JPH1118070A - Image compressing device, image extending device and transmission equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly extend a quantized subordinate image only for the required subordinate image by enciphering its required part. SOLUTION: A source image is divided into subordinate image groups of N hierarchies (1 to N) by a conversion encoding part 1. A quantizing part 2 respectively quantizes the subordinate image groups outputted from the conversion encoding part 7. An enciphering part 3 receives a block number to be enciphered in the source image as an enciphering part designate signal and enciphers a block having the prescribed number, in the case of dividing the subordinate image group of each hierarchy outputted from the quantizing part 2 into the blocks of pixels. Then, the enciphered block number is outputted as partial enciphered information. An entropy encoding part 4 performs entropy encoding to the output from the enciphering part 3. Thus, the image can be partially enciphered, while effectively utilizing the reversible and inreversible continuity of wavelet without performing excessive compression/extension.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image compression apparatus for compressing an image and encrypting a part of the image, an image decompression apparatus for decrypting the encrypted part and expanding the reproduced image,
The present invention relates to a transmission device configured such that an image compression device is a transmission side and an image decompression device is a reception side.

[0002]

2. Description of the Related Art With the advance of multimedia, the importance of security as well as its compression efficiency in the compression technology of still images and moving images is increasing. That is,
In telemedicine, since a diagnostic image flows on a network, it is necessary to encrypt a part of the image in order to protect the privacy of the patient. In video-on-demand and electronic newspaper services, it is necessary to make a part of the delivery image invisible to guest users in order to distinguish between paid users and guest users who use it for free.

In image compression technology, wavelet compression (JMShapiro, "Embedded Image Coding Using
Zerotrees of Wavelet Coefficients ", IEEE Trans. S
ignal Processing, Vol. 41, No. 12, pp. 3445-3462, 199
3) is drawing attention. In particular, in medical images, diagnosis based on still images and diagnosis based on moving images are mixed, and reversible compression is often used in current medical practice.

FIG. 14 shows a conventional method of encryption using wavelet compression. That is, some encryption is performed on a part of the original image, and it is subjected to wavelet transform. However, if this is quantized or a part of the sub-image is saved or transmitted in order to reduce the bit amount, the bit pattern of the encrypted part will be incorrect when dequantized and expanded by inverse transform. Cannot be reproduced. Therefore, even if the code is decrypted, the encrypted portion cannot be reproduced as a reproduced image close to the original image.

Therefore, A of Adobe System Incorporated
dobe Premiere Utility (Adobe Premiere User
s Guide, 1991) uses a compressed /
The reproduction image is generated by performing decompression, and the reproduced image is encrypted.

This is shown in FIG. In this case, even after decompression, the encrypted portion can be decompressed into a reproduced image close to the original image, but the amount of calculation is large because extra compression / decompression must be performed during compression.

One of the advantages of wavelet compression is that lossless compression and irreversible compression can be performed continuously. When all of the sub-images after decomposition are transmitted, lossless compression is performed. Lossy compression. However, since the reconstructed image is created once,
If you select / irreversible, the encrypted part cannot be decompressed correctly.

[0008]

As described above, in the conventional method, the encryption part may not be able to be decompressed correctly. In order to decompress correctly, the amount of calculation is increased by performing extra compression / decompression. In addition, there was a need to restrict the use of the reversible and irreversible continuity of wavelets.

In order to solve the above-mentioned problems, the present invention provides an image compression apparatus capable of correctly decompressing only a necessary sub-image by encrypting a necessary part of the quantized sub-image. It is an object to provide an image decompression device and an image transmission device.

[0010]

In order to achieve the above object, by encrypting a necessary portion of a sub-image which has been quantized, it is possible to correctly decompress only the necessary sub-image.

More specifically, the image compression apparatus according to the first aspect of the present invention includes a transform encoding unit that divides an original image into sub-images and encodes the same, such as a wavelet transform, a quantization unit that performs quantization, and an encryption unit. And an entropy encoding unit for minimizing the code length. The transform image encoding unit transforms the original image from four sub-images of Nth layer and three other layers. Sub-image group of N layers (1-N)
(I (i, j): i = 1 ... N, j = 0,1,2,3), and the quantization unit performs a process on the sub-image group output from the transform coding unit. Respectively, and the encryption unit performs MxM (M =
Original image (A, B) of size (AxB) consisting of blocks of 2 ^ N) pixels
Is a multiple of M) and the block number to be encrypted (P, Q) (P = 0 ...
A / M-1, Q = 0 ... B / M-1) as an encryption part designation signal, and the encryption unit outputs each layer of the output from the quantization unit.
The sub-image group I (i, j) (j = 0..3) of i (i = 1 to N) is LxL (L = 2
((Ni)) When the block is divided into pixel blocks, the (P, Q) -th block is encrypted, and the encrypted block number (P, Q) is output as encrypted partial information. The entropy encoding unit performs entropy encoding on an output from the encryption unit.

According to a second aspect of the present invention, there is provided an image decompression device, comprising: an inverse transform decoding unit for generating and decoding a reproduced image from sub-images divided by inverse wavelet transform; and an inverse quantization unit for performing inverse quantization. A deciphering section for deciphering a cipher, and an entropy decoding section for performing entropy decoding, wherein the entropy decoding section includes a sub-image having four Nth layers and three other layers each. N levels
(1 to N) Sub-image group (I (i, j): i = 1 ... N, j = 0,1,2,3) If the input is only a part, a zero code is generated for a compression code for a non-existent sub-image, the entropy decoding unit performs entropy decoding on the sub-image, and the decoding unit Receiving the output of the entropy decryption unit, and also receives the encrypted block number (P, Q) received as encrypted partial information, the decryption unit,
The sub-image group I (i, j) (j = 0..3) of each layer i (i = 1 to N) is represented by L
xL (L = 2 ^ (Ni)) Performs decryption of the (P, Q) -th block when divided into pixel blocks, and the inverse quantization unit outputs the sub-image output from the decryption unit. The group is subjected to inverse quantization, and the inverse transform decoding unit receives the output of the inverse quantizer, performs inverse transform decoding, and outputs a reproduced image.

According to a third aspect of the present invention, there is provided a transmission apparatus comprising the image compression apparatus of the first aspect, the image decompression apparatus of the second aspect, and a transmission unit for connecting the image compression apparatus and the image decompression apparatus.

According to a fourth aspect of the present invention, there is provided an image compression apparatus which divides an original image into sub-images and encodes the original image as in a wavelet transform, a quantization unit which performs quantization if necessary, and an encryption unit. And a zero-tree encoding unit that performs zero-tree encoding. The transform encoding unit converts the original image into N layers each including four N-th layers and three other sub-images. (1 to N) sub-image group (I
(i, j): i = 1 ... N, j = 0, 1, 2, 3), and the quantization unit is configured for each of the sub-image groups output from the transform coding unit. Quantization is performed, and the encryption unit performs MxM (M = 2 ^
(N) Original image of size (AxB) consisting of blocks of pixels (A and B are M
Block number (P, Q) (P = 0 ... A / M)
-1, Q = 0 ... B / M-1) as an encryption part designation signal, and the encryption unit outputs each layer of the output from the quantization unit.
The sub-image group I (i, j) (j = 0..3) of i (i = 1 to N) is LxL (L = 2
(P (Q))-th block when divided into (^ (Ni)) pixel blocks is a block to be encrypted, and the (3 * N + 1) number of blocks included in the block to be encrypted in the sub-image are included. Data, that is, d (m, n) (m: bit width of each data, n: 0 to 3 * N, d
= 0 or 1) to create data X (m) = d (m, 0), d (m, 1), .., d (m, 3 * N) and encrypt the data X (m) Is performed, and it is set as Y (m), and each bit of the LSB from the MSB of the data Y (m) is e.
(m, 0), e (m, 1), ..., e (m, 3 * N), e (m, n) (m: Bit width, n: 0 to 3 * N, e = 0 or 1), further outputs the block number to be encrypted (P, Q) as encrypted partial information, and the zero tree encoding unit outputs the encrypted The output from the section is subjected to zero tree encoding.

According to a fifth aspect of the present invention, there is provided an image decompression device which generates a decoded image from a sub-image divided by wavelet inverse transform and decodes the reproduced image, and an inverse transform unit which performs inverse quantization if necessary. It has a quantization unit, a decryption unit that decrypts a cipher, and a zero tree decryption unit that performs zero tree decryption. The zero tree decryption unit has four Nth layers and three other layers. N of sub-images of
Zero tree decoding is performed on the compression code corresponding to the sub-image group (I (i, j): i = 1 ... N, j = 0, 1, 2, 3) of the hierarchy (1 to N),
Notify the decryption unit when the threshold changes, the decryption unit receives the output of the zero tree decryption unit, and the encrypted block number (P, Q) received as encrypted partial information And the decryption unit receives
The sub-image group I (i, j) (j = 0..3) of each layer i (i = 1 to N) is represented by L
xL (L = 2 ^ (Ni)) when divided into pixel blocks, the (P, Q) -th block is the block to be decrypted, the decryption unit, the threshold changes from the zero tree decoding unit Is notified, the data included in the block to be decrypted is decrypted, and the inverse quantization unit performs inverse quantization on each of the sub-image groups output from the decryption unit. The inverse transform decoding unit receives the output of the inverse quantization unit, performs inverse transform decoding, and outputs a reproduced image.

According to a sixth aspect of the present invention, there is provided a transmission apparatus comprising the image compression apparatus of the fourth aspect, the image decompression apparatus of the fifth aspect, and a transmission unit for connecting the image compression apparatus and the image decompression apparatus.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) An image compression apparatus and an image decompression apparatus according to a first embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic configuration diagram of an image compression device and an image decompression device according to the present embodiment.

In FIG. 1, reference numeral 10 denotes an image compression device.
Reference numeral 0 denotes an image decompression device. Reference numeral 1 denotes a transform encoding unit that performs a wavelet transform with an original image as an input. The sub-image group (1 to N) of N layers (1 to N) including four N-th layers and three other sub-images. I (i, j): i = 1 ... N, j = 0,1,
Divide into 2,3). Reference numeral 2 denotes a quantization unit that performs quantization using an output from the transform encoding unit 1 as an input. Numeral 3 denotes an encryption part designating signal for designating a part to be encrypted and an output from the quantizing part 2 for encrypting the same. Output.
Reference numeral 4 denotes an entropy encoding unit that receives the output of each sub-image from the encryption unit 3 and performs entropy encoding for referring to the code length.

Reference numeral 5 denotes an entropy decoding unit for performing entropy decoding. The sub-image group (I (I (N)) includes four sub-images of the N-th layer and three sub-images of the other layers. i, j): Input all or some of the compression codes corresponding to i = 1 ... N, j = 0,1,2,3). A zero code is generated for a compression code for an image.

Reference numeral 6 denotes a decryption unit for receiving the input of the encrypted partial information and the output of the entropy decryption unit 5 and decrypting the encrypted portion. Reference numeral 7 designates the input of the output of the decryption unit 6 and the inverse quantization. And 8 is an inverse transform decoder for generating a reproduced image from the sub-image by inverse wavelet transform and decoding the reproduced image.

In the encryption unit 3, a plurality of MxM (M = 2 ^ N)
Original image (A, A, B) consisting of blocks of pixel size (AxB)
(B is a multiple of M) block number (P, Q) (P =
0 ... A / M-1, Q = 0 ... B / M-1) are received as encrypted part designation signals.

Further, the encryption unit 3 converts the sub-image group I (i, j) (j = 0..3) of each layer i (i = 1 to N) of the output from the quantization unit 2 into L
The encryption is performed on the (P, Q) -th block when divided into blocks of xL (L = 2 ^ (Ni)) pixels.

On the other hand, the decryption unit 6 receives the output of the entropy decryption unit 5, receives the encrypted block number (P, Q) received as the encrypted partial information, and
The sub-image group I (i, j) (j = 0..3) of (i = 1 to N) is represented by LxL (L = 2 ^ (N−
i)) Decrypt the (P, Q) -th block when divided into pixel blocks.

FIG. 2 summarizes this processing. First, the original image is compressed by transform coding and quantization, only the portion to be encrypted is encrypted, entropy-coded, and then stored or transmitted. If the transmitted or read data can be decrypted, it is decrypted and then expanded to reconstruct the entire image. If it cannot be decrypted, only the encrypted part is not reconstructed, and the rest is reconstructed.

The above will be described again using an example. The image on the left in FIG. 3 is the original image, which is obtained by wavelet transform (3 levels of hierarchy) and, if necessary, quantized.
As shown in FIG. 4, in the original image (48 × 64 size), 8 × 8
The part of the (3,4) th block of the (8 = 2 ^ 3) size block is a part to be encrypted. Three sub-images of layer 1 (2
(4x32 size) is divided into 4x4 size blocks and (3,
4) Encrypt the part corresponding to the third block. Similarly,
The three sub-images of layer 2 (12x16 size) are encrypted into the (3,4) th block in a 2x2 size block, and the four sub-images of layer 3 (6x8 size) are encoded in 1x1 size. Divide into blocks and encrypt the part corresponding to the (3,4) th block.

That is, as shown in the left diagram of FIG. 5, when a part of the compressed data is encrypted and decompressed without decryption, the data is decompressed as shown in the right diagram. Further, as shown in the left diagram of FIG. 6, when reconstructing only a part of the sub-image in order to reduce the bit amount, although the quality is deteriorated as shown in the right diagram, the encrypted portion is similarly encrypted. It will be reproduced as it is.

(Embodiment 2) Next, a transmission apparatus according to a second embodiment of the present invention will be described. The transmission device according to the present embodiment is obtained by connecting the image compression device and the image decompression device according to the first embodiment via a transmission path.

FIG. 7 shows a flowchart for transmitting and receiving data using a public key method (such as RSA) and a conventional encryption method (such as DES) for this embodiment.

First, the transmitting side performs compression processing before transmission. That is, 1) select a secret key (A), publish the corresponding public key (B), 2) perform wavelet conversion, quantize each sub-image, and 3) generate an encryption key (P) for conventional encryption. Then, a necessary part of each sub-image is encrypted, and 4) encrypted partial information, data (I (i)) of each sub-image and an encryption key (P) are stored.

At the time of transmission, transmission is performed according to the following transmission procedure. 1) Select the bit rate according to the transmission path conditions and the request of the receiving side, 2) determine the hierarchy of sub-images to be transmitted according to the selected bit rate, and 3) public key (S ) To encrypt the encryption key (P) (Q) (If a privileged user is statically identified, it may be encrypted at compression), 4) Level of hierarchy to be transmitted and encrypted part The information and the data (I (i)) and the encryption key (Q) of each sub-image are transmitted.

The receiving side having the privilege of being able to reproduce the encrypted portion receives the data in the following receiving procedure.
1) receive the level of the layer to be received and the encrypted partial information and the data (I (i)) of each sub-image thereof, the encryption key (Q),
2) Using its own secret key (T), decrypt the encryption key (Q) (P),
3) Decrypt the encrypted portion of each sub-image using the encryption key (P), and 4) Inversely quantize and inversely transform the wavelet to obtain a reproduced image.

The receiving side having no privilege receives data in the following receiving procedure. 1) the level of the layer to be received and the encrypted partial information and the data of each sub-image thereof (I (i)),
The encryption key (Q) is received, and 2) inverse quantization and inverse wavelet transform are performed to obtain a reproduced image (partially encrypted).

(Embodiment 3) Next, an image compression apparatus and an image decompression apparatus according to a third embodiment of the present invention will be described with reference to the drawings.

FIG. 8 is a schematic configuration diagram of an image compression device and an image decompression device according to the present embodiment.

In FIG. 8, reference numeral 30 denotes an image compression device;
Reference numeral 0 denotes an image decompression device. Reference numeral 11 denotes a transform coding unit that performs a wavelet transform with an original image as an input. The sub-image group (1 to N) of N layers (1 to N) includes four N-th layers and three other sub-images. I (i, j): i = 1 ... N, j = 0,
Divide into 1,2,3). Reference numeral 12 denotes a quantization unit that performs quantization by using an output from the transform encoding unit 11 as an input.

Reference numeral 13 designates an input of an encryption part designation signal for designating a part to be encrypted and an output from the quantization unit 12,
An encryption unit for performing encryption outputs the same content as the above-described encrypted portion designation signal to the outside. 14 receives the output of each sub-image from the encryption unit 13 as input, and outputs the output from Shapiro (JMShapir
o, "Embedded Image Coding Using Zerotrees of Wavel
et Coefficients ", IEEE Trans. Signal Processing, Vo
l.41, No.12, pp.3445-3462, 1993).

On the other hand, reference numeral 15 denotes a zero-tree decoding unit for performing zero-tree decoding, and a sub-image group (1 to N) of N layers (1 to N) in which the N-th layer is four and the other layers are each three sub-images. Performs zero-tree decoding on the compressed code corresponding to I (i, j): i = 1 ... N, j = 0,1,2,3) and decodes it when the threshold changes Notify.

A decryption unit 16 receives the encrypted partial information and the output of the zero tree decryption unit 15 as input, and decrypts the encrypted part. 17 receives the output of the decryption unit 16 as input and performs inverse quantization. Is an inverse transform decoder for generating a reproduced image from the sub-image by inverse wavelet transform and decoding the image.

The encryption unit 13 is a block number (P, Q) to be encrypted in an original image of size (AxB) (A, B is a multiple of M) composed of blocks of MxM (M = 2 ^ N) pixels. (P = 0 ... A / M-1, Q = 0 ... B / M-
1) is received as an encryption part designation signal.

Further, the encryption unit 13 outputs a sub-image group I (i, j) (j = 0...) Of each layer i (i = 1 to N) of the output from the quantization unit 12.
3) is divided into LxL (L = 2 ^ (Ni)) pixel blocks.
The (P, Q) -th block is a block to be encrypted.

(3 * N + 1) data included in the block to be encrypted in this sub-image, that is, d (m, n) (m: bit width of each data, n: 0 to 3 * N, d = 0or1) to X (m) = d (m, 0), d (m,
1), .., d (m, 3 * N) are created, the data X (m) is encrypted, and the result is defined as Y (m).

The encryption unit 13 converts the data Y (m) from the MSB to the LSB
Where e (m, 0), e (m, 1), ..., e (m, 3 * N)
E (m, n) (m: bit width of each data, n: 0 to 3 * N, e = 0 or 1) is output as encrypted data of the block to be encrypted, and the block number to be encrypted (P, Q) Is output as encrypted partial information.

On the other hand, the decryption unit 16 receives the output of the zero tree decryption unit 15 and receives the encrypted block number (P, Q) received as the encrypted partial information. The decryption unit 16 determines the sub-image group I of each layer i (i = 1 to N).
When (i, j) (j = 0..3) is divided into LxL (L = 2 ^ (Ni)) pixel blocks, the (P, Q) -th block is the block to be decrypted.

The decryption unit 16 includes a zero tree decoding unit 15
Is notified that the threshold will change,
The decryption is performed on the data included in the block to be decrypted.

This processing will be described using an example. As shown in FIG. 9, consider a case where when a 4 × 4 image is subjected to wavelet transform, only the lower right 2 × 2 portion of the original image is encrypted. That is, the wavelet coefficients -3, 2, 1, 0 are encrypted. At this time, each bit when each value is expressed in binary is made into one word, which is encrypted. That is, if each of the encrypted words is decrypted, the bits of the same digit for all data can be decrypted.

Therefore, assuming that the encrypted data is obtained in order from the upper bits, the lower bits include an error,
Generally, the original data can be decrypted, and as the decryption progresses, the accuracy increases, and finally, all the data can be restored. The rightmost diagram in FIG. 9 shows the coefficients after encryption.

Next, a case where this example is subjected to zero tree encoding is shown, and FIG. 10 shows a case where encryption is not performed.

Here, PS indicates that the data is significant and positive at the threshold, and NG indicates that the data is significant at the threshold.
Indicates ant and a negative number. Further, ZR indicates that the data and the child of the parent-child relationship are all zero, and IZ indicates that the data is zero, but some of the children include non-zero. In addition, ZR is represented by 1 bit, but the rest is represented by 3 bits.

Since the converted wavelet coefficients are expressed in 6 bits including the sign, the threshold is 16 bits.
Start with. FIG. 10 shows the result of encoding according to Shapiro's zero tree encoding method. If the block delimiters are not counted, all bits can be encoded with 76 bits. Therefore, since the original is 96 bits (16 pixels × 6 bits), it can be encoded by 20 bits less.

Next, FIG. 11 shows the result of the zero tree encoding in the case of encryption. As compared with FIG. 10, the number of ZRs is reduced, so that the coding efficiency is reduced. However, since the coding can be performed with a total of 88 bits, the number of codes can be reduced by 8 bits from the original code amount.

Consider a case where these codes are decoded with up to 40 bits. If the data is not encrypted, as shown in FIG. 12, the data is transmitted halfway when the threshold is 2. As shown in the lower right diagram of FIG. 12, six coefficients are obtained, and the other coefficients remain at 0. When compared with the coefficient of the original image, the sum of the absolute values of the differences is 13, and the sum of the differences in the low-frequency components affecting the image quality is 1.

FIG. 13 shows the case of encryption. 40
In the case of bits, it can be obtained only halfway when the threshold is 4. After the data of each threshold is read, the data is decrypted, and the decryption is performed from the upper bits.

At the time when the threshold 16 is completed, "PS1" and "NG1" are read as significant data, and in each case, the uncertain interval is [16, 32).
(16,24), (24,32), the absolute value of which is [2
4, 32). Therefore, the intermediate value is set as a representative value, and 28 and -28 are obtained. Here, the data at the location corresponding to the block to be encrypted is "-28,0,0,28", and the most significant bit matches the bit string before encryption. The upper bits can be correctly decoded (-3,0,0,3).

Further, at the time when the threshold value 8 is completed, "PS0" is newly read out, and uncertain i
nterval is (8,12), (12,16), (16,20), (20,24), (24,28), [2
8,32). For the data at the location corresponding to the block to be encrypted, "-30,0,0,30" is obtained, and the upper 2 bits match the bit string before encryption, so even if decrypted, the upper 2 bits Can be correctly decoded (-1,0,0,1).

As described above, when the reading of 40 bits is completed, the sum of the difference from the coefficient of the original image is 21, and in the low frequency portion,
It is 6. Compared to the case without encryption, the difference is large, but the image quality is not greatly impaired.

(Embodiment 4) Lastly, a transmission apparatus according to a fourth embodiment of the present invention will be described. The transmission device according to the present embodiment is a transmission device in which the image compression device and the image decompression device according to the third embodiment are connected by a transmission path.

This embodiment is similar to the second embodiment, and FIG. 7 is a flowchart showing a case where transmission and reception are performed using a public key system (such as RSA) and a conventional encryption system (such as DES).

[0059]

As described above, according to the present invention, it is possible to partially encrypt an image while utilizing the reversible and irreversible continuity of a wavelet without performing extra compression / decompression. Thereby, in communication at an arbitrary bit rate according to the state of the transmission path and the request of the receiving side,
Encrypted image communication can be performed.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image compression device and an image decompression device according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram for explaining processing according to the first embodiment;

FIG. 3 is an explanatory diagram illustrating a wavelet transform.

FIG. 4 is an explanatory diagram illustrating an encryption part.

FIG. 5 is an explanatory diagram for explaining a result of decompression of an encrypted part.

FIG. 6 is an explanatory diagram for explaining a result of decompression of an encrypted part of an irreversibly compressed image;

FIG. 7 is a flowchart illustrating processing according to a second embodiment.

FIG. 8 is a schematic configuration diagram of an image compression device and an image decompression device according to a third embodiment of the present invention.

FIG. 9 is an explanatory diagram for explaining operations of an image compression device and an image decompression device according to a third embodiment.

FIG. 10 is a code diagram in a case where encryption of the image compression apparatus according to the third embodiment is not performed.

FIG. 11 is a code diagram in the case where the image compression apparatus according to the third embodiment performs encryption.

FIG. 12 is an explanatory diagram showing coefficients after decryption in the case where the image decompression device according to the third embodiment does not perform encryption.

FIG. 13 is an explanatory diagram showing coefficients after decryption in the case where the image decompression device according to the third embodiment performs encryption.

FIG. 14 is an explanatory diagram for explaining processing of Conventional Example 1;

FIG. 15 is an explanatory diagram for explaining processing of Conventional Example 2;

[Explanation of symbols]

 1,11 Transformation encoding unit 2,12 Quantization unit 3,13 Encryption unit 4 Entropy encoding unit 5 Entropy decoding unit 6,16 Decryption unit 7,17 Inverse quantization unit 8,18 Inverse transformation decoding unit 14 Zero Tree Encoding Unit 15 Zero Tree Decoding Unit 10, 30 Image Compression Device 20, 40 Image Decompression Device

Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04N 7/24 H04N 7/13 Z

Claims (6)

[Claims] 1. A transform encoding unit that divides an original image into sub-images and encodes them as in a wavelet transform, a quantization unit that performs quantization if necessary, an encryption unit that performs encryption, An entropy encoding unit for minimizing the length, and the original image is N layers composed of four sub-images and three other sub-images by the transform encoding unit.
(1 to N) sub-image group (I (i, j): i = 1 ... N, j = 0, 1, 2, 3), and the quantization unit Each of the output sub-image groups is quantized, and the encryption unit performs an original image (A, B is a multiple of M) of a size (AxB) composed of blocks of MxM (M = 2 ^ N) pixels. ), The block number (P, Q) (P = 0 ... A / M-1, Q = 0 ... B / M-1) to be encrypted is received as an encryption part designation signal, and the encryption is performed. The unit outputs each layer i (i =
1 to N), the sub-image group I (i, j) (j = 0..3) is represented by LxL (L = 2 ^ (N−
i)) When the (P, Q) -th block is divided into pixel blocks, encryption is performed, and the encrypted block number is obtained.
(P, Q) is output as encrypted partial information, and the entropy coding unit performs entropy coding on an output from the encryption unit. 2. An inverse transform decoding unit for generating and decoding a reproduced image from a sub-image divided by wavelet inverse transform, an inverse quantizing unit for performing inverse quantization if necessary, A decoding unit for performing decoding; and an entropy decoding unit for performing entropy decoding, wherein the entropy decoding unit includes an N-th layer including four sub-images each having four N-th layers and three other layers. (1 ~
N) of the sub-image group (I (i, j): i = 1 ... N, j = 0,1,2,3) If it is an input, a zero code is generated for a compression code for a non-existent sub-image, the entropy decoding unit performs entropy decoding for the sub-image, and the decoding unit performs the entropy decoding. Receiving the output of the sub-image group, and receiving the encrypted block number (P, Q) received as the encrypted partial information, the decryption unit, the sub-image group I of each layer i (i = 1 to N)
When (i, j) (j = 0..3) is divided into LxL (L = 2 ^ (Ni)) pixel blocks, the (P, Q) -th block is decrypted, and the inverse quantum The decoding unit performs inverse quantization on each of the sub-image groups output from the decoding unit, and the inverse transform decoding unit receives the output of the inverse quantization unit and performs inverse transform decoding. An image decompression device for outputting a reproduced image. 3. A transmission device comprising: the image compression device of claim 1, the image decompression device of claim 2, and a transmission unit connecting the image compression device and the image decompression device. 4. A transform encoding unit that divides an original image into sub-images and encodes them as in a wavelet transform, a quantization unit that performs quantization if necessary, an encryption unit that performs encryption, and a zero tree. A zero-tree encoding unit for performing encoding; the transform image encoding unit converts the original image into N layers each including four N-th layers and three other sub-images;
(1 to N) sub-image group (I (i, j): i = 1 ... N, j = 0, 1, 2, 3), and the quantization unit Each of the output sub-image groups is quantized, and the encryption unit performs an original image (A, B is a multiple of M) of a size (AxB) composed of blocks of MxM (M = 2 ^ N) pixels. ), The block number (P, Q) (P = 0 ... A / M-1, Q = 0 ... B / M-1) to be encrypted is received as an encryption part designation signal, and the encryption is performed. The unit outputs each layer i (i =
1 to N), the sub-image group I (i, j) (j = 0..3) is represented by LxL (L = 2 ^ (N−
i)) The (P, Q) -th block when divided into pixel blocks is a block to be encrypted, and is included in the block to be encrypted in the sub-image.
X (m) = d (m, 0) from (3 * N + 1) data, that is, d (m, n) (m: bit width of each data, n: 0 to 3 * N, d = 0or1) ), d (m, 1), .., d
Data (m, 3 * N) is created, the data X (m) is encrypted, and it is set as Y (m) .Each bit of the data Y (m) from the MSB to the LSB is e ( m, 0), e (m,
1), ..., e (m, 3 * N), e (m, n) (m: bit width of each data, n:
0 to 3 * N, e = 0 or 1), and further outputs the block number to be encrypted (P, Q) as encrypted partial information.The zero-tree encoding unit outputs an output from the encryption unit. On the other hand, an image compression apparatus which performs zero tree coding. 5. An inverse transform decoding unit for generating and decoding a reproduced image from sub-images divided by inverse wavelet transform, an inverse quantizing unit for performing inverse quantization if necessary, A zero-tree decoding unit for performing zero-tree decoding; and a zero-tree decoding unit, wherein the zero-tree decoding unit includes four sub-images, each of which includes four sub-images and three sub-images. (1-N)
Performs zero tree decoding on the compressed code corresponding to the sub-image group (I (i, j): i = 1 ... N, j = 0,1,2,3), and when the threshold changes Notifying it to the decryption unit, the decryption unit receives the output of the zero tree decryption unit, and receives the encrypted block number (P, Q) received as encrypted partial information, The sub-image group I of each layer i (i = 1 to N)
When (i, j) (j = 0..3) is divided into LxL (L = 2 ^ (Ni)) pixel blocks, the (P, Q) th block is a block to be decrypted, and the decryption is performed. The decoding unit, when notified that the threshold is changed from the zero-tree decoding unit, performs decoding on the data included in the block to be decoded, and the inverse quantization unit transmits the data from the decoding unit. Inverse quantization is performed on each of the output sub-image groups, and the inverse transform decoding unit receives the output of the inverse quantization unit, performs inverse transform decoding, and outputs a reproduced image. Image decompression device. 6. A transmission device comprising: the image compression device according to claim 4; the image decompression device according to claim 5; and a transmission unit that connects the image compression device and the image decompression device.