JP3065393B2 - Image data restoration method and image data restoration device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image data restoring method and an image data restoring apparatus for restoring an original multi-valued image from code data obtained by performing variable length coding on information representing a multi-valued image for each of a plurality of layers. It is about.

2. Description of the Related Art An adaptive discrete cosine transform coding method using a two-dimensional orthogonal transform as a coding method for compressing a data amount of a multi-valued image such as a halftone image or a color image without deteriorating its characteristics.
m, hereinafter referred to as the ADCT method) is widely used.

In the ADCT method, a multi-valued image is divided into blocks each having a predetermined number of pixels (for example, 8 × 8 pixels), and the image is orthogonally transformed for each block to obtain a transform coefficient (hereinafter referred to as a DCT coefficient). )
The data amount is compressed by quantizing each component of the matrix using a corresponding visual adaptation threshold (described later) and then performing variable length coding.

A method of sequentially restoring a multi-valued image of each block based on code data obtained by performing variable length coding on information on all components of DCT coefficients of each block is called a successive restoration method. I have. This sequential restoration method is used when outputting a multi-valued image to a printer or the like.

On the other hand, when using an image database via a communication line, rather than providing detailed images sequentially for each block as described above, first, a rough image is provided promptly. It is convenient to provide detailed images sequentially.

For this reason, the DCT coefficient component of each block is divided into a plurality of layers, and the components corresponding to each layer are subjected to variable-length coding, thereby shortening the data length of the code data of each layer. Hierarchical restoration methods for hierarchically restoring detailed images sequentially from rough images based on hierarchical code data have been proposed.

[0007]

2. Description of the Related Art FIG. 14 shows a configuration of an image data compression apparatus to which a conventional ADCT method is applied. Also, in FIG.
An example of a block obtained by dividing a multi-valued image will be described.

A multi-valued image read by an image reading device or the like is sequentially input to the DCT converter 611 for each block described above, and the DCT converter 611 performs a two-dimensional discrete cosine transform (hereinafter referred to as DCT transform). Through the processing, the matrix is converted into an 8 × 8 matrix (hereinafter, referred to as DCT coefficient D) including DCT coefficients corresponding to the spatial frequency components. FIG. 16 shows an example of the DCT coefficient D.

Each component of the DCT coefficient D is quantized by the linear quantization section 620 using a component corresponding to the quantization threshold Q _TH . The above-described quantization threshold Q _TH is
It is obtained from the visual adaptation threshold value corresponding to each spatial frequency and the quantization control parameter SF. The visual adaptation threshold is predetermined based on an experimental result regarding the sensitivity of the visual sense to each spatial frequency component, and is given as a quantization matrix V _TH (see FIG. 17). Further, the quantization control parameter SF is a coefficient that determines the quantization accuracy of the image, and according to the image quality required for the restored image,
The setting is performed by an operator prior to the encoding process of the image data for one screen.

Here, the value of each component of the above-described quantization matrix V _TH is determined by the absolute value of the component corresponding to the low spatial frequency as shown in FIG. On the contrary, the absolute value of the component corresponding to the high spatial frequency is set to be large. For this reason, the quantization coefficient D _QU obtained by quantizing the DCT coefficient D by the linear quantization unit 620 is, as shown in FIG. 18, a component at the upper left corner of the matrix indicating the DC component (hereinafter, referred to as DC component).
And only a very small number of AC components indicating low spatial frequency components around this DC component are effective coefficients having a value other than zero, and most AC components are often invalid coefficients having a value of zero. .

When the thus obtained quantized coefficient D _QU is encoded for sequential restoration, first, it is scanned using a scanning order called zigza scan shown in FIG. I do. Next, this one-dimensional array is encoded by the encoding unit 6.
31 converts the combination into a combination of an effective coefficient (index) and a continuous length (run) of an invalid coefficient that is continuous before the index, and converts each combination into a code corresponding to the appearance frequency based on the code table 632. Variable length coding is performed by replacing each of them. Here, in the above-mentioned code table 632, a short code is stored corresponding to a combination having a high appearance frequency, and a long code is stored corresponding to a combination having a low appearance frequency. Therefore, by performing the variable-length encoding as described above, the data amount of the encoded data can be significantly reduced.

The code data thus obtained is restored to image data by the image data restoration device shown in FIG. Decoding unit 711 of image data restoration device
Is provided with a decoding table 712 indicating a combination of a run and an index corresponding to a code, which is opposite to the above-described code table 632, and decodes sequentially input codes to obtain a combination of an index and a run. And input to the inverse quantization unit 720.

The inverse quantization section 720 restores the quantization coefficient D _QU of each block from the combination of the input index and run, and _applies the above-described quantization threshold Q _TH to each component of the quantization coefficient D _QU. Are inversely quantized by multiplying by the corresponding components of .times. The DCT coefficient D obtained in this manner is converted into an inverse DCT
However, the image data of the corresponding block is restored by performing the inverse DCT transform processing.

As described above, the decoding process, the inverse quantization process, and the inverse DCT transform process are repeated for each block, and an image containing all the information of the DCT coefficients D of each block is sequentially restored, and one block is restored. Is referred to as a sequential restoration method. Further, an image data restoring device that restores image data by this successive restoration method is referred to as a successive restoration device.

On the other hand, when encoding the quantized coefficient D _QU ,
Groups corresponding to each component of the quantized coefficients D _QU into a plurality of layers, by encoding each this group the quantization coefficient D _QU of each block hierarchical coded data is obtained.

For example, as shown in FIG. 21, the quantization coefficient D _QU of each block may be divided into four groups, and each group may be associated with four layers. In FIG.
Components corresponding to the first to third layers are denoted by reference numerals indicating the numbers of the corresponding layers. However, FIG.
In 1, all components without reference numerals are components corresponding to the fourth hierarchy.

In this case, first, only the DC component is extracted from the quantized coefficient D _QU of each block, and the quantized coefficient D _QU is reconstructed assuming that all other AC components are invalid coefficients. The quantized coefficient D _QU of each block is encoded and transmitted as first layer code data. Next, the primary AC component, the secondary AC component, and all the tertiary and subsequent AC components may be encoded in the same manner and transmitted as code data of each layer. Such a method of grouping the components of the quantization coefficient D _QU according to the spatial frequency is called a spectral selection method.

As a method of restoring image data from the code data for hierarchical restoration obtained as described above, a DCT coefficient D of each layer obtained from the code data of each layer is sequentially added, and up to each layer. Including information on spatial frequency components belonging to groups corresponding to all layers of
There is a method in which a coefficient D is obtained, and the DCT coefficient D is subjected to inverse DCT transform to restore image data.

In this case, DCT coefficients D for all blocks
, The image data restoring apparatus is configured to include a DCT coefficient D of each layer and a corresponding DC in the buffer.
The DCT coefficient D including the information of all the layers up to the layer is obtained by adding the T coefficient D, and the DCT coefficient D may be stored in the above-described buffer and transmitted to the inverse DCT transform unit.

Thus, in response to the input of the coded data hierarchized using the above-described spectral selection method, first, a rough image in which each block is represented only by a DC component is promptly restored, and a high spatial image is sequentially obtained. Images containing frequency components can be restored hierarchically.

Further, D obtained from the code data of each layer
The CT coefficient D is directly subjected to inverse DCT transform to restore a difference image including only the spatial frequency components belonging to the group corresponding to the layer, and the difference image is cumulatively added for each layer to restore the image hierarchically. There are techniques. The present applicant has filed an application for this technique in Japanese Patent Application No. 3-27332, entitled "Image Data Restoring Apparatus".

In this case, an image data restoring device is provided with a buffer for storing image data of all blocks, and a difference image obtained from code data of each layer and an image of a corresponding block in the buffer are added. Then, the result of this addition may be stored in the above-described buffer and output as a restored image at that level.

As a result, a multi-valued image can be hierarchically restored, similarly to the case where the DCT coefficient D is cumulatively added for each layer. By the way, in the image database, code data for hierarchical restoration as described above is often stored in consideration of the convenience of the user of the database via the communication line. However, since the information on the image of each block is divided into a plurality of hierarchies, the multi-level image cannot be obtained by directly inputting the information on the image of each block into a plurality of hierarchies.

As a technique for resolving such inconvenience and making the image data restoration apparatus for successive restoration possible to use the image database, the applicant of the present invention has disclosed Japanese Patent Application No. 1-1957.
No. 53, "Image data encoding method and code data reading processing method".

In this technique, on the database side, code data for sequential restoration is created from code data for hierarchical restoration and transmitted. Specifically, at the time of the encoding process, the data length of the code data of each layer is obtained, and a header portion including information on the data length is added to the head of the code data and stored in the code data storage means. , When sending,
Based on the information in the header section, the code of each block is extracted from the code data of each layer, and the code data of each block including information on all spatial frequencies is reconstructed.

Thus, the database can transmit the code data suitable for the function of the destination image data restoring device, and the image data stored in the image database can be transmitted by using the successively restoring image data restoring device. Can be restored.

However, the technique described in Japanese Patent Application No. 1-195753 is a technique for enabling an image data restoring device for successive restoration to use an image database storing hierarchized code data. However, it does not make it possible to hierarchically restore images using an image data restoration device for sequential restoration.

[0028]

Therefore, conventionally, in order to restore an image hierarchically by using an image database in which code data for hierarchical restoration is stored, a DCT coefficient D is required.
Alternatively, an expensive image data restoration device having a function of cumulatively adding image data is required.

On the other hand, as a method of performing hierarchical restoration using an image data restoration device for successive restoration, there is a method described in "Transactions of the Institute of Electronics, Information and Communication Engineers Autumn National Convention 1988 D-72". This method decodes the code data for sequential restoration, _obtains and holds the quantized coefficients D _QU for all blocks, and extracts components corresponding to each layer from the quantized coefficients D _QU of each block. The quantization coefficient D _QU is reconstructed, and the reconstructed quantization coefficient D _QU is encoded again.

For example, first, the quantization coefficient D of each block is
Extracting only the DC component _QU, all other AC components to reconstruct the quantization coefficient D _QU as invalid coefficients, the quantization coefficient D _QU of each block reconstructed by coding, first
It is sent to the above-described image data restoration device as hierarchical code data. Next, the above-described first group and two primary AC components adjacent to the DC component are extracted, and the quantization coefficient D _QU is reconstructed and encoded in the same manner as the second-layer code data. Send out. Similarly, the quantized coefficient D _QU reconstructed by using each of the components up to the three secondary AC components is encoded and transmitted as code data of the third hierarchy.
The quantization coefficient D _{QU including} all the components of the third and subsequent orders is encoded and transmitted as code data of the fourth hierarchy. That is, as the code data of each layer, a code including information on the spatial frequency components included in the group corresponding to the layer and the groups corresponding to all the layers up to that layer is transmitted.

The code data of each layer obtained in this way is decoded, inversely quantized, and inversely DCT-transformed in the same manner as in the prior art. Can be restored.

However, in this technique, code data for successive restoration is required as input code data. Therefore, when using an image database storing hierarchical code data, On the image database side, it is necessary to convert the data into code data for sequential restoration by the technique of Japanese Patent Application No. 1-195753.

Further, since a large-capacity buffer for storing the quantized coefficients D _QU for all blocks is required, the circuit scale of the image data restoration device increases. On the other hand, on the image database side, it is necessary to unify the format of the stored code data, and the format of the stored code data is hierarchized in consideration of the convenience of use through a communication line. .

Along with this, a technique has been proposed which enables an image data restoration apparatus for sequential restoration which has a simple structure and can be manufactured at a low cost to perform a layer restoration based on layered code data. Requested.

In many cases, the image database stores code data hierarchized into a number of hierarchies. In some cases, quantization coefficients corresponding to blocks of 8 × 8 pixels are stored in 64 hierarchies. Hierarchical code data may be stored.

In the prior art, since the layers are sequentially restored in accordance with the input of the layered code data, it takes a long time until a detailed image is restored from the layered code data in a number of layers. There has been a demand for a reduction in the time required for restoration processing per layer.

According to the present invention, the image data restoring apparatus for successively restoring the image data based on the hierarchized code data uses a large-capacity buffer as in the prior art.
And to provide an image data restoration device that allows both the sequential restoration process a hierarchical restoration process in hierarchically restorable image data restoration method and simple construction of the multilevel image without having. In particular , claim 2 and claim 4
An object of the present invention is to provide an image data restoring method and an image data restoring apparatus that can reduce the time required for restoration processing per layer when images are restored hierarchically.

[0038]

FIG. 1A is a diagram showing the principle of the image data restoring method according to the first aspect. According to the first aspect of the invention, the original image is divided into blocks each including a plurality of pixels, and the code data of each layer obtained by performing variable-length coding on the information representing the image of each block for each of a plurality of layers is sequentially performed. The code data of the current layer that is input and input is decomposed for each block, and the code corresponding to each block and the code of the corresponding block included in the code data of the previous layer that has already been input are synthesized, respectively. Creates composite code data corresponding to the blocks, sequentially restores the image data of each block based on the composite code data corresponding to each block, combines the composite code data of all the blocks, and generates the code data of the previous layer. The code data of the next layer is used as the code data of the current layer, and the process of creating composite code data is repeated.

FIG. 1B is a diagram showing the principle of the image data restoring method according to the first aspect. The invention of Claim 2 is Claim 1
In the image data restoring method according to (1), the data amount of the combined code data is determined, and when the combined code data reaches a predetermined data amount, the image data of each block is determined based on the combined code data corresponding to each block. Are sequentially restored.

FIG. 2 is a diagram showing a configuration of the image data restoring device according to a third aspect. According to a third aspect of the present invention, transform coefficients obtained by orthogonally transforming an original image for each block composed of a plurality of pixels are divided into groups corresponding to a plurality of layers, and components of the transform coefficients belonging to a group corresponding to each layer Are sequentially input to each layer of code data obtained by performing variable length coding on each block, and in the code data of each layer, a block detection unit 111 that detects a break of code data corresponding to a transform coefficient of each block; And code data of each block indicated by a break detected by the block detection unit 111 and code data of the corresponding block stored in the code storage unit 112. The code synthesizing unit 1 outputs the synthesized code data corresponding to each block and inputs the code synthesized data to the code holding unit 112. 3, decoding means 114 for decoding a transform coefficient corresponding to each block from code data corresponding to each block obtained by the code combining means 113, and inverse orthogonal transform of the transform coefficient corresponding to each block to obtain image data And an inverse orthogonal transformation means 115 for restoring

FIG. 3 is a diagram showing the configuration of the image data restoring device according to the fourth aspect. According to a fourth aspect of the present invention, in the image data restoring apparatus according to the third aspect, the combined code data of each block obtained by the code combining means 113 in accordance with the input of the code data of the designated hierarchy is decoded by the decoding means 114.
Is provided with a sending control means 121 for sending to the user.

[0042]

According to the first aspect of the present invention, the information of the original image corresponding to all the layers up to the current layer is completely included by combining the code data of the current layer and the code data of the previous layer for each block. The composite code data of each block can be obtained. Therefore, by successively restoring the composite code data corresponding to each block, a large-scale
The original image can be hierarchically restored without using an amount of buffer .

According to a second aspect of the present invention, information corresponding to at least one layer of code data is accumulated until the combined code data reaches a predetermined data amount, and information of a plurality of layers is collected. , Image data can be restored. This makes it possible to reduce the apparent time required for the restoration processing per layer.

According to a third aspect of the present invention, the block detecting means 11
1, the code synthesizing unit 113 adds the code corresponding to each block to the code of the corresponding block held in the code holding unit 112, so that the code data of the current layer and the code of the previous layer are added. By synthesizing data with each block, it is possible to obtain synthesized code data of each block including information of original images corresponding to all layers up to the current layer without omission. Therefore, the decoding unit 114 and the inverse orthogonal transform unit 115 sequentially restore the image data of each block based on the composite code data of each block, thereby using a large-capacity buffer as in the related art.
And the original image can be restored hierarchically.

According to the fourth aspect of the present invention, the image data can be restored after the information included in the code data of each layer up to the specified layer is collected.
It is possible to reduce the apparent processing time required for the restoration processing per tier. In addition, if the last layer is specified to the transmission control unit 121, the layered code data can be sequentially converted into code data for restoration, and then the image data can be restored.

[0046]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 4 shows the configuration of an embodiment of the image data restoration apparatus according to the third aspect.

In FIG. 4, the image data restoring device receives a code update unit 20 according to the input of the hierarchized code data.
1 performs an update process to be described later, and sends out the obtained combined code data to the sequential restoration circuit 202 sequentially.

The sequential restoration circuit 202 includes a decoding unit 711
, Decoding table 712, inverse quantization section 720, and inverse DCT transform section 7
31 and is configured to sequentially restore the image data of each block based on the input code data, similarly to the conventional sequential restoration apparatus. The above-described decoding unit 711, decoding table 712, and inverse quantization unit 720
The decoding unit 114 is formed, and the inverse DCT transform unit 731 corresponds to the inverse orthogonal transform unit 115.

Hereinafter, the detailed configuration and operation of the code updating unit 201 will be described. In FIG. 4, the hierarchized code data is input to the detection circuit 211 and the code input unit 213.

Here, in the input code data,
The position of the effective coefficient represented by each code in each block is indicated by a run obtained based on the DC component as in the conventional sequential restoration method. Further, the code data of each layer is obtained by grouping the components of the quantized coefficient D _QU corresponding to each block into four layers (see FIG. 21) and coding the code data. Is
_Each block is separated by a code "R _eob " indicating the end of one block.

Therefore, by coding the quantized coefficient D _QU of each block as shown in FIG. 5A, coded data as shown in FIG. 5B can be obtained. However, in FIG. 5A, the quantization coefficients D of the first block and the second block are shown.
Effective coefficients included in the _QU are indicated by black circles. FIG.
In (b), the code corresponding to the DC component of the quantized coefficient D _QU is indicated by adding a subscript indicating the order of the block to the symbol “D”, and the codes corresponding to the other effective coefficients are indicated by the symbol “R”. The combination of a code with a suffix indicating the length of a run and a code with a suffix indicating the order of the hierarchy and blocks and the order of the effective coefficients in the group are added to the symbol "I".

[0052] In this case, the detection circuit 211, by detecting the code "R _EOB" described above, are implemented when the block detection unit 111, reference numeral "R _EOB"
The output of the detection signal to the effect that is detected indicates the break of each block in the code data of each layer.

The code input section 213 is configured to send the input code data to the synthesis processing section 215 on a word-by-word basis. In FIG. 4, a demultiplexer (DMPX) 221 and two buffers 222a, 222
b and the multiplexer (MPX) 223 form the code holding means 112, and control the write operation and read operation corresponding to the two buffers 222a and 222b by switching between the demultiplexer 221 and the multiplexer 223. It has a configuration. Hereinafter, the buffers 222a and 222b are simply referred to as the buffer 2
No. 22.

The synthesizing unit 215, write control unit 224, and read control unit 225 described above are
3 and the combination processing unit 215
25, the composite code data is created from the code data read out from the buffer 222 via the code input unit 213 and the code data of the current hierarchy from the code input unit 213, and the composite code data is written into the buffer 222 via the write control unit 224. It has become.

The write control unit 224 and the read control unit 225 are input with layer information indicating the layer of the input code data, and according to the layer information, the above-described demultiplexer 221 and multiplexer 223. , Respectively, so that the buffer 222 is alternately set to the write-enabled state, and the other is set to the read-enabled state.

For example, the write control unit 224 instructs the demultiplexer 221 to select the buffer 222a according to the layer information indicating that the layer is an odd-numbered layer, and outputs the layer information indicating that the layer is an even-numbered layer. According to the buffer 222b
May be selected. Further, the read control unit 225 instructs the multiplexer 223 to select the buffer 222b according to the layer information indicating that the layer is an odd-numbered layer, and the buffer 222a according to the layer information indicating that the layer is an even-numbered layer. May be selected. That is, the write control unit 224 determines whether the buffer 222a,
The output of the combination processing unit 215 is written by alternately switching 222b, and the read control unit 225 is configured to validate reading from the buffer 222 to which the output of the combination processing unit 215 has been written in the previous hierarchy. .

Next, the synthesis processing unit 215 and the write control unit 22
4 and the read control unit 225 will be described with respect to a process of creating composite code data of each block. FIG. 6 is a flowchart illustrating the code combining process.

First, the combining processing unit 215 determines whether or not input code data is code data of the first hierarchy based on the above-described hierarchy information (step 401). In case, code input unit 2
The code data input one word at a time from 13 is sent to the write control unit 224 as it is, and written into the corresponding buffer 222 of the code holding unit 112 (step 402).

At this time, the synthesizing unit 215 sends a write request signal to the write control unit 224 each time code data of one word is input from the code input unit 213 to instruct the writing of the code data. I just need. Also, the write control unit 224
May be instructed to the demultiplexer 221 to transmit input data to the buffer 222a in accordance with the layer information indicating that the layer is the first layer. Thus, the code data of the first hierarchy is held in the buffer 222a as it is.

On the other hand, in the case of a negative determination in step 401, the synthesis processing unit 215 sends a read request signal and
Via the read control unit 225, one block of the combined code data obtained in the processing of the previous layer is read (step 403).

At this time, the read control unit 225 holds the address of the code “R _eob ” included in the composite code data of the previous block as a pointer, and in response to the input of the next read request signal, The start address of the composite code data of the next block may be obtained from the pointer described above, and the composite code data for one block may be read.

Next, the synthesis processing unit 215 determines in step 40
3, the code "R _eob " is removed from the combined code data for one block obtained in step 3 and output.
24, the corresponding buffer 2 of the code holding unit 112
22 (step 404).

After that, the synthesizing unit 215 sequentially outputs the code data of the current hierarchy from the code input unit 213 one word at a time, and the corresponding buffer 222 of the code holding unit 112 via the write control unit 224. (Step 405), and Step 405 is repeated as a negative determination in Step 406 until a detection signal indicating that the code "R _eob " is detected is input from the detection circuit 211.

That is, by repeating steps 405 and 406, the code data of the corresponding block of the current layer is output following the composite code data of one block in the previous layer. As a result, it is possible to obtain synthesized code data including information on effective coefficients belonging to groups corresponding to all layers up to the current layer.

For example, the code “D ₁ ” corresponding to the DC component of the first block is replaced with the code string “R ₀ / R ₀ /” corresponding to the effective coefficient of the first block in the code data of the second hierarchy.
I _2,1,1 "," R ₀ / I _2,1,1 "," R _EOB "is added, the codes corresponding to all of the effective coefficients belonging to the group corresponding to the first and second layers The resulting combined code data is obtained.

In this manner, the codes are sequentially synthesized, and when a detection signal indicating that the code "R _eob " is detected is input, it is determined in step 406 that the processing of one block has been completed. Judgment.

At this time, the synthesis processing unit 215 determines whether or not processing has been completed for all blocks (step 407).
As a negative determination in step 407, the process returns to step 403.

On the other hand, in the case of an affirmative determination in step 407, it is determined that the processing for one layer has been completed, and the processing of the code data of the next layer may be started. FIG. 7 shows composite code data of each layer obtained by performing the above-described update processing in response to the input of the code data of each layer shown in FIG.

As shown in FIG. 7, the composite code data of each layer includes information on effective coefficients belonging to groups corresponding to all layers up to each layer. Accordingly, the code data from the code updating unit 201 is input to the decoding unit 711, a run and an index are obtained based on the decoding table 712, and the inverse quantization unit 720 performs an inverse quantization process on the run and the index. , DCT coefficients D including effective coefficients belonging to groups corresponding to all layers up to the current layer can be restored. That is, the DCT coefficient D of each block obtained in this manner is converted into the inverse DCT
1 and sequentially inverse DCT-transform to sequentially restore the image of each block, thereby obtaining an image of the current layer similar to the hierarchical restoration method.

For example, by performing an inverse DCT transform on the DCT coefficient D of each block obtained from the first-layer composite code data, a rough image in which each block is represented by a DC component is restored. Further, by performing an inverse DCT transform on the DCT coefficient D of each block obtained from the second-layer composite code data, a more detailed image including information on the DC component and the primary AC component is restored. Thus, more detailed images are sequentially restored.

As described above, through the above-described code updating unit 201, the image data restoring device for successive restoration can access the image database storing the hierarchized code data. Thus, the use of the image data for sequential restoration can be expanded. Also,
Since the image data restoration device for sequential restoration has a simple configuration and can be reduced in cost, it is possible to provide a user with an inexpensive system.

The above-described code updating unit 201 has a configuration in which the codes of the hierarchized code data are rearranged for each block and the code data is held using two buffers 222. It is sufficient to provide a buffer having a smaller capacity than the capacity of the buffer required by the image data restoration device for restoration. Further, since processing for decoding a code into fixed-length data including a run and an index and processing for restoring a quantization coefficient D _QU from a run and an index are not performed, the configuration is simple and the time required for the processing is short.

Accordingly, the addition of the code updating unit 201 does not significantly increase the price and does not increase the time required for the restoration processing. As a format of hierarchized code data, as shown in FIG. 8, for a block in which the last component belonging to a group corresponding to each layer is an effective coefficient, a code “ _Reob ” indicating the end of one block ] Is omitted and the data length of the code data is compressed.

In this case, it is necessary to decode the length and run of each code and cut out the code data corresponding to each block. FIG. 9 shows another embodiment of the composition processing unit.

In FIG. 9, one of the code data of the current layer from code input section 213 and the code data of the previous layer from read control section 225 is supplied to multiplexer 2.
The data is input to the code length decoding unit 252, the run decoding unit 254, and the code cutout unit 258 via 51. The above-described code length decoding unit 252 and code length table 253 are configured to determine the length of the input code and transmit the obtained code length to the code extraction unit 258. Further, the run is decoded from the input code by the run decoding unit 254 and the run decoding table 255, and the position calculation unit 256 calculates the position of the effective coefficient corresponding to each code in the block based on the obtained run. Is done. Also, the run decoding unit 2
_Reference numeral 54 denotes a _{configuration} for detecting the code "R _eob " from the input code and outputting a detection signal indicating the detection result.

On the other hand, the coefficient position table 257 stores a value indicating the position of the last component of each group in the block corresponding to the hierarchy information, and stores the corresponding value according to the input of the hierarchy information. It is configured to output. The output of the coefficient position table 257 is output by the comparator 259 to the output of the position calculation unit 256 and the coefficient position table 257.
, And the comparison result and the above-described detection signal are input to the code extracting unit 258 via the OR circuit 261.

That is, when the end of the code of one block is indicated by one of the above-mentioned comparison result and the detection signal, the code cutout unit 258 determines the code length based on the code length obtained by the code length decoding unit 252. Thus, a code for one block is cut out. At this time, the code extracting unit 258
If the output of the position calculation unit 256 is other than the last address of the block (for example, “64”), the code “R _eob ” is added to the cut out code and output.

When the output of the OR circuit 261 indicates the end of the code for one block, the switching control unit 262 switches the multiplexer 251 and the code data and code input from the read control unit 225 are switched. The code data from the unit 213 is alternately input to the code extraction unit 258 one block at a time.

In this case, the function of the block detecting means 111 is realized by the run decoding unit 254, the run decoding table 255, the position calculating unit 255, the coefficient position table 257, the comparator 259, and the OR circuit 261. Further, the code data up to the layer before the read control unit 225 reads out the data from the buffer 222 is also performed by these units.
In this case, it is not necessary for the read control unit 225 to have a function of detecting a block break.

Further, as shown in FIG. 10, there is also an encoding method in which a run value is calculated from a base point of a group corresponding to each layer. In this case, if the codes are simply rearranged for each block, it is not possible to obtain code data for sequential restoration, so for each block, a run starting from the DC component with the first code of the current layer as a starting point is used. Need to be replaced.

For example, as shown in FIG. 11, the decoding table 712 and the code table 632 are added to the code updating unit 201 shown in FIG. With reference to 712, the position of the effective coefficient corresponding to the last code of the previous layer in the block is obtained. Next, in step 404, the first code of the current layer is decoded using the decoding table 712, and the position of the corresponding effective coefficient in the block is obtained. Further, a run starting from a DC component is obtained from these positions, the obtained run and the value of the effective coefficient described above are input to the code table 632 to obtain a new code, and the original code may be replaced.

As described above, the image data restoring method of the present invention can be applied to code data hierarchized in various formats. It is sufficient to transmit the encoded data, and the format of the accumulated encoded data can be unified.

By the way, for example, in response to input of code data obtained by hierarchizing the quantization coefficient D _QU for a block of 8 × 8 pixels into 64 hierarchies, restoration processing is sequentially performed based on the code data of each hierarchy. Therefore, it takes a long time until a detailed image is obtained. In addition, since little information is newly added at each layer, the image appears to be hardly changed by human eyes, so that the waiting time is painful for the user.

As described above, when an image is hierarchically restored from code data hierarchized into a number of hierarchies, groups of components of the quantization coefficient D _QU corresponding to several hierarchies are grouped into one hierarchy. If the code data is generated and the hierarchy is restored based on the code data, the time required for restoring the image data per layer can be apparently reduced.

Hereinafter, a method of creating code data including all components of the quantized coefficient D _QU divided into these layers from code data of a plurality of layers will be described.
FIG. 12 is a block diagram showing an embodiment of the image data restoration apparatus according to claim 4.

Referring to FIG. 12, the image data restoring apparatus
The code updating unit 201 shown in FIG. 2 and the sequential restoration circuit 202 are connected via a gate circuit 311.
11 sequentially restores the code data obtained by the code updating unit 201 in accordance with an instruction from the gate control unit 312.
2. Further, the gate control unit 312 is previously assigned at least one layer number, and the gate control unit 312 updates the code data of the specified layer based on the layer information. , The opening of the gate circuit 311 is instructed.

That is, even when code data that has been hierarchized finely is input, only the composite code data created according to the input of the code data of the designated hierarchy is supplied to the restoration circuit 202 via the gate circuit 311. Sent out.

For example, when an image is restored in four stages based on code data hierarchized into 64 hierarchies, the first, third, sixth, and sixth hierarchies are transmitted to the gate controller 232.
What is necessary is just to specify each of four layers. In this case, as shown in FIG. 21, the quantization coefficient D _QU is divided into four layers and encoded in accordance with the input of the code data of each of these layers, as shown in FIG. Such composite code data is obtained.

In this case, since the code data of a plurality of hierarchies are restored collectively, the apparent time required for the restoration processing per one hierarchy can be reduced, and the waiting time of the user can be reduced. it can. Further, since the image changes step by step, the pain of the user until the image is restored can be reduced.

If only the 64th layer is designated in the gate control section 312, code data for successive restoration can be obtained. Therefore, it is necessary to realize both layer restoration and successive restoration by one image data restoration device. Can be.

As shown in FIG. 13, the above-described code updating unit 201 is connected to another sequential restoring device via a communication line, and the composite code data obtained by the code updating unit 201 is input. Is also good.

Thus, the conventional sequential restoring apparatus having no code updating unit 201 can hierarchically restore an image based on the hierarchically encoded code data stored in the image database. An existing image data restoration device can be used.

Further, the composite code data obtained by the code updating unit 201 may be transferred to an external storage device such as a floppy disk device and recorded on a recording medium. For example, if the composite code data created in response to the input of the code data of the last layer is recorded on a floppy disk or the like, this floppy disk can be read and restored by another sequential image data restoring device. It can be used for demonstrations on the go.

Here, since the amount of synthesized code data is much smaller than that of the image data itself, a plurality of images can be recorded even on a recording medium having a small capacity such as a floppy disk. Convenient for carrying or transporting.

[0095]

As described above, claims 1 to 4 are described.
According to the invention described in (1), synthesized code data that can be sequentially restored is created from the hierarchized code data , so that a large-capacity backup is conventionally used by using an image data restoration device for successive restoration.
It is possible to restore image data hierarchically without using a file, expand the use of existing image data restoration devices for sequential restoration, and unify the format of code data stored in an image database. it can.

The invention according to claim 2 or 4
Is a method of accumulating code data of a plurality of hierarchies, creating composite code data in which information divided into a plurality of hierarchies is collected, and then performing an image restoration process, thereby performing an apparent restoration per hierarchy. The time can be reduced, and the waiting time of the user can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing the principle of the image data restoring method according to claims 1 and 2.

FIG. 2 is a diagram showing a configuration of an image data restoration device according to a third embodiment.

FIG. 3 is a diagram showing a configuration of an image data restoration device according to a fourth embodiment.

FIG. 4 is a block diagram showing an embodiment of an image data restoring device according to claim 3;

FIG. 5 is a diagram illustrating an example of hierarchized code data.

FIG. 6 is a flowchart illustrating a code combining operation.

FIG. 7 is a diagram illustrating an example of composite code data.

FIG. 8 is a diagram illustrating an example of hierarchized code data.

FIG. 9 is a configuration diagram of another embodiment of the synthesis processing unit.

FIG. 10 is a diagram illustrating an example of hierarchized code data.

FIG. 11 is a configuration diagram of another embodiment of a code updating unit.

FIG. 12 is a block diagram showing an embodiment of an image data restoration apparatus according to claim 4;

FIG. 13 is a diagram showing a configuration example of a system using the image data restoration device of the present invention.

FIG. 14 is a configuration diagram of a conventional image data compression device.

FIG. 15 is a diagram illustrating an example of a block.

FIG. 16 is a diagram illustrating an example of a DCT coefficient D.

FIG. 17 is a diagram showing a quantization matrix V _TH .

FIG. 18 is a diagram illustrating an example of a quantization coefficient D _QU .

FIG. 19 is an explanatory diagram of a zigzag scan.

FIG. 20 is a configuration diagram of an image data restoration device.

FIG. 21 is an explanatory diagram of a spectral selection method.

[Explanation of symbols]

 111 Block detection means 112 Code holding means 113 Code synthesis means 114 Decoding means 115 Inverse orthogonal transformation means 121 Transmission control means 201 Code update unit 202 Sequential restoration circuit 211 Detection circuit 213 Code input unit 215 Synthesis processing unit 221 Demultiplexer (DMPX) 222 Buffer 223, 251 Multiplexer (MPX) 224 Write control unit 225 Read control unit 252 Code length decoding unit 253 Code length table 254 Run decoding unit 255 Run decoding table 256 Position calculation unit 257 Coefficient position table 258 Code extraction unit 259 Comparator 261 OR circuit 262 Switching control unit 311 Gate circuit 312 Gate control unit 611 DCT conversion unit 620 Linear quantization unit 631 Encoding unit 632 Code table 711 Decoding unit 712 Decoding table 720 Inverse quantization unit 73 1 Inverse DCT converter

Claims (4)

(57) [Claims] 1. An original image is divided into blocks each composed of a plurality of pixels, and code data of each layer obtained by performing variable length coding of information representing an image of each block for each of a plurality of layers is sequentially input. The code data of the current layer that is input is decomposed for each block, and the code corresponding to each block and the code of the corresponding block included in the code data of the previous layer that has already been input are synthesized, and Creating corresponding combined code data, based on the combined code data corresponding to each block,
The image data of each block is sequentially restored, the combined code data of all the blocks is combined into the code data of the previous layer, and the code data of the next layer is used as the code data of the current layer. Image data restoring method characterized by repeating step (a). 2. The image data restoration method according to claim 1, wherein a data amount of the combined code data is determined, and when the combined code data reaches a predetermined data amount,
Based on the synthesized code data corresponding to each block,
An image data restoration method characterized by sequentially restoring image data of each block. 3. A transform coefficient obtained by orthogonally transforming an original image for each block composed of a plurality of pixels is divided into groups corresponding to a plurality of layers, and the components of the transform coefficient belonging to the group corresponding to each layer are respectively determined. Block detection means (111) for sequentially receiving code data of each layer obtained by variable-length coding, and detecting, in the code data of each layer, a segment of code data corresponding to a transform coefficient of each block.
Code holding means (112) for holding code data corresponding to each block; code data of each block indicated by a break detected by the block detection means (111); and code holding means (112). The held code data of the corresponding block is combined, and the combined data is output as combined code data corresponding to each block, and the code combining means (113) input to the code holding means (112); Decoding means (114) for decoding a transform coefficient corresponding to each block from the code data corresponding to each block obtained in 113), and inverse orthogonal transform of the transform coefficient corresponding to each block to restore image data An image data restoration device comprising an inverse orthogonal transformation means (115). 4. The image data restoring apparatus according to claim 3, wherein the combined code data of each block obtained by the code combining means (113) is decoded by the decoding means (114) in response to the input of the code data of the designated hierarchy. ), A transmission control means (121) for transmitting the image data.