Patent Publication Number: US-2023138364-A1

Title: Display processing apparatus and method for processing image data

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority to Korean Patent Application No. 10-2021-0145313 filed on Oct. 28, 2021, which is hereby incorporated by reference for all purposes as if fully set forth herein. 
     BACKGROUND 
     1. Field of Technology 
     The present embodiment relates to a display processing apparatus and method for processing image data for driving a display panel. 
     2. Related Technology 
     As the information society is advanced, a need for a display device for displaying an image is increased in various forms. Recently, several display devices, such as a liquid crystal display device (LCD), a plasma display panel (PDP), and an organic light emitting display device (OLED), are used. 
     The display device displays an image on a panel by controlling brightness of each pixel based on image data that is received from a host device. In general, a self-emitting display device (e.g., an organic light-emitting display device) in which a pixel autonomously emits light without using a backlight may control brightness of each pixel by controlling the size of a driving current that is supplied to the pixel. 
     In the display device, the size of a driving current supplied to a pixel is controlled by an analog voltage (so-called a data voltage) converted from image data. As a result, the display device may control brightness of each pixel based on the image data. 
     In this case, as the brightness of each pixel is increased, the amount of power consumed of the display device is increased. 
     In other words, as more white-series colors are distributed in an image scene included in image data, the brightness of each pixel is increased. Accordingly, the amount of power consumed of the display device is increased, and a glare phenomenon for a user who uses the display device also occurs. 
     In order to solve the problem, in a conventional display device, the amount of power consumed is reduced and a glare phenomenon for a user is also prevented by uniformly reducing brightness of image data. 
     However, if the brightness of image data is uniformly lowered, brightness of an image scene, in which the brightness is unwanted to be reduced, is also reduced and thus there is a problem in that picture quality may be degraded. 
     For example, although many dark colors are distributed in an image scene, conventionally, there is a problem in that picture quality of the image scene in which the dark colors are distributed may be degraded because the display device has uniformly reduced the brightness of image data. 
     Furthermore, although many dark colors are distributed in an image scene, if brightness of image data is reduced, there is a problem in that the image scene is displayed with brightness unwanted by a user. 
     The discussions in this section are only to provide background information and does not constitute an admission of prior art. 
     SUMMARY 
     In this background, in an aspect, an object of the present embodiment is to provide a technology for flexibly changing brightness of each pixel based on a representative brightness value of an image scene. 
     Furthermore, in an aspect, an object of the present embodiment is to provide a technology for flexibly changing brightness of each pixel when a representative brightness value of an image scene is greater than a set threshold value. 
     An embodiment provides a display processing apparatus, including a memory circuit configured to store a threshold value related to the adjustment of brightness of a pixel, a representative brightness value calculation circuit configured to calculate a representative brightness value for input brightness values for each pixel, which are included in image data, and an image data conversion circuit configured to convert the input brightness values for each pixel into output brightness values for each pixel based on information corresponding to a reference curve for brightness adjustment when the representative brightness value is greater than a first threshold value stored in the memory circuit. 
     A method of processing, by a display processing apparatus, image data, includes receiving threshold values related to the adjustment of brightness of a pixel, calculating a representative brightness value for input brightness values for each pixel, which are included in image data, and converting the input brightness values for each pixel into output brightness values for each pixel based on information corresponding to a reference curve for brightness adjustment when the representative brightness value is greater than a first threshold value among the threshold values. 
     As described above, according to the present embodiment, the display processing apparatus generates a curve for brightness adjustment by properly adjusting the curve based on a representative brightness value of an image scene, and adjusts brightness of each pixel corresponding to the image scene through the curve for brightness adjustment. Accordingly, a phenomenon in which picture quality is degraded, which occurs due to uniform brightness adjustment conventionally, can be solved. 
     Furthermore, a circuit that constitutes the display processing apparatus can be simplified because the display processing apparatus generates a curve for brightness adjustment through a simple operation. 
     Furthermore, the display processing apparatus flexibly changes brightness of each pixel only when a representative brightness value of an image scene is greater than a set threshold value. Accordingly, if an adaptive current limit (ACL) is applied, although many dark colors are distributed, brightness of image data can be prevented from being reduced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a construction diagram of a display device according to an embodiment. 
         FIG.  2    is a construction diagram of an image data processing apparatus according to an embodiment. 
         FIG.  3    is a diagram illustrating an ACL application range according to an embodiment. 
         FIG.  4    is a construction diagram of a curve generation circuit according to an embodiment. 
         FIG.  5    is a diagram exemplifying set values according to an embodiment. 
         FIGS.  6  and  7    are diagrams for describing a construction for calculating an X axis point value according to an embodiment. 
         FIG.  8    is a diagram exemplifying a lookup table according to an embodiment. 
         FIG.  9    is a diagram for describing a construction for generating a first reference curve according to an embodiment. 
         FIG.  10    is a diagram for describing a construction for generating a second reference curve according to an embodiment. 
         FIG.  11    is a diagram for describing a construction for generating a curve for brightness adjustment according to an embodiment. 
         FIG.  12    is a diagram for describing a construction for generating a curve for brightness adjustment according to an embodiment. 
         FIG.  13    is a flowchart illustrating a process of processing image data in the image data processing apparatus according to an embodiment. 
         FIG.  14    is a flowchart illustrating a process of processing image data in the image data processing apparatus according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       FIG.  1    is a construction diagram of a display device according to an embodiment. 
     Referring to  FIG.  1   , the display device  100  may include an image data processing apparatus  110 , a panel driving device  120 , a gate driving device  130 , a display panel  140 , etc. The image data processing apparatus  110  may be denoted as a display processor (or a display processing apparatus). The display processor may be used as a concept that further includes the panel driving device  120  and/or the gate driving device  130  in addition to the image data processing apparatus  110 . The display processor may include one display driving device IC (DDI), but the present disclosure is not limited thereto. 
     The image data processing apparatus  110  may receive input image data RGB from the outside (e.g., an application processor (AP)  10  or another host device), and may convert the input image data RGB into output image data RGB′, and may transmit the output image data RGB′ to the panel driving device  120 . 
     The panel driving device  120  may receive the output image data RGB′ from the image data processing apparatus  110 , and may generate an analog voltage (e.g., a data voltage) by using the output image data RGB′. 
     Furthermore, the panel driving device  120  may supply the analog voltage to each pixel disposed in the display panel  140  through a data line DL. 
     In this case, each pixel, that is, multiple pixels, may be disposed in the display panel  140 . Each of the multiple pixels may be a pixel that autonomously emits light. For example, each pixel may include an organic light emitting diode (OLED), and may autonomously emit light by a driving current that is supplied to the OLED. In this case, brightness of each pixel may be controlled by the analog voltage supplied by the panel driving device  120 . 
     The gate driving device  130  may supply the display panel  140  with a scan signal through a gate line GL. 
     A specific line of the display panel  140  may be selected in response to the scan signal. The analog voltage supplied by the panel driving device  120  may be supplied to only a pixel of the selected line. 
     The image data processing apparatus  110  may control timing at which the scan signal is supplied and timing at which the analog voltage is supplied by supplying the panel driving device  120  and the gate driving device  130  with a synchronization signal and/or a control signal. 
     The image data processing apparatus  110  may be called a timing controller, the panel driving device  120  may be called a source driving device or a column driving device, and the gate driving device  130  may be called a gate driving device. Furthermore, each of the apparatuses may be constructed in the form of an independent integrated circuit or two or more of the apparatuses may be constructed as one integrated circuit (e.g., a DDI). 
     In an embodiment, the image data processing apparatus  110  may analyze brightness of a scene image corresponding to the input image data RGB that is received from the outside (e.g., the AP  10  or another host device), may adjust an input brightness values for each pixel, of the input image data RGB, based on the brightness of the scene image, and may transmit, to the panel driving device  120 , the output image data RGB′ including an output brightness value for each pixel, that is, the adjusted input brightness values for each pixel. 
     To this end, the image data processing apparatus  110  may apply an adaptive current limit or automotive current limit (ACL) technology. The image data processing apparatus  110  may receive, from the AP  10 , at least one threshold value (Th ACL ) related to the adjustment of brightness of a pixel. In an embodiment, the image data processing apparatus  110  may perform processing so that the ACL is applied to input image data when a representative brightness value for input brightness values for each pixel included in the input image data is greater than a first threshold value (Th L ) among the at least one threshold value (Th ACL ) received from the AP  10 . For example, when the representative brightness value is greater than the first threshold value (Th L ) of the at least one threshold value (Th ACL ) received from the AP  10 , the image data processing apparatus  110  may convert an input brightness values for each pixel into an output brightness value for each pixel based on a set reference curve for brightness adjustment. In contrast, when the representative brightness value is not greater than the first threshold value (Th L ) of the at least one threshold value (Th ACL ) received from the AP  10 , the image data processing apparatus  110  may set an input brightness values for each pixel as an output brightness value for each pixel without any change. 
     In another embodiment, when the representative brightness value is greater than a second threshold value (Th H ) among the at least one threshold value (Th ACL ) received from the AP  10 , the image data processing apparatus  110  may set an input brightness values for each pixel as an output brightness value for each pixel based on a maximum reference curve for brightness adjustment. 
     Hereinafter, various embodiments in which the image data processing apparatus  110  applies the ACL based on a representative brightness value are described with reference to  FIGS.  2  to  14   . 
       FIG.  2    is a construction diagram of the image data processing apparatus  110  according to an embodiment. 
     Referring to  FIG.  2   , the image data processing apparatus  110  may include a representative brightness value calculation circuit  210 , a memory circuit  220 , a curve generation circuit  230 , an image data conversion circuit  240 , and an image data transmission circuit  250 . 
     The image data processing apparatus  110  may receive, from the AP  10 , the at least one threshold value (Th ACL ) (e.g., the first threshold value (Th L ) and/or the second threshold value (Th H )) related to the adjustment of brightness of a pixel, and may store the at least one threshold value (Th ACL ) in the memory circuit  220 . In an embodiment, the at least one threshold value (Th ACL ) related to the adjustment of brightness of a pixel may be received from the AP  10  through communication using a mobile industry process interface (MIPI) (e.g., an MIPI-display serial interface (DSI)). According to various embodiments, the at least one threshold value related to the adjustment of brightness of a pixel may be stored in accordance with each address that is assigned to the AP  10  as in Table 1. 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                 R (read)/ 
                   
                   
               
               
                 Address 
                 Name 
                 W (write) 
                 Value 
                 Description 
               
               
                   
               
             
            
               
                 0X0010 
                 Th L   
                 R/W 
                 0100000000 
                 First threshold value (ACL 
               
               
                   
                   
                   
                   
                 application lower bound) 
               
               
                 0X0020 
                 Th H   
                 R/W 
                 0111000000 
                 Second threshold value (ACL 
               
               
                   
                   
                   
                   
                 application upper bound) 
               
               
                   
               
            
           
         
       
     
     The representative brightness value calculation circuit  210  may calculate a representative brightness value for input brightness values for each pixel, which are included in the input image data RGB. In this case, the representative brightness value may be called an average picture level (APL), and may be calculated by Equation  1  and Equation  2 . The input brightness values for each pixel may include a red (R) grayscale value that is a grayscale value of an R subpixel of each pixel, a green (G) grayscale value that is a grayscale value of a G subpixel of each pixel, and a blue (B) grayscale value that is a grayscale value of a B subpixel of each pixel. 
     
       
         
           
             
               
                 
                   Y 
                   = 
                   
                     
                       a 
                       ⁢ 
                       x 
                       ⁢ 
                       R 
                       ⁢ 
                           
                       grayscale 
                       ⁢ 
                           
                       value 
                     
                     + 
                     
                       b 
                       ⁢ 
                       X 
                       ⁢ 
                       G 
                       ⁢ 
                           
                       grayscale 
                       ⁢ 
                           
                       value 
                     
                     + 
                     
                       c 
                       ⁢ 
                       X 
                       ⁢ 
                       B 
                       ⁢ 
                           
                       grayscale 
                       ⁢ 
                           
                       value 
                     
                   
                 
               
               
                 
                   [ 
                   
                     Equation 
                     ⁢ 
                         
                     1 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               
                 
                   APL 
                   = 
                   
                     
                       avg 
                       ⁡ 
                       ( 
                       
                         
                           Y 
                           1 
                         
                         ❘ 
                         
                           Y 
                           N 
                         
                       
                       ) 
                     
                     = 
                     
                       
                         
                           Y 
                           1 
                         
                         + 
                         
                           Y 
                           2 
                         
                         + 
                         … 
                         + 
                         
                           Y 
                           n 
                         
                       
                       n 
                     
                   
                 
               
               
                 
                   [ 
                   
                     Equation 
                     ⁢ 
                         
                     2 
                   
                   ] 
                 
               
             
           
         
       
     
     In this case, Y may be a pixel grayscale value that is a luminance component for each of multiple pixels disposed in the display panel  140 . The R grayscale value may be a grayscale value of the R subpixel constituting each pixel. The G grayscale value may be a grayscale value of the G subpixel constituting each pixel. The B grayscale value may be a grayscale value of the B subpixel constituting each pixel. “n” may be the number of multiple pixels. Furthermore, “a” may be a weight of the R grayscale value. “b” may be the weight of the G grayscale value. “c” may be the weight of the B grayscale value. a, b, and c may have a relation “a+b+c=1.” 
     The representative brightness value calculation circuit  210  may also calculate a weighted average brightness value for input brightness values for each pixel. 
     Specifically, the representative brightness value calculation circuit  210  may calculate a weighted average brightness value for input brightness values for each pixel by dividing a maximum value, among a first square sum value of square numbers of R grayscale values for each pixel, a second square sum value of square numbers of G grayscale values for each pixel, and a third square sum value of square numbers of B grayscale values for each pixel, by a maximum value among a first sum value of the R grayscale values, a second sum value of the G grayscale values, and a third sum value of the B grayscale values. 
     In this case, the weighted average brightness value may also be called a weighted average picture level (WAPL). 
     In an embodiment, the representative brightness value calculation circuit  210  may compare the APL or the WAPL with the at least one threshold value (Th ACL ) (e.g., the first threshold value (Th L ) and/or the second threshold value (Th H )) that is stored in the memory circuit  220  and that is related to the adjustment of brightness of a pixel. 
       FIG.  3    is a diagram illustrating an ACL application range according to an embodiment. Referring to  FIG.  3   , when the APL or the WAPL is smaller than the first threshold value (Th L ) as a result of the comparison, this corresponds to a case where a corresponding image is relatively dark. The ACL may be applied in the image data conversion circuit  240  (ACL off). For example, when the APL or the WAPL is smaller than the first threshold value, the image data conversion circuit  240  may output the input brightness value for each pixel as an output brightness value for each pixel without any change, without adjusting the input brightness value for each pixel. 
     In an embodiment, when the APL or the WAPL is greater than the first threshold value as a result of the comparison, the image data conversion circuit  240  may perform control (ACL on) so that brightness of an image is adjusted by applying the ACL. An example in which the ACL is applied is described in detail with reference to  FIG.  4    and the drawings subsequent thereto. 
     According to various embodiments, when the APL or the WAPL is greater than the second threshold value (Th H ) as a result of the comparison, this corresponds to a case where an image has set brightness or more. The image data conversion circuit  240  may perform control so that the ACL is applied based on a maximum reference curve (Max Curve) for brightness adjustment. In an embodiment, although the ACL is applied based on the maximum reference curve (Max Curve) for brightness adjustment, the ACL may be considered as being applied (ACL on). 
     According to various embodiments, when the APL or the WAPL is greater than the first threshold value (Th L ) or when the APL or the WAPL is greater than the first threshold value (Th L ) and smaller than the second threshold value (Th H ), in order to apply the ACL to the input image data, the curve generation circuit  230  may generate a curve for brightness adjustment. In an embodiment, the memory circuit  220  may store data for generating, by the curve generation circuit  230 , the curve for brightness adjustment. 
     Specifically, the memory circuit  220  may store N set values, N first Y axis point values, and N second Y axis point values for generating the curve for brightness adjustment. In this case, an X axis coordinate value of the curve for brightness adjustment may be an input brightness value, and a Y axis coordinate value may be an output brightness value. 
     In an embodiment, in order to minimize the size of the memory circuit  220 , the memory circuit  220  does not store all of X and Y coordinate values of points that constitute the curve for brightness adjustment, and may store N set values, N first Y axis point values, and N second Y axis point values, that is, data that is basically necessary for the curve generation circuit  230  to generate the curve for brightness adjustment. 
     In this case, the N set values may mean data for calculating N X axis point values that are necessary for the curve generation circuit  230  to generate the curve for brightness adjustment. 
     The set values may include an exponent of power of two as in  FIGS.  5  and  6   . The reason why the N set values include an exponent of power of two is described in detail when the curve generation circuit  230  is described. 
     If the representative brightness value calculation circuit  210  calculates a weighted average brightness value for input brightness values for each pixel, as in  FIG.  7   , the memory circuit  220  may further store a lookup table that includes multiple weighted average brightness ranges and multiple representative brightness grades according to multiple representative brightness ranges versus the multiple weighted average brightness ranges. 
     The curve generation circuit  230  may generate a curve for brightness adjustment for properly adjusting an input brightness value for each pixel of input image data. 
     Specifically, the curve generation circuit  230  may calculate N X axis point values by using N set values. 
     In an embodiment, the curve generation circuit  230  may calculate first to N-th power values, that is, power values of 2 using the N set values as an exponent, through a shift operation. 
     For example, if the N set values include a point  1  set value to a point  8  set value, that is, eight set values, and a point  8  set value is 5 as in  FIG.  5    the curve generation circuit  230  may calculate a binary number “00010000” corresponding to 32, that is, a five-power value of two, by shifting a binary number “00000001” to the left by 5. 
     As described above, after calculating the first to N-th power values, the curve generation circuit  230  may preferentially calculate an N-th X axis point value by subtracting the N-th power value from the highest brightness value of a preset pixel as in  FIG.  6   . 
     Thereafter, the curve generation circuit  230  may second calculate an (N-1)-th X axis point value by subtracting an (N-1)-th power value from the N-th X axis point value. 
     Likewise, the curve generation circuit  230  may calculate an (N-2)-th X axis point value to the first X axis point value. 
     In other words, when calculating the N X axis point values, the curve generation circuit  230  may calculate the N X axis point values in order from a point value having the greatest brightness value to a point value having the smallest brightness value. 
     For example, if the N set values are the same as those in  FIG.  5   , the curve generation circuit  230  may preferentially calculate “991”, that is, an eighth X axis point value having the greatest brightness value, and may then calculate the remaining X axis point values in order of brightness values as in  FIG.  6   . 
     In an embodiment, a circuit that constitutes the curve generation circuit  230  can be simplified because the curve generation circuit  230  calculates the X axis point values through the shift operation and the subtraction operation as described above. 
     The curve generation circuit  230  may match (refer to square points in  FIG.  9   ) the N X axis point values calculated as described above and the N first Y axis point values (Min 1  to Min 8  in  FIG.  9   ) stored in the memory circuit  220 . 
     Thereafter, the curve generation circuit  230  may generate a first reference curve, such as that in  FIG.  9   , through a data interpolation method by calculating values that connect the N X axis point values. 
     Furthermore, the curve generation circuit  230  may match (refer to diamond points in  FIG.  10   ) the N X axis point values and the N second Y axis point values (Max 1  to Max 8  in  FIG.  10   ) stored in the memory circuit  220 . 
     Thereafter, the curve generation circuit  230  may generate a second reference curve, such as that in  FIG.  10   , by calculating values that connect the N X axis point values through a data interpolation method. 
     In this case, the first reference curve and the second reference curve may be a minimum adjustment criterion and a maximum adjustment criterion, respectively, which are necessary to generate curves for brightness adjustment in which a representative brightness value has been incorporated. 
     The curve generation circuit  230  that has generated the first reference curve and the second reference curve as described above may generate a curve for brightness adjustment through a data interpolation method using a first representative brightness value designated for the first reference curve, a second representative brightness value designated for the second reference curve, and the representative brightness value. In this case, the first representative brightness value and the second representative brightness value may be stored in the memory circuit  220 . The representative brightness value may be smaller than or equal to the first representative brightness value and may be greater than or equal to the second representative brightness value. 
     In an embodiment, an N-th Y axis point value of a curve for brightness adjustment, which has been matched with an N-th X axis point value, may be calculated by the following interpolation method equation. 
     
       
         
           
             
               
                 
                   
                     
                       [ 
                       
                         
                           Max 
                           . 
                               
                           N 
                         
                         × 
                         
                           ( 
                           
                             
                               Rv 
                               . 
                                   
                               B 
                             
                             - 
                             
                               Rv 
                               . 
                                   
                               
                                 B 
                                 1 
                               
                             
                           
                           ) 
                         
                       
                       ] 
                     
                     + 
                     
                       [ 
                       
                         
                           Min 
                           . 
                               
                           N 
                         
                         × 
                         
                           ( 
                           
                             
                               Rv 
                               . 
                                   
                               
                                 B 
                                 2 
                               
                             
                             - 
                             
                               Rv 
                               . 
                                   
                               B 
                             
                           
                           ) 
                         
                       
                       ] 
                     
                   
                   
                     
                       ( 
                       
                         
                           Rv 
                           . 
                               
                           B 
                         
                         - 
                         
                           Rv 
                           . 
                               
                           
                             B 
                             1 
                           
                         
                       
                       ) 
                     
                     + 
                     
                       ( 
                       
                         
                           Rv 
                           . 
                               
                           
                             B 
                             2 
                           
                         
                         - 
                         
                           Rv 
                           . 
                               
                           B 
                         
                       
                       ) 
                     
                   
                 
               
               
                 
                   [ 
                   
                     Equation 
                     ⁢ 
                         
                     3 
                   
                   ] 
                 
               
             
           
         
       
     
     In Equation 3, Max.N may be an N-th second Y axis point value, Rv.B may be a representative brightness value, Rv.B 1  may be a first representative brightness value, Min.N may be an N-th first Y axis point value, and Rv.B 2  may be a second representative brightness value. 
     The curve generation circuit  230  may calculate N Y axis point values of a curve for brightness adjustment through the interpolation method equation. Furthermore, the curve generation circuit  230  may generate a curve for brightness adjustment, such as that in  FIG.  11   , by also calculating values that connect the N X axis point values matched (refer to the origin in  FIG.  11   ) with the N Y axis point values through the data interpolation method. 
     If the representative brightness value calculation circuit  210  calculates a weighted average brightness value for input brightness values for each pixel and the memory circuit  220  further stores a lookup table, such as that in  FIG.  8   , the curve generation circuit  230  may extract, from the lookup table, a specific representative brightness grade according to a specific representative brightness range versus a specific weighted average brightness range. In this case, the specific representative brightness range may be a representative brightness range including a representative brightness value. The specific weighted average brightness range may be a weighted average brightness range including a weighted average brightness value. 
     The curve generation circuit  230  may generate the curve for brightness adjustment by using the first reference curve, the second reference curve, and the specific average brightness grade. 
     In other words, a first representative brightness grade may be designated in the first reference curve. A second representative brightness grade may be designated in the second reference curve. Furthermore, the curve generation circuit  230  may generate the curve for brightness adjustment through the data interpolation method using the first representative brightness grade, the second representative brightness grade, and the specific average brightness grade. 
     In an embodiment, as described above, the curve generation circuit  230  may properly adjust the curve for brightness adjustment based on a representative brightness value of the input image data RGB, that is, a representative brightness value for input brightness values for each pixel, which are included in the input image data RGB. 
     The image data conversion circuit  240  may convert an input brightness value for each pixel into an output brightness value for each pixel by using a curve for brightness adjustment. 
     For example, when any one pixel input brightness value included in the input image data RGB is  831 , the image data conversion circuit  240  may convert  831 , that is, any one pixel input brightness value, into  728 , that is, an output brightness value by substituting a curve for brightness adjustment for  831  as in  FIG.  11   . 
     Likewise, the image data conversion circuit  240  that has converted input brightness values of all pixels included in the input image data RGB into output brightness values may transmit, to the image data transmission circuit  250 , the output image data RGB′ including the output brightness values for each pixel. 
     Furthermore, the image data transmission circuit  250  may transmit the output image data RGB′ to the panel driving device  120 . 
     In an embodiment, the calculation of the representative brightness value and the resulting generation of the curve for brightness adjustment may be processed in a frame unit of image data. 
     In other words, whenever the image data processing apparatus  110  receives the input image data RGB of a frame unit, the representative brightness value calculation circuit  210  may calculate the representative brightness value. Accordingly, the curve generation circuit  230  may generate a curve for brightness adjustment. 
     In this case, if a representative brightness value of a current frame is suddenly changed compared to a representative brightness value of a previous frame, a user who watches the display device  100  may feel a sense of difference because brightness of a screen is greatly changed. 
     In an embodiment, in order to solve such a problem, a dimming scheme capable of reducing a sudden change in the representative brightness value may be applied. 
     Hereinafter, detailed elements of the curve generation circuit  230  are described. 
       FIG.  4    is a construction diagram of the curve generation circuit  230  according to an embodiment. 
     Referring to  FIG.  4   , the curve generation circuit  230  may include a shift operation circuit  310 , a subtraction circuit  320 , and a data interpolation circuit  330 . 
     The shift operation circuit  310  may calculate, through a shift operation, first to N-th power values, that is, power values of 2 having N set values as exponents. 
     For example, if the N set values include eight set values of a point  1  set value to a point  8  set value as in  FIG.  5    and the point  8  set value is 5, the shift operation circuit  310  may calculate a binary number “00010000” corresponding to 32, that is, a five-power value of two, by shifting a binary number “00000001” to the left by 5. 
     The subtraction circuit  320  may calculate an N-th X axis point value by subtracting an N-th power value from the highest brightness value of a preset pixel, and may calculate an (N-1)-th X axis point value by subtracting an (N-1)-th power value from the N-th X axis point value. 
     In other words, when calculating N X axis point values, the subtraction circuit  320  may calculate the N X axis point values in order from a point value having the greatest brightness value to a point value having the smallest brightness value through a subtraction operation. 
     The data interpolation circuit  330  may match the N X axis point values and N first Y axis point values stored in the memory circuit  220 , and may then calculate values that connect the N X axis point values through a data interpolation method. Accordingly, the data interpolation circuit  330  may generate a first reference curve, such as that in  FIG.  9   . 
     Furthermore, after matching the N X axis point values and the N second Y axis point values stored in the memory circuit  220 , the data interpolation circuit  330  may calculate values that connect the N X axis point values through the data interpolation method. Accordingly, the data interpolation circuit  330  may generate a second reference curve, such as that in  FIG.  10   . 
     The data interpolation circuit  330  that has generated the first reference curve and the second reference curve as described above may generate a curve for brightness adjustment through a data interpolation method using a first representative brightness value designated for the first reference curve, a second representative brightness value designated for the second reference curve, and a representative brightness value. In this case, the first representative brightness value and the second representative brightness value may be stored in the memory circuit  220 . The representative brightness value may be smaller than or equal to the first representative brightness value, and may be greater than or equal to the second representative brightness value. 
     The data interpolation circuit  330  may calculate N Y axis point values of the curve for brightness adjustment through the interpolation method equation (Equation 3). Furthermore, the data interpolation circuit  330  may generate a curve for brightness adjustment, such as that in  FIG.  12   , by also calculating values that connect N X axis point values matched (refer to the origin in  FIG.  12   ) with the N Y axis point values through the data interpolation method. 
     If the representative brightness value calculation circuit  210  calculates a weighted average brightness value for input brightness values for each pixel and the memory circuit  220  stores a lookup table, such as that in  FIG.  8   , the data interpolation circuit  330  may extract, from the lookup table, a specific representative brightness grade according to a specific average brightness range versus a specific weighted average brightness range. In this case, the specific representative brightness range means a representative brightness range including a representative brightness value for input brightness values for each pixel. The specific weighted average brightness range means a weighted average brightness range including a weighted average brightness value for input brightness values for each pixel. 
     The data interpolation circuit  330  may also generate a curve for brightness adjustment by using the first reference curve, the second reference curve, and the specific representative brightness grade. 
     In other words, a first representative brightness grade may be designated for the first reference curve. A second representative brightness grade may be designated for the second reference curve. Furthermore, the data interpolation circuit  330  may generate a curve for brightness adjustment through a data interpolation method using the first representative brightness grade, the second representative brightness grade, and the specific representative brightness grade. 
       FIG.  12    is a diagram for describing a construction for generating a curve for brightness adjustment according to an embodiment. Referring to  FIG.  12   , in an embodiment, the image data processing apparatus  110  may control the application of the ACL according to Equation 4. 
     
       
         
           
             
               
                 
                   
                     target 
                     ⁢ 
                         
                     Curve 
                   
                   = 
                   
                     ( 
                     
                       
                         
                           
                             OFF 
                             , 
                           
                         
                         
                           
                             APL 
                             &lt; 
                             
                               Th 
                               L 
                             
                           
                         
                       
                       
                         
                           
                             
                               
                                 
                                   
                                     Min 
                                     ⁢ 
                                     Curve 
                                   
                                   - 
                                   
                                     
                                       
                                         
                                           Min 
                                           ⁢ 
                                           Curve 
                                         
                                         - 
                                         
                                           Max 
                                           ⁢ 
                                           Curve 
                                         
                                       
                                       1024 
                                     
                                     × 
                                   
                                 
                               
                             
                             
                               
                                 
                                   
                                     
                                       1024 
                                       
                                         
                                           Th 
                                           H 
                                         
                                         - 
                                         
                                           Th 
                                           L 
                                         
                                       
                                     
                                     × 
                                     
                                       ( 
                                       
                                         APL 
                                         - 
                                         
                                           Th 
                                           L 
                                         
                                       
                                       ) 
                                     
                                   
                                   , 
                                 
                               
                             
                           
                         
                         
                           
                             
                               Th 
                               L 
                             
                             ≤ 
                             APL 
                             &lt; 
                             
                               Th 
                               H 
                             
                           
                         
                       
                       
                         
                           
                             
                               Max 
                               ⁢ 
                               Curve 
                             
                             , 
                           
                         
                         
                           
                             APL 
                             ≥ 
                             
                               Th 
                               H 
                             
                           
                         
                       
                     
                     ) 
                   
                 
               
               
                 
                   [ 
                   
                     Equation 
                     ⁢ 
                         
                     4 
                   
                   ] 
                 
               
             
           
         
       
     
     Referring to Equation 4 and  FIG.  12   , in an embodiment, when the APL or the WAPL is smaller than the first threshold value (Th L ) (e.g., the APL is between 0 and the first threshold value), this corresponds to a case where a corresponding image is relatively dark. Accordingly, the image data conversion circuit  240  may not apply the ACL (ACL off). For example, when the APL or the WAPL is smaller than the first threshold value, the image data conversion circuit  240  may output an input brightness value for each pixel as an output brightness value for each pixel without any change, without adjusting the input brightness value for each pixel. 
     According to various embodiments, as a result of the comparison, when the APL or the WAPL is greater than the second threshold value (Th H ), this corresponds to a case where an image has set brightness or more. Accordingly, the image data conversion circuit  240  may control the ACL so that the ACL is applied based on a set maximum reference curve (Max Curve) for brightness adjustment. In an embodiment, if the ACL is controlled to be applied based on the set maximum reference curve (Max Curve) for brightness adjustment, it may be considered that the ACL has been applied (ACL on). 
     According to various embodiments, when the APL or the WAPL is greater than the first threshold value (Th L ) and smaller than the second threshold value (Th H ), as in the descriptions of  FIGS.  4  to  11   , the image data conversion circuit  240  may apply the ACL to an input image data based on a curve for brightness adjustment, which is generated by the curve generation circuit  230 . 
     Hereinafter, a process of processing, by the image data processing apparatus  110 , image data is described. 
       FIG.  13    is a flowchart illustrating a process of processing image data in the image data processing apparatus according to an embodiment. 
     Referring to  FIG.  13   , the image data processing apparatus  110  (e.g., the display processing apparatus) may receive, from the AP  10 , a threshold value (a first threshold value or a second threshold value) for an APL application through the MIPI (S 1310 ). 
     As described above, the image data processing apparatus  110  may calculate a representative brightness value (e.g., an APL or a WAPL) for input brightness values for each pixel, which are included in input image data (S 1320 ). 
     The image data processing apparatus  110  may compare the representative brightness value with the first threshold value. When the APL or the WAPL is smaller than the first threshold value (Th L ) (e.g., when the APL is between 0 and the first threshold value) (S 1330 -N) as a result of the comparison, this corresponds to a case where a corresponding image is relatively dark, and thus the image data conversion circuit  240  may not apply the ACL (ACL off) (S 1340 ). 
     According to various embodiments, when the APL or the WAPL is greater than the first threshold value (Th L ) as a result of the comparison, the image data processing apparatus  110  may compare the representative brightness value with the second threshold value. When the APL or the WAPL is greater than the second threshold value (Th H ) (S 1350 -Y), this corresponds to a case where the image has set brightness or more, and thus the image data conversion circuit  240  may control the ACL so that the ACL is applied based on a set maximum reference curve (Max Curve) for brightness adjustment (S 1370 ). In an embodiment, if the ACL is controlled to be applied based on the set maximum reference curve (Max Curve) for brightness adjustment, it may be considered that the ACL is applied (ACL on). 
     According to various embodiments, when the APL or the WAPL is greater than the first threshold value (Th L ) and is smaller than or equal to the second threshold value (Th H ) (S 1350 -N), as in the description of  FIGS.  4  to  11   , the image data conversion circuit  240  may apply the ACL to the input image data based on a curve for brightness adjustment which is generated by the curve generation circuit  230  (S 1360 ). 
     Hereinafter, a detailed operation of applying the ACL in step S 1360  of  FIG.  13    is described with reference to  FIG.  14   . 
       FIG.  14    is a flowchart illustrating a process of processing image data in the image data processing apparatus according to an embodiment. 
     Referring to  FIG.  14   , after receiving input image data RGB from a host device, the image data processing apparatus  110  (e.g., the display processing apparatus) may calculate a representative brightness value for input brightness values for each pixel, which are included in the input image data RGB (S 1410 ). In this case, the representative brightness value may be called an average picture level (APL). The input brightness values for each pixel may include a red (R) grayscale value that is a grayscale value of an R subpixel of each pixel, a green (G) grayscale value that is a grayscale value of a G subpixel of each pixel, and a blue (B) grayscale value that is a grayscale value of a B subpixel of each pixel. The image data processing apparatus  110  may calculate the representative brightness value through Equation 1 and Equation 2. 
     The image data processing apparatus  110  that has calculated the representative brightness value as described above may calculate N X axis point values using N set values that are previously stored (S 1420 ). In this case, the image data processing apparatus  110  calculates the N X axis point values through a shift operation and a subtraction operation using the N set values, but may preferentially calculate an N-th X axis point value. 
     Thereafter, the image data processing apparatus  110  may match the N X axis point values and N first Y axis point values that have been previously stored, and may generate a first reference curve by calculating values that connect the N X axis point values through a data interpolation method (S 1430 ). 
     The image data processing apparatus  110  may match the N X axis point values and N second Y axis point values that have been previously stored, and may generate a second reference curve by calculating values that connect the N X axis point values through the data interpolation method (S 1440 ). In this case, the sequence in which the first reference curve and the second reference curve are generated may be randomly determined by a designer who designs the image data processing apparatus  110 . 
     Thereafter, the image data processing apparatus  110  may generate a curve for brightness adjustment through a data interpolation method using a first representative brightness value designated for the first reference curve, a second representative brightness value designated for the second reference curve, and the representative brightness value (S 1450 ). In this case, the representative brightness value may be smaller than or equal to the first representative brightness value, and may be greater than or equal to the second representative brightness value. 
     The image data processing apparatus  110  may convert the input brightness values for each pixel into output brightness values for each pixel by using the curve for brightness adjustment, and may transmit, to the panel driving device  120 , output image data RGB′ including the output brightness values for each pixel (S 1460 , S 1470 ). 
     In step S 1410 , the image data processing apparatus  110  may further calculate a weighted average brightness value for the input brightness values for each pixel. 
     In such a case, the image data processing apparatus  110  may further store a lookup table, such as that in  FIG.  8   . After step S 1440 , the image data processing apparatus  110  may extract, from the lookup table, a specific representative brightness grade according to a specific average brightness range including the representative brightness value versus a specific weighted average brightness range including the weighted average brightness value. 
     Furthermore, the image data processing apparatus  110  may also generate a curve for brightness adjustment by using the first reference curve, the second reference curve, and the specific representative brightness grade. 
     As described above, in an embodiment, the image data processing apparatus  110  generates a curve for brightness adjustment by properly adjusting the curve based on a representative brightness value of an image scene, and adjusts brightness of each pixel corresponding to the image scene through the curve for brightness adjustment. Accordingly, a phenomenon in which picture quality is degraded, which occurs due to uniform brightness adjustment conventionally, can be solved. 
     Furthermore, a circuit that constitutes the image data processing apparatus  110  can be simplified because the image data processing apparatus  110  generates a curve for brightness adjustment through a shift operation, a subtraction operation, and a data interpolation method.