JP3361201B2 - Image encoding apparatus, image encoding / decoding apparatus, and image encoding / decoding method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention applies a predetermined encoding method to multi-valued image data represented by a plurality of bits per pixel in a bit plane unit formed by collecting bit order data of each pixel. Image encoding apparatus for encoding and compressing to form encoded data, and multi-valued image data represented by a plurality of bits per pixel are grouped into bit plane units in which bit-order data of each pixel is collected. A predetermined encoding method is applied to encode and compress to form encoded data, and a decoding method corresponding to the predetermined encoding method is applied to each bit plane unit of the encoded data to perform decoding. An image encoding / decoding device for forming original multi-valued image data, and multi-valued image data represented by a plurality of bits per pixel are data of bit order of each pixel. A predetermined coding method is applied to the united bit plane unit to code and compress to form coded data, and a decoding method corresponding to the predetermined coding method for each bit plane unit of the coded data. The present invention relates to an image encoding / decoding method for applying and decoding to form original multi-valued image data.

[0002]

2. Description of the Related Art Generally, image data has an enormous amount of information.
When transmitting image data, the transmission time becomes very long, and when storing image data, the capacity required for storage becomes enormous, which is very disadvantageous in terms of cost.

Therefore, when transmitting or accumulating image data, the amount of data is reduced by encoding and compression, and the encoded data is handled in the encoded and compressed state. For example,
In the group 3 facsimile apparatus, image information encoded and compressed by either the MH encoding method or the MR encoding method is formed, and this image information is exchanged on the transmission path.

On the other hand, in recent years, high quality images are required for image data to be transmitted or stored. In the group 3 facsimile apparatus described above, an image for one page is 8 (dots / mm) in the main scanning direction and 3.
Image data is used, which is decomposed into pixels with a resolution of 85 (lines / mm) and each pixel is represented by 1-bit data. In this case, since the number of bits that can express the state of one pixel is 1 bit, each pixel is either white or black.
Only the state can be taken. In addition, 8 (dot / m
At a resolution of 3.85 (lines / mm) in the sub-scanning direction in m), the roughness (dot structure) of the image data is noticeable, and it is difficult to express a smooth image (that is, a high quality image). is there.

In recent years, image data handled as high-quality data has a resolution of 300 (dots / 25.4 mm) or more in the main scanning direction and the sub-scanning direction and a bit number of 8 bits or more per pixel. is there.

In this case, since the state of one pixel can be expressed in 256 gradations (stepwise density), a considerably smooth image can be expressed. In this way, multi-tone image data in which one pixel is represented by data of 8 bits or more is also referred to as natural image data (natural image data).

In this way, since the natural image data has a high resolution and a large number of bits per pixel, the data amount of image data per page of an A4 size original image is, for example, about 3. It is 0.8 MB, and it is difficult to directly handle this.

As a highly efficient encoding method for compressing such multi-gradation image data as natural image data, for example, the JBIG method and the JPEG method have been proposed, and these encoding methods are proposed. Are standardized by standardization organizations (JBIG, JPEG).

[0009]

However, even if the above-mentioned JBIG or JPEG coding method is applied, the amount of natural image data is very large, so the image information obtained by coding compression is obtained. The amount of data is also large, and the cost for transmitting and storing the image information becomes large.

The present invention has been made in view of the above circumstances, and an encoding device, an encoding / decoding device, and an encoding / decoding method capable of greatly improving the encoding compression rate of multi-tone image data. Is intended to provide.

[0011]

According to the present invention, an encoding method is applied to multi-valued image data represented by a plurality of bits per pixel in bit plane units formed by collecting data of bit order of each pixel. In an image encoding device that encodes and compresses to form encoded data, for image data of each bit plane, for image data at each pixel position, an image of an adjacent pixel adjacent in the bit direction at that pixel position Exclusive-OR means for forming an exclusive-OR with data, and image data output by the exclusive-OR means, data of a bit plane of a predetermined number of lower bits of the multi-valued image data of the bit planes. In the state where is deleted, the encoding means for forming the encoded data by applying the above encoding method to each bit plane, Depending on the image type data, at least a number of bit planes that the encoding means deletes 2
It is provided with an encoding control means for changing one or more bit planes.

Further, multi-valued image data represented by a plurality of bits per pixel is encoded and compressed by applying an encoding method in a bit plane unit formed by collecting data of bit order of each pixel. In an image encoding device for forming encoded data, for image data of each bit plane, the image data of each pixel position is subjected to exclusive OR with the image data of the adjacent pixel adjacent in the bit direction of the pixel position. With respect to the exclusive OR means for performing the above and the image data output by the exclusive OR means, each of the bit planes is deleted in a state in which the data of a predetermined number of lower-order bit planes of the multi-valued image data is deleted. Encoding means for forming the encoded data by applying the above-mentioned encoding method to the bit plane and the number of gradations of the multi-valued image data Te, those having an encoding control means for changing, leaving at least two or more bit planes the number of bit planes in which the coding means is deleted.

Further, multi-valued image data represented by a plurality of bits per pixel is encoded and compressed by applying an encoding method to each bit plane unit formed by collecting data of bit order of each pixel. In an image encoding device for forming encoded data, for image data of each bit plane, the image data of each pixel position is subjected to exclusive OR with the image data of the adjacent pixel adjacent in the bit direction of the pixel position. With respect to the exclusive OR means for performing the above and the image data output by the exclusive OR means, each of the bit planes is deleted in a state in which the data of a predetermined number of lower-order bit planes of the multi-valued image data is deleted. Encoding means for forming the encoded data by applying the above encoding method to the bit plane and a predetermined compression mode. Depending on de, those having an encoding control means for changing, leaving at least two or more of bit planes the number of bit planes in which the coding means is deleted.

Further, the present invention is applied to an image transmission device for transmitting multi-valued image data, and the multi-valued image data represented by a plurality of bits per pixel is formed by collecting data of bit order of each pixel. In an image coding apparatus that applies a coding method in units of planes to code and compress to form coded data, for the image data of each bit plane, for the image data of each pixel position, the bit of that pixel position A predetermined number of the multi-valued image data in the bit plane for the exclusive OR means for forming an exclusive OR with the image data of the adjacent pixels adjacent in the direction and the image data output by the exclusive OR means. Applying the above coding method to each bit plane while deleting the bit plane data of the lower bits of Encoding means for forming the data,
Coding control means for changing the number of bit planes to be deleted by the coding means, leaving at least two or more bit planes, according to the number of gradations of multi-valued image data that can be received by the partner terminal Is.

Further, the multi-valued image data represented by a plurality of bits per pixel is encoded and compressed by applying an encoding method in a bit plane unit formed by collecting data of bit order of each pixel. In an image encoding / decoding device that forms encoded data and decodes by applying a decoding method corresponding to the encoding method to each bit plane unit of the encoded data to form original multi-valued image data. An encoding unit that forms encoded data by applying the encoding method in a state in which data of a predetermined number of lower-order bit planes of the multi-valued image data is deleted from the bit planes; Coding control for changing the number of bit planes to be deleted by the above-mentioned coding means, leaving at least two bit planes, according to the image type of the image data. And the encoded data of the bit planes that have not been deleted among the encoded data form the original image data by applying the above decoding method, while the image data of a predetermined number of lower bit planes that have been deleted. Is formed by an interpolation method, and a decoding means for changing the bit position of the lower bit plane to which the interpolation method is applied is provided according to the image type of the multivalued image data.

Further, multi-valued image data represented by a plurality of bits per pixel is encoded and compressed by applying an encoding method to each bit plane unit formed by collecting data of bit order of each pixel. In an image encoding / decoding device that forms encoded data and decodes by applying a decoding method corresponding to the encoding method to each bit plane unit of the encoded data to form original multi-valued image data. An encoding unit that forms encoded data by applying the encoding method in a state in which data of a predetermined number of lower-order bit planes of the multi-valued image data is deleted from the bit planes; Coding control for changing the number of bit planes to be deleted by the above-mentioned coding means, leaving at least two bit planes, according to the image type of the image data. And the encoded data of the bit planes that have not been deleted among the encoded data form the original image data by applying the above decoding method, while the image data of a predetermined number of lower bit planes that have been deleted. Is formed by a prediction calculation, and a decoding means for changing the bit position of the lower bit plane to which the prediction calculation is applied is provided according to the image type of the multi-valued image data.

Further, multi-valued image data represented by a plurality of bits per pixel is encoded and compressed by applying an encoding method in a bit plane unit formed by collecting data of bit order of each pixel. In an image encoding / decoding device that forms encoded data and decodes by applying a decoding method corresponding to the encoding method to each bit plane unit of the encoded data to form original multi-valued image data. An encoding unit that forms encoded data by applying the encoding method in a state in which data of a predetermined number of lower-order bit planes of the multi-valued image data is deleted from the bit planes; Coding control for changing the number of bit planes to be deleted by the above-mentioned coding means, leaving at least two bit planes, according to the image type of the image data. And the encoded data of the bit planes that have not been deleted among the encoded data form the original image data by applying the above decoding method, while the image data of a predetermined number of lower bit planes that have been deleted. And a decoding means for changing the bit position of the lower bit plane to which the random number calculation is applied, according to the image type of the multi-valued image data.

Further, the multi-valued image data represented by a plurality of bits per pixel is encoded and compressed by applying an encoding method to each bit plane unit formed by collecting data of bit order of each pixel. In the image coding / decoding method for forming the original multi-valued image data by forming the encoded data and applying the decoding method corresponding to the above-described encoding method to each bit plane unit of the encoded data to form the original multi-valued image data. At the time of encoding, the encoding method is applied to form encoded data in a state where the data of a predetermined number of lower-order bit planes of the multi-valued image data in the bit planes is deleted, and Depending on the image type of the value image data, the number of bit planes to be deleted is changed while leaving at least two bit planes, and At the time of encoding, the encoded data of the bit plane that has not been deleted among the encoded data forms the original image data by applying the above decoding method, while the image data of the predetermined number of lower bit planes that have been deleted. Is formed by an interpolation method, and the bit position of the lower bit plane to which the interpolation method is applied is changed according to the image type of the multivalued image data.

Further, multi-valued image data represented by a plurality of bits per pixel is coded and compressed by applying a predetermined coding method to each bit plane unit in which data of bit order of each pixel is collected. Image coding and decoding to form original multi-valued image data by applying a decoding method corresponding to the predetermined encoding method to each bit plane unit of the encoded data to form encoded original data. In the encoding method, at the time of encoding, the encoded data is formed by applying the encoding method in a state in which the data of a predetermined number of lower-order bit planes of the multi-valued image data in the bit planes is deleted. , When decrypting,
The coded data of the bit planes that have not been deleted among the coded data form the original image data by applying the above decoding method, while the image data of a predetermined number of lower-order bit planes that have been deleted It is formed by an interpolation method.

[0020]

Therefore, among a large number of bit planes, a half tone image such as a photographic image is in the form of random noise, and a binary image such as a text original image has a lower bit plane having substantially the same content as the upper bit plane. Since the image is encoded in the state in which the data of 1 is deleted, the amount of encoded data of the multi-valued image data can be significantly reduced. In addition, by performing an exclusive OR process between pixels adjacent in the bit direction, the information source is operated so that the proportion of data 0 or data 1 in the entire data is biased so that either one becomes large. Therefore, the amount of encoded data can be reduced.

Further, since the deleted bit plane data can be formed by an appropriate interpolation calculation, prediction calculation or random number generation calculation, a relatively high quality image can be obtained and the coding compression rate can be improved. It is possible to obtain code data that is good and has good image quality.

The number of bit planes to be deleted is the type of image, the number of gradations, the designated compression mode, or
When applied to the image transmission device, an optimum value is set according to the number of gradations of the partner terminal, so that the coding compression rate is large and the required image quality can be secured.

[0023]

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

FIG. 1 shows an example of an image coding apparatus according to an embodiment of the present invention.

In the figure, an image input section 1 decomposes an original image into pixels with a predetermined resolution and converts the data of each pixel into 8-bit image data PA.
This image data PA is added to the bit plane development unit 2. The image mode data MDa representing the image mode (photograph mode or character mode) set by the user in the image input unit 1 is added to the deletion bit plane number determination unit 3 and the QM coder encoding processing unit 4, The compression mode data ST representing the compression mode (compression ratio priority mode or image quality priority mode) set in the image input unit 1 is added to the deletion bit plane number determination unit 3.

The bit plane expansion unit 2 decomposes the input image data PA into bit planes, and stores the image data of each bit plane in the image memory 5 in bit plane units.

The exclusive OR operation unit 6 has a work memory 7
Using as a work area, the image data of each bit plane stored in the image memory 5 is subjected to exclusive logic with respect to the image data of each pixel position and the image data of the adjacent pixel adjacent in the bit direction of the pixel position. The sum is formed, and the processing result is output to the QM coder encoding processing unit 4. Here, the exclusive OR calculation unit 6 starts the processing from the lowest bit plane, and executes the exclusive OR calculation processing with the pixel of the bit plane immediately above the same pixel position. Note that the pixel of the most significant bit plane is subjected to exclusive OR processing with the pixel of the bit plane formed of virtual all white pixels.

The deletion bit plane number determination unit 3 executes a predetermined deletion bit plane number determination process based on the image mode data MDa and the compression mode data ST,
The number of bit planes to be deleted in the multi-valued image data at that time (the number including the least significant bit plane from the least significant bit plane to the most significant bit plane) is determined, and the determination result is the deleted bit plane. The number data Dma is added to the QM coder encoding processing unit 4.

The QM coder encoding processing unit 4 applies to the image data input from the exclusive OR operation unit 6 for each bit plane, the image data excluding the deletion bit planes corresponding to the deletion bit plane number data Dma. Then, a predetermined QM coder encoding process is applied to encode and compress the encoded image data CDc obtained as a result.
It is output to the next stage device.

An example of the data format of the coded image data CDa formed by the QM coder coding processing section 6 is shown in FIG. 2 (a).

In this case, the encoded image data CDa for one page includes the header information representing the attribute information of the encoded image data CDa and the upper (8-m) number except the deleted m bit planes. Is a summary of the encoded data formed for each of the bit planes.

Further, the attribute information included in the header information includes 1 of the original multi-valued image data as shown in FIG.
The reference plane number n representing the number of bits per pixel, the deleted bit plane number m, the number of times of exclusive OR processing (1 in the above example), the image mode (photograph mode or character mode), and the main The resolutions in the scanning direction and the sub-scanning direction are included. Further, the file name, the comment information, the size in the main scanning direction, and the size in the sub scanning direction are also included.

FIG. 3 shows an example of a decoding device according to an embodiment of the present invention.

In the figure, the coded image data CDb having the same data format as the coded image data CDa formed by the coding apparatus shown in FIG. 1 is the QM coder decoding processing unit 1.
Added to 0.

The QM coder decoding processing unit 10 applies a predetermined QM coder decoding processing to each of the (n−m) bit plane coded data included in the coded image data CDa to apply each bit to each bit. The original image data is formed for each plane, and the image data is added to the exclusive OR calculation unit 11. Further, the QM coder decoding processing unit 10 outputs repetition number data Dx representing the number of repetitions of the exclusive OR processing of the header information included in the coded image data CDa to the exclusive OR calculating section 11 and the header. Image mode data MDb representing the content of the image mode of information, and deleted bit plane number data Dmb representing the number of deleted bit planes
Is output to the image insertion unit 12.

The exclusive OR operation unit 11 uses the work memory 13 as a work area, and with respect to the image data of each bit plane of the image data output from the QM coder decoding processing unit 10, the pixel position of each pixel position is determined. The image data is subjected to exclusive OR with the image data of the adjacent pixel adjacent to the pixel position in the bit direction to obtain the repetition count data D.
It is repeatedly executed the number of times specified by x, and the processing result is stored in the image memory 14 for each bit plane.

The image inserting section 12 applies the image generation method based on the image mode data MDb to the effective bit plane image data stored in the image memory 14 to specify the deletion bit plane number data Dmb. Image data of the lower bit plane
The image data of the formed deletion bit plane is stored in the image memory 14.

The data output unit 15 extracts the image data for each bit plane stored in the image memory 14 bit by bit corresponding to each pixel position, and sets the image data into 8 bits in bit order. Aligned, each pixel forms 8-bit multi-valued image data,
The multi-valued image data is output to the next stage device.

FIG. 4 shows an example of processing of the deletion bit plane number determination unit 3 in the encoding apparatus of FIG.

First, the compression mode data ST added at that time is examined to determine whether the compression ratio priority mode is designated by the user (decision 101).

When the result of judgment 101 is YES, the image mode data MDa added at that time is added.
Is checked to determine whether the character mode is designated by the user (decision 102).

When the result of judgment 103 is YES, the value of the number m of deleted planes is set to "5", and
When the result of determination 103 is NO, the value of the number m of deleted planes is set to "2".

Further, when the image quality priority mode is designated by the user, when the result of judgment 101 is NO, when the result of judgment 101 is YES, the image mode data MDa added at that time is stored. Look up,
It is determined whether the character mode is designated by the user (decision 105).

When the result of judgment 105 is YES, the value of the number of deleted planes m is set to "4", and
When the result of determination 105 is NO, the value of the number m of deleted planes is set to "1".

When the value of the number of deleted planes m is set in this way, the value is output as the number of deleted planes data Dma (process 108).

As described above, the value of the number m of deleted planes is set to an appropriate value depending on the image content and the compression mode (compression ratio priority or image quality priority) designated by the user, and therefore reflects the user's intention. Encoding processing is performed.

Here, the setting of the number of deletion planes can be determined under the following conditions.

(A) In the case of photographic data, the lower the bit plane, the more random noise it tends to be.

(B) In the case of photographic data, the larger the number of gradations, the larger the number of bit planes that become random noise, and the more lower bit planes can be deleted.

(C) In the case of photographic data in which the total number of bit planes is 8, even if the number of deleted bit planes is 1, there is almost no difference in image quality from the image data in which the bit planes are not deleted, and it cannot be visually distinguished. . Further, even if the number of deleted bit planes is increased to 3, almost no deterioration in image quality is recognized.

(D) In the case of character data, most of the image data can be reproduced only by the content of the most significant bit plane. Therefore, in the case of character data, more lower bit planes can be deleted.

It should be noted that the user does not specify the image content, but examines the content of the image data actually read and input to determine whether the read and input image is a halftone image or a binary image. It is also possible to determine the image mode based on the result of the determination.

FIG. 5 shows an example of processing of the image inserting section 12 in the decoding apparatus of FIG.

First, the image mode data MDb is examined,
Check whether the character mode is specified (decision 2
01). When the result of the determination 201 is YES, the bit plane into which the image data is to be inserted is selected based on the deleted bit plane number data Dmb (process 202), and the one bit position of the selected bit plane is the image of the bit plane above. The data is inserted into the image memory 14 as the image data of the selected bit plane (Process 20).
3).

When the processing of one bit plane is completed, it is checked whether or not the processing of all bit planes is completed (decision 204). When the result of the judgment 204 is NO, the process returns to step 202 and the next deletion is performed. Insertion processing of bit plane image data is performed. The result of judgment 204 is Y
When it becomes ES, the image data of all the bit planes are gathered in the image memory 14, so this processing is ended.

When the photograph mode is designated and the result of the determination 201 is NO, the bit plane into which the image data is to be inserted is selected based on the deleted bit plane number data Dmb (process 205), It is then checked whether the selected bit plane is the least significant bit (decision 206).

When the result of judgment 206 is NO,
The image data of the bit plane whose one bit position is higher than that of the selected bit plane is inserted into the image memory 14 as the image data of the selected bit plane (process 20).
7) Returning to step 205, the process of inserting the image data of the next deleted bit plane is performed.

When the result of the judgment 206 is NO, the image data randomly generated by the predetermined random number operation is inserted into the image memory 208 as the image data of the selected plane (process 208), and this process is executed. finish.

As described above, in the present embodiment, the code data is formed in the portion that does not affect the image quality and the image data of the lower bit plane is deleted. Therefore, the coding compression rate is very high. Get better In particular, in the case of a photographic image, the coding compression rate of the data of the lower bit plane, which is close to noise, is not so good, so the improvement of the coding compression rate according to the present embodiment is very large.

Further, in the present embodiment, the exclusive OR processing is performed between the pixels adjacent in the bit direction so that the proportion of data 0 or data 1 in the entire data is biased such that either one becomes large. Moreover, since the information source is operated, the amount of encoded data can be reduced.

According to the experiment of the inventor, when the exclusive OR processing is applied between the pixels adjacent in the bit direction and the subsequent image data is arithmetically coded (QM coder coded), the code is obtained. Efficiency is improved by more than 10%.

FIG. 6 shows a group 3 facsimile apparatus according to another embodiment of the present invention.

In the figure, the control section 21 performs control processing of each section of the group 3 facsimile apparatus and facsimile transmission control procedure processing. The system memory 22 is a control processing program executed by the control section 21. , And various kinds of data necessary for executing the processing program, and also constitutes a work area of the control unit 21.
Is for storing various information unique to the group 3 facsimile apparatus.

The scanner 24 is for reading an original image at a predetermined resolution and a predetermined number of gradations, and the plotter 25 is for recording and outputting an image at a predetermined resolution and a predetermined number of gradations. The operation display unit 26 is for operating the facsimile apparatus and includes various operation keys and various display devices.

The encoding / decoding unit 27 is for encoding and compressing the image signal and for decoding the encoded and compressed image information into the original image signal.
Is for storing a large number of coded and compressed image information.

The group 3 facsimile modem 29 is for realizing the modem function of the group 3 facsimile, and has a low speed modem function (V.21 modem) for exchanging a transmission procedure signal and mainly exchanging image information. High-speed modem function (V.17 modem,
V. 33 modem, V. 29 modem, V.29. 27ter modem etc.).

The network control device 30 is for connecting the facsimile device to a public telephone line network, and has an automatic call originating / receiving function.

These control unit 21 and system memory 2
2, parameter memory 23, scanner 24, plotter 2
5, operation display unit 26, encoding / decoding unit 27, image storage device 28, group 3 facsimile modem 29, and
The network control device 30 is connected to an internal bus 31, and data is exchanged between these elements mainly via the system bus 31.

Data is exchanged directly between the network controller 30 and the group 3 facsimile modem 29.

In this case, the encoding / decoding unit 27 is provided with the one shown in FIG. 7 as an encoding device for encoding / compressing image data. Further, as a decoding device for decoding the encoded image data into the original image data, the same decoding device as that shown in FIG. 3 is provided. In FIG. 7, the same parts as those in FIG. 1 and corresponding parts are designated by the same reference numerals.

In the figure, the bit plane expansion unit 2
Is for decomposing the 8-bit image data PA input from the scanner 4 into a bit plane,
The image data of each bit plane is stored in the image memory 5 in bit plane units.

The exclusive OR operation unit 6 has a work memory 7
Using as a work area, the image data of each bit plane stored in the image memory 5 is subjected to exclusive logic with respect to the image data of each pixel position and the image data of the adjacent pixel adjacent in the bit direction of the pixel position. The sum is formed, and the processing result is output to the QM coder encoding processing unit 4. Here, the exclusive OR calculation unit 6 starts the processing from the lowest bit plane, and executes the exclusive OR calculation processing with the pixel of the bit plane immediately above the same pixel position. Note that the pixel of the most significant bit plane is subjected to exclusive OR processing with the pixel of the bit plane formed of virtual all white pixels.

The QM coder encoding processing unit 35, among the image data input for each bit plane from the exclusive OR calculation unit 6, deletes bits corresponding to the deletion bit plane number data Dmc designated by the control unit 21. A predetermined QM coder coding process is applied to the image data excluding the planes to perform coding compression, and the coded image data CDc obtained as a result is output to the next stage device. Further, the content of the image mode data MDc designated by the control unit 21 is also set in the header information of the encoded image data CDc.

FIG. 8 shows a processing example when the group 3 facsimile apparatus transmits image information.

First, the designated destination is called (process 30).
1), called station identification signal CED, non-standard function identification signal NS
Each of F and the digital identification signal DIS is received (process 302). Then, the non-standard function identification signal NSF
Also, the content of the digital identification signal DIS is checked to confirm the reception capability of the partner terminal for multi-valued image data.

Then, the transmission function used for transmitting the image information at that time is set, and the non-standard function setting signal NSS for notifying the set transmission function is transmitted (process 303).
Here, the setting contents of this transmission function are the common modem speed that can be set with the partner terminal, the image (paper) size, the number of gradations of multi-valued image data that can be received by the partner terminal (or,
The number of bit planes per pixel) and the encoding method are included.

Then, a predetermined modem training procedure is executed with the partner terminal at the modem speed set at that time to determine the modem speed to be used (process 30).
4) The gradation number judgment processing (processing 305) for judging the number of deleted bit planes is executed based on the gradation number of the multi-valued image data that can be processed by the partner terminal, and designated to the QM coder encoding processing unit 35. The value of the deleted bit plane number data Dmc to be set is set, and the value of the image mode data MDc is set based on the user setting at that time (Process 3).
06).

When the preparation for image information transmission is completed in this way, the transmission original image set on the scanner 4 is read (step 307), and the multivalued image data obtained thereby is encoded / decoded. Encoding with 8 (process 30
8), the multi-valued image information obtained thereby is transmitted to the partner terminal (process 309), and the processes 307 to 309 are repeated for one page of the transmitted document image (decision 31).
0 NO loop).

When the transmission of the multivalued image information of the transmission original image for one page is completed and the result of judgment 310 is YES,
A post-message signal corresponding to the transmission original set on the scanner 4 is transmitted (process 311), and a response signal from the partner terminal is received.

Then, it is checked whether or not the transmission operation of all pages has been completed (decision 313). When the result of determination 313 is NO, the process returns to step 307 and the transmission operation of the transmission original image of the next page is performed. .

When the transmission operation of all pages is completed and the result of the judgment 313 is YES, the disconnection command signal DCN is sent (step 314), the line is restored (step 315), and The transmission operation ends.

FIG. 9 shows an example of gradation number determination processing (processing 305).

First, it is checked whether the number of processable gradations notified from the partner terminal is larger than the number of gradations read by the scanner 4 of the self terminal (decision 401). When the result of judgment 401 is YES, it is checked whether or not the image mode designated by the user is the character mode (decision 4).
02).

When the result of judgment 402 is YES, the number m of deleted bit planes is set to "4" (process 403). When the result of judgment 402 is NO, the number m of deleted bit planes is set to "3". set. If the result of the determination 401 is NO, the number m of deleted bit planes is set to "1" (process 405).

In this way, according to the present embodiment, the number m of deleted bit planes is set according to the number of gradations that the partner terminal can process.
Since the value of is adjusted, it is possible to obtain image data with good image quality at the partner terminal, reduce the amount of multivalued image information to be transmitted, and reduce the communication cost.

Although the present invention is applied to the black-and-white multi-valued image data in the above-described embodiment, the present invention can be similarly applied to the color multi-valued image data. In that case, for example, in the case of color multi-valued image data of three primary colors of RGB, it is preferable to perform a process of handling the data of each color component as the above-mentioned multi-valued image data.

Further, in the above description, the embodiment in which the present invention is applied to the group 3 facsimile machine has been described, but the present invention can be similarly applied to the group 4 facsimile machine.

In addition, in the above-described embodiment, 8 pixels per pixel are used.
The case where the present invention is applied when processing multi-valued image data of bits has been described, but the present invention is also applied to the case where multi-valued image data in which the number of bits per pixel is 9 or more or 7 or less is processed. The same can be applied.

Further, in the above-mentioned embodiment, in order to further improve the coding efficiency, the exclusive OR processing between the data before coding and the immediately above bit plane is executed as preprocessing. However, the present invention can be applied to the case where this pretreatment is not performed, and
Even in that case, the present invention has a sufficient effect.

Further, in the above-mentioned embodiment, the QM coder coding system is applied as the coding system, but the present invention can be implemented by applying other high efficiency coding system.

[0091]

As described above, according to the present invention,
Of a large number of bit planes, halftone images such as photographic images have random noise, and binary images such as text document images have lower bit plane data that has almost the same contents as the upper bit planes. Since the image is encoded in this state, the amount of encoded data of multi-valued image data can be significantly reduced.
In addition, by performing an exclusive OR process between pixels adjacent in the bit direction, the information source is operated so that the proportion of data 0 or data 1 in the entire data is biased so that either one becomes large. Therefore, there is an effect that the amount of encoded data can be reduced.

Further, since the deleted bit plane data can be formed by an appropriate interpolation calculation, prediction calculation or random number generation calculation, a relatively high quality image can be obtained and the coding compression rate can be improved. There is also an effect that it is possible to obtain code data that is good and has a good image quality.

The number of bit planes to be deleted is the type of image, the number of gradations, the designated compression mode, or
When applied to an image transmission device, an optimum value is set according to the number of gradations of the partner terminal, so that the coding compression rate is large and the necessary image quality can be secured.

[Brief description of drawings]

FIG. 1 is a block diagram showing an encoding device according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing an example of encoded data.

FIG. 3 is a block diagram showing a decoding device according to an embodiment of the present invention.

4 is a flowchart showing a processing example of a deletion bit plane number determination unit of the encoding device in FIG.

5 is a flowchart showing a processing example of an image inserting unit of the decoding device in FIG.

FIG. 6 is a block diagram showing a group 3 facsimile apparatus according to another embodiment of the present invention.

7 is a block diagram showing an example of an encoding device of an encoding / decoding unit in FIG.

FIG. 8 is a flowchart showing a processing example at the time of transmission of the apparatus of FIG.

9 is a flowchart showing a specific example of the gradation number determination process of FIG.

[Explanation of symbols]

1 Image input section 2-bit plane development unit 3 Deletion bitplane number determination unit 4,35 QM coder encoding processing unit 5,14 image memory 6,11 Exclusive OR operation unit 7,13 work memory 12 Image insertion part 15 Data output section

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H04N 1/41-1/419

Claims (8)

(57) [Claims] 1. Multi-valued image data represented by a plurality of bits per pixel is encoded and compressed by applying an encoding method to a bit plane unit in which data of bit order of each pixel is collected. In an image encoding device that forms encoded data, for image data of each bit plane, the image data of each pixel position forms an exclusive OR with the image data of the adjacent pixel adjacent in the bit direction of the pixel position. And the image data output by the exclusive OR means,
Coding means for forming coded data by applying the above-mentioned coding method to each bit plane in a state in which data of a predetermined number of lower-order bit planes of the multi-valued image data is deleted from the bit planes. An image code including an encoding control unit that changes the number of bit planes to be deleted by the encoding unit while leaving at least two or more bit planes according to the image type of multi-valued image data. Device. 2. Multi-valued image data represented by a plurality of bits per pixel is encoded and compressed by applying an encoding method to each bit plane unit in which data of bit order of each pixel is collected. In an image encoding device that forms encoded data, for image data of each bit plane, the image data of each pixel position forms an exclusive OR with the image data of the adjacent pixel adjacent in the bit direction of the pixel position. And the image data output by the exclusive OR means,
Coding means for forming coded data by applying the above-mentioned coding method to each bit plane in a state in which data of a predetermined number of lower-order bit planes of the multi-valued image data is deleted from the bit planes. An image including encoding control means for changing the number of bit planes to be deleted by the encoding means while leaving at least two or more bit planes according to the number of gradations of multi-valued image data Encoding device. 3. Multi-valued image data represented by a plurality of bits per pixel is encoded and compressed by applying an encoding method to a bit plane unit in which data of bit order of each pixel is collected. In an image encoding device that forms encoded data, for image data of each bit plane, the image data of each pixel position forms an exclusive OR with the image data of the adjacent pixel adjacent in the bit direction of the pixel position. And the image data output by the exclusive OR means,
Coding means for forming coded data by applying the above-mentioned coding method to each bit plane in a state in which data of a predetermined number of lower-order bit planes of the multi-valued image data is deleted from the bit planes. An image code comprising an encoding control means for changing the number of bit planes to be deleted by the encoding means while leaving at least two bit planes in accordance with a predetermined compression mode. Device. 4. A bit, which is applied to an image transmission device for transmitting multi-valued image data, and which combines multi-valued image data represented by a plurality of bits per pixel into data of bit order of each pixel. In an image encoding device that applies an encoding method in units of planes to encode and compress to form encoded data, for image data for each bit plane, for image data at each pixel position, the bit at that pixel position The exclusive OR means for forming an exclusive OR with the image data of the adjacent pixels adjacent in the direction, and the image data output by the exclusive OR means,
Coding means for forming coded data by applying the above-mentioned coding method to each bit plane in a state in which data of a predetermined number of lower-order bit planes of the multi-valued image data is deleted from the bit planes. An encoding control unit is provided for changing the number of bit planes deleted by the encoding unit, leaving at least two or more bit planes, according to the number of gradations of multi-valued image data that can be received by the partner terminal. An image encoding device characterized by the above. 5. Multi-valued image data represented by a plurality of bits per pixel is encoded and compressed by applying an encoding method in a bit plane unit in which data of bit order of each pixel is collected. In an image encoding / decoding device that forms encoded data and decodes by applying a decoding method corresponding to the encoding method to each bit plane unit of the encoded data to form original multi-valued image data. An encoding unit that forms the encoded data by applying the encoding method in a state in which data of a predetermined number of lower-order bit planes of the multi-valued image data in the bit planes is deleted; Encoding control means for changing the number of bit planes to be deleted by the encoding means while leaving at least two or more bit planes according to the image type of the image data. Of the encoded data, the encoded data of the bit planes that have not been deleted form the original image data by applying the above decoding method, while the image data of a predetermined number of lower bit planes that have been deleted are included. The image coding is characterized by including a decoding means which is formed by an interpolation method and changes the bit position of the lower bit plane to which the interpolation method is applied according to the image type of the multi-valued image data. Decoding device. 6. A multi-valued image data represented by a plurality of bits per pixel is encoded and compressed by applying an encoding method to a bit plane unit in which data of bit order of each pixel is collected. In an image encoding / decoding device that forms encoded data and decodes by applying a decoding method corresponding to the encoding method to each bit plane unit of the encoded data to form original multi-valued image data. An encoding unit that forms the encoded data by applying the encoding method in a state in which data of a predetermined number of lower-order bit planes of the multi-valued image data in the bit planes is deleted; Encoding control means for changing the number of bit planes to be deleted by the encoding means while leaving at least two or more bit planes according to the image type of the image data. The coded data of the bit planes that have not been deleted among the coded data form the original image data by applying the above decoding method, while predicting the image data of the predetermined number of lower bit planes that have been deleted. An image encoding / decoding device including a decoding unit which is formed by calculation and changes the bit position of the lower bit plane to which the prediction calculation is applied according to the image type of the multi-valued image data. apparatus. 7. The multi-valued image data represented by a plurality of bits per pixel is encoded and compressed by applying an encoding method to a bit plane unit in which data of bit order of each pixel is collected. In an image encoding / decoding device that forms encoded data and decodes by applying a decoding method corresponding to the encoding method to each bit plane unit of the encoded data to form original multi-valued image data. An encoding unit that forms the encoded data by applying the encoding method in a state in which data of a predetermined number of lower-order bit planes of the multi-valued image data in the bit planes is deleted; Encoding control means for changing the number of bit planes to be deleted by the encoding means while leaving at least two or more bit planes according to the image type of the image data. The coded data of the bit planes that have not been deleted among the coded data form the original image data by applying the above decoding method, while the image data of a predetermined number of deleted lower bit planes are randomly generated. An image encoding / decoding device including a decoding unit which is formed by calculation and changes the bit position of the lower bit plane to which the random number calculation is applied according to the image type of the multivalued image data. apparatus. 8. Multi-valued image data represented by a plurality of bits per pixel is encoded and compressed by applying an encoding method to a bit plane unit in which data of bit order of each pixel is collected. In the image coding / decoding method for forming the original multi-valued image data by forming the encoded data and applying the decoding method corresponding to the above-described encoding method to each bit plane unit of the encoded data to form the original multi-valued image data. At the time of encoding, the above-mentioned encoding method is applied to form encoded data while deleting the data of a predetermined number of lower-order bit planes of the multi-valued image data of the above-mentioned bit planes. Depending on the image type of the value image data, the number of bit planes to be deleted is changed while leaving at least two bit planes, and decoding is performed. In the encoded data of the bit plane that has not been deleted among the encoded data, the above-described decoding method is applied to form the original image data, while the image data of the predetermined number of lower bit planes that have been deleted. Is formed by an interpolation method, and the bit position of the lower bit plane to which the interpolation method is applied is changed according to the image type of the multivalued image data. Method.