Abstract:
A method of controlling brightness of a user-selected area on a monitor screen is disclosed. First, a starting point of a topmost line of a displayed image is determined as a new reference point. Then a line pattern being included in one of image lines of the displayed image is detected. The pattern includes an indicator whose ends are horizontally aligned with vertical edges of the user-selected area. Next, horizontal distances of the vertical edges with respect to the reference point, and a highlight area is identified using the measured horizontal distances. Finally, a brightness gain of the identified highlight area is amplified.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to an image display device, and more particularly, to a method of controlling brightness of a user-selected area for an image display device.  
           [0003]    2. Discussion of the Related Art  
           [0004]    Typical computer-related display systems use a Cathode Ray Tube (CRT) monitor for displaying various types of data including video and text. For displaying video data such as motion pictures, graphics, and photographs on the CRT monitor, a reasonably high level of luminosity is often required because far more colors are used to provide realistic shading and variations in color. The increase in the luminosity range of the video data on the CRT monitor makes the video image richer in contrast and brightness, improving the perceptual quality of the image.  
           [0005]    However, compared to TV systems, the existing computer-related display systems that include a CRT monitor usually do not provide enough luminosity when displaying the mentioned video data. For example, when a video signal for an ordinary TV system (e.g., a broadcasting video signal or any other signal for display on a TV screen) is displayed on one of the oridinary CRT monitors, the brightness of the displayed image is typically too low and the image is too dark and shadowy. This is because the brightness parameters of the existing computer-related display systems are usually much less than those of the TV systems.  
           [0006]    In order to obviate the problem set above, it would be highly desirable to have a method of greatly increasing the luminosity level of a user-selected area of the CRT screen while retaining the luminosity of the all other areas at a relatively lower level. In this way, the perceptual image-quality of the user-selected area can be greatly improved without increasing the brightness of the whole screen, providing a desirable solution to the above-mentioned problem.  
         SUMMARY OF THE INVENTION  
         [0007]    Accordingly, the present invention is directed to a method of controlling brightness of a user-selected area on a monitor screen that substantially obviates one or more problems due to limitations and disadvantages of the related art.  
           [0008]    An object of the present invention is to provide a method of controlling brightness of a user-selected area on a monitor screen that compensates delays that occur between a video signal and horizontal sync signals that a CRT monitor receives from a video card.  
           [0009]    Another object of the present invention is to provide a method of controlling brightness of a user-selected area on a monitor screen that compensates a vertical offset due to difference display settings between a CRT monitor and an application of a PC.  
           [0010]    Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.  
           [0011]    To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a method of controlling brightness of a user-selected area on a monitor screen includes the steps of determining a starting point of a topmost image line of a displayed image as a new reference point; detecting a line pattern included in one of image lines of the displayed image, the pattern including an indicator whose ends are horizontally aligned with vertical edges of the user-selected area; measuring horizontal distances of the vertical edges with respect to the reference point; identifying a highlight area by calculating horizontal coordinates of the highlight area from the measured horizontal distances; and amplifying a brightness gain of the identified highlight area.  
           [0012]    In another aspect of the present invention, a method of controlling brightness of a user-selected area on a monitor screen includes the steps of determining a starting point of a topmost image line of a displayed image as a reference point; detecting a line pattern included in one of image lines of the displayed image, the pattern including vertical distances of the user-selected area with respect to the pattern-included image line; measuring a vertical offset distance between the reference point and the pattern-included image line; identifying a highlight area by calculating vertical coordinates of the highlight area from the measured offset distance; and amplifying a brightness gain of the identified highlight area.  
           [0013]    In another aspect of the present invention, a method of controlling brightness of a user-selected area on a monitor screen includes steps of determining a starting point of a topmost line of a displayed image as a new reference point; detecting a line pattern included in one of image lines of the displayed image, the pattern including an indicator whose ends are horizontally aligned with vertical edges of the user-selected area, the pattern further including vertical distances of the user-selected area with respect to the pattern-included image line; measuring horizontal distances of the vertical edges with respect to the reference point and further measuring a vertical offset distance between the reference point and the pattern-included image line; identifying a highlight area by calculating horizontal and vertical coordinates of the highlight area, the horizontal coordinates being calculated from the measured horizontal distances, the vertical coordinates being calculated from the measured offset distance; and amplifying a brightness gain of the identified highlight area.  
           [0014]    It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings;  
         [0016]    [0016]FIG. 1 illustrates an image display system;  
         [0017]    [0017]FIG. 2 illustrates an example of an active image represented by image information generated by an application of a PC;  
         [0018]    [0018]FIG. 3 illustrates an example of a displayed image based on a video signal and SYNC signals;  
         [0019]    [0019]FIG. 4 illustrates SYNC signals and a pattern line signal;  
         [0020]    [0020]FIG. 5 illustrates a method of controlling brightness of a user-selected area on a monitor screen in accordance with the present invention; and  
         [0021]    [0021]FIG. 6 illustrates the graphical representation of coordinate parameters of a highlight area calculated in accordance with the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0022]    Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.  
         [0023]    [0023]FIG. 1 illustrates an image display system. The system includes an image source device  100  (e.g., a computer) that generates a video signal (an R/G/B signal) and horizontal and vertical sync signals (H-SYNC and V-SYNC) and a CRT (Cathode Ray Tube) monitor  200  that receives the video signal and SYNC signals from the image source device  100  and displays an image based on the received video and SYNC signals. The image source device  100  includes an application unit (e.g., an installed program or driver)  102  that receives information representing an original image and adds a line pattern to the topmost image line of the original image, and a video card  101  that receives the information representing the pattern-added original image and generates a video signal and H-SYNC and V-SYNC signals. The line pattern includes coordinate information of an area selected by a user in the original image.  
         [0024]    The CRT monitor  200  includes panel keys  204 , a microcomputer  202 , a highlighting video preamplifier  201 , a main video amplifier  203 , and a CRT  205 . The highlighting video preamplifier  201  receives the R/G/B signal and SYNC signals from the video  101  and controls brightness of the user-selected area by detecting the pattern previously included by the application unit  102 . The microcomputer  202  of the CRT monitor provides a pixel frequency to the highlighting video preamplifier  201  so as to properly display an image in response to the drive signal received from the video card  100 . The panel key inputs a command received from the user for controlling display settings of the CRT monitor  200 , and the main video amplifier  203  amplifies each of the R, G, and B signals. Then the CRT  205  displays the amplified signals.  
         [0025]    [0025]FIG. 2 illustrates an active image represented by the image information that the application unit  102  provides to the video card  101 . The application unit  102  of the image source device  100  allows a user to select a desired area (a rectangular box) that needs to be highlighted. The desired area can be selected by, for example, clicking the upper left comer of the desired area with a mouse pointer controlled by a mouse (not illustrated) connected to the image source device  100  and dragging the mouse pointer to the lower right comer of the desired area. Alternatively, the desired area can be simply selected by clicking a window being currently displayed within the active image or by pressing one or more key buttons provided on a keyboard (not illustrated).  
         [0026]    When the user selects the desired area for highlighting, the application unit  102  stores the coordinate information of the selected highlight area. The coordinate information includes V_START and V_END, the vertical positions of the upper and lower edges of the selected area with respect to a reference point (e.g., Po′ shown in FIG. 2) of the active image. The application unit  102  may further stores H_START and H_END, the horizontal positions of the left and right edges of the selected area with respect to the reference point, but these information are not necessarily required for highlighting the selected area in accordance with the present invention. The values of the vertical positions that are stored by the application unit  102  are in lines while the values of the horizontal positions are in pixels. This is because the application unit  102  uses a coordinate system, in which the vertical and horizontal positions of any point in the active image are in lines and pixels, respectively.  
         [0027]    After the application unit  102  stores the required coordinate information, then it adds a line pattern to the topmost line of the active image. The pattern includes pattern data that includes coordinate information of the user-selected area (V_START and V_END), a control code, and a pattern-verification code (e.g., checksum). The pattern may further include position information indicating the horizontal positions of the user-selected area. The control code is a code that includes brightness parameters for highlighting one or more user-selected areas and/or any other video parameters such as contrast or emphasis parameters. The application unit  102  ensures proper transmission of the pattern by including a pattern-verification code such as a checksum that allows operations of the CRT monitor  200  to verify that the data in the transmitted pattern has not changed during transmission and to prevent detecting any non-pattern portion of a video signal as a pattern. Typically, a checksum is a number that represents the summation of representative values of all the text in the transmitted pattern data that both the application unit  102  and the CRT monitor  200  may determine. Then, the receiver can verify the data in the pattern by comparing the checksum included in the pattern to a checksum determined by the CRT monitor  200 .  
         [0028]    Referring back to FIG. 1, after the video card  101  of the image source device  100  receives image information that defines the pattern-added active image from the application unit  102 , the video card  101  processes the received image information to generate a RGB signal and horizontal and vertical sync signals (H-SYNC and V-SYNC) to control the operation of the CRT monitor  200 . Then the highlighting video preamplifier  201  of the CRT monitor receives the RGB and SYNC signals and performs the highlighting function on the user selected area. Thereafter, the pre-amplified RGB signals are sent to the main video amplifier  203  that amplifies each of the RGB signals and sends the amplified signals to the CRT  205 .  
         [0029]    [0029]FIG. 3 illustrates an actual image being displayed on the CRT  205  in response to the RGB signals and the SYNC signals that the CRT monitor  200  receives from the video card  101 . Referring to FIG. 3, it is important to note that the image being actually displayed on the CRT  205  does not exactly coincide with the active image that application unit  102  sends to the video card  101 , but it is rather a complete image being larger than the active image due to different display settings between the CRT monitor  200  and the application unit  102 . The coordinate system used for representing the position of a point on the complete image shown in FIG. 3 is different from that of the active image shown in FIG. 2. This means that the position of any point in the complete image is measured with respect to a reference point (e.g., Po″) in the complete image instead of a reference point (Po′) in the active image. In addition, a delay often occurs between the RGB signals and SYNC signals that the CRT monitor receives from the video card  101 . This delay generates a further coordinate inconsistency between the complete image and the active image.  
         [0030]    [0030]FIG. 4 illustrates the actual V-SYNC, H-SYNC, and a video line signal including a pattern that the highlighting video preamplifier  201  receives from the video card  101 . As explained earlier, the video signal corresponding to the first line of the active image includes a pattern signal. The pattern signal is composed of PCLOCK, PDATA, and PWINDOW signals, each of which is included, for example, in the first R, G, and B signals, respectively. More details regarding FIG. 3 and FIG. 4 will be further explained later in this section.  
         [0031]    Reference will now be made in detail to the method of controlling brightness of a user-selected area for a monitor in according to the present invention, which is illustrated in FIG. 5. First of all, the highlighting video preamplifier  201  of the CRT monitor starts receiving a RGB signal and H-SYNC and V-SYNC signals from the video card  101  of the image source device  100  (S 501 ). Referring back to FIG. 4, the preamplifier  201  initially detects a V-SYNC pulse and a first H-SYNC pulse at time=T1 (S 502 ). The detected SYNC pulses correspond to the beginning point (Po″) of the first video line of the complete image shown in FIG. 3. Between T1 and T2, the preamplifier detects further H-SYNC pulses and a line counter of the preamplifier  201  keeps counting the line number of the video lines detected by the preamplifier  201  before T2.  
         [0032]    At time=T2, the preamplifier detects a H-SYNC pulse that correspond to the beginning of the video line of the complete image that includes the topmost line of the active image (S 503 ). Thereafter, the preamplifier  201  detects a first rising edge of the PCLOCK signal at time=T3 (S 508 ). At this time, the preamplifier  201  is able to determine V-OFFSET which represents the number of the video lines detected by the preamplifier  201  before detecting the video line that includes the topmost line of the active image (S 509 ). The V-OFFSET can be simply calculated by taking a number counted by the line counter of the preamplifier  201 .  
         [0033]    In addition, the preamplifier  201  extracts the pattern data from the received PDATA signal (S 510 ). PDATA is a signal that includes “0” or “1” according to the real pattern data included therein as shown in FIG. 4. As mentioned earlier, the extracted pattern data includes V_START and V_END, a control code, and a checksum. V_START and V_END represent the vertical positions of the upper and lower edges of the user-selected area with respect to a reference point (e.g., Po′ shown in FIG. 2) in the active image. The control code is a code that includes the brightness parameter for highlighting the user-selected area and/or other type of video parameters such as contrast, color temperature, distortion, or emphasis parameters. The checksum is a pattern-verification code that allows the preamplifier  201  of the monitor  200  to verify the pattern data.  
         [0034]    The pattern further includes a PWINDOW signal that indicates the horizontal positions of the user-selected area with respect to a reference point in the complete image (e.g., Po″ shown in FIG. 3). At time=T4, the preamplifier  201  detects the rising edge of the PWINDOW signal (S 504 ). Then the preamplifier  201  determines RCV_H_START, which represents the horizontal position of the left edge of the user-selected area shown in FIG. 3 with respect to Po″ in the complete image, using a pixel counter that counts the number of pixels that exist between T2 and T4. The pixel counter uses the pixel frequency value provided by the microcomputer  202  in order to count each pixel. Thereafter, the preamplifier  201  detects the falling edge of the PWINDOW signal (S 506 ) at T5. Similarly, the preamplifier  201  uses the pixel counter to determines RCV_H_END, which represents the horizontal position of the right edge of the user-selected area shown in FIG. 3 with respect to Po″ in the complete image, using the pixel counter that also counts the number of pixels that exist between T2 and T5 (S 507 ).  
         [0035]    After RCV_H_END is obtained in the step S 507  and the pattern data is completely received in the step S 510 , the preamplifier  201  verifies whether the pattern data is valid by comparing the checksum included in the pattern data and a checksum that it determines (S 511 ). If it is found to be invalid, the preamplifier  201  repeats the steps S 502  to S 511 . Otherwise, it calculates the coordinate parameters of an actual highlight area with respect to the reference point of the complete image as shown in FIG. 6 by using the following equations (S 512 ):  
         WIN —   V _START= V _OFFSET+ V _START,  
         WIN —   V _END= V _OFFSET+ V _END,  
         WIN_H_START=RCV_H_START,  
         WIN_H_END=RCV_H_END, and  
         V_BLANKPOS=V_OFFSET.  
         [0036]    [0036]FIG. 6 illustrates the graphical representation of the coordinate parameters of the actual highlight area, which are calculated by using the above equations. As shown, WIN_V_START and WIN_V_END represent the vertical positions of the upper and lower edges of the highlight area with respect to the reference point, Po″, and WIN_H_START and WIN_H_END represent the horizontal positions of the left and right edges of the highlight area with respect to the same point. In addition, V_BLANKPOS represents the vertical position of the video line of the complete image that can be optionally blanked out. By blanking out the video line that includes the topmost video line of the active image shown in FIG. 6, the user may not be disturbed from viewing the pattern line on the monitor.  
         [0037]    Referring back to FIG. 5, when all the coordinate parameters of the highlight area are calculated, the preamplifier  201  sets the highlight parameter of the highlight area to the brightness parameter value included in the control code, which is included in the pattern data extracted in the step S 510  (S 513 ). Finally, the preamplifier  201  performs the highlight function on the highlight area by amplifying the brightness gain of the highlight area, whose positions are defined by WIN_V_START, WIN_V_END, WIN_H_START, and WIN_H_END as shown in FIG. 6 (S 514 ).  
         [0038]    Alternatively, WIN_H_START and WIN_H_END can be calculated by using the following equations:  
         WIN —   H _START= RCV   —   H _START+ HDELAY 1, and  
         WIN —   H _END= RCV   —   H _END+ HDELAY 2,  
         [0039]    where HDELAY1 and HDELAY2 represent additional adjustments for compensating the delays that occurs between an analog input and a hardware output when amplifying the brightness gain.  
         [0040]    It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.