JP2002290743A - Image information encoding method, encoding device, digital copying machine, digital facsimile device, and digital filing device - Google Patents

Abstract

(57) [Summary] [Problem] To provide an image information encoding method and apparatus capable of setting a constant code amount after encoding and performing high-quality encoding. An encoding side creates prediction information by performing Markov separation of an information source on the basis of the situation of a pixel to be encoded and surrounding pixels by a prediction information creation circuit 401 for an input image data, The encoding circuit 402 performs encoding while dynamically evaluating the prediction information based on the above-described prediction information. In this encoding, two-dimensional wavelet transform is performed on the multi-valued image information, the obtained transform coefficients are divided into blocks of a certain arbitrary block, and the coefficient information obtained by blocking is encoded. The amount of coefficient information at the time of encoding is controlled based on the statistics of the amount of code created in block units to control the amount of code. On the decoding side, the same prediction information generation circuit 404 as at the time of encoding performs Markov separation according to the situation of the pixels that are already decoded and the surrounding pixels of the pixel to be decoded to generate prediction information of decoded data,
The arithmetic decoding circuit 403 performs decoding while dynamically evaluating the prediction information based on the prediction information.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an image information encoding method, an encoding device, a digital copying machine, a digital facsimile device, and a digital filing device, and more particularly to a digital copying machine, a facsimile device, a filing device, and the like. A preferred image information encoding method to use,
The present invention relates to an encoding device, a digital copying machine, a digital facsimile device, and a digital filing device each including the image information encoding device.

[0002]

2. Description of the Related Art ITU-T and ISO have been developed as encoding technologies for reversibly encoding multi-valued image (especially color image) information.
JPEG standardized by [ISO 10918-1, Com
pression and Coding of Continuous-tone Still Image
s (JPEG)] is known.

[0003] Also, as an encoding method used when encoding multi-valued image information, an encoding method called sub-band encoding or wavelet encoding is known. The sub-band coding scheme divides an input signal into a plurality of frequency bands, and improves the coding efficiency by using a bias in the amount of information for each band. Also,
In the wavelet coding method, in the sub-band coding, the lower band is recursively divided into two bands, and hierarchical sub-band coding is performed. To improve the coding efficiency. In the wavelet encoding method, image data has a pyramid structure because a reduced image over multiple layers is naturally generated at the time of decoding. As a result, progressive (gradual improvement in image quality) reproduction and display is possible. There is a feature that there is.

FIG. 6 is a diagram for explaining a wavelet encoding method according to the prior art. In the example shown in FIG. 6, a low pass filter and a high pass
Apply a filter and adjust the vertical band for the lower band.
Apply low pass filter and high pass filter,
The encoding is performed by performing a process of recursively dividing into two.

Conventional techniques relating to the wavelet coding method include, for example, JP-A-6-245077, JP-A-7-50836, and JP-A-6-3191.
No. 28, JP-A-4-343577, JP-A-6
A technique described in JP-A-113292 is known.

[0006]

In recent digital devices that handle image information, means for increasing the resolution, increasing the number of gradations, and the like are used to improve image quality. Digital equipment having such means can improve the image quality by increasing the amount of information contained in the image, but on the other hand, it must process a lot of information contained in the image, and the equipment configuration becomes large. This causes a problem. For example, in the case of increasing the number of gradations, if the image information, which has conventionally been a two-gradation (white or black) value, is converted into an image of 256 gradations in black and white, the information amount is increased eight times. The fact that the amount of information is increased eight times means that the storage capacity required for storing the image information is eight times as much as calculated simply, resulting in an increase in equipment cost.
Therefore, a method of encoding image information is usually applied to reduce storage capacity.

As one of the methods for solving the large data amount, a method of efficiently encoding a multi-tone image can be considered. As a typical encoding method for multi-tone images (including color images), JP is recommended as a standard by ISO and ITU-T.
The EG method is known. The JPEG format has the basic DCT
There is a method and a method using the optional DPCM. Former
The DCT method is an encoding method (referred to as an irreversible encoding method) that performs encoding by reducing a part of the information amount of an original image to the extent that image quality is not impaired by utilizing human visual characteristics. In this method, image information is converted to frequency information using conversion, and then information is encoded. The latter method using DPCM is an encoding method (called a lossless encoding method) that performs encoding without impairing the information amount of the original image, and predicts the level of a target pixel from the level of surrounding pixels. This is a method of encoding the prediction error.

When encoding is performed with an emphasis on image quality, it is preferable to use an efficient DCT method. However, in terms of information preservation, the DCT method is irreversible, so that the reversible DPT method is used.
It is better to use the CM method. Ideally, a reversible and highly efficient one is preferable.However, the current reversible method using DPCM has a problem that it is not possible to obtain such a large efficiency. The use of the JPEG-DCT method for compressing many multi-valued images has become mainstream. However, in the DCT method, when the compression ratio is increased, mosquito noise is generated at specific block distortion and contours, and the image quality is extremely deteriorated. It is a problem.

The coding of an image is roughly divided into a variable length and a fixed length from the code word length after coding. The features of variable-length coding are that the coding efficiency is higher than that of fixed-length coding and that reversibility is possible. The feature of fixed-length coding is that the position of the image before coding in the coding state Therefore, it is possible to reproduce only an arbitrary part of the image. From these characteristics, the variable-length coding is suitable for a device such as a facsimile, and the fixed-length coding is suitable for a device that involves image processing such as a copying machine.

Here, considering the fixed length coding method suitable for a copying machine or the like, the simplest method is to fix the code word length assigned to one pixel. For example, there is a method in which a 2-bit code word per pixel is made to correspond to a pixel having 8 bits per pixel. However, this method cannot reflect the partial characteristics of the image in the code. In other words, it is not possible to distinguish between visually important image regions and non-visually important image regions. Become. In order to improve the image quality, the number of bits assigned to one pixel must be increased, which causes a problem that encoding efficiency is deteriorated.

As described above, as one method for efficiently encoding a multi-tone image, a JPEG method using DCT is known.
If the compression ratio is increased, block distortion or mosquito noise at the contour may occur, which causes a problem in image quality. One method for solving this problem is to use a wavelet transform instead of DCT. Coding using wavelet transform is also called sub-band coding, which divides an input signal into a plurality of frequency bands and improves the compression ratio by using the bias for each band. The biggest feature of the wavelet transform is that it has higher image quality than DCT.

When image information is encoded to have a fixed length, an image is divided into regions each having a fixed size and the fixed length is set in units of divided regions, rather than averaging the amount of information for each pixel. Therefore, assigning an information amount by weighting the pixels in the area can reflect the importance of each pixel, and can improve the image quality. Furthermore, if it is possible to collect these fixed areas and distribute the amount of information therein, the image quality can be further improved.

A first object of the present invention is to divide the coefficient value after the wavelet transform into a certain area in order to make use of the above-mentioned feature of the wavelet, perform coding in units of the divided area, and perform coding after the coding. Image information that dynamically controls the amount of coefficients to be encoded so that the amount of code becomes a constant amount of code, thereby making the amount of code constant, and enabling high-quality encoding An object of the present invention is to provide an encoding method and an image information encoding device, and to provide a digital copying machine, a digital facsimile device, and a digital filing device using such an image information encoding device.

On the other hand, when a low pass filter is applied in the horizontal and vertical directions in the wavelet transform, a coefficient (LL coefficient) reflecting the density component of the entire image is created. Also, a low pass filter in the horizontal direction and hi in the vertical direction
When the gh pass filter is applied, a coefficient (LH coefficient) that reflects the density component in the horizontal direction of the image is created. Conversely, when the low pass filter is applied in the vertical direction and the high pass filter is applied in the horizontal direction, the density in the vertical direction is applied. Coefficient reflecting component (HL
Coefficient) is created. Further, when a high pass filter is applied in the horizontal direction and a high pass filter is also applied in the vertical direction, a coefficient (HH coefficient) that reflects an oblique density component that is not extracted in the above two cases is created. Among these created coefficients, the one considered most important is the LL coefficient reflecting the density component of the entire image, followed by the LH or HL coefficient, and finally the HH coefficient, and in this order is important.

Since the wavelet transform coefficients themselves have a hierarchical structure, the importance of the coefficients in each layer is also different. In general, information becomes more important as it goes down the hierarchy because information is aggregated.

A second object of the present invention is to configure the code amount control means so as to dynamically control the code amount in consideration of the subband and the hierarchy by utilizing the advantage of the wavelet transform described above. This provides an image information encoding method and an image information encoding device that have the advantage that the code amount is constant and that can perform high-quality encoding. An object of the present invention is to provide a digital copying machine, a digital facsimile apparatus, and a digital filing apparatus using the apparatus.

One method of encoding a multi-valued image is to treat the multi-valued image as bit plane information of a binary image and perform encoding for each bit plane. The advantages of this method are that a binary image coding method (MH, MR, MMR) as used in facsimile coding can be used, and the code amount can be easily controlled in bit plane units. That is, since the encoding is performed from the most significant bit, by encoding a lower bit plane, the accuracy of the coefficient to be encoded can be improved. In particular, it can be said that the last merit is great in controlling the image quality.

A third object of the present invention is to make use of the above-mentioned advantage of the method of performing encoding for each bit plane so that the encoding means encodes the coefficients from the most significant bit using bit plane encoding. And the code amount control means is configured to dynamically control the number of bit planes to be encoded,
Accordingly, an image information encoding method and an image information encoding device having an advantage that a code amount is constant and capable of encoding with high image quality are provided. An object of the present invention is to provide a digital copying machine, a digital facsimile apparatus, and a digital filing apparatus used.

Further, contrary to the method of controlling the code amount by dynamically controlling the coding, the user may want to control the code amount by himself.

According to a fourth object of the present invention, in order to satisfy the above-mentioned requirement, the code amount control means controls the coding by the block coding means based on the code amount control information specified from the outside. The present invention provides an image information encoding method and an image information encoding device which enable a user to control the code amount by himself / herself, and a digital signal using such an image information encoding device. A copying machine, a digital facsimile apparatus, and a digital filing apparatus are provided.

[0021]

According to the present invention, the above-mentioned first method is provided.
An object of the present invention is to provide an image information encoding method for encoding image information, performing a two-dimensional wavelet transform on input multi-valued image information, and converting a transform coefficient obtained by the wavelet transform into an arbitrary block. Performs block division into units, performs encoding of blocked coefficient information, and controls the amount of coefficient information at the time of encoding the coefficient information based on the statistics of the code amount created in block units to reduce the amount of code. Achieved by controlling.

A first object of the present invention is to provide an image information encoding apparatus for encoding image information, which performs two-dimensional wavelet transform on input multi-valued image information.
-Dimensional wavelet transform means, coefficient blocking means for dividing the transform coefficients obtained by the wavelet transform means into arbitrary blocks, and block coding means for coding the blocked coefficient information And code amount control means for controlling the amount of coefficient information when the coefficient information is encoded by the block encoding means, and controlling the code amount, wherein the code amount control means By controlling the amount of coefficient information at the time of encoding the coefficient information based on the statistics of the code amount, and by using such an image information encoding device, This is achieved by configuring a copier, a digital facsimile machine, and a digital filing machine.

Further, the second object is that in the above-described image information encoding method, the code amount is controlled in consideration of a subband and a layer. Since the code amount control means controls the code amount in consideration of the subband and the hierarchy, a digital copying machine, a digital facsimile apparatus , And a digital filing device.

Further, the third object is that, in the above-described image information encoding method, the encoding of the blocked coefficient information is bit plane encoding for encoding coefficients from the most significant bit, and The control of the code amount is performed by controlling the number of bit planes to be coded, and in the above-described image information coding apparatus, the block coding unit codes the coefficient from the most significant bit. To perform bit plane encoding,
Further, since the code amount control means controls the number of bit planes to be coded, further, using such an image information coding device, a digital copying machine, a digital facsimile device, and This is achieved by configuring a digital filing device.

A fourth object of the present invention is to provide the image information encoding method, wherein the control of the code amount is performed based on code amount control information specified in advance from outside. In the information coding device, the code amount control means controls the code amount based on code amount control information specified in advance from the outside, so that such an image information coding device is further used. Digital copiers, digital facsimile machines,
It is achieved by configuring a digital filing device.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of an image information encoding apparatus, an image processing apparatus and a multifunction apparatus according to the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram showing a configuration of a facsimile to which an image information encoding apparatus according to an embodiment of the present invention is applied. First, a facsimile will be described as an example when the encoding apparatus according to the present invention is specifically implemented. explain. In FIG. 1, reference numeral 101 denotes an image reading unit;
Is an image processing unit, 103 is an encoding unit, 104 is a decoding unit,
Reference numeral 106 denotes an image output unit.

In FIG. 1, first, the transmitting side reads a document using a CCD image sensor or the like in an image reading unit 101, performs processing for converting transmission data into appropriate data in a subsequent image processing unit 102, Next, the encoding unit 103 transmits the encoded code to the transmission path. On the other hand, on the receiving side, in order to reproduce an image, the received encoded data is decoded by the decoding unit 104, the image processing unit 105 performs image processing suitable for the output device, and outputs the image data from the image output unit 106 such as a plotter. Make a hard copy. Note that the image processing units 102 and 105
Examples of the processing performed in (2) include processing such as resolution conversion and size conversion for a binary image, and processing for color (color component) conversion, resolution conversion, and size conversion for a multivalued image including color. Processing.

As an example of the encoding method used in the encoding unit 103 and the decoding unit 104, in the case of a binary image, MH and M used in a conventional facsimile are used.
There are the R, MMR and JBIG methods, and the JPEG method is used for multi-valued images.

Next, a brief description will be given of the JPEG / Spatial system which has already been standardized and capable of reversibly encoding a multi-tone image. The basics of JPEG are DCT (D
Although the DCT method uses an iscrete cosine transform, the DCT method is an irreversible coding method.
al PCM) for JPEG / Spatial.

FIG. 2 is a block diagram showing a basic configuration of the JPEG / Spatial system. FIG. 3 is a diagram showing a prediction operation formula in the predictor shown in FIG. 2, a target pixel (y) to be coded at present, and three surrounding pixels used for prediction. FIG. 3 is a diagram for explaining the positional relationship of (a, b, c), and these will be described below. In FIG. 2, 201 is a predictor, and 202 is an entropy encoder.

The bit precision of the image information input to the predictor 201 shown in FIG. 2 can take any number of bits from 2 bits to 16 bits. 2, a prediction error signal obtained by a predictor 201 is entropy-encoded by an entropy encoder 202, and compressed data is output. The prediction calculation formula used in the predictor 201 is a calculation formula for predicting the level of the target pixel (y) to be currently coded from the levels of three surrounding pixels (a, b, c) used for prediction. Can be used. These prediction calculation expressions can be selected. Then, the predictor 201 obtains a prediction error value by subtracting the predicted value from the actual level of the pixel of interest (y).

Huffman coding or arithmetic coding can be used for entropy coding of the prediction error.

In Huffman coding, prediction errors are first grouped according to Table 1, and the grouping results in a group number SSSS and an additional bit indicating the prediction error value in the group (the number of bits is the same as the value indicated by SSSS). Divided into
The SSSS is encoded using a one-dimensional Huffman code table, and an additional bit is added after each Huffman code.

[0035]

[Table 1]

On the other hand, in the arithmetic coding, after a prediction error is binarized, the arithmetic coding is performed using a statistical model. The binarization procedure is performed as follows. (1) Judgment of zero “0” when the prediction error is zero, and “1” when it is not zero
Is output. (2) Sign (positive / negative sign) determination Outputs “0” when the prediction error is positive, and outputs “1” when the prediction error is not positive. (3) Group number Sz is defined as the value obtained by subtracting 1 from the absolute value of the prediction error. It is determined whether Sz belongs to the group n (n = 0 to 15). This determination is performed in ascending order of group number, and is performed until a group to which Sz belongs is found. At this time, if Sz does not belong to group n, “1”
And outputs “0” if it belongs to group n
(See Table 2). (4) Additional bits The additional bits used for identifying the coefficients in the group are output as they are.

[0037]

[Table 2]

After the prediction error is binarized by the above-described means, Table 3
The encoding is performed by dividing the state as shown in FIG. In Table 3,
The reason of 5 × 5 is that the prediction error between the pixel immediately above and the pixel immediately to the left is divided into five types according to the magnitude and the sign.

[0039]

[Table 3]

FIG. 4 is a block diagram showing a circuit configuration of the arithmetic coding system. 4, reference numeral 401 denotes a prediction information creation circuit, 402 denotes an arithmetic coding circuit, 403 denotes an arithmetic decoding circuit, and 404 denotes a prediction information creation circuit. Next, the arithmetic coding circuit will be described with reference to FIG. I do.

In the circuit of the arithmetic coding system shown in FIG. 4, the coding side converts the input image data into a prediction information generation circuit (sometimes called a template) 401.
Based on the situation of the pixel to be coded and surrounding pixels, prediction information is generated by performing Markov separation of the information source, and the arithmetic coding circuit 402 dynamically evaluates the prediction information based on the prediction information described above. Encoding. On the other hand, the decoding side performs Markov separation of the information source according to the situation with the pixels surrounding the pixel to be decoded by the pixels already decoded by the same prediction information creation circuit 404 as the encoding when the input code data is encoded. To create prediction information for the data to be decrypted,
The arithmetic decoding circuit 403 performs decoding while dynamically evaluating the prediction information based on the prediction information.

The arithmetic coding method generally has higher coding efficiency than the conventional run-length coding method (MH, MR). In the encoding method, a corresponding section (in binary decimal, [0.0... 0, 0.1... 1]) on the number line of (0, 1) is not changed according to the occurrence probability of each symbol. Divide into equal lengths,
The coordinates of the points included in the section obtained by allocating the target symbol sequence to the corresponding partial section and repeating the division recursively are represented by at least a binary decimal number that can be distinguished from other sections. In this method, the result is used as a code.

FIG. 5 is a diagram for explaining the concept of arithmetic coding. Next, the concept of arithmetic coding will be described using the symbol sequence "0100" as an example.

First, at the time of encoding the first symbol, the entire section is divided into sections A (0) and A (1) according to the symbol occurrence probability ratio of "0" and "1". , The section A (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 (01) is selected as a section corresponding to the generated symbol sequence. In the arithmetic coding, the coding proceeds by repeating the processing of the division and the selection. On the other hand, at the time of decoding, processing completely opposite to encoding is performed, and symbols are reproduced based on the binary decimal number indicated by the code. What is important here is the width of the number line when encoding the 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's what it means. Generally, the width of this number line is set to 1 on the encoding side and the decoding side.

The JPEG / Spatial method described above is mainly applied to a multi-valued image, and the arithmetic coding method is mainly applied to a binary image.

FIG. 7 is a block diagram showing the configuration of an image information encoding apparatus according to an embodiment of the present invention, FIG. 8 is a diagram for explaining an example of wavelet transform, and FIG. 9 is a block showing the configuration of code amount control means. FIG. 9 is a diagram illustrating an encoding device according to an embodiment of the present invention, with reference to FIGS. 7 to 9.
7 and 9, 701 is a two-dimensional wavelet transform unit, 702 is a coefficient blocking unit, 703 is a block coding unit, 704 is a code amount control unit, 901 is a subband control unit, and 902 is a hierarchy control unit. .

An image information encoding apparatus according to one embodiment of the present invention includes a two-dimensional wavelet transform unit 701 for performing two-dimensional wavelet transform on input multi-valued image information, and a signal obtained by the wavelet transform unit 701. A coefficient blocking unit 702 that divides the obtained transform coefficients into arbitrary blocks, and a block coding unit 703 that codes the blocked coefficient information.
And code amount control means 704 for controlling the amount of coefficients to be encoded by the encoding means 703 to dynamically control the code amount.

The operation will be briefly described. First, image information input for encoding is input to a two-dimensional wavelet transform unit 701, where a two-dimensional wavelet transform process is performed to convert the image information into coefficients. Conversion is performed. There are various methods of the two-dimensional wavelet transform. As an example, a method of creating a two-dimensional coefficient by performing a wavelet transform as shown in FIG. In general, a two-dimensional coefficient is created by performing a one-dimensional wavelet transform in the horizontal and vertical directions, and the example shown in FIG. 8 is basically the same. The above transformation is
This is a transformation that recursively transforms the lower band (LL component) described with reference to FIG. 6 to achieve a hierarchical structure of coefficients. The coefficients created by the wavelet transform unit 701 are input to the coefficient blocking unit 702, and a coefficient block serving as an encoding processing unit is configured.
There are various types of blocking as well as the wavelet transform, but it is generally a rectangular block that is easy to handle. The coefficients blocked by the coefficient blocking unit 702 are input to the block coding unit 703, and the coefficients are coded. For the encoding performed here, for example, a predictive encoding such as the JPEG / Spatial scheme described above, an arithmetic encoding scheme, or the like can be used. The block coding means 703 is subjected to recursive control by the code amount control means at the subsequent stage. The code created by the block encoding unit 703 is immediately input to the code amount control unit 704,
The code amount is controlled. As a method of controlling the code amount,
The code amount of each block created by the block coding unit 703 is statistically performed. If the code amount is larger than the desired code amount, the amount of coefficients to be coded by the encoder is reduced. If the number is smaller, it is possible to use a method of dynamically controlling the encoding by the block encoding unit 703, such as increasing the amount of coefficients to be encoded by the encoder.

The embodiment of the present invention described above is characterized in that coding is performed while dynamically controlling the amount of coefficients to be coded so that the coded amount becomes constant. This makes it possible to perform high-quality encoding while having the advantage that the code amount is constant.

The code amount control means 704 includes a frequency sub-band control section 901 and a hierarchical control section 902, as shown in FIG. Is controlled. That is, the code amount control means 704 uses the fact that the importance of the transform coefficient is generally LL coefficient> LH or HL coefficient> HH coefficient, and the information is aggregated in the lower hierarchy from the higher hierarchy. Therefore, the code amount is controlled taking advantage of the increasing importance. The above-described embodiment of the present invention has the advantage that the code amount can be made constant by providing the code amount control means as described above, and also enables high-quality encoding.

In the above-described embodiment of the present invention, the block coding means 703 can be configured by using a bit plane coding method for performing coding from the most significant bit of the coefficient. The amount control means 704
It can be configured to control the number of bitplanes to be coded. As an example of the bit plane coding, there is the arithmetic coding method described above, and highly efficient coding can be performed. The merit of using this bit plane is that the most significant bit is more important in information. Therefore, by coding from the most significant bit, even if the coding is interrupted in the middle, the part that is more important in information becomes more important. The point is that the precision of the coefficients is not significantly reduced because they are encoded first. Therefore, even when the block encoding unit 703 and the code amount control unit are configured as described above, it is possible to obtain the advantage that the code amount can be made constant and to perform high-quality encoding. Becomes possible.

FIG. 10 is a block diagram showing another configuration example of the image information encoding apparatus according to the embodiment of the present invention, and the reference numerals in FIG. 10 are the same as those in FIG.

In the coding apparatus shown in FIG. 10, the code amount control means 704 in the coding apparatus described with reference to FIG. 7 controls the block coding means 703 based on information for controlling the code amount input from the outside. It is something to do. The information for controlling the code amount may be, for example, information on the number of bit planes specified in advance when coding is bit plane coding. The code amount control unit 704 controls the number of bit planes to be encoded based on the number of bit planes specified from the outside. According to the coding apparatus as described above, the user can freely control the code amount by himself / herself, contrary to the method of controlling the code amount by dynamically controlling the coding.

[0054]

According to the first and fifth aspects of the present invention, in an image information encoding method and an image encoding apparatus for encoding image information, a two-dimensional wavelet is applied to input multi-valued image information. Performing a transform, performing a block division of the transform coefficient obtained by the wavelet transform into a certain arbitrary block unit, performing encoding of the blocked coefficient information, and calculating the amount of the coefficient information at the time of encoding the coefficient information, Since the code amount is controlled based on the statistics of the code amount created in block units, it is possible to obtain an effect that the code amount after encoding can be a constant code amount, and
The effect that high-quality encoding can be performed can be obtained.

According to the second and sixth aspects of the present invention, in the image information encoding method and the encoding apparatus according to the first and fifth aspects, the control of the code amount is performed in consideration of the subband and the hierarchy. Therefore, in the same manner as in the first and fifth aspects of the present invention, it is possible to obtain an effect that the code amount after encoding can be set to a constant code amount, and high image quality can be obtained. The effect that coding can be performed can be obtained.

According to the third and seventh aspects of the present invention, in the image information encoding method according to the first and second aspects, and in the encoding apparatus according to the fifth and sixth aspects, the coefficient divided into blocks is The information encoding is bit plane encoding for encoding coefficients from the most significant bit, and the control of the code amount is performed by controlling the number of bit planes to be encoded. As in the inventions described in the first and fifth aspects, it is possible to obtain an effect that the code amount after encoding can be made constant, and it is possible to perform high-quality encoding. The effect can be obtained.

According to the fourth and eighth aspects of the present invention, in the image information encoding method according to the first to third aspects and the encoding apparatus according to the fifth to seventh aspects, the control of the code amount is performed. ,
Since the control is performed based on the code amount control information specified in advance from the outside, when the user wants to control the code amount by himself, it is possible to obtain the effect that the user can control the code amount by himself. Can be.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a facsimile to which an image information encoding device according to an embodiment of the present invention is applied.

FIG. 2 is a block diagram showing a basic configuration of a JPEG / Spatial system.

FIG. 3 is a diagram for explaining a prediction operation formula in the predictor shown in FIG. 2, a current pixel of interest (y) to be encoded, and a positional relationship between three surrounding pixels (a, b, c) used for prediction. .

FIG. 4 is a block diagram showing a circuit configuration of an arithmetic coding system.

FIG. 5 is a diagram illustrating the concept of arithmetic coding.

FIG. 6 is a diagram illustrating a wavelet encoding method according to the related art.

FIG. 7 is a block diagram illustrating a configuration of an image information encoding device according to an embodiment of the present invention.

FIG. 8 is a diagram illustrating an example of a wavelet transform.

FIG. 9 is a block diagram illustrating a configuration of a code amount control unit.

FIG. 10 is a block diagram illustrating another configuration example of the image information encoding device according to the embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 101 Image reading unit 102, 105 Image processing unit 103 Encoding unit 104 Decoding unit 106 Image output unit 201 Predictor 202 Entropy encoder 401 Prediction information creation circuit 402 Arithmetic encoding circuit 403 Arithmetic decoding circuit 404 Prediction information creation circuit 701 Two-dimensional wavelet transform means 702 coefficient blocking means 703 block coding means 704 code amount control means 901 subband control section 902 hierarchical control section

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5C059 KK22 MA00 MA24 MA35 MA41 MA45 MC38 ME02 ME11 PP01 PP14 RE07 TA60 TA74 TB17 TC18 TC36 TD06 UA02 UA05 5C078 AA04 BA44 BA53 BA64 CA01 DA01 DB04 DB19 5J064 AA01 BA04 BA10 BA06 BB03

Claims (20)

[Claims] In an image information encoding method for encoding image information, a two-dimensional wavelet transform is performed on input multi-valued image information, and a transform coefficient obtained by the wavelet transform is converted into an arbitrary coefficient. Performs block division into block units, encodes block-wise coefficient information, and controls the amount of coefficient information when encoding the coefficient information based on the statistics of the code amount created in block units. Controlling the image information. 2. The image information encoding method according to claim 1, wherein the control of the code amount is performed in consideration of a subband and a hierarchy. 3. The coding of the blocked coefficient information is bit plane coding for coding coefficients from the most significant bit, and the control of the code amount controls the number of bit planes to be coded. 3. The image information encoding method according to claim 1, wherein the image information encoding method is performed. 4. The image information coding method according to claim 1, wherein the control of the code amount is performed based on code amount control information specified in advance from outside. 5. An image information encoding apparatus for encoding image information, comprising: two-dimensional wavelet transform means for performing two-dimensional wavelet transform on input multi-valued image information; Coefficient blocking means for dividing the transformed coefficients into blocks of a given arbitrary block unit, block coding means for coding the blocked coefficient information, and coding of the coefficient information by the block coding means Control the amount of coefficient information at the time, code amount control means for controlling the code amount, the code amount control means performs the statistics of the code amount created in block units, the coefficient at the time of encoding the coefficient information The amount of information
An image information encoding apparatus, wherein the code amount is controlled based on the statistics of the code amount. 6. The image information encoding apparatus according to claim 5, wherein said code amount control means controls the code amount in consideration of a subband and a hierarchy. 7. The block encoding means performs bit plane encoding for encoding coefficients from the most significant bit, and the code amount control means controls the number of bit planes to be encoded. 7. The image information encoding apparatus according to claim 5, wherein 8. The image information according to claim 5, wherein said code amount control means controls the code amount based on code amount control information designated in advance from outside. Encoding device. 9. A digital copying machine comprising an image information encoding device for encoding image information, wherein the image information encoding device converts the input multi-valued image information into a two-dimensional wavelet. A two-dimensional wavelet transform unit for performing a transform, a coefficient blocking unit for dividing the transform coefficient obtained by the wavelet transform unit into a certain arbitrary block unit, and performing encoding on the blocked coefficient information Block encoding means, comprising a code amount control means for controlling the amount of coefficient information at the time of encoding the coefficient information by the block encoding means, to control the code amount, the code amount control means, Performing statistics of the code amount created in block units, the amount of coefficient information at the time of encoding of the coefficient information, controlling the code amount based on the statistics of the code amount, Digital copier. 10. The digital copying machine according to claim 9, wherein said code amount control means controls the code amount in consideration of a subband and a hierarchy. 11. The block encoding means performs bit plane encoding for encoding coefficients from the most significant bit, and the code amount control means controls the number of bit planes to be encoded. 11. The digital copying machine according to claim 9, wherein: 12. The code amount control means controls the code amount based on code amount control information specified in advance from outside.
2. The digital copying machine according to 1. 13. A digital facsimile apparatus comprising an image information encoding device for encoding image information, wherein the image information encoding device converts the input multi-valued image information into a two-dimensional wavelet. Convert 2
-Dimensional wavelet transform means, coefficient blocking means for dividing the transform coefficients obtained by the wavelet transform means into arbitrary blocks, and block coding means for coding the blocked coefficient information And code amount control means for controlling the amount of coefficient information when the coefficient information is encoded by the block encoding means, and controlling the code amount. The code amount control means is created in units of blocks. A digital facsimile apparatus, wherein statistics of the calculated code amount are performed, and the amount of coefficient information at the time of encoding of the coefficient information is controlled based on the code amount statistics. 14. The digital facsimile apparatus according to claim 13, wherein said code amount control means controls a code amount in consideration of a subband and a hierarchy. 15. The block coding means performs bit plane coding for coding coefficients from the most significant bit, and the code amount control means controls the number of bit planes to be coded. 15. The digital facsimile apparatus according to claim 13, wherein 16. A digital facsimile apparatus according to claim 13, wherein said code amount control means controls the code amount based on code amount control information specified in advance from outside. apparatus. 17. A digital filing apparatus comprising an image information encoding device for encoding image information, wherein the image information encoding device performs two-dimensional wavelet conversion on input multi-valued image information. Convert 2
-Dimensional wavelet transform means, coefficient blocking means for dividing the transform coefficients obtained by the wavelet transform means into arbitrary blocks, and block coding means for coding the blocked coefficient information And code amount control means for controlling the amount of coefficient information when the coefficient information is encoded by the block encoding means, and controlling the code amount. The code amount control means is created in units of blocks. A digital filing apparatus for performing statistics on the amount of code obtained, and controlling the amount of coefficient information at the time of encoding the coefficient information based on the statistics of the amount of code. 18. The digital filing apparatus according to claim 17, wherein said code amount control means controls the code amount in consideration of a sub-band and a hierarchy. 19. The block encoding means performs bit plane encoding for encoding coefficients from the most significant bit, and the code amount control means controls the number of bit planes to be encoded. 19. The digital filing apparatus according to claim 17, wherein: 20. The digital filing device according to claim 17, wherein said code amount control means controls the code amount based on code amount control information specified in advance from outside. apparatus.