predicted pixel of the target pixel for each surrounding pixel information determined by the surrounding pixel information determining unit 901 and the surrounding pixel information determining unit 901 that extract the surrounding pixel state of the decoding target pixel. A prediction pixel storage unit 902 that outputs a prediction pixel corresponding to the surrounding pixel information is provided.
Also, the arithmetic decoding device for main image information stores the appearance probability of the predicted pixel for each piece of surrounding pixel information determined by the surrounding pixel information determination unit 901, and outputs the appearance probability of the predicted pixel corresponding to the surrounding pixel information. A prediction probability storage unit 903 and an arithmetic decoding unit 904 that performs arithmetic decoding based on the appearance probability of the prediction pixel and the prediction pixel value are provided.
Further, the arithmetic decoding apparatus for main image information changes and controls the prediction pixel stored in the prediction pixel storage unit 902 based on the result of the prediction pixel determined by the prediction pixel storage unit 902 and the decoded target pixel. Prediction pixel control means 905 for performing the prediction probability control means for changing and controlling the prediction probability stored in the prediction probability storage means 903 based on the result of the prediction pixel determined by the prediction pixel storage means 902 and the decoded target pixel 906 includes an aspect ratio changing unit 907 that changes the ratio between the horizontal direction and the vertical direction of the input image and outputs the image.
Next, the operation will be described. First, information on the target pixel position to be decoded is input to the surrounding pixel information determining unit 901, and surrounding pixel information on the target pixel position is created. When the surrounding pixel information is created, the prediction pixel value and the prediction appearance probability of the target pixel corresponding to the surrounding pixel information are subsequently derived from the prediction pixel storage unit 902 and the prediction probability storage unit 903, respectively. Using the determined predicted pixel value, predicted appearance probability, and input code information, decoding is performed by the arithmetic decoding means 904 to reproduce the image information.
After decoding the image information, if necessary, the prediction pixel control unit 905 and the prediction probability control unit 906 change the prediction pixel value and the prediction appearance probability, respectively. The changing method needs to be the same as that at the time of encoding, and examples thereof are as described in the first and second aspects of the invention. The decoded image is reproduced by the aspect ratio changing means 907 based on the information about the aspect ratio inserted in the code.
According to the present invention, even if the aspect ratio is arbitrarily changed on the encoding side, it is possible to change the aspect ratio of the image after decoding by determining it from the code, so that the image can be reproduced without error.

1 is a block diagram of a facsimile to which an image information arithmetic coding apparatus and an image information arithmetic decoding apparatus according to the present invention are applied. FIG. It is a basic block diagram of QM-Coder which is one of arithmetic coding methods. It is a block diagram of the arithmetic coding apparatus of the image information which concerns on embodiment of this invention. It is a figure which shows the creation example of surrounding pixel information. It is a figure which shows the concept of arithmetic coding. It is a figure which shows a mode that the aspect ratio of the image to input is changed. It is explanatory drawing regarding the pixel position of a and b in case resolutions differ. It is a figure which shows an example of the code | symbol to output. It is a block diagram of the arithmetic decoding apparatus of the image information which concerns on embodiment of this invention.

Explanation of symbols

301 Aspect ratio changing means 302 Surrounding pixel information determining means 303 Predicted pixel storage means 304 Predictive probability storage means 305 Arithmetic encoding means 306 Predictive pixel control means 307 Predictive probability control means

Claims (6)

An aspect ratio changing unit that changes a ratio between a horizontal direction and a vertical direction of an input image; a prediction pixel storage unit that stores a prediction pixel of a target pixel for each piece of surrounding pixel information and outputs a prediction pixel corresponding to the surrounding pixel information; A prediction probability storage means for storing a prediction pixel appearance probability for each surrounding pixel information and outputting a prediction pixel appearance probability corresponding to the surrounding pixel information; and an arithmetic operation based on the prediction pixel, the target pixel, and the prediction pixel appearance probability. And at least arithmetic encoding means for performing encoding,
Using the characteristics of the input image, the aspect ratio of the input image is changed by the aspect ratio changing unit, and the predicted pixel is predicted from the surrounding pixel information of the target pixel with respect to the changed image by the predicted pixel storage unit Determine the pixel, simultaneously determine the appearance probability of the prediction pixel by the prediction probability storage means, perform arithmetic encoding of the pixel of interest based on the appearance probability of the prediction pixel by the arithmetic encoding means, and store it if necessary An arithmetic coding apparatus for image information, wherein the prediction pixel and the prediction probability are changed. Aspect ratio changing means for changing the ratio between the horizontal direction and the vertical direction of the input image, surrounding pixel information determining means for extracting the surrounding pixel state of the target pixel in the image changed by the aspect ratio changing means, and the surrounding pixels Predicted pixel storage means for storing a predicted pixel of the target pixel for each surrounding pixel information determined by the information determining means, and outputting a predicted pixel corresponding to the surrounding pixel information, and surrounding pixels determined by the surrounding pixel information determining means Prediction probability storage means for storing prediction pixel appearance probabilities for each information and outputting prediction pixel appearance probabilities corresponding to surrounding pixel information; results of prediction pixels determined by the prediction pixel storage means and target pixels; A prediction pixel control unit that changes and controls a prediction pixel that is originally stored in the prediction pixel storage unit, and a prediction probability storage unit that is based on the result of the prediction pixel and the target pixel determined by the prediction pixel storage unit Based on the prediction probability control means for changing and controlling the stored prediction probability, the prediction pixel determined by the prediction pixel storage means, the target pixel, and the appearance probability of the prediction pixel determined by the prediction probability storage means Arithmetic coding means for performing arithmetic coding;
Using the characteristics of the input image, the aspect ratio of the input image is changed by the aspect ratio changing unit, and the predicted pixel is predicted from the surrounding pixel information of the target pixel with respect to the changed image by the predicted pixel storage unit A pixel is determined, the appearance probability of the prediction pixel is simultaneously determined by the prediction probability storage means, and the target pixel is arithmetically encoded based on the appearance probability of the prediction pixel by the arithmetic encoding means, and stored if necessary. An arithmetic coding apparatus for image information, wherein the prediction pixel and the prediction probability are changed.   3. The picture information arithmetic coding apparatus according to claim 1, wherein said aspect ratio changing means increases the number of horizontal samples and decreases the number of vertical samples.   4. The image information arithmetic coding apparatus according to claim 3, wherein the aspect ratio changing means is a ratio between a resolution m (distance between reference pixels) assumed by the surrounding pixel information determining means and a resolution n actually inputted ( n / m) is determined as an integer k, and the number of horizontal samples is set to k times the original size, and the number of vertical samples is set to (1 / k) times. .   5. The arithmetic coding apparatus for image information according to claim 1, wherein information relating to an aspect ratio is inserted into a generated code. The peripheral pixel information for extracting the peripheral pixel state of the pixel to be decoded in the arithmetic decoding device for image information for decoding an image generated by the image information arithmetic encoding device according to claim 1 and reproducing an image. Determining means; prediction pixel storage means for storing a prediction pixel of the target pixel for each surrounding pixel information determined by the surrounding pixel information determining means; and outputting a prediction pixel corresponding to surrounding pixel information; and the surrounding pixel information determination Prediction probability storage means for storing the appearance probability of the prediction pixel for each surrounding pixel information determined by the means, and outputting the appearance probability of the prediction pixel corresponding to the surrounding pixel information, based on the appearance probability and the prediction pixel of the prediction pixel A prediction pixel for performing change control on the prediction pixel stored in the prediction pixel storage unit based on the result of the arithmetic decoding unit that performs arithmetic decoding on the prediction pixel and the prediction pixel determined by the prediction pixel storage unit and the decoded target pixel And a prediction probability control means for changing and controlling the prediction probability stored in the prediction probability storage means based on the result of the prediction pixel determined by the prediction pixel determination means and the decoded target pixel. An aspect ratio changing means for changing the ratio between the horizontal direction and the vertical direction of the image and outputting the image,
At the same time as predicting the predicted pixel of the target pixel from the surrounding pixel information of the decoding target pixel, its appearance probability is obtained, and if the aspect ratio has been changed from the given code, the aspect ratio of the output image is changed. An arithmetic decoding apparatus for image information, which reproduces an image.

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