JP3249661B2 - Image transmission method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image transmission method for dividing multivalued image data into a plurality of bit planes and applying an encoding process to each bit plane to compress the information amount of the multivalued image data. About.

[0002]

2. Description of the Related Art In recent years, an image recording apparatus used in a facsimile apparatus or the like has realized multi-gradation image recording while having a low gradation of about 16 gradations. Therefore, there is a request to input a transmission document image as multi-valued image data and transmit the image.

Also, since multi-valued image data has a very large data amount, if it is transmitted as it is, a great deal of communication time and communication cost will be required. For this reason, it is necessary to transmit the multi-valued image data in a state where it is encoded and compressed.

As a method of encoding such multi-valued image data, the multi-valued image data is divided into a plurality of bit planes, and an encoding process such as a binary arithmetic encoding process is applied to each bit plane. An image coding method for compressing the information amount of multi-valued image data has been put to practical use.

As an application of such an image encoding method, for example, statistical processing of each bit plane is disclosed in Japanese Patent Application Laid-Open No. 63-104578 ("Image Information Compressor"). To form a code table,
When encoding and compressing the binary image data of each bit plane, there is a type in which a code table corresponding to each is used.

[0006]

However, such a conventional apparatus has the following disadvantages.

That is, in such a conventional apparatus, it is possible to improve the average coding compression ratio for an image having a tendency similar to the image referred to when the code table is created. For other images, a situation occurs in which the encoding compression ratio does not improve so much. In particular, when the contents of the binary image data of each bit plane are very similar as in the case of a character image, this tendency appears strongly.

The present invention has been made in view of such circumstances, and has as its object to provide an image encoding method capable of improving the encoding compression rate of a character image.

[0009]

According to the present invention, multi-valued image data is divided into a plurality of bit planes, and an encoding process is applied to each bit plane to compress the information amount of the multi-valued image data. In the image transmission method to be transmitted, for one page of multi-valued image data, the number of pixels having the same data content at the same pixel position among a plurality of bit planes is counted, and when the counted value exceeds a predetermined value, the page is counted. For about, while the binary data of the multi-valued image data is encoded and transmitted, when the count value is equal to or less than a predetermined value,
For that page, the image data of each bit plane is encoded and transmitted.

Also, in an image transmission method for dividing multi-valued image data into a plurality of bit planes and applying an encoding process to each bit plane to compress the information amount of the multi-valued image data, For multi-valued image data, the number of pixels whose data contents match at the same pixel position among a plurality of bit planes is counted, and when the counted value exceeds a predetermined value, the bit plane corresponding to the most significant bit is determined for the page. When the count value is equal to or less than a predetermined value, the image data of each bit plane is encoded and transmitted, when the count value is equal to or less than a predetermined value. .

Also, in an image transmission method for dividing multi-valued image data into a plurality of bit planes and applying an encoding process to each bit plane to compress and transmit the information amount of the multi-valued image data, For multi-valued image data for a page, the number of pixels whose data contents match at the same pixel position between a plurality of bit planes is counted, and when the counted value exceeds a predetermined value, the multi-valued image data is The image data is formed by encoding the binarized data, and when the receiving side requests transmission of data of a plurality of bit planes, the image information is repeatedly transmitted as data of each bit plane, while the count value is transmitted. Is less than or equal to a predetermined value, for the page, the image data of each bit plane is individually Forming image information, when the receiving side sends request data of a plurality of bits planes is obtained so as to transmit the image information corresponding to the requested bit plane.

Further, in an image transmission method for dividing the multi-valued image data into a plurality of bit planes and applying an encoding process to each bit plane to compress the information amount of the multi-valued image data, For multi-valued image data, the number of pixels whose data contents match at the same pixel position among a plurality of bit planes is counted, and when the counted value exceeds a predetermined value, the bit plane corresponding to the most significant bit is determined for the page. The image data is encoded to form image information, and when the receiving side requests transmission of data of a plurality of bit planes, the image information is repeatedly transmitted as data of each bit plane, while the count value is a predetermined value. If the value is less than or equal to the value, the image data of each bit plane is encoded for each Forming the image information of the lane, when the receiver transmits request data of a plurality of bit planes is obtained so as to transmit the image information corresponding to the requested bit plane.

Further, in an image transmission method for dividing the multi-valued image data into a plurality of bit planes and applying an encoding process to each bit plane to compress the information amount of the multi-valued image data, For the multi-valued image data, a pixel whose data content matches among a plurality of bit planes is determined, and a rectangular continuous tone area is extracted based on the determination result. While the image data of each bit plane excluding the most significant bit plane is encoded and transmitted for each of the extracted continuous tone area units.

[0014]

Therefore, for each page, image data corresponding to the content of the image is selected and formed, and the image data is encoded to form image information, so that the image data can be compressed efficiently. Thus, it is possible to suppress a situation where the image quality is reduced.

[0015]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 shows a facsimile apparatus according to one embodiment of the present invention. In this embodiment, a transmission control procedure based on the group 3 facsimile function is used as a transmission control procedure when exchanging image information of multi-valued image data.

In FIG. 1, a control unit 1 performs a control process of each unit of the facsimile apparatus and a facsimile transmission control procedure process.
The control unit 1 stores a control processing program to be executed, various data necessary for executing the processing program, and the like, and constitutes a work area of the control unit 1. This is for storing various information unique to the facsimile machine.

The scanner 4 is for reading an original image at a predetermined resolution, the plotter 5 is for recording and outputting an image at a predetermined resolution, and the operation display unit 6 is a facsimile apparatus. To operate,
It consists of various operation keys and various indicators.

The encoding / decoding section 7 encodes and compresses the image signal, and decodes the encoded and compressed image information into the original image signal.
This is for storing a large number of image information in a coded and compressed state.

The group 3 facsimile modem 9 is for realizing a group 3 facsimile modem function, and is a low-speed modem function (V.21 modem) for exchanging transmission procedure signals and mainly exchanging image information. High-speed modem function (V.33 modem, V.33
29 modem, V.29. 27ter modem etc.).

The network control device 10 is for connecting the facsimile machine to a public telephone network and has an automatic transmission / reception function.

The control unit 1, the system memory 2,
The parameter memory 3, the scanner 4, the plotter 5, the operation display unit 6, the encoding / decoding unit 7, the image storage device 8, the group 3 facsimile modem 9, and the network control device 10
It is connected to a system bus 11 and exchanges data between these elements mainly with the system bus 1.
One is done through.

Data exchange between the network controller 10 and the group 3 facsimile modem 9 is directly performed.

FIG. 2 shows an example of an image reading processing system of the scanner 4.

In FIG. 1, an image input unit 20 decomposes an original image into pixels at a predetermined resolution, and converts each pixel into 8 pixels.
The output data is converted into bit multivalued image data and output. The output data is applied to a bit plane developing unit 21.

The bit plane developing unit 21 extracts, for each pixel, data at each bit position of the first to eighth bits of the input multi-valued image data, and extracts the extracted 1
Bit plane data is formed from a group of data in which bit data are arranged at positions corresponding to the pixels (see FIG. 3), and each bit plane B is formed.
The data of P1 to BP8 are respectively stored in the corresponding storage areas of the bit plane memory 22.

The data coincidence counting section 23 includes bit planes BP3 to BP corresponding to the third to eighth bits of the image data stored in the bit plane memory 22.
This is for counting the number of coincidences of the data at the same pixel position in the image data of P8, and the count value is output to the image input control unit 24.

The image input control unit 24 controls the operation of the image reading system of the scanner 4 and determines whether the page is a character image based on the count value added from the data coincidence counting unit 23. Is determined, and the operation of the binarization processing unit 25 is controlled based on the determination result.

The binarization processing unit 25 applies a predetermined binarization process to the data of each bit plane stored in the bit plane memory 22, and performs the processing of the bit plane specified by the image input control unit 24. The image data is read from the bit plane memory 22.
The output data is output to the next-stage device as binary image data.

Here, a method of character image area determination will be described.

For example, the test chart N of the Institute of Image Electronics Engineers of Japan
o. Considering a photographic image (not shown) disposed on the left side of 1 (test chart for facsimile), when this image is represented by 8-bit multi-valued image data,
The state of the image represented by the eighth bit plane data (bit plane data of the MSB) is as shown in FIG. 4A, and the state of the image represented by the seventh bit plane data is as shown in FIG. The state of the image represented by the sixth bit plane data is as shown in FIG. 3C, and the state of the image represented by the fifth bit plane data is as shown in FIG. The state of the image represented by the plane data is as shown in FIG. 3E, and the state of the image represented by the third bit plane data is as shown in FIG. 4F. The image represented by the second bit plane data (G), and the image represented by the first bit plane data (LSB bit plane data) is (h) in FIG.
become that way.

On the other hand, when a character image is read, when this image is represented by 8-bit multi-valued image data, the state of the image represented by the eighth bit plane data is, for example, as shown in FIG. The state of the image represented by the seventh bit plane data is as shown in FIG. 3B, and the state of the image represented by the sixth bit plane data is as shown in FIG. The state of the image represented by the plane data is as shown in FIG. 3D, and the state of the image represented by the fourth bit plane data is as shown in FIG. 4E, and the image represented by the third bit plane data. Is as shown in FIG. 11F, and the state of the image represented by the second bit plane data is as shown in FIG. 13G, which is represented by the first bit plane data. State of the image is as shown in FIG. (H). Note that this image is a CCITT test chart N
o. Part of 1.

Therefore, in the multi-valued image data obtained by reading the character image, the data of all the bit planes is
This is an image in which the features of the original image have been well-represented.In the multiple bit plane data on the high-order bit side, the portion where the data at the same pixel position matches often increases, but the multi-valued image data obtained by reading the photographic image , There are few portions where data at the same pixel position matches.

Therefore, in this embodiment, the matching status of a plurality of bit plane data on the higher bit side (in this case, bit planes BP3 to BP8) is determined for the same pixel position, and the number of matching pixels is determined. If the value is equal to or more than a certain value, the image is determined as a character image.

FIG. 6 shows an example of the data coincidence counting section 23.

In the figure, data PD8 output from a bit plane BP8 of an eighth bit plane is applied to one input terminal of an AND circuit AD1 and is inverted via an inverter IV1 and then inverted by an AND circuit A.
D2 is applied to one input terminal. Data PD output from bit plane BP7 of the seventh bit plane
7 is applied to the other input terminal of the AND circuit AD1 and, after being inverted via the inverter IV2, applied to the other input terminal of the AND circuit AD2.

The bit plane BP of the sixth bit plane
6 is applied to one input terminal of an AND circuit AD3, and is also supplied to an inverter IV3.
, And is applied to one input terminal of an AND circuit AD4. The data PD5 output from the bit plane BP5 of the fifth bit plane is applied to the other input terminal of the AND circuit AD3, and after being inverted via the inverter IV4, the AND circuit AD4
Is applied to the other input terminal.

The bit plane BP of the fourth bit plane
4 is applied to one input terminal of an AND circuit AD5, and the data PD4 is supplied to an inverter IV5.
, And is applied to one input terminal of an AND circuit AD6. The data PD3 output from the bit plane BP3 of the third bit plane is applied to the other input terminal of the AND circuit AD5 and, after being inverted via the inverter IV6, is turned on.
Is applied to the other input terminal.

The output of the AND circuit AN1 is
The output of the AND circuit AN2 is applied to one input terminal of N7, and the output of the AND circuit AN2 is applied to the other input terminal of the AND circuit AN7 and one input terminal of the AND circuit AN8.
Is applied to the other input terminal of the AND circuit AN8.

The output of the AND circuit AN2 is
The output of the AND circuit AN4 is applied to one input terminal of the AND circuit AN9 and the other input terminal of the AND circuit AN10.
The output of 6 is applied to the other input terminal of the AND circuit AN10.

The output of the AND circuit AN7 is
The output of the AND circuit AN8 is applied to one input terminal of the N11, and the output of the AND circuit AN8 is applied to the other input terminal of the AND circuit AN11. The output of the AND circuit AN9 is
The output of the AND circuit AN10 is applied to the other input of the AND circuit AN12.

The output of the AND circuit AN11 is
R, and the output of the AND circuit AN12 is applied to the other input of the OR circuit OR.
The output of the OR circuit OR is applied to the count input terminal of the counter CT. The counter CT has a count input terminal of data 1
The count data DD is output to the image input control unit 24.

Here, the data PD8, PD7, PD6,
PD5, PD4, and PD3 are bit planes B, respectively.
From P8, BP7, BP6, BP5, BP4, BP3,
Those having the same address are output and their data PD
When all of PD8, PD7, PD6, PD5, PD4 and PD3 become data 1 or all become data 0, the output of the OR circuit OR becomes data 1, whereby the counting operation of the counter CT is executed, The value of the count data CT increases by one.

Therefore, when the data reading for all the pixels of one page is completed, the value of the count data CT is the bit plane BP among the pixels of the page.
8, BP7, BP6, BP5, BP4, and BP3 have a value corresponding to the number of data that all match.

In this embodiment, when the value of the count data CT at this time exceeds a predetermined value, it is determined that the image of the page is a character image. The binarization processing unit 25 applies a predetermined binarization process to the stored data of each bit plane, and outputs the binarized data as image data of the page.

If the value of the count data CT is equal to or less than a predetermined value, it is determined that the image of the page is a continuous tone image. In this case, the image is stored in the bit plane memory 22. The data of each bit plane is directly output via the binarization processing unit 25.

Thus, when the read document image is a character image, the data amount of transmission image information can be significantly reduced, and an efficient data transmission operation can be performed.

It is to be noted that the data of the bit planes BP1 and BP2 are not processed by the data coincidence counter 23 in this embodiment because the data of the lower bit plane has a high probability of containing a noise component. I have to.

FIG. 7 shows an example of processing when transmitting one page according to an embodiment of the present invention. Note that this process is executed in a state in which the other terminal is called, a predetermined pre-transmission procedure (corresponding to the transmission procedure of the group 3 facsimile function) is completed, and the preparation for transmitting image information is completed.

First, one page of a document image is read by the scanner 4 (process 101). Thus, the image data for one page of the document image is stored in the bit plane memory 22.

Next, the data coincidence counter 23 counts the number of data coincidences (process 102), and substitutes the value of the count data DD output from the data coincidence counter 23 into a variable CA as a count value (process 102). 103).

Here, it is checked whether or not the value of the variable CA is larger than a predetermined value KA (decision 104). If the result of decision 104 is YES, then
The image data stored in the bit plane memory 22 is binarized by the binarization processing unit 25 (processing 10).
5) The image data after the binarization processing is encoded and compressed by the encoding / decoding unit 7 (processing 106), and the obtained image information is transmitted to the partner terminal (processing 107), and the data for one page is processed. The image information transmission operation ends.

When the result of determination 104 is NO, a bit plane to be transmitted is selected (Step 10).
8) The image data of the bit plane is encoded and compressed by the encoding / decoding unit 7 (process 109), and the image information obtained thereby is transmitted to the partner terminal (process 110). Then, it is checked whether or not the transmission of the image data of all the bit planes has been completed (decision 111). When the result of the decision 111 is NO, the process returns to the step 108, and the process returns to the step 108. Execute the transmission operation. When the result of the determination 111 is YES, the transmission operation of the image information for one page is ended.

FIG. 8 shows another example of processing for transmitting one page.

First, one page of a document image is read by the scanner 4 (process 201). Thus, the image data for one page of the document image is stored in the bit plane memory 22.

Next, the data coincidence counting section 23 counts the number of data coincidences (process 202), and substitutes the value of the count data DD output from the data coincidence count portion 23 as a count value into a variable CA (process 202). 203).

Here, it is checked whether or not the value of the variable CA is larger than a predetermined value KA (decision 204). If the result of decision 204 is YES, then
The image data of the bit plane BP8 of the most significant bit stored in the bit plane memory 22 is extracted, and is encoded and compressed by the encoding / decoding unit 7 (process 205).
The image information obtained thereby is transmitted to the partner terminal (step 20).
6) The operation of transmitting the image information for one page ends.

When the result of determination 204 is NO, a bit plane to be transmitted is selected (step 20).
7), the image data of the bit plane is encoded and compressed by the encoding / decoding unit 7 (process 208), and the obtained image information is transmitted to the partner terminal (process 209). Then, it is checked whether or not the transmission of the image data of all the bit planes has been completed (decision 210). If the result of the decision 210 is NO, the process returns to the process 207, and the process returns to the step 207. Execute the transmission operation. When the result of determination 210 is YES, the operation of transmitting the image information for one page is ended.

As described above, in this case, when it is determined that the read original is a character image, only the data of the bit plane BP8 of the most significant bit is extracted and handled as image data. Therefore, the processing time at the time of image encoding can be reduced. Here, in the case of a character image, as described above, the features of the original image appear in the data of the high-order bit plane.
Even when only the image data of the bit plane BP8 is used, there is almost no deterioration in image quality, and the partner terminal can reproduce an appropriate image.

By the way, when transmitting multi-valued image data, a transmission control procedure may be considered in which the receiving side sequentially requests the necessary bit plane data. FIG. 9 shows an example of processing for transmitting one page in this case.

First, one page of a document image is read by the scanner 4 (process 301). Thus, the image data for one page of the document image is stored in the bit plane memory 22.

Next, the number of data matches is counted by the data match counter 23 (process 302), and the value of the count data DD output from the data match counter 23 is substituted into the variable CA as a count value (process 302). 303).

Here, it is checked whether the value of the variable CA is larger than a predetermined value KA (decision 304). If the result of decision 304 is YES, then
The image data stored in the bit plane memory 22 is binarized by the binarization processing unit 25 (processing 30).
5), the image data after the binarization processing is encoded and compressed by the encoding / decoding unit 7 and stored (processing 306), and the stored image information is transmitted to the partner terminal (processing 307).

At this time, if the image information of the next bit plane is requested from the partner terminal (the result of decision 308 is YE
S), the process returns to step 307, and the image information stored at that time is transmitted again. When there is no longer a request for the image information of the next bit plane from the partner terminal (the result of determination 308 is NO), the operation of transmitting the image information for one page ends. .

When the result of determination 304 is NO, a bit plane to be transmitted is selected (step 30).
9) The image data of the bit plane is encoded and compressed by the encoding / decoding unit 7 (process 310), and the image information obtained thereby is transmitted to the partner terminal (process 311).

At this time, if the image information of the next bit plane is requested from the partner terminal (the result of decision 312 is YES), the process returns to step 309 to transmit the image data of the next bit plane to be transmitted. I do. When there is no request for the image information of the next bit plane from the partner terminal (NO in decision 312), the operation of transmitting the image information for one page is ended.

In this way, in this case, when transmitting the image data of the character image, if the image information of the next bit plane is requested from the partner terminal, the stored image information is transmitted. Therefore, the time for transmitting the image information of the character image can be reduced.

In the above-described embodiment, it is determined whether a document image for one page is a character image or a continuous tone photographic image, and image processing corresponding to each is performed. As shown in FIG. 10A, in a document image in which the photograph image PD and the character image CR are mixed, in this case, the ratio of the character image CR is large.
Since the image is determined to be a character image, the image quality of the photographic image PD deteriorates.

In such a case, as shown in FIG. 9B, the image area of the area MA of the photographic image PD and the area AA of the character image CR are determined, and the image data of the area MA of the photographic image PD is determined. Preferably transmits multi-valued image data.

Here, the image area is determined by examining the distribution of pixels having the same data at the same position in the image data of the high-order bit plane, as in the above-described embodiment, and determining the same data at the same position. It is possible to use a method in which an area where consecutive pixels are determined is determined as an area of a character image, and other areas are determined as areas of a photographic image.

Further, as shown in FIG. 7C, the area MB determined as a photographic image is divided into the X direction (direction parallel to the short side of the original) and the Y direction (parallel to the long side of the original) of the original. If the directions are not parallel to each other, the side parallel to the X direction and the side parallel to the Y direction, including the region MB, as shown in FIG. The smallest area MBa in the enclosed area is used as the area of the photographic image.

As shown in FIG. 11A, two photographic images are included in the image of one page, and rectangular areas MBCa and MDa corresponding to the areas MC and MD determined as the respective photographic images are included. When they overlap, the smallest area MCa 'is an area surrounded by the sides parallel to the X direction and the sides parallel to the Y direction, including those areas MC and MD.
Is determined as a region of a photographic image.

In this embodiment, the image information having the data format shown in FIG. 12A is used.

In this data format, the image information of the data plane BP8 of the most significant bit for one page is arranged first, and then the continuous tone data of each area determined as a photographic image is arranged.

As shown in FIG. 7B, each continuous tone data is obtained by referring to the upper left reference point (for example,
The reference point coordinates representing the coordinates of the point PP in the area MA and the coordinates of the points PPa and PPc in the areas MBa and MCa ', the size in the X direction and the size in the Y direction, and the data (image information) of the bit planes BP7 to BP1 are shown. , Are sequentially arranged.

Here, the reference point coordinates are obtained by expressing the distance in the X direction and the Y direction by the number of pixels with the upper left point of the original paper as the origin. Similarly, the X direction size and Y
The direction size is a value that represents the size of the region in the X direction and the Y direction in terms of the number of pixels.

FIG. 1 shows an example of the one-page transmission process in this case.
3 is shown.

First, a document image of one page is read by the scanner 4 (process 401). Next, the data matching status between bit planes is detected, and a data matching status map representing the arrangement status is created (Process 4).
02) Based on the data matching status map, a continuous tone area (photographic image area) is extracted by the above-described method (process 403).

Then, the image data of the bit plane BP8 is encoded and compressed by the encoding / decoding unit 7 (processing 40).
4) The image information obtained thereby is transmitted to the partner terminal (process 405).

Next, it is checked whether or not one or more continuous tone areas have been extracted (decision 406). If the result of decision 406 is YES, one continuous tone area is selected (processing 407). For the continuous tone area, data in the data format as described above is formed (process 408),
The formed data is transmitted to the partner terminal (step 40).
9). Then, it is checked whether or not there is a remaining continuous tone area (decision 410). When the result of decision 410 is NO, the process returns to step 407 to transmit the data of the remaining continuous tone area. If the result of determination 410 is NO, this process ends. When the result of determination 406 is NO, this process is immediately terminated.

As described above, in this embodiment, a document image in which a photographic image and a character image are mixed can be appropriately transmitted.

In the above embodiment, the case where the present invention is applied to a group 3 facsimile apparatus has been described. However, the present invention is similarly applied to a group 4 facsimile apparatus and other image data transmission apparatuses. can do.

[0083]

As described above, according to the present invention,
For each page, image data corresponding to the content of the image is selected and formed, and the image data is encoded to form image information, so image data can be compressed efficiently and image quality deteriorates. Can be suppressed. It is possible to achieve an encoding process in which the encoding efficiency and the encoding speed are balanced, and to achieve an encoding process according to the characteristics of the character image.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a group 3 facsimile apparatus according to one embodiment of the present invention.

FIG. 2 is a block diagram illustrating an example of an image reading processing system of the scanner.

FIG. 3 is a schematic diagram showing an example of a bit plane.

FIG. 4 is a schematic diagram showing an example of bit plane data of multi-valued image data of a photographic image (continuous tone image).

FIG. 5 is a schematic diagram showing an example of bit plane data of multi-valued image data of a character image.

FIG. 6 is a block diagram showing an example of a data coincidence counting unit.

FIG. 7 is a flowchart illustrating an example of a one-page transmission process.

FIG. 8 is a flowchart illustrating another example of the one-page transmission process.

FIG. 9 is a flowchart illustrating still another example of the one-page transmission process.

FIG. 10 is a schematic diagram illustrating an example of a document in which a character image and a photographic image are mixed and an example of image area determination.

FIG. 11 is a schematic diagram showing another example of image area determination.

FIG. 12 is a schematic diagram showing an example of a data format of transmission data.

FIG. 13 is a flowchart illustrating another example of the one-page transmission process.

Claims (5)

(57) [Claims] An image transmission method for dividing multi-valued image data into a plurality of bit planes, applying an encoding process to each bit plane, compressing the amount of information of the multi-valued image data, and transmitting the compressed data. For multi-valued image data for a page, the number of pixels whose data contents match at the same pixel position between a plurality of bit planes is counted, and when the counted value exceeds a predetermined value, the multi-valued image data is When the binarized data is encoded and transmitted, when the count value is equal to or less than a predetermined value, for the page, the image data of each bit plane is encoded and transmitted. Image transmission method. 2. An image transmission method which divides multi-valued image data into a plurality of bit planes and applies an encoding process to each bit plane to compress the information amount of the multi-valued image data. For multi-valued image data, the number of pixels whose data contents match at the same pixel position among a plurality of bit planes is counted, and when the counted value exceeds a predetermined value, the bit plane corresponding to the most significant bit is determined for the page. When the count value is equal to or less than a predetermined value, the image data of each bit plane is encoded and transmitted, and the image data is transmitted. Transmission method. 3. An image transmission method for dividing multi-valued image data into a plurality of bit planes, applying an encoding process to each bit plane, compressing the amount of information of the multi-valued image data, and transmitting the compressed data. For multi-valued image data for a page, the number of pixels whose data contents match at the same pixel position between a plurality of bit planes is counted, and when the counted value exceeds a predetermined value, the multi-valued image data is The image data is formed by encoding the binarized data, and when the receiving side requests transmission of data of a plurality of bit planes, the image information is repeatedly transmitted as data of each bit plane, while the count value is Is less than or equal to a predetermined value, for that page, the image data of each bit plane is subjected to encoding processing, and the Forming a multi-address, when the receiver transmits request data of a plurality of bit planes, the image transmission method and transmits the image information corresponding to the requested bit plane. 4. An image transmission method for dividing multi-valued image data into a plurality of bit planes and applying an encoding process to each bit plane to compress the information amount of the multi-valued image data. For multi-valued image data, the number of pixels whose data contents match at the same pixel position among a plurality of bit planes is counted, and when the counted value exceeds a predetermined value, the bit plane corresponding to the most significant bit is determined for the page. When the receiving side requests transmission of data of a plurality of bit planes, the image information is repeatedly transmitted as data of each bit plane, while the count value is a predetermined value. If the value is less than or equal to the value, the image data of each bit plane is encoded for each Forming the image information of the emission, when the receiver transmits request data of a plurality of bit planes, the image transmission method and transmits the image information corresponding to the requested bit plane. 5. An image transmission method for dividing multi-valued image data into a plurality of bit planes and applying an encoding process to each bit plane to compress the information amount of the multi-valued image data. For multi-valued image data, a pixel whose data content matches among a plurality of bit planes is determined, and a rectangular continuous tone area is extracted based on the determination result. And transmitting the image data of each bit plane excluding the most significant bit plane for each of the extracted continuous tone area units.