JPH1074173A - Device for transmitting and receiving data, device for transmitting data, device for receiving data and method for compressing data - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a terminal equipment light, eliminate a fear that data are stolen or that a CPU is becoming old-fashioned, to save a trouble such as the install work of an application or the like or data maintenance, and to simply and highly efficiently compress data. SOLUTION: This data transmitting and receiving device transmits the data of a screen to a terminal equipment by radio or by wire. Then, the data of the screen are transmitted to the terminal equipment as bit map data constituting the screen, and screen display is operated. At that time, the bit map data are divided into blocks, the number of indexes for displaying each picture element is reduced according to the number of colors to be used in each block is small, and the data are converted into the index with the further small number of bits, compressed, and transmitted. Also, the blocks are defined as the units of the number of 10K-50K picture elements. Moreover, this device is provided with a changed rectangle detecting means 12 which detects only a part changed compared with the previous screen in the data constituting one screen, and the changed rectangle is detected, and the data of the changed rectangle part are transmitted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an apparatus for transmitting and receiving data and a method for compressing data. In particular, the present invention relates to an improvement in data transmission / reception technology which is preferably applied to a case where a computer serving as a host at a remote location is remotely operated via a LAN or the like.

[0002]

2. Description of the Related Art Conventionally, when a remote host computer is remotely operated via a LAN, it is necessary to temporarily transfer the screen of the remote host computer to a terminal device which is to be remotely operated. To perform such a transfer, the terminal device needs to have a function equivalent to that of the host computer. For example, the hardware and software configurations include a high-performance CPU, an additional memory, an HDD,
There is a need for wireless or wired interface devices, various sophisticated OSs, terminal applications, and the like.

[0003] Further, when performing in-store operations, for example, merchandise sorting work or inventory management work, the arrangement of merchandise is displayed on a portable terminal device as an image or the number of the stock state is displayed. Checking the execution of sorting work and the stock quantity. In the case of such an operation, a portable terminal device is purchased and operated independently of a POS terminal such as a cash register placed in a store.

[0004] On the other hand, conventionally, images called multi-color images have been used in computers and game machines. The multi-color image is also called a representative color image, a limited color image, or the like. As shown in FIG. 15, specific colors, that is, specific R (red), G (green), B
An index is assigned to a color having a value of (blue), and is represented by a limited representative color such as 16 colors or 256 colors using data of the index.

[0005] Such multi-color image data is
If each color of R, G, and B is represented by 8 bits (256 types), a total of 24 bits are required. However, since the index itself is also represented by 8 bits, a considerable compression ratio is obtained. It has become. However, although the data is compressed, the amount of information is still large, and if the data is processed as it is without any contrivance, the memory capacity is increased and the communication speed is reduced, which is not practical. Therefore, the compression technique of a multi-color image is extremely important, like other image data and character data. Especially,
Since the number of colors of a multicolor image is limited, lossless encoding and decoding, that is, a reversible compression technique is required.

In recent years, a technique using an entropy encoder and a decoder has attracted attention as one of data compression techniques. As one of the entropy coding and decoding techniques, for example, there is one using an arithmetic coding and decoding technique. The outline of this technology is described in, for example,
It is described in JP-A-2-185413, JP-A-63-74324, JP-A-63-76525, and the like.

FIG. 16 shows a conventional multi-color image encoding system 50 and decoding system 60 using such a technique. The encoding system 50 includes a line buffer 51 and an entropy encoder 52. The input index data, that is, the color pixel data 100A, is input to the line buffer 51 and the entropy encoder 52. As shown in FIG. 17, all of the color pixel data 100A are raster-scanned and sequentially input as pixel data in the horizontal scanning order. As a method of creating the data of the index, that is, the method of creating the color pixel data 100A, a method of assigning an index in the order of the input colors is general, and as shown in FIG. For example, the colors of “1” and “2” are significantly different, and those with distant index numbers, for example, “10”
A phenomenon occurs in which the colors are similar even for “0” and “200”. In order to avoid such a phenomenon, Japanese Patent Application Laid-Open No. 5-32
As indicated by reference numeral 8142, there is a case in which serial numbers are assigned to objects having similar colors.

The line buffer 5 in the encoding system 50
1 generates reference pixel data A, B, C, and D for the encoding target pixel X from the already input color pixel data 100A as reference pixel generation means (see FIG. 17). That is, the line buffer 51 stores histories for n lines (often about 1 to 5 lines) when scanning an image. Each time the color pixel data 100A of the encoding target pixel X is input, a series of pixel data including the immediately preceding pixel A and surrounding pixels B, C, and D is used as the reference pixel data 110 as an entropy encoder. Output to 52.

The entropy encoder 52 has, for example,
It is formed using a technique such as arithmetic coding or Huffman coding. Then, using the reference pixel data 110 as a state signal, the target color pixel data 100A is converted and output to the encoded data 200.

On the other hand, the decoding system 60 includes a line buffer 61 and an entropy decoder 62. Here, the line buffer 61 and the entropy decoder 62 are formed so as to decode and output the input coded data 200 in a procedure completely opposite to that of the line buffer 51 and the entropy coder 52 of the coding system 50. I have.

Thus, the encoding system 50,
The decoding system 60 converts the color pixel data 100A into the coded data 2 using completely opposite algorithms.
00, and the encoded data 200 can be decoded into color pixel data 100B and output. Therefore, this system can be widely used for various applications.

By the way, in such a system, when the value of the color pixel data 100A, that is, the index number is biased near a certain number, the compression ratio of the data is improved. In this system, the reference pixel data 110
From the entropy encoder 52 and the entropy decoder 62
Is used as a status signal. Therefore, if the number of states, that is, the number of reference pixels is increased, the data compression ratio is similarly improved. That is, when the entropy encoder 52 and the decoder 62 are configured by using a technique such as arithmetic coding or Huffman coding, if there is a large bias in the probability of occurrence of 0 or 1 symbol, the data compression ratio is reduced. Can be enhanced. This is because, in the entropy coding technique, short coded data is assigned to input data having a high occurrence probability, and relatively long coded data is assigned to input data having a low occurrence probability.

[0013] A run-length encoding technique is known for encoding a binary signal of 0 or 1. This is to increase the data compression ratio using the bias of the occurrence probability of 0 or 1 as described above.

As a method of image compression, a method of calculating a color symbol of a target pixel, that is, a bias in the appearance frequency of an index number corresponding to a color, and rearranging the index numbers in accordance with the appearance frequency order ( JP-A-6
No. 276041). That is, by this, short coded data is assigned to those having a high appearance frequency,
Increases the compression ratio.

As the index conversion, there are a method based on the appearance frequency shown in the prior art, and a method shown in FIGS. 15 and 18 in which image data is numbered in the order of scanning. In the index conversion shown in FIGS. 15 and 18, the compression ratio is improved to some extent, as in the case of the appearance frequency. FIG. 18A shows an index before conversion and FIG. 18 shows an index after conversion.
As can be seen by comparing FIG. 18C with FIG.
(C) is because the tendency tends to concentrate on the index of the small number, and the bias of the index occurs.

By the way, such a general method of arithmetic coding and decoding has already been described in the one-picture coding standard JBIG.
(International standard ISO / IEC11
544), pp. 26-44 and p44-p50, but here will be briefly described as a prerequisite technique for developing the present invention described later.

FIG. 19 shows an example of the arithmetic code type entropy encoder 52 used in FIG. Note that the configuration of the arithmetic decoding type entropy decoder 62 is substantially the same as the configuration of the entropy encoder 52, and a description thereof will be omitted.

The entropy encoder 52 includes an arithmetic operation unit 55 and an occurrence probability generation means 56 functioning as a state storage. This occurrence probability generation means 56
In the table, a state parameter table necessary for determining a symbol occurrence probability required for encoding is written. The above status parameters are specified by the input status signal. The arithmetic operation unit 55 adds the state parameter table specified by the state signal to the table.
Outputs the data at the time of updating the operation parameter as a read address, and the occurrence probability generation means 5 specified by this
6 is output to the arithmetic operation unit 55. The arithmetic operation unit 55 converts the input color rank data 120 into the encoded data 20 based on the data thus input.
Converted to 0 and output. In this manner, the data subjected to the index conversion, for example, the color rank data 120 is compressed and encoded.

[0019]

However, the conventional terminal device for remote operation is a heavy equipment having the same function as the host computer.
As a result, it is expensive. In addition, it is necessary to drive the same application, and if another application is used, it becomes difficult to achieve data compatibility. In particular, at the time of data transfer, commands are often transferred using commands specific to the OS or application, and command decoding is not possible with devices or other applications using other OSs. As described above, a conventional terminal device or a computer serving as a host does not have a good interface with other devices or other data.

Further, the conventional terminal device has a CPU having the same function as the CPU used for the host computer.
It is assumed to have. However, application software and the basic OS have evolved along with the evolution of the CPU. Therefore, when the CPU of the host computer is made more sophisticated, not only the terminal device but also the application software and the basic OS are newer. You have to As a result, costs rise and installation work of various software becomes difficult.

Further, since the conventional terminal device takes in the data of the host computer into the terminal device side, if the terminal device is stolen, important data will be stolen. Create a problem. Further, if data is manipulated on the terminal device side, consistency with the data in the computer on the host side is lost, so that the handling of the data must be sufficiently considered. That is, data maintenance work is required, which is troublesome.

In order to carry out the conventional in-store operations, such as sorting products and managing inventory, it is necessary to purchase a portable terminal device separately from the POS terminal and arrange operators. For this reason, labor costs increase and the system is expensive. In addition, since the number of POS terminals to be installed is determined on the basis of a large number of customers such as daytime and evening, many POS terminals are vacant during other time zones. That is, the conventional mobile terminal device is:
Independent of the POS terminal, since the application is executed as an independent one, the non-operating time of the POS terminal is not eliminated.

Furthermore, the conventional image data compression technique using reference pixel data has a considerably high compression ratio, but requires a number of encoding parameter tables corresponding to the number of states of the reference pixel data. For this reason, the larger the number of reference pixels is set to increase the compression ratio, the larger the encoding and decoding parameter tables become. This causes a problem that the entropy encoder 52 and the entropy decoder 62 become large and expensive.

On the other hand, the method of calculating the bias of the appearance frequency of the index number corresponding to the color and rearranging the index numbers in the order of appearance frequency or the method of numbering the image data in the scanning order increases the compression efficiency to some extent. Index conversion is preferable. However, in spite of the fact that the color of an image generally tends to be biased depending on the position of the screen, since each of these methods targets the entire screen and requires the color (index) of the entire screen, However, the actual compression efficiency is not so high.

According to the present invention, a data transmitting and receiving apparatus and a data transmitting apparatus can be provided which can make a terminal device light and have no fear of data theft or obsolescence of a CPU, and which does not require installation work of an application or data maintenance. And a data receiving device. It is another object of the present invention to provide a data transmitting / receiving device, a data transmitting device, and a data receiving device capable of transmitting and receiving compressed data with ease and high efficiency. Still another object of the present invention is to provide a data compression method capable of easily and efficiently compressing bitmap data.

[0026]

According to the first aspect of the present invention, there is provided a data transmitting / receiving apparatus for transmitting screen data to a terminal device wirelessly or by wire. The data is transmitted to the terminal device as bitmap data to be configured, and is displayed on the screen.

As described above, the screen data is transmitted to the terminal device as bitmap data.
The need for a DD, a high-performance OS, and the like is eliminated, and the equipment is light and inexpensive. Moreover, since the data operated on the terminal side is data existing in the host on the transmission side, there is no need to consider the consistency between the data on the transmission side and the data on the terminal side. Even if the terminal device is broken or stolen, the basic data is safe and no problem occurs. In addition, since the terminal device handles simple data such as bitmap data, a low-cost CPU can be employed and the functional value of the CPU can be maintained for a long time. Further, since the data to be handled is bitmap data, installation of high-performance application software or the like is not required, and an interface between the transmitting device and the terminal device can be easily obtained.

According to the second aspect of the present invention, the first aspect is provided.
In the data transmitting and receiving apparatus described, the bitmap data is divided into blocks, the smaller the number of colors used in each block, the smaller the number of indexes for displaying each pixel, and converted to an index with fewer bits, After compression, it is sent. As a result, depending on the divided block, a very small number of colors may be formed. In that case, the compression efficiency of the block increases, and the data transmission time is shortened. Furthermore, in the invention according to claim 3, in a data transmitting / receiving device that transmits screen data of a computer on the host side to a terminal device wirelessly or by wire, the screen data is converted into bitmap data, and the screen is divided into blocks. As the number of colors used in the block is smaller, the number of indexes for displaying each pixel is reduced, the data of the pixel to be transmitted is converted into an index with a smaller number of bits, compressed, and then transmitted to the terminal device. Screen display.

As described above, since the screen data is transmitted to the terminal device as bitmap data, the terminal device does not need an HDD, a high-performance OS, or the like, and is light and inexpensive. Moreover, since the data operated on the terminal side is data existing in the host on the transmission side, there is no need to consider the consistency with the screen data on the transmission side. Also, even if the terminal device is broken or stolen, the basic screen data is safe and no problem occurs. In addition, since the terminal device handles simple screen data called bitmap data, a low-cost CPU can be employed and the functional value of the CPU can be maintained for a long time. Further, since the data to be handled is bitmap data, installation of high-performance application software or the like is not required, and an interface between the host computer and the terminal device can be easily obtained.

According to the fourth aspect of the present invention, there is provided the second aspect.
Alternatively, in the data transmission / reception device described in 3, the block is performed in units of 10K to 50K pixels. For this reason, one screen is divided into several blocks,
If there is a color bias in one screen, data such as images is compressed with high efficiency. Note that in a normal screen, color deviation occurs depending on the position of the screen, that is, an image composed of many colors is often composed of several types of colors depending on blocks, and usually, most screens At
Increases compression efficiency.

According to a fifth aspect of the present invention, in a data transmitting / receiving apparatus for transmitting screen data to a terminal device wirelessly or by wire, the screen is converted to bitmap data, and
Change rectangle detection means is provided for detecting only a portion of the data constituting the screen which has changed compared to the previous screen, and the change rectangle detection means includes a vertical and horizontal portion of the start portion of the bitmap data of the change portion. When the position is X1, Y1 and the vertical and horizontal positions of the end portion are X2, Y2, | X1-X2
The area calculated by | × | Y1-Y2 | is detected as a changed rectangle, and the data of the changed rectangle is transmitted.

As described above, the screen data is transmitted to the terminal device as bitmap data, so that the terminal device
The need for a DD, a high-performance OS, and the like is eliminated, and the equipment is light and inexpensive. Moreover, since the data operated on the terminal side is data existing in the host on the transmission side, there is no need to consider the consistency between the data on the transmission side and the data on the terminal side. Even if the terminal device is broken or stolen, the basic data is safe and no problem occurs. In addition, since the terminal device handles simple data such as bitmap data, a low-cost CPU can be employed and the functional value of the CPU can be maintained for a long time. Further, since the data to be handled is bitmap data, installation of high-performance application software or the like is not required, and an interface between the transmitting device and the terminal device can be easily obtained. In addition, in the fifth aspect of the present invention, the changed portion is regarded as a changed rectangle and the data of the portion is transmitted to the receiving device, so that the transmission efficiency of the screen data is extremely high.

In addition, according to the invention of claim 6, in the data transmission / reception device of claim 5, when a non-changed rectangle that has not been changed exists in the changed rectangle, the non-changed rectangle area is displayed on the previous screen. There is provided a non-change signal generating means for generating a signal indicating the same as the above. As described above, the data of the unchanged portion in the deformed rectangle is transmitted as a small amount of data, so that the transmission efficiency of the screen data is further improved.

Further, in the invention according to claim 7, in the data transmission / reception apparatus according to claim 5 or 6, the bitmap data is divided into blocks in units of 10K to 50K pixels, and a changed rectangle is set in the divided blocks. I'm trying to get Therefore, a converted rectangle can be obtained for each divided block. That is, while one screen is divided into about 10 blocks, in a normal image, a change rectangle is generated only in a small number of blocks in one screen because a change portion is limited. For this reason,
The transmission efficiency of the screen data is further improved.

In addition, according to the invention described in claim 8, in the data transmitting / receiving apparatus according to claim 5, 6, or 7, the number of colors detected in the changed rectangle is detected by the color number detecting means. Index conversion means for setting the value of the index for displaying each pixel as an index having a smaller number of bits as the number of colors obtained is smaller, and data compression means for compressing bitmap data using the new index. Provided. For this reason, some change rectangles have a very small number of colors, and the index of the color can be set to a value with a small number of bits. As a result, the image compression ratio can be increased, and the transmission efficiency of the screen data can be further increased.

According to the ninth aspect of the present invention, the screen is bitmap data, and the number of indexes for displaying each pixel is reduced as the number of colors used in a predetermined area of each screen decreases. After converting the data of the pixel to be compressed into an index having a smaller number of bits, the bitmap data in the predetermined area is compressed.

Therefore, when the number of colors used in a predetermined area of the screen is small, the value of the index for displaying the color becomes small, and the compression efficiency increases. Thus, data compression can be efficiently performed by a very simple method.

In addition, according to the tenth aspect of the present invention, in the data compression method of the ninth aspect, the screen is set to 10K-5K.
The block is divided into units of 0K pixels, and each of the divided blocks is a predetermined area. Thus, 1
If the block is divided into units of 0K to 50K pixels, that is, if one screen is 640 × 480 dots (= number of pixels), if it is divided into a fraction to a tenth, one screen is obtained.
When there is a color bias in the screen, data such as an image is compressed with high efficiency. Note that in a normal screen, color bias occurs, that is, even if the image data is composed of multiple colors, depending on the block, it is often composed of a very small number of colors. The compression efficiency increases on the screen.

In the data compression method for extracting and compressing only a portion of a picture constituting one screen which has been changed compared to the previous screen, the screen is converted into bitmap data. , The vertical and horizontal positions of the start portion of the changed portion of the bitmap data are X1,
Assuming that Y1 and the vertical and horizontal positions of the end portion are X2 and Y2, the bitmap data in the changed rectangular area calculated by | X1-X2 | × | Y1-Y2 | is compressed.

As described above, since the changed portion is regarded as the bit map data of the changed rectangle, the data compression does not become special and can be performed efficiently. Also, since the data is compressed as bitmap data, if the compressed data is transmitted to, for example, a terminal device, the terminal device does not need an HDD, a high-performance OS, or the like.
It is light and cheap. Moreover, since the data operated on the terminal side is data existing in the host on the transmission side, there is no need to consider the consistency between the data on the transmission side and the data on the terminal side. Even if the terminal device is broken or stolen, the basic data is safe and no problem occurs. In addition, since the terminal device handles simple data such as bitmap data, a low-cost CPU can be employed and the functional value of the CPU can be maintained for a long time. Further, since the data to be handled is bitmap data, installation of high-performance application software or the like is not required, and an interface between hardware can be easily obtained.

According to a twelfth aspect of the present invention, in the data compression method according to the eleventh aspect, when there is an unchanged rectangular area that has not been changed in the changed rectangle, the non-changed rectangular area is displayed on the previous screen. Is generated. As described above, the data in the unchanged portion of the changed rectangle is compressed as a small amount of data, so that the compression ratio of the screen data is further increased.

In addition, according to the thirteenth aspect of the present invention, in the data compression method according to the eleventh or twelfth aspect, the bitmap data is divided into blocks in units of 10K to 50K pixels and changed within the divided blocks. I try to get a rectangle. Therefore, a changed rectangle can be obtained for each divided block. That is, while one screen is divided into about 10 blocks, in a normal image, a change rectangle is generated only in a small number of blocks in one screen because a change portion is limited. Therefore, the compression ratio of the screen data is further increased.

According to a fourteenth aspect of the present invention, in the data compression method according to the eleventh, twelfth, or thirteenth aspect, the number of colors in the changed rectangle is detected.
The index for displaying each pixel is an index having a smaller number of bits, and the bitmap data is compressed using the index. As described above, as the number of colors in the changed rectangle is smaller, an index having a smaller value is assigned to compress the data, so that the data compression ratio is improved.

According to the fifteenth aspect of the present invention, in a data transmitting apparatus for transmitting data of a screen of a host computer to a terminal device wirelessly or by wire, the screen of the host computer is constituted by bitmap data. Screen storage means for storing the bitmap data, change part detection means for detecting a changed partial area of the previous screen in the screen data, and bit map of the changed partial area from the screen storage means. Bitmap acquisition means for acquiring data, color number detection means for detecting the number of colors in the changed partial area of the bitmap data, and each pixel is displayed as the number of colors detected by the color number detection means is smaller. Index conversion means for converting the index into an index having a smaller number of bits; And data compression means for compressing bit map data by using the index was, are provided and transmission means for transmitting the data compressed by the data compressor.

As described above, since the screen data can be transmitted to the terminal device as bitmap data, the terminal device does not need an HDD, a high-performance OS, or the like, and is light and inexpensive. Moreover, the data operated on the terminal side is
Since the data exists in the host on the transmission side, it is not necessary to consider the consistency between the data on the transmission side and the data on the terminal device side. Further, even if the terminal device is broken or stolen, the basic data is safe and no problem occurs. in addition,
Since the terminal device handles simple data such as bitmap data, a low-cost CPU can be adopted and its CP
The functional value of U can be kept for a long time. Further, since the data to be handled is bitmap data, installation work of high-performance application software or the like is not required, and an interface with the receiving side can be easily obtained. In addition, since only the changed partial area is transmitted as data, transmission efficiency is increased. Further, when the number of colors in the changed portion area is small, the compression efficiency is increased, and the transmission efficiency is further improved.

Further, in the invention according to claim 16, in the data transmission apparatus according to claim 15, the bitmap data stored in the screen storage means is data of the number of dots composed of 1024 × 768. Therefore, data on a large screen can be displayed.

In addition, according to the seventeenth aspect of the present invention, in the data transmitting apparatus according to the fifteenth or sixteenth aspect, a unit to be detected when the changed part detection unit detects the changed part area is divided into one screen. Blocks. As described above, since the changed partial area is detected within the divided block in one screen, the compression rate of the transmission data can be improved. That is, there is a case where there is no change portion in some blocks or a case where the number of colors is extremely small. In such a case, the transmission data is reduced, the compression ratio is increased, and the data transmission efficiency is extremely improved.

In the data transmission apparatus for transmitting the data of the screen of the host computer to the terminal device wirelessly or by wire, the screen of the host computer is constituted by bitmap data. Screen storage means for storing the bitmap data, change part detection means for detecting a changed partial area of the previous screen in the screen data, and bit map of the changed partial area from the screen storage means. Bitmap acquisition means for acquiring data, data compression means for compressing the bitmap data of the changed partial area, and transmission means for transmitting data compressed by the data compression means,
When the vertical and horizontal positions of the start portion of the changed portion of the bitmap data are X1 and Y1, and the vertical and horizontal positions of the end portion are X2 and Y2, |
A modified rectangle detecting means for detecting the modified rectangle calculated by × | Y1-Y2 | as a modified partial area.

As described above, since the screen data can be transmitted to the terminal device as bitmap data, the terminal device does not need an HDD, a high-performance OS, or the like, and is light and inexpensive. Moreover, the data operated on the terminal side is
Since the data exists in the host on the transmission side, it is not necessary to consider the consistency between the data on the transmission side and the data on the terminal device side. Further, even if the terminal device 11 is broken or stolen, the basic data is safe and no problem occurs. In addition, since the terminal device handles simple data such as bitmap data, a low-cost CPU can be employed and the functional value of the CPU can be maintained for a long time. Further, since the data to be handled is bitmap data, installation work of high-performance application software or the like is not required, and an interface with the receiving side can be easily obtained. In addition, since only the changed partial area is transmitted as data, transmission efficiency is increased. Further, when the number of colors in the changed portion area is small, the compression efficiency is increased, and the transmission efficiency is further improved. In addition, since the changed portion area is set as a changed rectangle and the data of that portion is sent, the transmission efficiency is improved.

Further, according to the nineteenth aspect of the present invention, in the data transmitting apparatus according to the eighteenth aspect, a color number detecting means for detecting the number of colors in the changed rectangle, and a color number detected by the color number detecting means. Accordingly, an index conversion unit that assigns an index having a different number of bits to each pixel is provided,
When there is a non-changed rectangular area that has not been changed in the changed rectangle, the changed rectangle detecting means generates a signal indicating that the non-changed rectangular area is the same as the previous screen. The number of colors is detected for a rectangular area other than the non-changed rectangular area, and the index conversion unit assigns a smaller number of bits to the index for displaying each pixel as the detected number of colors is smaller.

For this reason, the data amount of the non-changed rectangular area in the changed rectangle is reduced. In addition, the number of colors is detected in areas other than the non-changed rectangular area. If the number of colors is small, the index value becomes small, and the data compression ratio increases. As a result, even if the same screen is transmitted, data can be transmitted in a short time by using this data transmission device.

According to the twentieth aspect of the present invention, the receiving means for receiving the bitmap data constituting the screen, the data decompressing means for decompressing the bitmap data, and the number of colors of the bitmap data for each predetermined block are determined. Based on the signal, the smaller the number of colors, the smaller the number of colors, and the number of color conversion means for specifying each index in which an index for displaying each bit is given a value with a smaller number of bits, and the color is specified by the number of color conversion means. Screen storage means for storing bitmap data based on the pixels, and a display unit for displaying the bitmap data stored in the screen storage means.

As described above, since the bit map data is received, the data receiving apparatus does not require an HDD, a high-performance OS, or the like, and is light in equipment and inexpensive. Moreover, since the data operated on the terminal side is the data existing on the host on the transmitting side, it is not necessary to consider the consistency between the data on the transmitting side and the data on the data receiving apparatus side. Also,
Even if the data receiving device is broken or stolen, the basic data is safe and no problem occurs. In addition, since the data receiving apparatus handles simple data such as bitmap data, a low-cost CPU can be employed and the functional value of the CPU can be maintained for a long time. Further, since the data to be handled is bitmap data, installation of high-performance application software or the like is not required, and an interface with a host computer or the like can be easily obtained. In addition, when the number of colors is small, data with a high compression rate is received, and data with a large display area can be received in a short time.

[0054]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

The device shown in this embodiment is a data transmitting / receiving device 1 using a POS device 2 installed in a retail store. That is, the data transmitting / receiving device 1 calls the data on the host (not shown) via the LAN 3 or the like, and displays the data on the screen 4 of the POS device 2.
And the data displayed on the screen 4 is wirelessly received,
And a terminal device 6 for displaying on the display unit 5.
The POS device 2 functions as a cash register and transmits the display contents of the screen to the terminal device 6 as bitmap data constituting the screen.

First, the general configuration of the POS device 2 and the terminal device 6 which are the main devices constituting the data transmitting / receiving device 1 will be described. POS device 2 serving as a data transmission device
As shown in FIG. 2, a VRAM 11 serving as screen storage means for storing bitmap data displayed on the screen 4 under the control of a CPU (not shown) in the POS device 2
A changed rectangle detecting means 12 serving as a changed part detecting means for detecting a changed part area of the previous screen in the bitmap data; and a bit for obtaining the bitmap data of the above changed area from the VRAM 11. The map acquisition means 13, the color number detection means 14 for detecting the number of colors of the bitmap data in the changed partial area, and the smaller the number of colors detected by the color number detection means, the more the index for displaying each pixel becomes. An index conversion means 15 for setting an index having a small number of values, a data compression means 16 for compressing bitmap data using the index given by the index conversion means 15, and a data compressed by the data compression means 16 And a transmitting unit 17 for wirelessly transmitting the data. The changed rectangle detecting means 12 has a non-change signal generating means 18 described later.

Here, the CPU in the POS device 2 has a high speed and a high function. POS device 2
Has a high-performance OS, various application software, a HDD of about 1 GB, a RAM of 16 MB or more, and the like. The VRAM 11 is what is called a video ram, and in this embodiment,
Data of 640 dots horizontally and 480 dots vertically is stored as bitmap data. In order to eliminate flickering when switching screens, VR
The AM 11 may be capable of storing two screens. The screen 4 may be a high-definition screen having 1,024 dots in width and 768 dots in height, and the VRAM 11 may correspond thereto.

On the other hand, terminal device 6 serving as a data receiving device
Means for receiving bitmap data and 21;
Based on the expansion means 22 for expanding the bitmap data and the signal indicating the number of colors for each predetermined block of the bitmap data, the smaller the number of colors, the smaller the number of bits in the index for displaying each pixel. A color number conversion means 23 for specifying each index to which a value is assigned, and a VRAM serving as a screen storage means for storing bitmap data based on the pixel whose color is specified by the color number conversion means 23
24, a display unit 5 for displaying the bitmap data stored in the VRAM 24, and each of the means 21, 22, 23, 24
And the like, and a RAM 27 that functions as a storage unit when the receiving unit 21, the data decompressing unit 22, and the like operate.

The CPU 26 in the terminal device 6 has a lower function and a lower price than the CPU 12 in the POS device 2. However, if it is desired that the terminal device 6 perform other functions, the terminal device 6 may have the same function as the CPU in the POS device 2. Here, the display unit 5 is made of liquid crystal and has a size of 640 ×
A screen of 480 dots can be configured. The receiving means 21 comprises a commercially available general-purpose wireless LAN card. In the data transmitting / receiving apparatus 1, not only when the screen 4 is an image but also text data, the screen data is transmitted to the terminal device 6 as bitmap data. Then, the received data is only the data of the part related to the changed rectangle which is the changed part area. The changed rectangle detecting means 12 for detecting the changed rectangle has a configuration shown in FIG.
That is, using the data in the VRAM 11, the previous screen 1
The difference between 2a and the current screen 12b is calculated and extracted by the comparison calculator 12c. The extracted part is the changed rectangular area 12d.
And the information is sent to the bitmap acquisition means 13.

The comparison calculator 12c may compare the entire screen 4 with each other, but in this embodiment,
As shown in FIG. 5, the screen 4 is vertically divided into 10 blocks, and each of the divided blocks 4a,.
Compared to Each block 4a,...
× 48 dots, that is, about 30K dots (= pixel).

As shown in FIG. 5, if there are only two changed portions, the changed rectangle 31 of the block 4a and the changed rectangle 32 of the block 4b, the bitmap data transmitted on the screen 4 is the changed rectangle. Only the portions 31 and 32 are provided. Note that each of the change rectangles 31 and 32 represents the vertical and horizontal positions of the start portion of the change portion of the bitmap data by X.
Assuming that the vertical and horizontal positions of the end portion are X2 and Y2, the area is calculated and represented by | X1−X2 | × | Y1−Y2 |. When the changed rectangle 31 is viewed in more detail, the actual changed portion is as shown in FIG.
If the small change rectangles 33 and 34 are set as shown in FIG. 7, non-change rectangle areas 35 and 36 exist.

The changed rectangle detecting means 12 outputs the changed rectangle 31,
32, and the small change rectangles 33 and 34 and the non-change rectangle areas 35 and 36 are also detected. Then, it instructs the bitmap acquisition means 13 to acquire the bitmaps of the small change rectangles 33, 34, and outputs a signal indicating that the portions of the non-change rectangle regions 35, 36 are the same as the previous screen. Generated by the change signal generating means 18,
It is sent to the bitmap acquisition means 13.

Similarly, for the changed rectangle 32 in the block 4b, the bit map obtaining means 13 is instructed to obtain the bit map of the small changed rectangles 37, 38, and 39, and the non-changed rectangular areas 40, 41, 42, Regarding 43 and 44, a signal to the effect that it is the same as the previous screen is sent to the bitmap acquisition means 13.

The bitmap obtaining means 13 outputs the changed rectangle,
In the above example, the small change rectangles 33, 34, 37, 3
The bitmap data of the portions 8 and 39 is obtained from the VRAM 11. Then, the data is sent to the color number detecting means 14. The signal that is the same as the previous screen received from the changed rectangle detecting means 12 passes through the color number detecting means 14 as it is, and
Sent to

The number-of-colors detecting means 14 is provided for each block 4a,
, 4j, the number of colors of a changed rectangle, for example, changed rectangles 31, 32, etc., is detected. The number of detected colors,
The bitmap data in the changed rectangle and the signal indicating that it is the same as the previous screen are sent to the index conversion unit 15.
Sent to The index conversion means 15 has a different color conversion table according to the number of colors detected by the color number detection means 14, and converts the index based on the color conversion table.
For example, as shown in FIG. 7, each block 4a,.
When the number of colors of the changed rectangles in 4j is different,
Index conversion is performed based on the criteria shown in FIG.

As shown in FIG. 8, this criterion is that the number of colors is four.
The color conversion table has 4 bytes when the number of colors is less than 8 colors, 8 bytes when the number of colors is 16 or less, and does not have any value when the number of colors is 17 or more. That is, when the number of colors is four or less, an index having four types of bit representations of "00", "01", "10", and "11" is assigned instead of the original index. Since each index has an original index consisting of 8-bit data, the color conversion table has a total of 4 bytes.
As described above, the original index is an index for a multi-color image having 256 kinds of colors, that is, 8 bits, but is compressed to 2-bit data by the color conversion table. Similarly, when there are 16 colors or less, the data is compressed to 4-bit data. On the other hand, if there are 17 or more colors, the data is the 8-bit data as it is, so no special color conversion table is prepared and the original index is used as it is.

The bitmap data in the changed rectangle represented by the index converted and the signal indicating the same as the previous screen are both sent to the data compression means 16. The data compression means 16 employs a run-length encoding method to compress data by an arithmetic encoder, and transmits the data to the transmission means 17. The data compression means 16 may use a method using state division of reference pixels, such as a method using a Markov model or a DP, in addition to run-length coding.
Various compression methods such as a method of obtaining a difference from a previous pixel such as a CM can be appropriately adopted. Also, various entropy encoders can be employed as the encoder.

The transmitting means 17 transmits the compressed data to the terminal device 6 as a radio signal. Since a signal to be transmitted is digital, phase modulation or amplitude phase modulation is used at the time of transmission. Also,
As the used frequency band, a high frequency band such as a Bayer line or satellite communication can be used in addition to the band of several MHZ. In this embodiment, a commercially available general-purpose wireless LAN card is employed.

Next, the operation flow in the data transmitting / receiving apparatus 1 configured as described above will be described with reference to FIGS.
0 will be described.

When the POS device 2 starts transmitting data (step S1), it is first detected whether or not there is a changed rectangle in the first block 4a in which one screen is divided into tenths. A changed rectangle detection step S2 is executed. If there is no change rectangle, the process returns to step S2 to immediately detect the change rectangle of the next block 4b. On the other hand, if there is a deformed rectangle, the non-changed rectangular area in the changed rectangle is distinguished from the other parts, and a signal indicating that the non-changed rectangular area is the same as the previous screen (= for the non-changed rectangular area) Is performed at step S3. For other changed rectangles, a bitmap acquisition step S4 for acquiring a bitmap from the VRAM 11 is executed. At the start of screen data acquisition, since there is no screen to be compared, the entire block is recognized as a changed rectangle. For this reason, the return process without the change rectangle,
It does not occur together with the branch in step S3.

Thereafter, a step S for detecting the number of colors in the changed rectangle
Step 5 is executed. Then, based on the number of colors, an index conversion step S6 for converting an index based on the reference shown in FIG. 8 is executed. In this way, the converted rectangle is represented as changed rectangle data composed of bitmap data represented by the index that has been subjected to the index conversion and a signal indicating that it is the same as the previous screen. Then, a data compression step S7 in which the changed rectangular data is compressed by the data compression means 16 is executed. The compressed data is transmitted in a data transmission step S8. In the data compression step S7, data is compressed by run-length encoding. When one screen is completed by this data transmission, the presence / absence of transmission of the next screen is detected, and when the next screen is transmitted, the process proceeds to the next screen start step S9. However, if the processing has not been completed for all 10 blocks, the process returns to the changed rectangle detection step S2. Upon completion of the ten blocks and transmission of the next screen, the process proceeds to the next screen start step S9. If the next screen is not transmitted, the data transmitting / receiving device 1
Ends the data transmission (step S10).

In transmitting the data, the same data, for example, the data in one block is sent out several times or the data in one screen is transmitted in consideration of the reception error and the transmission environment on the terminal device 6 side. It is preferable to adopt a method of sending out several times in a lump. However, data transmission may be performed only once, if slight omission of reception is not considered.

The terminal device 6 for receiving data is always on, and is ready to receive data. The terminal device 6 is set in an operable state (power-on state),
It is also possible to receive the transmission start signal of the transmission data and shift to the reception state. Alternatively, the terminal device 6 and the POS device 2 may be manually turned on at the same time and transmitted and received.

When the terminal device 6 starts reception (step S11), first, a data reception step S12 is executed for the first block, and then a data expansion step S13 for expanding the data is executed. In the data decompression step S13, the run-length coded signal is decoded by an algorithm reverse to the above algorithm.
As the decoder at this time, various types of entropy decoders can be employed in addition to the arithmetic coding type decoder.

The decompressed data is converted to the original index based on a table similar to the previous color conversion table, and a signal indicating that it is the same as the previous screen is added, so that the data in the changed rectangle is restored. (Step S1
4). The restored data is stored in the VRAM 24 and displayed on the display unit 5 (step S1).
5). That is, in the data in the VRAM 24, only the changed rectangular portion is rewritten, and only the rewritten portion is changed and displayed on the display unit 5.

Steps S12, S13, S14 and S15 are repeated until the data display for all 10 blocks is completed.
repeat. Then, when one screen is completed, it is determined whether or not reception of the next screen has started, and when there is reception, the next screen start step S16 is executed. If the data of the next screen has not been received, the reproduction display ends (step S17).
When transmitting a signal to the effect that the transmission of the screen data is completed at the time of data transmission, the terminal device 6 can enter the termination step S17 when receiving the signal.

It should be noted that the changed rectangle detection step S2 is the same as that shown in FIG.
It comprises the steps shown in FIG. That is, when the start step S1 is executed, the changed rectangle detection step S2 is started (step S21). Then, the previous screen stored in the VRAM 11 is taken out (step S22).
Next, the current screen newly input to the VRAM 11 is taken out (step S23), and both screens are compared (step S2).
4). Then, a changed rectangle is detected from the difference between the two screens (step S25), and the data is stored in the bitmap obtaining unit 13 (step S25).
Send to

Next, the second method in which the method of detecting the changed rectangle is changed.
Will be described with reference to FIGS. 12 and 13. FIG. In the description, the same members as those of the first embodiment shown in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

This detection method is performed in such a manner that the drawing command to the VRAM 11 is intercepted. That is, normally, the drawing command from the OS 46 of the POS device 2 is transmitted to the display driver 47 and drawn in the VRAM 11. However, as shown in FIGS. 12 and 13, the change detection means 45 in the second embodiment
It is inserted between 46 and the display driver 47. For this reason, the drawing command from the OS 46 is transmitted to the display driver 47 through the changed rectangle detecting means 45. At this time, the changed rectangle detecting means 45 copies and extracts a changed portion from the previous screen. On the other hand, the drawing command itself is transmitted to the display driver 47 and drawn in the VRAM 1 as before.

The changed portion extracted by the changed rectangle detecting means 45 is transmitted to the bitmap obtaining means 13,
The bitmap data of the corresponding part is obtained from the VRAM 11. Subsequent processing is the same as in the first embodiment. The modified rectangle detecting means 45 of the second embodiment
Plays the role of a dummy driver.
The configuration can be simplified.

In each of the embodiments described above, since the screen data is transmitted as bitmap data, the versatility is increased as compared with the conventional method using a command. That is, since the conventional command method depends on the OS used by the host computer serving as the data transmission device, data cannot be reproduced by a terminal device having a different OS. However, in this embodiment, since the bitmap data is used, if the data format is the same, the screen can be reproduced by a terminal device using another OS. Further, the data transmitting / receiving device 1 according to this embodiment
Indicates that the POS device 2 is not
Using the high-performance OS environment of the S device 2, the operator of the POS device 2 can perform sorting of goods, inventory work, and the like on the terminal device 6. For this reason, the operating time of the POS device 2 can be increased and labor costs can be reduced.

Each of the above embodiments is an example of a preferred embodiment of the present invention. However, the present invention is not limited to this, and various modifications can be made without departing from the scope of the present invention. It is. For example, as the terminal device 6, C
The PU may be the latest one, and an ordinary computer equipped with an HDD or the like may be used. Also, a multi-color image to be handled is not 8 bits (256 colors) but 4 bits (16 bits).
(Color) or 16 bits (64,000 colors). The conversion table is also 4 bytes and 1
An image of 8 bytes (within 8 colors) can be inserted in the middle of 6 bytes, and when the image has another bit number such as 4 bits or 16 bits as described above, various changes can be made to another image. In addition, the terminal device shown in each embodiment described above and each embodiment described below, an Internet-compatible terminal,
That is, if the operation is performed by TCP / IP, the applicable range becomes wide and the cost can be reduced. Further, regarding the screen resolution, 640 × 4
In addition to 80 dots and 1024 x 768 dots, 800 x
The screen may have another resolution such as 600 dots or 1280 × 1024 dots.

The size of a block that divides the screen 4 is about one tenth of the size of the screen 4, for example, if the screen 4 is 640 × 480 dots, the size is 64.
0x48 dots is appropriate, but 640x
If it is about 20 dots or more, head information for representing a block is reduced, which is preferable. 640 divided into 5
If it is about × 96 dots or less, the number of colors in each block is less likely to increase, which is preferable. In the case of the screen 4 corresponding to high resolution of 1024 × 768 dots and the like, the number of pixels in the divided block is also different, but the number of pixels is set to about 10K to 50K pixels. This is preferable because information does not increase and the number of colors in each block decreases.

Further, the data transmission / reception device 1 of each of the above-described embodiments performs in-store operations in cooperation with the POS device 2, but can be used for various other purposes.
For example, as shown in FIG. 14, a computer 48 serving as a host is placed outside a store, a plurality of terminal devices 6 are placed in a place where the customer can easily operate the store, and various information is transmitted to the operation unit 6a by the customer. Can be taken out using.

In this way, since the terminal device 6 is small and does not take up space, it can be installed in various places. Further, since the layout change in the store is facilitated, the cost can be suppressed when the store is renovated.
In addition, by the operating means 48a of the computer 48,
The operation of the terminal device 6 can be monitored, and the operation of the terminal device 6 can also be performed. Therefore, the computer 48
A more interactive system can be realized between the device and the terminal device 6. However, when the terminal device 6 accesses the computer 48, the terminal device 6 needs to obtain an access right and then access to retrieve the data because it is multi-user. It should be noted that a terminal computer 49 connected to the computer 48 by wire may be added to this system, and may be placed in a plaza or a rest area in a store.

Further, the data transmitting / receiving apparatus 1 may be used in an office. For example, when leaving a seat in a meeting or the like, data from a computer of the user's own desktop, which is a host, can be used from another location via a wired or wireless LAN. Further, the host computer may be a computer that is used in common by employees or section members instead of the computer of the host.
However, also in this case, it is necessary to gain access right and then access the common computer as in the case of FIG.

In addition to the above-mentioned applications, in various classes such as a computer class, the screen state of the instructor's computer is displayed on a plurality of terminal devices 6 of the student.
Alternatively, the screen state of the student's terminal device 6 may be displayed on the instructor's computer for use.
Similarly, the data transmission / reception device 1 can be used in a lesson in an elementary school or the like, for example, a lesson in arithmetic or the like.

Further, with respect to the wireless LAN card used for the transmitting means 17 and the receiving means 21, data can be transmitted from a rewritable recording device, for example, an HDD or a rewritable memory card, so that a user can register a program driver. You may make it attach to an apparatus side. Furthermore, the program may be provided by a ROM card so that the wireless LAN card can be changed to a high-performance wireless LAN card. The use of a commercially available general-purpose wireless LAN card as described above makes it easy to cope with the problem and makes it possible to improve the performance in the future.

Further, in the above-described embodiment, the terminal device 6 is a dedicated device as a terminal. However, the terminal may be a general personal computer like a computer 49 shown in FIG. In this way, various effects can be obtained, such as being able to connect to a plurality of hosts and opening a window that can be independently moved on the terminal side.

After transmitting the bitmap data to the terminal device 6, the terminal device 6 may perform command control such as scrolling the screen. Such a command may be transferred together with the bitmap data from the data transmission device on the host side such as the POS device 2 to the terminal device 6 side. In this way, various data transmitted to the terminal device 6 can be used. Regarding this command transfer, for example, the following copy command can be used to reduce the data amount. That is, when a copy is made in the terminal device 6, the copy source rectangle and the copy destination rectangle are stored in the host-side data transmission device. When the copy information is stored when the current screen 12b is sent to the terminal device 6, if the copy source rectangle of the previous screen 12a matches the copy destination rectangle of the current screen 12b, it is checked. . If they match, a copy command is transmitted to the terminal device 6, and the copy source rectangle of the previous screen 12a is copied to the copy destination portion of the current screen 12b, and the saved previous screen 12a is also copied. Copies from the rectangle to the destination rectangle. Then, since the copy destination rectangles of the previous screen 12a and the current screen 12b match, that part does not become a changed rectangular area, and the data of that part is compressed. This reduces the amount of data transmitted.

As described above, in addition to the case where the copy operation is detected and the command is utilized, a method of comparing the contents of the screen of the terminal device 6 to extract a copy portion, and utilizing the command can also be adopted. For example, regarding the scroll operation, a matching line between the previous screen 12a and the current screen 12b is detected,
If there is more than N rows, it is determined that scrolling has been performed, and data can be compressed by utilizing the copy command in the same manner as in the previous example. Here, N is an integer other than 1. If N is set to 1, one line may coincide by chance,
In order to eliminate such a case, N = 1 is excluded.

[0092]

As described above, in the data transmitting / receiving apparatus, the data transmitting apparatus, and the data receiving apparatus of the present invention, the terminal device can be lightly equipped, and there is no fear of data theft or obsolescence of the CPU. This eliminates the need for installation work for applications and the like and data maintenance. Furthermore, since bitmap data is handled, the interface is good in terms of both hardware and software, and it is difficult to be restricted by hardware standards and OS types. Therefore, when configuring the system, the selection range of hardware and software is widened, and an efficient and low-cost data transmitting / receiving device, and a data transmitting device and a data receiving device can be provided. In addition, compressed data can be transmitted and received simply and efficiently.
Further, according to the data compression method of the present invention, bitmap data can be compressed easily and with high efficiency.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of a data transmission / reception device of the present invention.

FIG. 2 is a block diagram showing a main configuration of the POS device of FIG. 1;

FIG. 3 is a block diagram illustrating a main configuration of the terminal device of FIG. 1;

FIG. 4 is a diagram for explaining a configuration of a changed rectangle detection unit in FIG. 2;

FIG. 5 is a diagram showing a screen configuration and a changed rectangle of the POS device of FIG. 1;

6 is an enlarged view of a block in the screen of FIG. 5,
(A) is a figure which shows the 1st block, (B) is a figure which shows a 2nd block.

FIG. 7 is a table for explaining the operation of the index conversion means of FIG. 2;

FIG. 8 is a table for explaining the contents of a color conversion table in the index conversion means of FIG. 2;

FIG. 9 is a flowchart for explaining the operation of the POS device in FIG. 2;

FIG. 10 is a flowchart illustrating an operation of the terminal device of FIG. 3;

FIG. 11 is a flowchart for explaining the operation of a changed rectangle detection unit in FIG. 4;

FIG. 12 is a diagram showing a second embodiment of the data transmission device used for the data transmission / reception device of the present invention.

FIG. 13 is a flowchart for explaining the operation of the changed rectangle detection means in FIG. 12;

FIG. 14 is a diagram for explaining another application example of the data transmitting / receiving device of the present invention.

FIG. 15 is a diagram for explaining properties of a multi-color image transmitted in the present invention and the conventional data transmitting / receiving apparatus.

FIG. 16 is a diagram showing a conventional multicolor image encoding system and decoding system.

FIG. 17 is a diagram illustrating a reference pixel method used for conventional data compression.

FIG. 18 is a diagram for explaining a method of numbering indices in the order of scanning, which is one of conventional data compression.

FIG. 19 is a diagram showing a configuration of an arithmetic code type entropy coder used for the present invention and conventional data compression.

[Explanation of symbols]

 Reference Signs List 1 data transmission / reception device 2 POS device (computer on host side) 3 LAN 4 screen 5 display unit 6 terminal device 11 VRAM 12 changed rectangle detection means (changed part detection means) 13 beat map acquisition means 14 color number detection means 15 index conversion means Reference Signs List 16 data compression means 17 transmission means 21 reception means 22 data decompression means 23 color number conversion means 24 VRAM

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical indication location H04N 1/41 H04N 1/41 C 7/32 9185-5C 11/04 Z 11/04 7/137 Z

Claims (20)

[Claims] 1. A data transmitting / receiving apparatus for transmitting screen data to a terminal device wirelessly or by wire, transmitting the screen data as bitmap data constituting the screen to the terminal device, and performing screen display. A data transmission / reception device, characterized in that the data transmission / reception device is configured to perform the above operation. 2. The bitmap data is divided into blocks, and the smaller the number of colors used in each block is, the smaller the number of indexes for displaying each pixel is, and the data is converted into an index having a smaller number of bits. 2. The data transmission / reception device according to claim 1, wherein the data transmission / reception is performed after the transmission. 3. A data transmitting / receiving apparatus for transmitting screen data of a computer on a host side to a terminal device wirelessly or by wire, the screen data being bitmap data, the screen being divided into blocks, and each block being divided into blocks. As the number of colors used is smaller, the number of indexes for displaying each pixel is reduced, the data of the pixel to be transmitted is converted into an index with a smaller number of bits, compressed, transmitted to the terminal device, and displayed on the screen. A data transmitting / receiving device characterized by performing the following. 4. The data transmission / reception apparatus according to claim 2, wherein the block is performed in units of 10K to 50K pixels. 5. A data transmission / reception device for transmitting screen data to a terminal device wirelessly or by wire, wherein said screen is bitmap data, and is changed compared to a screen preceding one screen in the data constituting one screen. A changed rectangle detecting means for detecting only the portion is provided. The changed rectangle detecting means sets the vertical and horizontal positions of the start portion of the bitmap data of the changed portion as X1 and Y1, and sets the vertical and horizontal positions of the end portion. X
2, Y2, | X1-X2 | × | Y1-Y2 |
A data transmission / reception apparatus, which detects an area calculated by (1) as a changed rectangle and transmits data of the changed rectangle. 6. A non-change signal generating means for generating a signal indicating that a non-change rectangle which is not changed in the change rectangle is the same as the previous screen in the non-change rectangle area. The data transmitting / receiving device according to claim 5, wherein: 7. The method according to claim 6, wherein the bitmap data is in a range of 10K to 50K.
7. The data transmitting / receiving apparatus according to claim 5, wherein the data is divided into blocks in units of the number of K pixels, and the changed rectangle is obtained in the divided blocks. 8. A color number detecting means for detecting the number of colors in the changed rectangle, and the smaller the number of colors detected by the color number detecting means, the smaller the number of bits in the index value for displaying each pixel. 8. The data transmitting / receiving apparatus according to claim 5, further comprising: an index conversion unit for setting an index having the following; and a data compression unit for compressing bitmap data using the new index. 9. A screen as bitmap data, and the smaller the number of colors used in a predetermined area of each screen is,
A data compression method comprising: reducing the number of indices for displaying each pixel; converting data of a pixel to be compressed into an index having a smaller number of bits; and compressing the bitmap data in the predetermined area. 10. The data compression method according to claim 9, wherein the screen is divided into blocks of 10K to 50K pixels, and each of the divided blocks is used as the predetermined area. 11. A data compression method for extracting and compressing data of only a portion changed from a previous screen in an image constituting one screen and compressing the data, wherein the screen is used as bitmap data, and the bitmap data is changed. The vertical and horizontal positions of the start part of the location are X1 and Y1, and the vertical and horizontal positions of the end part are
When the horizontal position is X2, Y2, | X1-X2 | × |
A data compression method characterized in that bitmap data in an area of a changed rectangle calculated by Y1-Y2 | is compressed. 12. When a non-changed rectangular area that has not been changed exists in the changed rectangle, a signal indicating that the non-changed rectangular area is the same as the previous screen is generated. The data compression method according to claim 11, wherein 13. The method according to claim 10, wherein the bitmap data is 10K to 5K.
13. The data compression method according to claim 11, wherein a block is divided into units of the number of 0K pixels, and the changed rectangle is obtained in the divided block. 14. The number of colors in the changed rectangle is detected, and as the number of colors decreases, an index for displaying each pixel is set to an index having a smaller number of bits, and the bitmap data is compressed using the index. 14. The image data compression method according to claim 11, 12 or 13, wherein: 15. A data transmitting apparatus for transmitting data of a screen of a host computer to a terminal device wirelessly or by wire, wherein the screen of the host computer is configured by bitmap data, and the bitmap data is Screen storing means for storing, changing part detecting means for detecting a changed partial area with respect to the previous screen in the screen data, and obtaining bitmap data of the changed partial area from the screen storing means Bitmap acquisition means;
A number-of-colors detecting means for detecting the number of colors in the changed partial area of the bitmap data; and the smaller the number of colors detected by the number-of-colors detecting means, the more the index for displaying each pixel is set to a value having a smaller number of bits. Index conversion means for setting the index to have, data compression means for compressing the bitmap data using the index given by the index conversion means, and transmission means for transmitting the data compressed by the data compression means. A data transmission device, comprising: 16. The data transmission apparatus according to claim 15, wherein the bitmap data stored in said screen storage means is data of the number of dots composed of 1024 × 786. 17. The data transmitting apparatus according to claim 15, wherein a unit to be detected when the changed part detection unit detects the changed part area is a block obtained by dividing one screen into a plurality of screens. 18. A data transmitting apparatus for transmitting data on a screen of a host computer to a terminal device wirelessly or by wire, wherein the screen of the host computer is constituted by bitmap data, and the bitmap data is Screen storage means for storing, and one of the screen data
Changing part detecting means for detecting a changed partial area with respect to the screen before the screen, bitmap obtaining means for obtaining the bitmap data of the changed partial area from the screen storage means, and bitmap data of the changed partial area And a transmitting unit for transmitting the data compressed by the data compressing unit. The changing unit detecting unit sets the vertical and horizontal positions of the start portion of the changed portion of the bitmap data to X1. , Y1 and the vertical and horizontal positions of the end portion are X2 and Y2, | X1-X2 | × | Y1-
A data transmitting apparatus, wherein a changed rectangle calculated by Y2 | is used as a changed rectangle detecting means for detecting the changed rectangle as the changed partial area. 19. A color number detecting means for detecting the number of colors in the changed rectangle, and an index converting means for giving an index of a different bit number to each pixel according to the number of colors detected by the color number detecting means. The changed rectangle detection means, when there is a non-changed rectangular area that has not been changed in the changed rectangle, for the non-changed rectangular area,
A signal indicating that it is the same as the previous screen is generated, the color number detection means detects the number of colors in a rectangular area other than the non-changed rectangular area, and the index conversion means determines that the detected number of colors is smaller. 19. The data transmitting apparatus according to claim 18, wherein a value having a smaller number of bits is added to the index for displaying each pixel. 20. Receiving means for receiving bitmap data constituting a screen, data decompression means for decompressing the bitmap data, and color data based on a signal indicating the number of colors for each predetermined block of the bitmap data. Color number conversion means for specifying each index in which a smaller number of bits is added to an index for displaying each bit as the number is smaller, and bitmap data based on a pixel whose color is specified by the color number conversion means And a display unit for displaying bitmap data stored in the screen storage means.