KR100202560B1 - Apparatus and method displaing gray-level image in television having fax function - Google Patents

Abstract

The present invention relates to a gray level image printing apparatus and method for a fax-embedded television which can reduce an error from an actual image by allowing a printed image to have a gray level when printing a television screen by fax. By capturing 256 gray levels of luminance signals in frames and dithering them with a predetermined mask, the viewer can print an image having a predetermined gray level by a conventional binary fax printer. Not only is it useful for preserving a screen as a document while watching a video, but it is also possible to document gray levels of all the devices displayed on TV (CD, CDG, Video-CD, I-TV, Video, Computer). Will be effective.

Description

Gray Level Video Display Apparatus and Method for Fax-embedded Television

1 is a block diagram showing a conventional fax embedded television.

2 is a block diagram showing a gray level video display device of the present invention fax embedded television.

3 is an internal block diagram of a dither portion of FIG.

4 is a view showing the type and shape of the dither mask according to the present invention.

5 is a diagram illustrating a mapping state of a frame memory of FIG. 3;

6 is a diagram showing a mapping state of FIG. 3 binary memory;

7 is a flowchart showing a gray level image display method of the present invention, a built-in fax machine.

* Explanation of symbols for main parts of the drawings

200: modem 201: interface unit

202: signal conversion unit 203: encoding / decoding unit

210: buffer memory 220: reading part

230: printing unit 240: video signal conversion unit

250: fax control unit 260: TV system

270: dithering unit 271: analog / digital conversion unit

272: frame memory 273: dither processor

274: binary memory

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display function of a fax-embedded television. In particular, the present invention relates to a fax-embedded television that can reduce an error from an actual image by having a gray level printed on a television screen. A gray level image display apparatus and method are provided.

As shown in FIG. 1, a conventional built-in fax machine includes a modem 100 for communicating by connecting a fax and a telephone line, data read from the reading unit 120, and data output from the modem 100. As shown in FIG. A buffer memory 110 for temporarily storing and outputting the data, the reading unit 120 for reading data to be transmitted, a printing unit 130 for printing the received data in writing, and the buffer memory 110. The video signal converter 140 converts the data to be displayed on the TV system 160, the FAX controller 150 for controlling the data, and the TV system 160, which will be described in detail.

First, the reception process, when a call is received through the telephone line, the interface unit 101 of the modem 100 detects a ring signal and sends a ring detection signal to the fax control unit 150, the fax control unit 150. Is connected to the fax line and the telephone line again by applying a control signal to the interface (101).

Then, the content received through the telephone line is input to the signal conversion unit 102 through the interbase unit 101, is converted into a digital signal, and then input to the encoding / decoding unit 103, the encoding / decoding unit ( 103 is applied to perform decoding.

The decoded signal is temporarily stored in the buffer memory 110 and then printed in a binary image through a printing unit (! 30), or an image signal conversion unit (by a control signal of the fax control unit 150). 140 is input to the luminance signal (Y), color signal (C), the synchronization signal (Sync) is reorganized to display on the screen of the TV system 160.

Looking at the next transmission process, the content of the original to be transmitted is read by the reading unit 120, the read data is temporarily stored in the buffer memory 110, the image signal conversion unit to be displayed on the TV system 140 140, or to modem 100 for fax transmission.

The encoding / decoding method 103 of the modem 100 encodes data input from the buffer memory 110 into data of a form suitable for transmission, and the encoded data is converted into an analog signal by the signal conversion unit 102. It is converted and then input to the interface unit 101.

Then, the interface unit 101 dials the telephone to the other party by the control signal of the fax control unit 150, connects the lines, and transmits the input data through the telephone line.

However, in such a case, it is not possible to capture and print a TV image, and even if the TV image is printed, the TV image may have a gray level of 256 or a fax printer can only print a binary image. There was a problem that the printed image is much different from the original image.

Accordingly, in view of the above problem, the present invention captures 256 gray level luminance signals of TV images by frame, and then uses the dithering technique to capture an image having a predetermined gray level by a conventional binary fax printer. It is an object of the present invention to be able to print or transmit via a modem, and the present invention having this purpose will be described in detail.

According to the present invention, a gray level image display method of a FAX-embedded television receives a luminance signal of a frame image output from a TV, reads four pixel values corresponding to one dithering unit by row address values, and then averages the pixel values. A first process of obtaining the second process, a second process of turning all four pixels to black if the average value obtained by the first process has a gray level value between 0 and 52, and an average value obtained by the first process If the gray level value between 53 and 102 has a gray level value between 103 and 152, the third step is to turn only one pixel of the four pixels to white and the other to black. In the fourth process, two pixels out of four pixels are white and the other two pixels are black. If the average value obtained has a gray level value between 153 and 202, the fifth step of turning three of the four pixels to white and the other one to black, and the average value obtained by the first step is 203. If the gray level value is between 255 and 6, the sixth step is to turn all four pixels to white, and after executing the corresponding step, the row address value of the first step is increased by two, and then it is determined whether the line is the end. If it is not the end of the line, the process is performed again from the first process, while if the end of the line, the seventh process of determining whether the end of the frame is increased by increasing the column address value by two, and the end of the frame is If it is determined that the answer is no, the process is performed again from the first step. On the other hand, if it is determined that the end of the frame, the dithering is terminated to output an image of one frame having a gray level value. Is made of.

On the other hand, the gray level image display apparatus of the present invention fax-embedded television for realizing the method made of each of the above process, as shown in Figure 2, TV system 260 to read the binary image data read from the reading unit 220 In a fax-embedded television which is displayed by or transmitted through the modem 200, and displays the received binary data on the TV system 260 or printed through the printing unit 230, it is output from the TV system 260 And a dithering unit 270 configured to receive a luminance signal of the gray image and have a gray level value close to the original image during printing.

Also, as shown in FIG. 3, the dithering unit 270 receives a gray level luminance signal Y and a synchronization signal Sync output from the TV system 260 and converts the analog signal into a digital signal. A digital memory 271, a frame memory 272 for storing luminance signals output from the analog / digital converter 271 in units of frames, and image data of one frame stored in the frame memory 272. A dither processing unit 273 for receiving binary image data having a predetermined gray level value by dithering four pixels, which are one dithering unit, and sequentially receiving the outputs of the dither processing unit 273 and storing the dither processing unit 273. It consists of a binary memory 274.

The present invention configured as described above will be described in detail with reference to FIGS. 2 to 7.

First, a brief description of dithering is that a human image is a combination of gray and color images, and gray images are more sensitive to the human eye than color images. The picture quality depends.

In addition, the most ideal printing method when printing this gray image on a print medium should be able to express all the gray levels.

However, most commonly used printing presses print only black and white binaries, but since the image to be output usually includes gray levels of binary or higher, a large amount of information is lost during printing.

Therefore, in order to reduce the loss of information, it is necessary to develop a printing medium capable of printing all gray levels. However, in order to overcome this problem, various image processing methods can be used to print gray images as binary printing media to overcome this problem. This has been proposed and one example is the dithering technique.

A typical example of this dithering technique is the printing of black and white photographs in newspapers, which consist of only black and white colors. The reason why these black and white photographs look natural is that they contain a lot of gray levels in a high resolution printing machine with very fine pixels. This is because the printing was performed using.

In other words, such a dithering technique is to adjust the amount of gray, that is, the gray level, according to the density of black and white spots for the same area.

Assuming three gray levels are given for a pixel, the first level is 100% black for that pixel, the second level is 50% black, and the other three The second level is that 0% black, or white, is painted.

This can be said that one pixel has three gray levels.

In addition, how to paint black for all levels other than pure white and black is entirely dependent on dithering techniques, and these techniques have been proposed so far, and the performance of dithering is somewhat fine for any one pixel. It depends on how well you express it, how many gray levels you have, and how evenly you paint black.

Next, the present invention using the dithering technique will be described.

The gray level image printing apparatus of the FAX-embedded television of FIG. 2 has the same basic operation as that of the image output apparatus of the conventional FAX-embedded television shown in FIG. 1. Thus, as shown in FIG. 270 will be described in detail.

The luminance signal (Y) and the synchronization signal (Sync) of the 256 gray level image for one frame of image displayed by the TV system 260 are inputted from the analog / digital converter 271 to be converted into a digital signal. The converted luminance signal is stored in the frame memory 272 in one frame unit.

The luminance signal of the 256 gray level image stored in the frame memory 272 is a brightness signal of each pixel of one frame, and the value of one pixel is represented by one byte.

The gray level image data stored in this way is read by one byte, that is, one pixel, and input to the dither processor 273 by the address signal and the control signal, and dithering is performed. The dither processor 273 is inputted. 4 pixels, which are dithering units, are dithered to output pixel values represented by 1 bit to the binary memory 274. The binary memory 274 stores binary pixel values of one frame and then buffers the memory. The output is 210.

The operation of the dither processor 273 will now be described in detail with reference to FIGS. 4 to 7.

Figure 4 shows the type and shape of the dither mask proposed in the present invention. The smallest medium that can be printed by a fax print medium is 1 pixel unit and 1 pixel because it is printed in a 1: 1 correspondence with the luminance signal displayed by the TV system. You can no longer split and dithering is impossible.

Therefore, the type and shape of the mask are defined by using 4 pixels as a unit of dithering.

As shown in Fig. 5, the dither processor 273, from the frame memory 272, shows four pixel values (a _ij , a _{ij + 1} , a) of two horizontal and column pixels among the stored gray level pixel values. _{i + 1j} , a _{i + 1j + 1} ) are input to calculate the average of these values ((a _ij , a _{ij + 1} , a _{i + 1j} , a _{i + 1j + 1} ) / 4) Each pixel is 256 gray level, so that is 1 byte of data.

The average value of the calculated pixels falls within the range of the gray level shown in FIG. 4. If the average value of the pixel has a value between 0 and 52 of the gray level, as shown in FIG. 0 is written to b _ij , b _{ij + 1} , b _{i + 1j} , b _{i + 1j + 1} of the binary memory map corresponding to the addresses of the four gray level data values. It means that all the pixels are black.

If the average value is between 53 and 102, it represents 75% black in one dithering unit, so three out of four pixels means black and one means white, and one white In order to make a _payment , the pixel value having the largest value among the four pixels (a _ij , a _{ij + 1} , a _{i + 1j} , a _{i + 1j + 1} ) is obtained and then the binary memory map corresponding to the address of the obtained pixel value is obtained. Write a value of 1 and 0 for the rest.

That is, for example, if the average of four pixel values is 53 or more and 103 or less in the gray level range, and the pixel value of a _{i + 1j} has the gray level value of the largest value, the binary memory map shown in FIG. The addresses b _ij , b _{ij + 1} , b _{i + 1j + 1} are 0, and b _{i + 1j} is 1 so that the third mask of Group 1 in FIG. 4 is printed.

In addition, if the average value has a value between 103 and 152, it means that the black density corresponds to 50%, so that there are two black pixels and two white pixels, where the black distribution is four pixels. Among the pixels having the highest gray level value and the next largest pixel, 1 is assigned to the address of the binary memory map, and the other two are assigned 0.

Next, if the average value has a value in the gray level range between 153 and 202, one black pixel means three pixels, and the remaining three pixels mean white pixels. For the binary memory map, 0 is given, and the remainder is 1, so that the black density is 25%.

When the average value is between 203 and 255, it means 100% white, so that 1 is given to b _ij , b _{ij + 1} , b _{i + 1j} and b _{i + 1j + 1} of the binary memory map.

If the dithering is performed for one basic unit by the above process, the horizontal address value is increased by 2 and the dithering operation is performed for the next dithering unit. If the horizontal address value is increased, the column address value is increased by 2 if the end of the line is increased. If the end of the frame, it means that the dithering process for one frame is finished.

The binary image processed by the dither processor 273 is temporarily stored in the buffer memory 210 and then printed as an image near the gray level through the printer 230.

As described above, the present invention captures the screen displayed on the TV system, receives only the luminance signal thereof, and dithers the mask using the mask proposed in the present invention to obtain an image close to gray level when printed by a fax printer. This is not only useful when preserving a screen as a document while watching, but also a documentable effect with gray levels such as all devices displayed on TV (CD, CDG, Video-CD, I-TV, Video, Computer). Will be.

Claims (6)

A first step of reading the four pixel values corresponding to one dithering unit by the row address value by receiving the luminance signal of one frame image output from the TV, and then obtaining the average value of the pixels; A second process of turning all four pixels to black if the average value obtained has a gray level value between 0 and 52, and four if the average value obtained by the first process has a gray level value between 53 and 102, A third process of making only one pixel of the pixels white and the other being black, and if the average value obtained by the first process has a gray level value between 103 and 152, two pixels of the four pixels become white. A fourth process in which the remaining two pixels are black, and four picks if the average value obtained by the first process has a gray level value between 153 and 202. The fifth step is to make three pixels white and the other one is black, and if the average value obtained by the first step has a gray level value between 203 and 255, all four pixels are white. After the sixth process and the corresponding process are executed, the row address value of the first process is increased by two, and it is determined whether it is the end of the line, and if it is not the end of the line, the process is performed again from the first process. If it is the end of step 7, the column address value is increased by 2 to determine whether the end of the frame, and if it is determined that the end of the frame by the seventh step is performed again from the first step, whereas the end of the frame And if it is determined that the dithering is terminated, an eighth process of outputting an image of one frame having a gray level value is performed. How the display. The gray level image display method according to claim 1, wherein the third step is to make the pixel having the largest value among the four pixel values white. The gray level image display method according to claim 1, wherein the fourth process sets the pixel having the largest value and the next largest value among the four pixel values to white. The gray level image display method according to claim 1, wherein the fifth step is to make the pixel having the smallest value among the four pixel values white. A modem for communicating by connecting a fax and a telephone line, a reading unit for reading data to be transmitted, a buffer memory unit for temporarily storing data read from the reading unit and data output from the modem, and the modem It consists of a printing unit for outputting the data received through the video signal conversion unit for converting the data stored in the buffer memory unit to be detmed by the TV system, and a fax control unit for overall control of the fax component A fax embedded television further comprising a dithering unit configured to receive a luminance signal of a gray image output from the video signal converter and to process a gray level value close to the original image during printing. Gray level video display. The analog and digital converter of claim 5, wherein the dithering unit receives a gray level luminance signal and a synchronization signal output from the image signal converter and converts the digital signal into a digital signal, and the luminance signal output from the analog / digital converter. A dither processor that receives frame data stored in frame units and image data of one frame stored in the frame memory by four pixels, which are one dithering unit, and dithers them to output binary image data having a predetermined gray level value. And a binary memory configured to sequentially receive the output of the dither processor and store the same.