JPH0993560A - Ciphering and decoding device for picture and writing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily circulate the picture and writing by providing a ciphering means and a means or the like storing ciphered picture and writing information and ciphering a picture element of the original picture and writing information at a designated position so as to decode each pattern or the like served through ciphering with charge thereby paying the charge. SOLUTION: An A/D converter section 101 of a transmitter side converts an analog signal such as a TV signal into digital signal picture element information 102. The digitized image for each pattern is ciphered (103) in the unit of picture elements, the entire transmission image is compressed (104) to make high speed transmission and the compressed data are transferred (200) to the receiver. The compressed image signal is received and digital image information 303 is decoded and displayed on a display screen 304. In this case, three kinds of picture element signals are adopted as a factor of configuring one picture element and the signal is ciphered by designating the picture element individually.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to encryption and / or decryption of moving image / stopped image, and written image information such as characters / symbols that can be viewed on the screen.

[0002]

2. Description of the Related Art In recent years, beginning with television broadcasting, N-ISD
A communication medium environment in which educational image and calligraphic image information such as a movie / appreciation picture image is provided as multimedia information to which voice or the like is added via a network such as N, B-ISDN and a high-speed LAN or a network such as CATV. Is ready. Then, the calligraphic image information is provided online or on-demand via the network. However, since these programs are provided for a fee only to subscribers who have paid a contract for the purpose of using or watching, they are provided by being encrypted in program units. It will be used or viewed from.

The program providing method in the conventional multimedia information pay providing system is, so to speak, secret communication, and is provided by the following means. That is, the information transmission source performs transmission processing after transmitting the transmission information or all pages or frames of the program in page units or frame units, and transmits the information encrypted at the receiving end in page units or frame units. Decode all pages or frames,
It was provided to users. As such an object, CA
There are TV services and BS / CS broadcasting services.

In addition, a large number of "programs" are prepared, and the user is allowed to select programs on a program-by-program basis, and the information source sends only the programs selected based on the program selection information from the user to the user terminal such as a dedicated line. Was sent in. Such objects include CATV services and database services provided in the video on demand format.

[0005]

The viewer's request for such multimedia information is that it is possible to easily select a "program to be watched" from a plurality of provided programs, and to select a specific "scene / screen" in the program. However, it is possible to easily obtain "information that you want to know". However, since the above-mentioned conventional providing system encrypts each program, There is no system or operation means for decrypting only the scenes and images and paying only for the decrypted portion.

Since no such or system or operating means is provided, a variety of images, such as specific images / partial images / specific pages / specific sentences, which the user has, for example, scattered or scattered in the program, are displayed. There is an inconvenience that it is not possible to satisfy the request to browse or obtain only paragraphs / specific terms / special expressions / specific charts.

The present invention is an invention created in order to solve such a problem and individually decrypts individual phrases and individual screens in a program encrypted and provided for a fee. , The purpose is to provide a means that can be easily viewed or obtained by paying a fee for this decryption part.

[0008]

The above-mentioned object is achieved by the present invention having the following construction. FIG. 1 is a principle diagram of the present invention, and FIG. 1A is an encryption device according to claim 1, in which a plurality of pixels forming a document are arranged, and color information of each of the plurality of pixels is arranged. The present invention is applied to a document image encryption device that displays document image information that is made meaningful by chain expansion or localization.

In the figure, reference numeral 1 is a storage means for storing a plurality of pixels constituting an original document image, and stores a plurality of pixels which should be arranged in a two-dimensional array when displayed on a screen. Reference numeral 2 is a numbering means for designating a pixel at a position to be encrypted and assigning a number to the pixel. When encrypting one screen, all pixels in the screen are designated, and a specific position in one screen is designated. When encrypting a pixel, specify the position of the pixel individually. Reference numeral 3 is a read-out means for encrypting the numbered pixels designated by the numbering means 2, and 4 is one or more factors (for example, a factor "that is the three primary colors of light" that constitute the read-out pixels. A red means, a factor "green", and a factor "blue") are acting means for operating the operator respectively, and 5 is a storing means for storing the writing information specifying the position of the encrypted pixel.

FIG. 2B shows a decoding device according to a second aspect of the present invention, in which a plurality of pixels forming a calligraphy are arranged and the meaning is obtained by chain expansion or localization of color information of each of the plurality of pixels. The present invention is applied to a decoding device for the written document information.

In the figure, 5 is provided in the decoding device,
Reference numeral 6 is a storage unit for storing the document image information specifying the position of the encrypted pixel, 6 is a reading unit for reading the encrypted pixel from the document image information, and 7 is a unit for returning the operation of the operator from the encrypted pixel. The restoring means 8 is a display means for decoding and displaying the pixel at the specified position of the encrypted document image information.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 2 is a control procedure of encryption and decryption when the present invention is applied. In the figure, the former stage of the transfer 200 is the process on the transmission side, and the latter stage is the process on the reception side.

That is, on the transmitting side, an analog signal such as a TV signal is converted into a digital signal by an analog / digital (A / D) converter 101 and supplied as image information 102 of the digital signal. The digitized image for each screen is encrypted 103 on a pixel-by-pixel basis, and subsequently, a compression process 104 for all transmitted images is performed in order to perform transmission at high speed, and transfer 200 to the receiving side is performed.

On the receiving side that receives this compressed image signal, decompression processing 301 is performed, and pixel-by-pixel decoding 302 is further performed to restore image information 303 of the digital signal and display it on a display screen 304. To do.

In the embodiment of the present invention, pixels are individually designated and encrypted. Here, three types of element signals are adopted as factors forming pixels. Incidentally, a color signal that meets the purpose of encryption is adopted as the element signal, and for example, if all of the designated pixels are to be monochromatic, the three primary colors of light (R, G,
It is effective to use B), or when it is desired to process encryption by brightness adjustment, it is effective to use a brightness signal (Y) and two color difference signals (RY) and (BY). . Alternatively, other color signals (for example, hue / brightness / saturation) can be used according to the purpose.

The following means are adopted as an encryption method for the element signals forming the above three types of pixels. The first encryption method is "addition" processing for each element signal of the pixel to be encrypted, and the second encryption method is "replacement by pattern" processing.

When the simultaneous color development of the digitally processed image is full color (commonly known as 16.77 million colors) and is displayed in the three primary colors of light (R, G, B), each constituent bit is 8
It becomes a bit (1 byte). In the first “addition” process described above, color conversion can be performed by performing an arithmetic process (for example, addition of a specific value = α) for each 1 byte. However, if an arbitrary α is set, the color after conversion cannot be predicted, and therefore the color of the original pixel is simulated in advance so that it can be converted into a desired color. Further, it is assumed that overflow may occur in simple addition and information for decoding may be lost. Therefore, preservation of overflow bits due to addition is considered.

In the second "replacement" process described above,
A pattern table that replaces all 1-byte patterns (256 patterns) for each element is prepared in an exchangeable manner, and the above-mentioned replacement pattern is selected from each 1-byte pattern of the three elements of the pixel at the specified position. Collate the table,
It replaces with the corresponding pattern.

The above encryption process will be described with reference to FIG. FIG. 3 is an encryption processing block diagram, 10 is a memory for storing a signal of a digital original image serially input from a terminal 10G, and 20 is a pixel to be encrypted in the image input through a terminal 20P. Is a memory for storing the position signal of
Receives a signal indicating one pixel or a block pixel from
This is an encryption position matching unit that reads the pixel at the specified position in the memory 20 pixel by pixel or block pixel from the memory 10 and matches the pixel data to be encrypted.

Reference numeral 41 is a memory for holding an instruction signal of the encryption type input from the terminal 41T, and a single pixel or a block pixel is designated as the encryption type.
In addition, the "addition" process is instructed to each pixel, or the "replacement" process is instructed. In the "replacement" process, the replacement pattern is instructed and input. Reference numeral 42 is a pattern table for replacement of a single pixel or a block pixel selected by this instruction signal read from the memory 41 when the above replacement processing is instructed.

Next, a pattern table search unit 43 receives the output (single pixel instruction; C // block pixel instruction in FIG. 4; C in FIG. 7) from the position matching unit 30 and receives an encryption type instruction signal. By the "addition" or "replacement" instruction signal read from the memory 41, the pattern table 42 (FIG. 5) for replacement in pixel units is read as it is in the case of the addition instruction, and the encryption processing unit in the subsequent stage 40
Output to

When the encryption is "addition", the encryption processing section 40 performs encryption by addition on the pixel at the designated position of the original image, and when the encryption specifies "replacement", the original image is displayed. Of the encrypted pixel in which the pixel at the designated position in FIG. 4 is replaced by the designated pattern table (single pixel designation;
C // block pixel instruction of FIG. 7; stored in C) of FIG. 7, and when transmitting to the receiving end, encryption type instruction signal 51, encrypted pixel position signal 53, and encryption corresponding decryption pixel information 52 (FIG. 4 C // C of FIG. 7) is also transmitted.

Details of the above-described encryption and decryption of the original image will be described with reference to FIGS. 4, 5 and 7. (1) First, a case where a pixel position is designated by a single pixel will be described.

4A and 4B are explanatory diagrams for specifying a single pixel of an original image pixel to be encrypted. FIG. 4A shows an example of a display image, FIG. 4B shows an example of pixel numbering, and FIG. FIG. 6C is a memory explanatory diagram of encrypted numbered pixels. The screen of FIG. 9A is formed by, for example, 6 lines vertically with 8 pixels in each line.
The positions indicated by “◯” are the individual pixel positions, and “shaded pixels” are encrypted in the figure. If the encrypted pixel is displayed on the receiving end without being restored, it will be displayed in an encrypted state. For example, if the encryption is set to "white", the screen of the receiving end will have a "shaded" part. Is "blank"
Will be displayed.

The designated pixel position is as shown in FIG.
The pixels are numbered from the upper left corner of the screen toward the lower right corner, and are, for example, "00" to "47" for 48 pixels.
Therefore, the numbering of the "shaded pixels" position in the figure (A) is "25" to "30", and the arrangement in the memory is stored in one vertical column as shown in the figure (C). There is.

Then, the encryption position verification unit 3 shown in FIG.
0 performs the work of forming the “presence / absence” column, the “numbering” column, and the “original image pixel information (X, Y, Z)” column of FIG. "25" to "3" in the "Numbering" column
In the "0""presence / absence" column, a symbol "○" is given as a symbol indicating a numbering target. It should be noted that the inside of the chain line frame in FIG. 7C shows the object of encryption processing, and the position signal 53 is inside the chain line frame in the “Numbering” column, and the inside of the chain line frame in the “Pixel information of original image” column is Pixel information for decryption 52, encrypted pixel pattern 54 in the dotted line frame in the "Pixel information of encrypted image" column
Are shown respectively.

Next, the encryption processing unit 40, for example, the terminal 4
If the instruction input from 1T is “addition”, the input or preset constant (α) is set at the designated position (25 to 3).
0) Add to each pixel information (X, Y, Z) of the original image,
The result is the pixel information (X / L, Y /
(L, Z / L) are stored as the encrypted pixel pattern 54 in the chain line frame of FIG. 7C, and the pixels at other positions store the original image information as it is.

If the instruction input from the terminal 41T is "replacement" and "pattern (1)", then FIG.
The pattern table 421 shown in is selected. If each of the three elements of the pixel is an 8-bit pattern, the "original image pattern" of the pattern table 421 for each element
The column is searched, and when the corresponding pattern is searched, the pattern “LLLLLLLLL” in the right column of the pattern is selected and replaced. (Encrypted Pixel Pattern 54 of Chained Frame of C of FIG. 4) Here, the pattern “LL to L” means a combination of arbitrary bit patterns, and when the encryption process is desired to be “white”, “00” is selected. ~ 0 ", or if you want to set it to" black ", set it to" 11-1 "and replace each of the three elements (X, Y, Z) for one pixel with the above pattern. Good.

Alternatively, when it is desired to make all the pixels at the specified position "pure red", the three elements of the pixel, X, Y, and Z, are the three primary colors (red =
R, green = G, blue = B), and the replacement pattern for R is “11 to 1” in the pattern table and other G and B are set.
The replacement pattern for
It is sufficient to use the table set to "0".

Alternatively, when it is desired to use a code in which the state of the encrypted pixel is adjusted at the "luminance" level, the three elements of the pixel are
A signal (y, u, v) depending on the luminance and the hue may be set, and a pattern table for adjusting the level for the y of the luminance may be set in FIG.

As described above, the original image is encrypted on a pixel-by-pixel basis, and as shown in FIG.
The “presence / absence” column corresponding to “5” to “30” is marked with “◯”, and the pixel information (X / L, Y / L, Z) in which the pixel elements (X, Y, Z) in the same row are encrypted / L) is stored. That is, the encrypted image memory 50 shown in FIG.
(C) "Pixel information of encrypted image" in the right column is stored, and an encryption type instruction signal (for example,
The addition instruction and the constant α, or the replacement instruction and the pattern table number) 51, the position signal 53 for specifying the encryption, and the encryption corresponding decryption pixel information 52 are transmitted together.

Next, a description will be given of the processing at the time of decryption when an image encrypted by designating a single pixel is received. FIG. 6 is a decoding block diagram corresponding to the processing block diagram of FIG. In the figure, the same reference numerals as those used in FIG. 3 indicate the same things, 60 is a pixel reading unit for decoding, 73 is a decoding pattern searching unit, 70 is a decoding processing unit, and 80 is a display of the decoded image. It is a department.

The operation of the decoding process having the above configuration will be described below. The encrypted image data (right column of C in FIG. 4; “pixel information of encrypted image”) is received in the encrypted image memory 50 as described above. At the same time, the encryption type instruction signal 51, the position signal 53, and the encryption corresponding decryption pixel information 52 are also received.

The decryption pixel reading section 60 confirms that the encryption pixel designation from the encryption type designation signal 51 is designated on a pixel-by-pixel basis, and the pixel information (X / L, Y / L, Z / L) are read line by line and the last line is sequentially output to the decoding pattern search unit 73 in the subsequent stage while adding a number.

Upon receipt of the output for each line, the decryption pattern search unit 73 determines from the encryption type instruction signal 51 whether the encryption is "addition" or "replacement", and if it is "addition", it is received at the same time. The constant α to be read is read in advance, and the number (C in FIG. 4) is read from the position signal 53.

Next, the decryption pattern search unit 73 collates the numbering of the input pixel signals (X / L, Y / L, Z / L) for one line, and if it is not the line to be encrypted, it remains as it is. The decryption processing unit 70 is passed through and is sent to the display unit 80. On the other hand, if it is determined that the line is the encryption target line, the encrypted pixel signal (X /
(L, Y / L, Z / L) is output to the decoding processing unit 70.

The decoding processing unit 70 uses this pixel information (X /
L, Y / L, Z / L) are received, and encrypted pixels (X / L,
Y / L, Z / L) are each subtracted by a constant α to be decoded and output to the display unit 80 in the subsequent stage.

On the other hand, the decryption pattern search unit 73 which has received the output for each line shows that the encryption is “replacement” from the encryption type instruction signal 51 and that the process is performed with the replacement pattern (1) 421. Determine. Therefore, the numbering of the replacement position (C in FIG. 4) is read from the position signal 53.

Next, the decryption pattern search unit 73 collates the numbering of the input pixel signals (X / L, Y / L, Z / L) for one line, and if it is not the line to be encrypted, it remains as it is. The decryption processing unit 70 is passed through and is sent to the display unit 80. On the other hand, when it is determined that the line is the encryption target line, the original pixel (X, Y, Z) for one line is read from the encryption corresponding decryption pixel information 52, and the encrypted pixel for one line is read. The signal is output to the decoding processing unit 70 together with the signals (X / L, Y / L, Z / L).

The decoding processing unit 70 outputs both signals (X, Y,
Z; X / L, Y / L, Z / L) is received, and the encrypted pixel (X / L, Y / L, Z / L) is replaced with the original pixel (X, Y, Z) and decrypted. , And output to the display unit 80 in the subsequent stage.

By performing the above-mentioned decryption process on the received image for each screen, the image encrypted for each pixel is restored and displayed. In the above embodiment, as the encryption-compatible decryption pixel information 52, the pixels before the encryption of the original image are transmitted to the decryption side, but pixel information other than the pixels of the original image may be transmitted. I can. For example, if the original image is 16770,000 full colors, and the encryption is 16
The pixels are replaced with colors and transmitted, and the pixel for decoding is made variable, and the pixel for decoding is set to "full color", "32K color", "256 color", etc. according to the amount paid by the viewer. Either one can be selected and transmitted, and the decoded images can be displayed with different image qualities.

The above-mentioned encryption / decryption process requires transmission / reception for each screen if the target document is a still document, but if the target document is a moving image, it will be applied to all images in one frame. It will be processed for each screen.

The process in FIG. 6 described above is for decrypting an encrypted image. However, since the received image is not necessarily decrypted, a determination unit for determining the necessity of decryption is provided in the preceding stage. Incidentally, it is also possible to display the received document image in an encrypted state without decrypting it, and perform the decryption process when the viewer desires to browse the document image.

As described above, according to the embodiment of the present invention, the pixel to be encrypted is designated for each pixel. The means for designating the pixel position on the display screen is a technique well known in the application of the image processing system. Specify using. For example, by enlarging the display screen and scrolling to move the desired image position within the screen, and increasing the enlargement ratio at this time, the position of each pixel can be set using the numeric keypad of the keyboard or a pointing device (mouse, trackball, etc.). This is for pointing and fetching the pointing position coordinates. Alternatively, a movable window with an increased magnification may be opened on the screen by a technique generally known as a loupe. (2) Next, a case where the pixel position is designated by the block pixel will be described. Since the block designation only differs from the pixel designation in the extraction position of encryption, the characteristic point of this operation will be described in the case where the encryption is "replacement".

As a block designating means, a number is assigned to each N × M adjacent pixels on the screen, and an arbitrary plurality of blocks are designated and input to the numbered position with a ten-key of the keyboard or the like. Alternatively, the blocks are designated and input on the screen by using the cursor movement keys of the keyboard or the dragging of the mouse cursor in the frame designation, or the mask function of the scanner.

7A and 7B are explanatory diagrams for specifying the original image pixels to be encrypted in blocks. FIG. 7A is a block diagram of 2 × 2 blocks, and FIG. 7B is a block numbering diagram. Further, FIG. 3C is a memory explanatory diagram of the encryption numbered pixels. The screen of FIG. 9A is composed of, for example, 6 vertical lines with 8 pixels in each line, and the positions indicated by "○" are individual pixel positions.
In the case where four pixels in the chain line frame are set as one block, "shaded blocks" are encrypted in the figure. When the encrypted block pixel is displayed without being restored at the receiving end, it is displayed in the encrypted state, similarly to the case where the pixel unit is instructed.

This block pixel designation position is numbered from the pixel at the upper left corner to the lower right corner of the screen, as shown in FIG. 7B, for example, "0" to "7" for 8 block pixels. Become. Therefore, the numbering of the "hatched block" position in FIG. 7A is "1", and the layout in the memory is 4 places in a vertical column as shown by the chain line frame in FIG. It is distributed and stored in. Incidentally, in the figure (C), "Ad" at the left end is an in-memory address, and "BNo." Is a block numbering.

Then, the encryption position collation unit 3 shown in FIG.
0 determines that the encryption is instructed in blocks by the instruction from the encryption type instruction signal memory 41, and the "Ad" column, the "BNo." Column, and the "original image" in FIG. Pixel information (X, Y, Z) "of
A mark "○" is given to "1" in the "B No." column of FIG. 9C as a symbol meaning the numbering target.

Subsequently, the pattern table search block 4
3 uses the table shown in FIG. 8 to encrypt the block pixel at the designated position. FIG. 8 is a 2 × 2 block pixel replacement pattern table configuration diagram, which is an encryption composition pattern. In this example, a table with four columns (421-1, 421-2, ..., 421-n) is used for one block. In the figure, the first column corresponds to the upper left corner of the block pixel, the second column corresponds to the upper right corner, the third column corresponds to the lower left corner, and the fourth column corresponds to the lower right corner. If the block number is 1 and is designated as pattern 2, the in-memory address is "02, 03, 1".
0, 11 ”becomes the replacement target, and the replacement pattern (2) 42
1-2 are applied.

At this time, for example, "filled square" is displayed on the pixel.
Is being displayed and the encryption is set to “filled triangle”, BNo. = 1 row, the first column of “MMM to M” 421-2 in the replacement pattern column is “00 to 0”.
Then, the second to fourth columns are set to “11 to 1”.

The pattern table search unit 43 in FIG. 3 corresponds to Ad = 02, 03, 10, 11 in FIG. 7C.
No. Is searched for, and the pattern table (2) 421-2 in FIG. 8 is searched and output to the encryption processing unit 40 in the subsequent stage.

Upon receipt of this output, the encryption processing unit 40 is shown in FIG.
Pixel information (X / M, Y /
BN of the replacement pattern (2) at the corresponding position of (M, Z / M)
o. “MMM to MM” in the row of = 1 is read and replaced.

The block pixel encrypted as described above is transferred to the decryption side. The transfer information and the processing process on the decryption side at this time are the same as those for the single pixel designation, and the description thereof will be omitted. .

[0054]

As described above in detail, by applying the pixel-by-pixel or block-pixel-by-pixel encryption technology of the present invention, it is possible to obtain a great effect of utilizing it in a CATV system, a VDO system, or an educational field. Is.

By applying the present invention, the charge system can be changed from the conventional fixed amount system to the variable amount system, that is, the charge request can be limited to only one screen of the document including the decrypted portion of the encrypted portion to be charged.

This means that it is not necessary for the information provider to determine the price of a product (provided program) with a uniform amount of money, and particularly for a program including a document with high commercial value as one scene, It produces a special effect that can be bought and sold on a screen-by-screen basis.

Also, the viewer does not have to pay an ambiguous uniform fee for each program, and requests a proper price for a product (document or one scene in the program) desired to be viewed or obtained. Has an exceptional effect that can meet the.

Further, the information provider has an effect that the price for the same drawing can be set corresponding to the definition of the decoding. The definition in this case is because the decoded image can be adjusted by brightness / luminance / hue by selecting RGB / yuv / HVS or the like as a factor for setting the pixel element of the original image.

Further, by enciphering in block pixel units, "curve" forming an image is "straightened", or the original "kanji" part is "hiragana", which is requested by the decryption side. Accordingly, there is a special effect that an operation of gradually bringing the restored state closer to the original image is possible.

[Brief description of drawings]

FIG. 1 is a principle diagram of the present invention.

FIG. 2 is a control procedure diagram of encryption / decryption.

FIG. 3 is a block diagram of an encryption process.

FIG. 4 is an explanatory diagram of designation of original image pixels to be encrypted.

FIG. 5 is a configuration diagram of a replacement pattern table for each pixel.

FIG. 6 is a processing block diagram of decoding.

FIG. 7 is an explanatory diagram of designation of original image pixels encrypted in a block.

FIG. 8 is a block pixel replacement pattern table configuration diagram.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Original document image storage means 2 Numbering means 3 Encryption target pixel reading means 4 Actuating means 5 Encrypted document image storage means 6 Decoding target pixel reading means 7 Restoring means 8 Display means 10 Original image memory 20 Position signal memory 30 Encryption position matching unit 40 Encryption processing unit 41 Encryption type instruction signal memory 42 Replacement pattern table 43 Pattern table search unit 50 Encrypted image memory

Claims (9)

[Claims] 1. An encryption device for a document image, wherein a plurality of pixels are arranged, and the document image information that is meaningful by chain expansion or localization of color information of each of the plurality of pixels is displayed. A storage means for storing pixels, a means for numbering the pixels, a means for reading out the numbered pixels, and an operator acting on one or more factors constituting the read pixels for encryption. An apparatus for encrypting a document image, comprising: an operating device; and a storage device for storing encrypted document image information, and encrypting a pixel at a specified position of the original document image information. 2. A device for decoding a document image, wherein a plurality of pixels are arranged, and the document image information that is meaningful by chain expansion or localization of color information of each of the plurality of pixels is displayed. A storage means for storing, a means for reading out an encrypted pixel from the document image information, and a restoring means for returning the action of an operator from the encrypted pixel are provided at a specified position of the encrypted document image information. A document decoding device characterized in that pixels are decoded and displayed on a display means. 3. The document encryption apparatus according to claim 1, wherein a target of encryption is designated for each single pixel and / or for each block including a plurality of pixels. 4. The encrypted pixel is a single pixel and / or
3. The document decoding apparatus according to claim 2, wherein a pixel at a designated position of the document information processed by a block including a plurality of pixels is decoded and displayed. 5. The pixel is composed of a plurality of numerical factors, and an operator acting on the factor is an arithmetic operator, and an overflow or an underflow due to the action of the operator in the encryption is compensated at the time of decryption. The encryption device for a document image according to claim 1, wherein 6. The pixel is composed of a plurality of numerical factors, and has a substitution table for replacing a numerical pattern constituted by the factor at the encryption designated position of the original pixel with a different numerical pattern, and the operator is the factor. 2. The document image encryption apparatus according to claim 1, wherein is operated so as to be replaced with a pattern selected from the replacement table. 7. The replacement table according to claim 6 corresponds to three primary colors of light or luminance / hue, or hue / brightness / saturation for each factor in a state where the original pixel is described by three factors. A device for encrypting a calligraphy that is a table provided in the table. 8. The information and the pixel position of the original pixel are received together with the encrypted pixel when the pixel encrypted by the replacement by the replacement table is decrypted. Decoding device for the described calligraphy. 9. The decompression unit receives a pixel for diminishing the effect of encryption and a pixel position together with the encrypted pixel when decrypting the pixel encrypted by the replacement by the replacement table, and encrypts the pixel. 5. The document decoding apparatus according to claim 2, wherein pixels are replaced by the diminishing pixels.