JP2000232586A - Image coder and image decoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To conduct coding by providing an encryption coding means or the like that encodes data parts together with encryption coding after marker data in coding object image data so as to maintain compatibility between conventional coded image data and encrypted coded image data. SOLUTION: Whether or not a current coding mode is an 'encryption mode' is discriminated on the basis of a flag stored in a RAM 4. When the coding mode is the 'encryption mode', parts of the read image data are replaced with marker data stored in advance in a ROM 3. Thus, the head of the coding object image data is replaced with the marker data. Then the data of the replaced marker data are read and the processing of encoding the coding object image data is repeated till reading of all the coding object image data is finished in an encryption mode adopting encryption on the basis of prescribed key information.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image encoding apparatus and an image decoding apparatus, and more particularly, to encoding of image data to be encoded and, when set to a secret mode, the image encoding apparatus. An image encoding device that also performs confidentiality processing by encryption when encoding data, and decodes the encoded image data to be decoded,
The present invention relates to an image decoding apparatus that performs a decryption process when the image data to be decrypted is encrypted.

[0002]

2. Description of the Related Art Usually, when communicating image data,
If it is necessary to keep the contents confidential to a third party, a password is attached to the image data to be transmitted from the transmission side to the reception side, and a notification is given. The reception side does not unconditionally output the received image data. Therefore, a so-called confidential communication function of outputting received image data only when the password input on the receiving side matches the password notified from the transmitting side is used.

[0003] In addition, various methods have been proposed for scrambling image data so as to prevent the output image from being discriminated when interception is taken into account when communicating image data. However, in order to obtain high secrecy, there are problems that the algorithm becomes complicated and a large-scale circuit for concealment processing must be provided.

[0004] In the "communication apparatus" described in Japanese Patent Application Laid-Open No. Hei 8-107506, JBIG (Joint Bi-level Image experts Gr), which is an international standard for binary image coding, is used.
oup) method (JIS X 4311: ISO / IEC 11544), which describes a concealment method for progressive mode (an encoding method in which an image is restored from a low resolution to a high resolution step by step during decoding).

[0005] In the communication device, encryption processing is performed on the lowest resolution layer in the JBIG system. In the JBIG method, processing is performed with reference to the restored image of the lowest resolution layer at the time of decryption, and an image having a higher resolution by one step is restored. Therefore, if the lowest resolution layer is encrypted, unless the encryption is plaintexted, The next-stage resolution layer cannot be decoded correctly, and the subsequent high-resolution layer also refers to the image of the respective first-stage resolution, making it impossible to correctly reproduce the image in the subsequent processing. Achieving image concealment.

On the other hand, when decoding the encoded image data and restoring the original image data, the encoded image data is simply encoded, or is encoded and encrypted. Correctly coded image data, simply decode the coded image data, and decrypt the coded image data with decryption. Need to do.

Therefore, when the encoded image data is passed from the encoding side to the decoding side, information as to whether or not the encoded image data has been encrypted must be attached. Specifically, the encoding side adds, to the encoded image data to be passed to the decoding side, information indicating whether or not the image is encrypted as header information, or transmits the encoded image data in the communication of the encoded image data. The side (encoding side) needs to separately notify a protocol signal of information indicating whether or not the encoded image data to be transmitted to the receiving side (decoding side) is encrypted.

[0008] Thereby, the receiving side (decoding side) simply decrypts the encoded image data from the transmitting side (encoding side) if the encoded image data is not encrypted, and if the encoded image data is unencrypted, encrypts the image data. For example, the original image data can be restored by decryption and decryption processing based on predetermined key information.

[0009]

However, when the presence or absence of encryption is described in the header information of the encoded image data, or when the presence or absence of encryption is notified by a protocol signal accompanying the encoded image data, the encryption is performed. Since the presence / absence information is separated from the image data body, it is easy to determine whether the encoded image data is encrypted.

[0010] Also, special bits for describing the presence or absence of encryption are provided in the header information of the file of the encoded image data, and in the case of communication, special data indicating the presence or absence of encryption is provided in the protocol signal. Since it is necessary to carry the data, there is a problem that compatibility with encoded image data that has not been encrypted is lost or compatibility is reduced.

On the other hand, if the transmitting side (encoding side) does not notify the receiving side (decoding side) of the presence / absence of encryption of the encoded image data, the receiving side (decoding side) is encrypted. In order to recover the encoded image data, the receiving side (decoding side) needs to know that the encoded image data from the transmitting side (encoding side) is encrypted without exception. Only the original image data can be restored. That is, the receiving side (decoding side) can automatically determine whether or not the encoded image data from the transmitting side (encoding side) is encrypted, and perform adaptive decoding. Can not.

The present invention has been made in view of the above circumstances, and has been made in consideration of the above circumstances, and an image encoding apparatus capable of performing encoding while maintaining compatibility between normal encoded image data and encrypted encoded image data, and It is an object of the present invention to provide an image decoding device which can automatically identify whether or not the image data encoded by the image encoding device is encrypted, and can correctly restore the original image data.

[0013]

In order to achieve the above object, an image encoding apparatus according to claim 1 encodes image data to be encoded, and when the image data is set to a secret mode, In an image encoding apparatus that also performs encryption processing when encoding the encoding target image data, when the encryption mode is set, a part of the encoding target image data is Marker replacement means for replacing the marker data with the marker data, up to the marker data in the coding target image data, and normal coding means for coding the marker data in a normal mode, And a secret encoding means for encoding the portion after the marker data with encryption.

According to a second aspect of the present invention, the image encoding apparatus encodes the image data to be encoded, and when the mode is set to the secret mode, encrypts the image data at the time of encoding the image data to be encoded. In the image encoding apparatus that also performs the concealment process according to the above, when the concealment mode is set, marker insertion means for inserting predetermined marker data into the encoding target image data; Normal encoding means for encoding the marker data in the normal mode up to the marker data of the image data, and encoding with encryption for the part of the image data to be encoded subsequent to the marker data And a secret encoding means for performing

According to a third aspect of the present invention, in the image encoding apparatus of the first or second aspect, the marker data is located at a leading end of the encoding target image data. Features.

According to a fourth aspect of the present invention, in the image encoding apparatus of the first, second or third aspect, the marker data comprises a plurality of bits.

According to a fifth aspect of the present invention, the image decoding apparatus decodes the encoded image data to be decoded and, when the image data to be decoded is encrypted, performs a decryption process. In an image decoding apparatus that performs the decoding together, a normal decoding unit that decodes the decoding target image data in a normal mode until a marker detection unit detects predetermined marker data, and a decoding unit that decodes the decoding target image data by the normal decoding unit. Marker detecting means for detecting the marker data from the decoded image data, and when the marker data is detected by the marker detecting means, thereafter, the decryption target image data is decrypted in a decryption mode involving a decryption process. Decoding means.

According to a sixth aspect of the present invention, the image decoding apparatus decodes the encoded image data to be decoded and, when the image data to be decoded is encrypted, also performs a decryption process. In the image decoding apparatus, the decoding device decodes the image data to be decoded in a normal mode until the marker detection unit detects predetermined marker data, and decodes the image data by the normal decoding unit. Marker detection means for detecting the marker data from the decoded image data, marker removal means for removing the marker data detected by the marker detection means from the decoded image data, and marker data by the marker detection means And decryption means for decrypting the decryption target image data in a decryption mode involving decryption processing thereafter. Characterized in that was.

According to a seventh aspect of the present invention, the image encoding apparatus encodes the image data to be encoded and, when set to a secret mode, encrypts the image data when encoding the image data to be encoded. In the image encoding device that also performs the concealment process according to the above, when the confidential mode is set, a part of the encoding target image data is replaced with specific figure data, Normal encoding means for encoding up to the specific graphic in the image data to be encoded and the specific graphic in the normal mode, and enciphering a portion of the image data to be encoded after the specific graphic. Secret encoding means for performing encoding.

According to an eighth aspect of the present invention, in the image encoding apparatus according to the seventh aspect, the specific graphic data is located at a predetermined specific position of the image data to be encoded. It is characterized by the following.

According to a ninth aspect of the present invention, in the image encoding apparatus according to any one of the seventh and eighth aspects, the specific graphic replacing means converts a plurality of the specific graphic data into the object to be coded. It is characterized in that it is replaced in the image data.

According to a tenth aspect of the present invention, an image decoding apparatus decodes encoded image data to be decoded,
When the image data to be decrypted is encrypted, an image decryption device that also performs decryption processing,
A normal decoding unit that decodes the decoding target image data in a normal mode until the specific figure extracting unit extracts specific figure data, and the specific figure data from the image data decoded by the normal decoding unit. A specific graphic extracting means to be extracted, and a decryption / decoding means for decrypting the decryption target image data in a decryption mode involving a decryption process after the specific graphic data is extracted by the specific graphic extracting means. It is characterized by having.

According to an eleventh aspect of the present invention, in the image decoding apparatus of the tenth aspect, the specific graphic extracting means extracts the specific graphic data from a specific position of the image data to be decoded. It is characterized by doing.

According to a twelfth aspect of the present invention, the image decoding apparatus decodes the encoded image data to be decoded,
When the image data to be decrypted is encrypted, an image decryption device that also performs decryption processing,
A normal decoding unit that decodes the decoding target image data in a normal mode until a specific graphic extraction unit extracts a plurality of specific graphic data of a predetermined combination, which is described later; A specific graphic extracting means for extracting the plurality of specific graphic data from the image data; and, when the plurality of specific graphic data is extracted by the specific graphic extracting means, the decryption processing of the decryption target image data is performed thereafter. Decoding means for decoding in the accompanying decoding mode.

[0025]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
An embodiment of the present invention will be described in detail.

First, FIG. 1 shows a block configuration of a facsimile apparatus 1 as a communication terminal apparatus according to an embodiment of the present invention.

In FIG. 1, a facsimile apparatus 1 includes a system control unit 2, a ROM 3, a RAM 4, an image input unit 5, an image output unit 6, an encoding / decoding unit 7, an operation display unit 8, a communication control unit 9, a modem 10 , A network control unit 11, and
It is constituted by a system bus 12.

The system control unit 2 is a microcomputer that controls each unit of the apparatus according to the control program written in the ROM 3 while using the RAM 4 as a work area.

As described above, the ROM 3 is a read-only memory in which a control program for the system control unit 2 to control each unit of the apparatus is stored.

The RAM 4 is a random access memory used as a work area of the system control unit 2 as described above, and is also used for temporarily storing image data before encoding and image data after encoding. Is done.

The scanner 5 has 3.85 lines / mm, 7.7
This is for obtaining image information by reading a document image at a predetermined reading line density such as book / mm and 15.4 book / mm.

The image input means 5 is a means for taking in image data into the facsimile machine 1.
A scanner device for reading a document image, performing necessary correction and quantizing to obtain image data, a data reading device for reading image data recorded on a storage medium such as a CD-ROM, a floppy disk, and other devices such as a personal computer. , An interface device for receiving image data via a Centronics interface, a local area network, or the like.

The image output means 6 is a means for outputting image data from the facsimile machine 1, and more specifically, a plotter device for visually outputting the image data on recording paper,
A display device that visually outputs image data on a display, a data recording device that records image data on a storage medium such as a floppy (registered trademark) disk, and other devices such as a personal computer, via a Centronics interface or a local area network. Interface device for transferring the data.

In the normal encoding mode, the encoding / decoding section 7 converts the transmission image data into an MH encoding scheme, an MR encoding scheme, and an M encoding scheme conforming to G3 and G4 facsimile.
On the other hand, in a normal decoding mode, the received image data is MH-encoded, MR-encoded, MM-encoded and compressed in a predetermined encoding system such as MR encoding or JBIG.
The decoding is performed by a predetermined decoding method corresponding to the R encoding method, JBIG, or the like. The encoding / decoding unit 7
, Also performs an encoding process involving encryption based on predetermined key information in the secret mode, as described later.

The operation display section 8 is provided with a numeric keypad for designating a destination telephone number, a transmission start key, a one-touch dial key, and various other keys. It displays the operating state of the device to be notified and various messages.

The communication control unit 9 includes the modem 10 and the network control unit 1
1 to perform G3 facsimile communication.
The modem 10 is a G3 facsimile modem, and the network control unit 1
1 for modulating data to be transmitted to the line via the network control unit 1, demodulating a signal received from the PSTN or ISDN line via the network control unit 11, performing G3 facsimile communication, and performing transmission and reception of encoded image data. Things. Further, the modem 10 also transmits a DTMF signal corresponding to the input dial number. The network control unit 11 is connected to the line, and closes and releases the DC loop of the line, detects the reversal of the line polarity, detects the line release, detects the dial tone, and outputs a tone signal such as a busy tone (busy). It controls connection with a line such as detection and detection of a call signal, and generates dial pulses. The communication control unit 9, the modem 10, and the network control unit 11 function as an input device and an output device for encoded image data. In the present embodiment, the case where the image encoding apparatus and the image decoding apparatus according to the present invention are applied to the facsimile apparatus 1 is taken as an example, so that encoded image data is transmitted to another apparatus via a line (PSTN or ISDN). It goes without saying that the input and output between the encoded image data and other devices may be in other forms, such as a LAN, a Centronics interface, and an RS-232C interface.

The system bus 12 is a signal line through which the above components exchange data.

The facsimile apparatus 1 having the above configuration is similar to that shown in FIG.
As shown in the figure, the operation display unit 8
Is provided with a [confidential mode] key 8a. Each time the [Confidential Mode] key 8a is pressed, the encoding mode is switched to "Normal Mode" or "Confidential Mode". In "Confidential Mode", the indicator lamp 8b is turned on. The indicator lamp 8b is turned off to indicate the current mode state to the user.
Whether the current encoding mode is a shift between the “normal mode” and the “secret mode” is stored in the RAM 4 as a value of a predetermined flag, and the system control unit 2
The current encoding mode can be known by reading the value of the flag stored in AM4.

Further, the facsimile machine 1 will be described later.
For the encoding process shown in FIG. 4 or FIG. 6 and the decoding process shown in FIG. 8 or FIG.
Marker data is stored in the storage area 3a of M3.

The encoding procedure shown in FIG. 4 will be described. It is to be noted that what is encoded by the processing shown in FIG. 4 is the image data input from the image input means 5, and the encoded image data is transmitted to the facsimile by the communication control unit 9, the modem 10 and the network control unit 11. Although the message is transmitted to the destination via the line, in the processing shown in FIG. 4, only the procedure in which the facsimile apparatus 1 encodes the encoding target image data as the image encoding apparatus will be described. The description of the transmission procedure is omitted.

In FIG. 4, the system controller 2 reads the encoding target image data input from the image input means 5 and temporarily stored in the RAM 4 (process 101). In addition,
Reading of the encoding target image data in the process 101 is performed by RA
The processing may be performed directly from the image input unit 5 without going through the M4.

After the process 101, it is determined whether or not the current encoding mode is the "secret mode" based on the value of the flag stored in the RAM 4 (decision 102). If it is not the “secret mode” but the “normal mode” (decision 10
No. 2), normal mode encoding without concealment processing by encryption is performed on the data read in process 101 (process 103), and image data to be encoded is read (process 104). The process of encoding in the normal mode (process 105) is repeated until reading of all data of the encoding target image data is completed (No in decision 106).
loop). When the encoding of all the image data to be encoded is completed and the reading is completed (Y in decision 106)
es), the process ends.

If it is determined in the decision 102 that the encoding mode is the "secret mode" (Yes in the decision 102), a part of the image data read in the process 101 is stored in the ROM 3 in advance as shown in FIG. Replaced with the marker data being processed (process 107). As a result, the head of the encoding target image data is replaced with the marker data.

Then, the data for the marker data replaced in step 107 is encoded in the normal mode (step 108).
Further, the image data to be encoded is read (step 10
9), the process of encoding in the secret mode by encryption based on predetermined key information (process 110) is repeated until reading of all data of the encoding target image data is completed (No loop of judgment 111). When the encoding of all the data of the encoding target image data is completed and the reading is completed (Yes in decision 111), the processing is terminated. The present invention is not limited by the form of encoding in the confidential mode in the process 110, and further encodes the data obtained by encrypting the encoding target image data once, and the encoding process includes the encoding process. It may be something.

FIG. 5A shows an image data sequence after encoding when the judgment 102 in FIG. 4 is No.
FIG. 4B shows a case where the determination 102 in FIG.
4 shows an image data sequence after encoding. As shown in FIG. 5B, when the determination 102 in FIG. 4 is Yes, the head of the encoded image data sequence is replaced with marker data.

Next, a description will be given of the encoding process shown in FIG. 6, which is a modification of the encoding process procedure shown in FIG.

In FIG. 6, the system control unit 2 determines whether the current encoding mode is the “secret mode” based on the value of the flag stored in the RAM 4 (determination 20).
1). And "Normal mode" instead of "Hidden mode"
In the case of (No in decision 201), the encoding target image data input from the image input means 5 and temporarily stored in the RAM 4 is read (process 202), and the code in the normal mode without the concealment process by encryption is read. The process of performing the conversion on the data read in the process 202 (process 203) is repeated until reading of all the data of the encoding target image data is completed (No loop of the determination 204). When the encoding of all the data of the encoding target image data is completed and the reading is completed (Yes in decision 204), the processing is terminated.

In the judgment 201, when the encoding mode is the "secret mode" (Yes in the judgment 201), the marker data previously stored in the ROM 3 as shown in FIG. (Process 20)
5). As a result, the marker data is inserted at the head of the encoding target image data.

Then, the data for the marker data inserted in step 205 is encoded in the normal mode (step 206).
Further, the encoding target image data is read (step 20).
7), the process of encoding the predetermined key information in the secret mode by encryption with mode (process 208) is repeated until reading of all the data of the encoding target image data is completed (No loop of judgment 209). When the encoding of all the image data to be encoded is completed and the reading is completed (Yes in decision 209), the processing is terminated.

FIG. 7A shows an image data sequence after encoding when the judgment 201 in FIG. 6 is No.
FIG. 6B shows a case where the judgment 201 in FIG.
4 shows an image data sequence after encoding. As shown in FIG. 7B, when the determination 201 in FIG. 6 is Yes, marker data is inserted at the beginning of the encoded image data sequence, and the encoded image data sequence is Figure 4
Since the marker data is not partially replaced with the marker data as in the encoding process shown in FIG. 9, the original content of the image data is not lost, and the decoding side performs the processing shown in FIG.
If the marker data inserted into the decoding target image data is discarded at the time of decoding by the decoding process shown in (1), the original image data can be restored without loss of information.

As described above, the judgment 102 in FIG.
Is No, and the image data obtained by encoding all the data of the encoding target image data in the normal mode, or the judgment 102 in FIG. 4 or the judgment 201 in FIG.
In s, only the marker data at the head of the encoding target image data is encoded in the normal mode, and the image data obtained by encoding the data after the marker data in the secret mode is transmitted to the other party via the line without distinction. Is done.

On the other hand, on the receiving side, regardless of whether the judgment 102 in FIG. 4 or the judgment 201 in FIG.
Since the encoded image data starts from a code sequence encoded in the normal mode, the original image data is decoded by decoding in the normal mode corresponding to the encoding in the normal mode until marker data is detected. Can be restored.

The judgment 102 in FIG. 4 or the judgment 201 in FIG.
Is No, the marker data is not included in the decoding target image data. Therefore, if the decoding target image data is decoded to the end in the normal mode, correct image data can be restored.

On the other hand, if the judgment 102 in FIG. 4 or the judgment 201 in FIG. 6 is Yes, the marker data is included in the image data to be decoded. Because it is encoded with encryption concealment processing, if it is decoded in the normal mode as it is, the correct image data cannot be restored,
It is necessary to perform a decoding process shown in FIG. 8 described later corresponding to the encoding process procedure shown in FIG. 4, and a decoding process shown in FIG. 9 described later corresponding to the encoding process procedure shown in FIG. Need to do.

However, the encoded image data transmitted from the encoding side (transmission side) to the decoding side (reception side) is encoded in the normal mode without encryption, or in the secret mode with encryption. Since information indicating whether or not the image is encoded is included as marker data in the encoded image data,
Information indicating whether the coded image data to be transmitted is coded in the normal mode without encryption or coded in the confidential mode with encryption is appended to the coded image data to be transmitted. There is no need to separately notify by a protocol signal such as the non-standard function setting signal NSS of the G3 facsimile protocol, and it is not necessary to change the communication protocol control procedure depending on whether or not the encoded image data to be transmitted is encrypted.

Considering a case where image data encoded according to the processing procedures shown in FIGS. 4 and 6 is passed from the encoding side to the decoding side as a file, a general image file is composed of data called a header. Have at the beginning of the image data sequence. In the header, information relating to the image size and the encoding method can be recorded. However, when a standard file format is used, it is necessary to describe information such as whether or not encryption is performed in the header information, so that the file format may be special.

However, in the encoded image data obtained by the encoding processing shown in FIGS. 4 and 6, the encoded image data passed from the encoding side to the decoding side is encoded in the normal mode in which no encryption is performed. Since the information indicating whether the data is encoded in the confidential mode with encryption is included in the encoded image data as marker data, the information as to whether or not the data is encrypted is described in the header. do not have to.

Thus, for example, even in the case of an image format in which there is no portion in the header indicating whether or not encryption is performed, encrypted encoded image data can be stored.

In the encoding procedure of FIG. 4 or FIG. 6, only the marker data replaced or inserted at the head of the image data to be encoded is encoded in the normal mode, and the data after the marker data is encoded in the secret mode. Encoded,
In the present invention, the marker data can be replaced or inserted at any position of the encoding target image data, and the encoding target image data, up to the replaced or inserted marker data,
Alternatively, the marker data itself may be encoded in the normal mode, and data subsequent to the marker data may be encoded in the secret mode.

However, as shown in FIG. 4 or FIG.
By replacing or inserting the marker data at the beginning of the encoding target image data, the entire encoding target image data can be concealed, and the marker data is located at a predetermined position, which is the beginning of the image data. This arrangement makes it possible to immediately determine at the time of decoding on the decoding side that the decoding target image data has been encoded in the secret mode and needs to be decoded in the decoding mode.
Also, by replacing the marker data with the beginning of the image data, marker data remaining on the image when decoded and restored on the decoding side is less noticeable than when replaced at an arbitrary position. There is.

However, when it is necessary to encode the image data in the normal mode without encrypting a part of the image data and to make it visible to anyone, the marker data is replaced or replaced after the corresponding position. In some cases, it is better to insert and encode only the subsequent data in the secret mode.

The marker data to be replaced in the encoding processing procedure shown in FIGS. 4 and 6 is preferably composed of a plurality of bits, and is preferably a bit string having a certain length. That is, when data having the same bit array as the marker code is accidentally decoded on the decoding side in the unencrypted image data before the marker code, the bit array is encoded in the normal mode and the secret mode. This is because there is a possibility that decoding may not be performed correctly due to an erroneous determination that the marker code indicates a boundary with the encoding.

In practice, the size of the marker code is 3
It is considered that about two bits are sufficient. If it is 32, the probability of coincidence of the bit strings is less than 2/32 (approximately 4 billion) or less, which is practically sufficient. Even when the marker code remains on the decoded image data as in the encoding procedure shown in FIG. 4, the 32-bit marker data becomes an image having a length of about 4 mm at a resolution of 200 dpi. Inconspicuous, if the resolution is 200 dpi or more, it becomes even less noticeable.

Next, a decoding procedure corresponding to the encoding procedure shown in FIG. 4 will be described with reference to FIG. It is to be noted that what is decoded by the processing shown in FIG. 8 is encoded by the encoding processing procedure shown in FIG. 4 in the destination apparatus, and the communication control unit 9, the modem 10 and the network control unit 11 change the line as a facsimile message. Image data (image data to be decoded) received through
The image data after decoding is output by the image output means 6. In the processing shown in FIG. 8, only the procedure in which the facsimile apparatus 1 decodes the image data to be decoded as the image decoding apparatus will be described. A description of the reception / output procedure of the encoding target image data is omitted.

In FIG. 8, the system control unit 2 receives a facsimile message from the
Code data is input from the decoding target image data temporarily stored in the encoding / decoding unit 7 (process 301), and is decoded in the normal mode corresponding to the normal mode encoding (process 3).
02).

Then, as shown in FIG. 3, it is determined whether or not there is marker data stored in the ROM 3 in advance in the decoded data, and the decoding of the image data to be decoded is completed. Processing 3 until power code data ends
01 and the process 302 are repeated (No in decision 303, No loop in decision 304).

If the code data ends without detecting the marker data (Yes in decision 304), the decoding process ends. The judgment 304 is Yes because
This is the case where the marker data is not included in the decoding target image data, that is, the decoding target image data has been encoded in the normal mode on the encoding side. As a result, the decoding target image data encoded in the normal mode can be correctly decoded and restored to the original image data.

If there is marker data in decision 303 (Yes in decision 303), code data from the decoding target image data is further input to the encoding / decoding section 7 (step 30).
5) The process of decoding in the decryption mode based on the same key information as used in the encryption in the secret mode (process 306), the code data to be decoded after the decoding of the decoding target image data is completed Is repeated until the process ends (decision 3
07 No loop). When the decoding of all the image data to be decoded is completed and the code data ends (Yes in decision 307), the processing ends.

As a result, both the image data encoded in the normal mode and the image data encoded in the confidential mode by the encoding process shown in FIG. 4 can be performed without additional information attached to the image data to be decoded. Correct decoding can restore the original image data.

Next, a description will be given of a procedure shown in FIG. 9, which is a modification of the decoding procedure shown in FIG. 8, and corresponds to the encoding procedure shown in FIG.

In FIG. 9, the system control unit 2 receives a facsimile message from the
Is input to the encoding / decoding unit 7 from the image data to be decoded temporarily stored in the encoding / decoding unit 7 (processing 401), and is decoded in the normal mode corresponding to the encoding in the normal mode (processing 4).
02).

Then, as shown in FIG. 3, it is determined whether or not there is marker data stored in the ROM 3 in advance in the decoded data, and the decoding of the image data to be decoded is completed. Processing 4 until power code data is completed
01 and the process 402 are repeated (No in the judgment 403, No loop in the judgment 404).

If the code data ends without detecting the marker data (Yes in decision 404), the decoding process ends. The decision 404 is Yes because
This is the case where the marker data is not included in the decoding target image data, that is, the decoding target image data has been encoded in the normal mode on the encoding side. As a result, the decoding target image data encoded in the normal mode can be correctly decoded and restored to the original image data.

If there is marker data in decision 403 (Yes in decision 403), the marker data after decoding is discarded, removed from the decoded image data sequence (process 405), and then decoded. The encoded data is further input from the encoding target image data to the encoding / decoding unit 7 (process 406), and the process of decoding in the decryption mode based on the same key information used in the encryption in the secret mode (process 406) 407),
Repeat until decoding of the image data to be decoded is completed and code data to be decoded ends (No in decision 408).
loop). When the decoding of all the image data to be decoded is completed and the code data ends (Yes in decision 408), the process ends.

As a result, both the image data encoded in the normal mode and the image data encoded in the secret mode by the encoding process shown in FIG. 6 can be performed without additional information attached to the image data to be decoded. Correct decoding can restore the original image data.

Next, FIG. 4 or FIG.
And the image encoding process and the image decoding process different from those of the image decoding process shown in FIG. 8 or FIG. 9 will be described below.

In the image encoding process described below, as shown in FIG. 2, the operation display section 8 is provided with a [secret mode] key 8a, and the [secret mode] key 8a is depressed. Every time the encoding mode is switched to the “normal mode” or the “secret mode”, the indicator lamp 8b is turned on in the “secret mode”, and the indicator lamp 8b is turned off in the “normal mode” to set the current mode. In addition to indicating the mode state to the user, whether the current encoding mode is a shift between the “normal mode” and the “secret mode” is stored in the RAM 4 as a value of a predetermined flag, and the system control unit 2 The fact that the current encoding mode can be known by reading the value of the flag stored in the RAM 4 is described in the case of the image encoding process described above. It is the same.

Further, the facsimile machine 1 will be described later.
For the encoding process shown in FIG. 11 or FIG. 13 and the decoding process shown in FIG. 14 or FIG. 16, specific graphic data is stored in the storage area 3b of the ROM 3 as shown in FIG.

The encoding procedure shown in FIG. 11 will be described. It is to be noted that what is encoded by the processing shown in FIG. 11 is the image data input from the image input unit 5,
The encoded image data is transmitted as a facsimile message to the other party via a line by the communication control unit 9, the modem 10, and the network control unit 11. In the processing shown in FIG. 11, the facsimile apparatus 1 As the apparatus, only the procedure for encoding the encoding target image data will be described, and the description of the procedure for transmitting the encoded image data will be omitted.

In FIG. 11, the system control unit 2 determines whether the current encoding mode is the “secret mode” based on the value of the flag stored in the RAM 4 (determination 50).
1). And "Normal mode" instead of "Hidden mode"
If (No in decision 501), the image data to be encoded is read (process 502), the process of encoding in the normal mode is performed (process 503), and the reading of all data of the image data to be encoded ends. Repeat until (decision 504)
No loop). When the encoding of all the image data to be encoded is completed and the reading is completed (decision 50)
4 (Yes), the process ends.

When the encoding mode is the "secret mode" in the decision 501 (Yes in the decision 501), the image data to be encoded is read (process 505), and it is determined whether or not a predetermined specific figure insertion position has been reached. While judging (judgment 50
No. 6), the process of encoding in the normal mode is repeated (process 507).

If it is determined in step 506 that the specific figure is to be inserted (Yes in step 506), a part of the image data read in step 505 is converted to the R data as shown in FIG.
The specific graphic data stored in advance in OM3 is replaced (process 508). As a result, the specific graphic data is replaced at the predetermined specific graphic insertion position of the encoding target image data.

Then, the specific graphic data replaced in the process 508 is encoded in the normal mode (process 509), the image data to be encoded is read (process 510), and the secret mode by encryption based on predetermined key information is obtained. (Processing 511), and is repeated until reading of all data of the encoding target image data is completed (N in decision 512).
o loop). When the encoding of all the data of the encoding target image data is completed and the reading is completed (Yes in decision 512), the processing is terminated. The present invention is not limited by the encryption mode of the secret mode in the process 511, and the data obtained by once encrypting the image data to be encoded is further encoded. It may be something.

FIG. 12 shows, as a decoded image, the image data encoded when the judgment 501 in FIG. 11 is Yes. In FIG. 12, the specific graphic data written in the process 508 of FIG.
The predetermined specific graphic insertion position at 06 is the beginning of the image data, the area of the image data where the specific graphic data is replaced is encoded in the normal mode, and the area after the specific graphic data is replaced is in the secret mode. . However, if the predetermined specific graphic insertion position in the determination 506 is not the head of the image data, the encoding is performed in the communication mode even before the area where the specific graphic data is replaced in the image data. It should be noted that the specific graphic data shown in FIG. 12 is relatively large with respect to the image data for easy understanding.

Next, the encoding process shown in FIG. 13 which is a modification of the encoding process procedure shown in FIG. 11 will be described.

In FIG. 13, the system control unit 2 determines whether the current encoding mode is the “secret mode” based on the value of the flag stored in the RAM 4 (determination 60).
1). And "Normal mode" instead of "Hidden mode"
When (No in decision 601), the encoding target image data is read (process 602), the process of encoding in the normal mode is performed (process 603), and reading of all data of the encoding target image data ends. Repeat until (decision 604)
No loop). When the encoding of all the image data to be encoded is completed and the reading is completed (decision 60)
4 (Yes), the process ends.

If the encoding mode is the “secret mode” in decision 601 (decision 601: Yes), the image data to be encoded is read (process 605), and the specified specific figure insertion first position is set. While performing the determination (No in determination 606), the process of encoding in the normal mode is repeated (process 607).

If it is determined at the judgment 606 that the specific figure insertion first position has been reached (Yes at the judgment 606), the process 605 is executed.
A part of the image data read in is replaced with specific graphic data stored in the ROM 3 in advance as shown in FIG. 10 (process 608). As a result, the specific graphic data is replaced at the first specific graphic insertion first position of the encoding target image data.

Then, the specific graphic data replaced in the processing 608 is coded in the normal mode (processing 609), and the image data to be coded is read (processing 610). (No in decision 611), the process of encoding in the normal mode is repeated (process 612).

If it is determined that the specific figure insertion second position has been reached in the judgment 611 (Yes in the judgment 611), the process 610 is executed.
A part of the image data read in is replaced with specific graphic data stored in the ROM 3 in advance as shown in FIG. 10 (process 613). As a result, the specific graphic data is replaced at the predetermined specific graphic insertion second position of the encoding target image data.

Then, the specific graphic data replaced in the process 613 is encoded in the normal mode (process 614), the image data to be encoded is read in (process 615), and the secret mode by encryption based on predetermined key information is obtained. (Process 616), and is repeated until reading of all data of the encoding target image data is completed (N in decision 617).
o loop). When the encoding of all the image data to be encoded is completed and the reading is completed (Yes in decision 617), the processing is terminated.

As described above, in the encoding processing procedure shown in FIG. 13, the specific graphic data is written at each of the specific graphic insertion first position and the second position in the encoding target image data, thereby Accordingly, when the same pattern as the replaced specific graphic data is included in the encoding target image data, it is possible to reduce a situation in which the decoding side erroneously decodes the image data in the decoding mode. Of course, as the number of specific graphic data to be replaced in the encoding target image data increases, the number of erroneous determinations on the decoding side decreases. However, since the specific image data becomes noise for the actual image data, it is better to reduce the specific image data as much as possible.The number of specific graphic data to be replaced depends on the prevention of erroneous determination on the decoding side and the quality of the image data. It is necessary to consider the balance. In addition, it is considered that there is a method of arranging specific graphic data in which the replaced specific graphic data is inconspicuous visually or on an image layout.

As described above, the judgment 501 in FIG. 11 or the judgment 601 in FIG. 13 is No, and the image data obtained by encoding all the data of the image data to be encoded in the normal mode, or the image data in FIG. If the determination 501 or the determination 601 in FIG. 13 is Yes, the predetermined graphic insertion position of the encoding target image data or the specific graphic data replaced with the predetermined specific graphic insertion second position is encoded in the normal mode. The image data obtained by encoding the data after the specific graphic data in the secret mode is transmitted to the other party via the line without distinction.

On the other hand, even if the judgment 501 in FIG. 11 or the judgment 601 in FIG.
Even when becomes, since the encoded image data received as the decoding target image data is started from the code sequence encoded in the normal mode, a predetermined specific graphic insertion position, or a predetermined Until the specific graphic data at the specific graphic insertion second position is detected, the original image data can be restored by decoding in the normal mode corresponding to the encoding in the normal mode.

Judgment 501 in FIG. 11 or Judgment 6 in FIG.
When 01 is No, the specific graphic data is not included in the decoding target image data. Therefore, if the decoding target image data is decoded to the end in the normal mode, correct image data can be restored.

On the other hand, if the judgment 501 in FIG. 11 or the judgment 601 in FIG. 6 is Yes, the specific graphic data is included in the image data to be decoded. Alternatively, since the data after the specific graphic data replaced at the predetermined specific graphic insertion second position is encoded with concealment processing by encryption, if it is decoded in the normal mode as it is, correct image data Cannot be restored, it is necessary to perform a decoding process shown in FIG. 14, which will be described later, corresponding to the encoding process shown in FIG. 11, and FIG. 16, which will be described later, corresponding to the encoding process shown in FIG. Must be performed.

However, the encoded image data transmitted from the encoding side (transmission side) to the decoding side (reception side) is encoded in the normal mode without encryption, or in the secret mode with encryption. Since the information indicating whether or not the image data is encoded is included in the encoded image data as specific graphic data, the encoded image data to be transmitted is encoded in the normal mode in which encryption is not performed, or the encoded image data is encrypted. There is no need to attach information indicating whether or not the image is encoded in the confidential mode to the transmitted encoded image data, and to separately notify by a protocol signal such as a non-standard function setting signal NSS of the G3 facsimile protocol. There is no need to change the protocol control procedure depending on whether or not the encoded image data to be transmitted is encrypted.

Also, considering a case where image data encoded according to the processing procedures shown in FIGS. 11 and 13 is transferred as a file from the encoding side to the decoding side, a general image file includes data called a header. Have at the beginning of the image data sequence. In the header, information relating to the image size and the encoding method can be recorded. However, when a standard file format is used, it is necessary to describe information such as whether or not encryption is performed in the header information, so that the file format may be special.

However, in the coded image data obtained by the coding processing shown in FIGS. 11 and 13, the coded image data passed from the coding side to the decoding side is coded in the normal mode in which no encryption is performed. Since the information indicating whether the data is encoded in the confidential mode with encryption is included in the encoded image data as specific graphic data, information as to whether or not the header is encrypted is included in the header. No need to describe.

Thus, for example, even in the case of an image format in which there is no portion in the header indicating whether or not encryption is performed, it is possible to store the encoded image data that has been encrypted.

Also, in the encoding processing procedure of FIG. 11 or FIG. 13, a predetermined specific figure insertion position or a predetermined specific figure insertion opposite position and a second position are not set at an arbitrary position in the encoding target image data. In addition, by replacing the specific graphic data, the search processing of the specific graphic data on the decoding side can be facilitated, the amount of memory required for the search processing can be reduced, and the search processing speed can be increased. Can be Further, if the predetermined specific graphic insertion position, or the predetermined specific graphic insertion opposite position and the second position are the beginning of the encoding target image data, the entire encoding target image data can be concealed. At the time of decoding on the decoding side, it is possible to immediately determine that the image data to be decoded has been encoded in the secret mode and needs to be decoded in the decoding mode. Of course, the specific graphic data may be replaced at an arbitrary position in the encoding target image data, but in that case, the process of searching for the specific graphic data on the decoding side becomes complicated. However, if it is necessary to encode the image data in the normal mode without encrypting the middle part of the image data, so that anyone can see it, replace the specific figure data after the corresponding position, It may be better to encode only the data in the secret mode.

Next, a decoding procedure corresponding to the encoding procedure shown in FIG. 11 will be described with reference to FIG. It is to be noted that what is decoded by the processing shown in FIG. 14 is encoded by the encoding processing procedure shown in FIG. 11 in the destination apparatus, and the communication control unit 9, the modem 10 and the network control unit 11 switch the line as a facsimile message. Image data (image data to be decoded) received via
The decoded image data is output by the image output means 6. In the processing shown in FIG. 11, only the procedure in which the facsimile apparatus 1 operates as an image decoding apparatus to decode the image data to be decoded. This will be described, and the description of the receiving / outputting procedure of the encoding target image data will be omitted.

In FIG. 14, the system control unit 2 receives a facsimile message from the
4 is input to the encoding / decoding unit 7 from the decoding target image data temporarily stored in the decoding unit 4 (processing 701), and is decoded in the normal mode corresponding to the encoding in the normal mode (processing 7).
02), a process of searching for the specific graphic data stored in the ROM 3 in advance as shown in FIG. 10 in the data after decoding (process 703), and the decoding of the decoding target image data is completed. The code data to be decoded ends or
Alternatively, the process is repeated until specific graphic data is found by the process 703 (No in the judgment 704, No loop in the judgment 705).

If the code data ends without finding the specific graphic data (Yes in decision 705),
The decoding process ends. The judgment 705 is Yes when the specific graphic data is not included in the image data to be decoded, that is, when the image data to be decoded has been encoded in the normal mode on the encoding side. . As a result, the decoding target image data encoded in the normal mode can be correctly decoded and restored to the original image data.

If there is specific graphic data in the judgment 704 (Yes in the judgment 704), code data from the image data to be decoded is further input to the coding / decoding section 7 (processing 70).
6) The process of decoding in the decryption mode based on the same key information as used in the encryption in the secret mode (process 707), and the code data to be decoded after the decoding of the decoding target image data is completed Is repeated until the process is completed (judgment 7
08 No loop). When decoding of all the image data to be decoded is completed and the code data ends (Yes in decision 708), the process ends.

As a result, both the image data encoded in the normal mode and the image data encoded in the secret mode by the encoding process shown in FIG. 11 can be performed without additional information attached to the image data to be decoded. Correct decoding can restore the original image data.

Here, a method of searching for specific graphic data in the process 703 in FIG. 14 will be described with reference to FIG.

The black pixel group shown in FIG. 9A is specific graphic data to be searched. There are various methods for searching for such bitmap graphic data. For example, image data after decoding is displayed in a 5 × 4 matrix window as shown in FIG. The raster scan is performed as shown in c), and the state of the bitmap is
The part which becomes the same as the pattern shown in FIG. In this way, when trying to find a graphic from specific graphic data replaced at an arbitrary position in the image data, a line memory of at least about 4 lines is required, and the required hardware resources are relatively large. Would. However, by determining the replacement position of the specific graphic data between the encoding side and the decoding side in advance, the search becomes easy and the necessary hardware resources can be reduced.

Next, a procedure shown in FIG. 16, which is a modification of the decoding procedure shown in FIG. 14, and which corresponds to the encoding procedure shown in FIG. 13, will be described.

In FIG. 16, the system control unit 2 receives a facsimile message from the
4 is input to the encoding / decoding unit 7 from the decoding target image data temporarily stored in the decoding unit 4 (process 801), and is decoded in the normal mode corresponding to the normal mode encoding (process 8).
02), a process for searching for specific graphic data stored in the ROM 3 in advance as shown in FIG. 10 in the decoded data (process 803), and the decoding of the decoding target image data is completed. The code data to be decoded ends or
Alternatively, the process is repeated until specific graphic data is found by the process 803 (No in the judgment 804, No loop in the judgment 805).

If the code data ends without finding the specific graphic data (Yes in decision 805),
The decoding process ends. The determination 805 is Yes when the specific graphic data is not included in the image data to be decoded, that is, when the image data to be decoded has been encoded in the normal mode on the encoding side. . As a result, the decoding target image data encoded in the normal mode can be correctly decoded and restored to the original image data.

If there is specific graphic data in the judgment 804 (Yes in the judgment 804), code data from the image data to be decoded is inputted to the coding / decoding section 7 (step 80).
1) The decoding is performed in the normal mode corresponding to the encoding in the normal mode (process 802), and it is searched whether or not the decoded data includes the specific graphic data stored in the ROM 3 in advance as shown in FIG. The process is repeated (process 803) until the decoding of the image data to be decoded is completed and the code data to be decoded ends, or until the specific graphic data is found by the process 803 (No in decision 804, decision 80)
No. 5 loop).

If the code data ends without finding the specific graphic data (Yes in decision 805),
The decoding process ends. The determination 805 is Yes when the specific graphic data is not included in the image data to be decoded, that is, when the image data to be decoded has been encoded in the normal mode on the encoding side. . As a result, the decoding target image data encoded in the normal mode can be correctly decoded and restored to the original image data.

If there is specific graphic data in the judgment 804 (Yes in the judgment 804), code data from the image data to be decoded is further input to the coding / decoding section 7 (step 80).
6), decoding is performed in the normal mode corresponding to the encoding in the normal mode (process 807), and it is searched whether there is specific graphic data stored in the ROM 3 in advance in the decoded data as shown in FIG. The process is repeated (process 808) until the decoding of the image data to be decoded is completed and the code data to be decoded ends, or until the specific graphic data is found by the process 808 (No in decision 809, decision 81)
No loop of 0).

If the code data ends without finding the specific graphic data (Yes in decision 810),
The decoding process ends. The determination 805 is Yes when the second specific graphic data is not included, that is, when the decoding target image data is the one encoded in the normal mode on the encoding side. As a result, the decoding target image data encoded in the normal mode can be correctly decoded and restored to the original image data.

If there is specific graphic data in the judgment 809 (Yes in the judgment 804), code data from the image data to be decoded is further inputted to the coding / decoding section 7 (step 81).
1) The process of decoding in the decryption mode based on the same key information as used in the encryption of the secret mode (process 812), the code data to be decoded after the decoding of the decoding target image data is completed Is repeated until the process is completed (decision 8
13 No loop). When the decoding of all the image data to be decoded is completed and the code data ends (Yes in decision 813), the process ends.

As a result, both the image data encoded in the normal mode and the image data encoded in the confidential mode by the encoding process shown in FIG. 13 can be performed without additional information attached to the image data to be decoded. Correct decoding can restore the original image data. Further, when the same pattern as the specific graphic data is included in the decoding target image data, it is possible to prevent the decoding mode from being erroneously decoded.

[0118]

According to the first aspect of the present invention, in the case of the normal mode other than the secret mode, the image data to be encoded is encoded in the normal mode without the secret process by encryption. On the other hand, in the case of the secret mode, a part of the encoding target image data is replaced with the predetermined marker data, a part of the encoding target image data up to the marker data, and the marker data. Is encoded in the normal mode without concealment processing by encryption, and the portion of the target image data after the marker data is encoded in the concealment mode with encryption. When the image decoding apparatus decodes the encoding target image data later as the decoding target image data, the decoding target image data corresponds to the encoding in the normal mode. If the marker data is not detected during the sequential decoding to the end by the decoding in the normal mode, the decoding target image data encoded in the normal mode can be correctly decoded. If the marker data is detected during the sequential decoding to the end by the decoding of the normal mode corresponding to the coding of the normal mode, if the marker data is detected in the decoding mode corresponding to the coding of the secret mode thereafter, the encryption It is possible to correctly decode image data to be decoded which has been encoded with concealment processing. Therefore, there is no need to separately notify the information as to whether or not the image data to be decrypted is encrypted, and the compatibility between normal encoded image data and encrypted encoded image data is not required. Thus, the effect that the encoding can be performed while maintaining the above is obtained.

According to the second aspect of the present invention, in the case of the normal mode other than the secret mode, the image data to be encoded is encoded in the normal mode without the secret process by encryption. In the confidential mode, the predetermined marker data is inserted into the encoding target image data, and a portion of the encoding target image data up to the marker data and the marker data are encrypted. Is encoded in the normal mode without the concealment process, and the portion of the image data to be encoded after the marker data is encoded in the concealment mode with the encryption. When the image decoding apparatus decodes the image data to be decoded as image data to be decoded, the image data to be decoded is passed to the normal mode encoding. If the marker data is not detected during the sequential decoding to the end by the decoding in the mode, the decoding target image data encoded in the normal mode can be correctly decoded, and the decoding target image data is converted to the normal mode. If the marker data is detected during the sequential decoding to the end by the decoding in the normal mode corresponding to the encoding of the above, the decryption in the decryption mode corresponding to the encoding in the above-described confidential mode, and the concealment process by the encryption Can correctly decode the decoding target image data. Therefore, there is no need to separately notify the information as to whether or not the image data to be decrypted is encrypted, and the compatibility between normal encoded image data and encrypted encoded image data is not required. Thus, the effect that the encoding can be performed while maintaining the above is obtained. In addition, the marker data is
Instead of being replaced with a part of the encoding target image data, since it is inserted into the encoding target image data, the content of the encoding target image data is passed to the image decoding device without loss. In the image decoding apparatus, if the marker data is discarded, an effect is obtained that original image data that does not include the marker data and has no loss of content can be restored.

According to the third aspect of the present invention, when the image decoding apparatus decodes the encoded image data after encoding as the image data to be decoded, the image data to be decoded is encrypted. There is an effect that it is possible to immediately judge whether or not the data is correct.

According to the fourth aspect of the present invention, since the marker data is composed of a plurality of bits, it is possible to reduce erroneous determination when detecting the marker data on the decoding device side. can get.

According to the fifth aspect of the present invention, the image data to be decoded is completely processed by decoding in the normal mode corresponding to the normal mode encoding in the image coding apparatus and the like according to the first aspect. If the marker data is not detected during the sequential decoding, the encoding target image data encoded in the normal mode can be correctly decoded, and the decoding target image data is converted to the normal mode corresponding to the encoding in the normal mode. If the marker data is detected during the sequential decoding to the end by the decoding of the mode, the decoding of the decoding mode corresponding to the encoding of the secret mode in the image encoding apparatus or the like according to claim 1 will be described. In addition, it is possible to correctly decode the encoding target image data that has been encoded with the concealment process by encryption. Therefore, there is no need to notify the image encoding apparatus of information as to whether or not the image data to be decrypted is encrypted, and normal encoded image data and encrypted encoded image data are not required. The image encoding device can perform encoding while maintaining compatibility with the image encoding device, and automatically identifies whether or not the image data encoded by the image encoding device is encrypted. The effect that data can be restored is obtained.

According to the invention of claim 6, the image data to be decoded is completely processed by decoding in the normal mode corresponding to the coding in the normal mode in the image coding apparatus or the like according to claim 2. If the marker data is not detected during the sequential decoding, the encoding target image data encoded in the normal mode can be correctly decoded, and the decoding target image data is converted to the normal mode corresponding to the encoding in the normal mode. If the marker data is detected during sequential decoding to the end by mode decoding, decoding in a decoding mode corresponding to encoding in a secret mode in the image encoding apparatus or the like according to claim 1 thereafter. Thus, the encoding target image data encoded with the concealment process by encryption can be correctly decoded, and the marker data is removed from the decoded image data. That. Therefore, there is no need to notify the image encoding apparatus of information as to whether or not the image data to be decrypted is encrypted, and normal encoded image data and encrypted encoded image data are not required. The image encoding device can perform encoding while maintaining compatibility with the image encoding device, and automatically identifies whether or not the image data encoded by the image encoding device is encrypted. An effect is obtained that data can be restored without including the marker data and without loss of contents.

According to the invention of claim 7, when the normal mode is not the secret mode, the image data to be encoded is encoded in the normal mode without the secret process by encryption. In the case of the secret mode, a part of the encoding target image data is replaced with the specific graphic data, a part of the encoding target image data up to the specific graphic data, and the specific graphic data are In this case, the image data is encoded in the normal mode without concealment processing by encryption, and the portion of the image data to be encoded subsequent to the specific graphic data is encoded in the concealment mode with encryption. When the image decoding apparatus decodes the encoding target image data later as the decoding target image data, the decoding target image data corresponds to the encoding in the normal mode. If the specific graphic data is not extracted during the sequential decoding to the end by the decoding in the normal mode, the decoding target image data encoded in the normal mode can be correctly decoded. If the specific graphic data is extracted during sequential decoding to the end by decoding in the normal mode corresponding to the encoding in the normal mode, the decryption in the decryption mode corresponding to the encoding in the secret mode is performed. It is possible to correctly decode the image data to be decoded which has been encoded with the concealment process by the encryption. Therefore, there is no need to separately notify the information as to whether or not the image data to be decrypted is encrypted, and the compatibility between normal encoded image data and encrypted encoded image data is not required. Thus, the effect that the encoding can be performed while maintaining the above is obtained.

According to the eighth aspect of the present invention, since the specific graphic data is located at a predetermined specific position of the encoding target image data, the specific graphic data is extracted on the image decoding apparatus side. And the decoding speed is improved.

According to the ninth aspect of the present invention, a plurality of the specific graphic data are present in the image data to be encoded. Therefore, only one specific image data is replaced in the image data to be encoded. If you do, by pure chance,
The same content as the specific graphic data is included in the image data to be encoded, and the image decoding apparatus determines that the decoding start position in the decoding mode is shifted from the original position and is normal. An effect is obtained that it is possible to make it difficult to cause a situation where decoding cannot be performed.

According to the tenth aspect of the present invention, the image data to be decoded is completely processed by decoding in the normal mode corresponding to the coding in the normal mode in the image coding apparatus according to the seventh aspect. If the specific graphic data is not extracted during the sequential decoding, the encoding target image data encoded in the normal mode can be correctly decoded, and the decoding target image data corresponds to the encoding in the normal mode. If the specific graphic data is detected during the sequential decoding to the end by the decoding in the normal mode, the decoding in the decoding mode corresponding to the coding in the secret mode in the image coding apparatus or the like according to claim 7 thereafter. Thus, the encoding target image data encoded with the concealment process by encryption can be correctly decoded. Therefore, there is no need to notify the image encoding apparatus of information as to whether or not the image data to be decrypted is encrypted, and normal encoded image data and encrypted encoded image data are not required. The image encoding device can perform encoding while maintaining compatibility with the image encoding device, and automatically identifies whether or not the image data encoded by the image encoding device is encrypted. The effect that data can be restored is obtained.

According to the eleventh aspect, according to the eighth aspect,
It is possible to extract the specific graphic data substituted at a specific position of the decoding target image data by the image encoding device or the like according to the above, so that the decoding target image data is encrypted. It is possible to quickly determine whether or not the decoding process is to be performed, and the decoding speed is improved.

According to the twelfth aspect, in the first aspect,
10. In addition to the same effect as that of 0, in the image encoding device or the like according to claim 9, if the specific graphic data replaced with a plurality in the decoding target image data is not detected, the process shifts to decoding in decoding mode. Therefore, if only one specific image data is replaced in the image data to be decoded on the image encoding device side, the same content as the specific graphic data is completely accidentally replaced by the image data to be decoded. This has the effect that it is possible to prevent the occurrence of a situation in which the decoding start position in the decoding mode is shifted from the original position and normal decoding cannot be performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a block configuration of a facsimile apparatus as an image encoding device and an image decoding device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a partial configuration of an operation display unit of the facsimile apparatus according to the embodiment of the present invention.

FIG. 3 is a diagram showing storage contents of a ROM of the facsimile apparatus according to the embodiment of the present invention.

FIG. 4 is a flowchart showing an encoding processing procedure in the facsimile apparatus according to the embodiment of the present invention.

5 is a diagram showing an image data sequence, a part of the image data sequence, and marker data replaced by the processing shown in FIG. 4;

FIG. 6 is a flowchart showing an encoding processing procedure different from that shown in FIG. 4 in the facsimile apparatus according to the embodiment of the present invention.

7 is a diagram showing an image data sequence and marker data inserted into the image data sequence by the processing shown in FIG. 6;

FIG. 8 is a flowchart showing a decoding processing procedure in the facsimile apparatus according to the embodiment of the present invention.

FIG. 9 is a flowchart showing another decoding processing procedure different from that shown in FIG. 8 in the facsimile apparatus according to the embodiment of the present invention.

FIG. 10 is a diagram different from FIG. 3, showing the contents stored in the ROM of the facsimile apparatus according to the embodiment of the present invention.

FIG. 11 is a flowchart showing another encoding processing procedure different from that shown in FIG. 4 or FIG. 6 in the facsimile apparatus according to the embodiment of the present invention.

12 is a diagram showing an image data sequence, a part of the image data sequence, and specific graphic data to be replaced by the processing shown in FIG. 11;

FIG. 13 is a flowchart showing an encoding processing procedure different from that shown in FIG. 4, FIG. 6, or FIG. 11 in the facsimile apparatus according to the embodiment of the present invention.

FIG. 14 is a flowchart showing another decoding processing procedure different from that shown in FIG. 8 or 9 in the facsimile apparatus according to the embodiment of the present invention.

FIG. 15 is a schematic diagram illustrating a method for searching for specific graphic data.

FIG. 16 is a flowchart showing a decoding processing procedure different from that shown in FIG. 8, FIG. 9, or FIG. 14 in the facsimile apparatus according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Facsimile apparatus 2 System control part 3 ROM 3a Storage area for marker data 3b Storage area for specific figure data 4 RAM 5 Image input means 6 Image output means 7 Encoding / decoding part 8 Operation display part 8a [Confidential mode ] Key 8b indicator lamp 9 communication control unit 10 modem 11 network control unit 12 system bus

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) H04N 7/167 H04N 7/167 Z 5J104 F-term (Reference) 5C059 KK43 MA00 MC26 PP01 RC24 RC35 SS06 UA02 UA05 UA39 5C064 CA14 CB01 CC01 CC04 5C075 AA02 AA03 AA05 CD27 EE03 EE06 5C078 BA21 CA47 DA01 DA02 DB00 5J064 AA00 BA08 BB08 BB13 BC01 BD02 5J104 AA33 NA10 PA00

Claims (12)

[Claims] An image code which encodes image data to be encoded and, when the image data to be encoded is set to a confidential mode, performs a concealment process by encryption at the time of encoding the image data to be encoded. In the encoding device, when the secret mode is set, a part of the encoding target image data is replaced with a predetermined marker data, a marker replacing unit, and the marker data of the encoding target image data And a normal encoding unit that encodes the marker data in the normal mode, and a concealment encoding unit that performs encoding with encryption for a portion of the image data to be encoded subsequent to the marker data. An image encoding device, comprising: 2. An image code which encodes image data to be encoded and, when the image data to be encoded is set to a confidential mode, performs concealment processing by encryption when encoding the image data to be encoded. In the encoding device, when the secret mode is set, in the encoding target image data, a marker insertion unit that inserts into predetermined marker data, up to the marker data of the encoding target image data, And a normal encoding unit that encodes the marker data in the normal mode, and a secret encoding unit that performs encoding with encryption for a portion of the image data to be encoded subsequent to the marker data. An image encoding device, characterized in that: 3. The image encoding apparatus according to claim 1, wherein the marker data is located at a leading end of the encoding target image data. 4. The image encoding apparatus according to claim 1, wherein said marker data is composed of a plurality of bits. 5. An image decoding apparatus that decodes encoded image data to be decoded and, when the image data to be decoded is encrypted, also performs a decryption process. A normal decoding unit for decoding the decoding target image data in a normal mode until the marker detection unit detects predetermined marker data, and detecting the marker data from the image data decoded by the normal decoding unit Marker detection means, and decryption decryption means for decrypting the decryption target image data in a decryption mode involving decryption processing after the marker data is detected by the marker detection means. An image decoding device characterized by the following. 6. An image decoding apparatus for decoding encoded image data to be decoded and, when the image data to be decoded is encrypted, also performing a decryption process. A normal decoding means for decoding the image data to be decoded in a normal mode until the marker detecting means detects predetermined marker data, and detecting the marker data from the image data decoded by the normal decoding means Marker detecting means, marker removing means for removing the marker data detected by the marker detecting means from the decoded image data, and when the marker data is detected by the marker detecting means, Decryption means for decrypting image data to be decrypted in a decryption mode involving decryption processing. . 7. An image code for encoding image data to be encoded and, when the encryption mode is set, performing a concealment process by encryption when encoding the image data to be encoded. In the encoding apparatus, when the secret mode is set, a specific graphic replacement unit that replaces a part of the encoding target image data with specific graphic data, and the specific graphic of the encoding target image data. And a normal encoding unit that encodes the specific graphic in the normal mode, and a confidential encoding unit that performs encoding with encryption for a portion of the image data to be encoded after the specific graphic. An image encoding device, comprising: 8. The image encoding apparatus according to claim 7, wherein the specific graphic data is located at a predetermined specific position of the image data to be encoded. 9. The image encoding apparatus according to claim 7, wherein the specific graphic replacing unit replaces the plurality of specific graphic data in the encoding target image data. 10. An image decoding apparatus which decodes encoded image data to be decoded and, when the image data to be decoded is encrypted, also performs a decryption process. A normal decoding unit for decoding the image data to be decoded in a normal mode until the specific figure extracting unit extracts the specific figure data, and extracting the specific figure data from the image data decoded by the normal decoding unit A specific graphic extracting means for performing the decoding and the decryption decoding means for decrypting the image data to be decrypted in a decryption mode involving a decryption process after the specific graphic data is extracted by the specific graphic extracting means. An image decoding device, comprising: 11. The image decoding apparatus according to claim 10, wherein the specific graphic extracting means extracts the specific graphic data from a specific position of the image data to be decoded. 12. An image decoding apparatus for decoding encoded image data to be decoded and, when the image data to be decoded is encrypted, also performing a decryption process. A normal decoding unit for decoding the image data to be decoded in a normal mode until the specific figure extracting unit extracts a plurality of specific figure data of a predetermined combination, and an image decoded by the normal decoding unit; A specific figure extracting means for extracting the plurality of specific figure data from the data; and when the plurality of specific figure data is extracted by the specific figure extracting means, thereafter, the decryption target image data is accompanied by a decryption process. An image decoding apparatus, comprising: decoding decoding means for decoding in a decoding mode.