An image processing method, in which three primary color data of an input RGB data format are rendered on a display panel according to a sub-pixel structure of the display panel, the display panel having as many G sub-pixels as the display resolution of the input G data and as many R and B sub-pixels as half the display resolution of the input R and B data, respectively, the method comprising: separating the R and B data and the G data from the input data; gamma-converting the separated R and B data, and loading data corresponding to respective odd rows of gamma-converted R and B data to a register, and storing data corresponding to respective even rows of the R and B data adjacent to the loaded odd rows; loading two R data of the even row, along with two R data of the odd row corresponding to a first display position, so as to form a 2x2 R pixel area, and loading two B data of the even row, along with two B data of the odd row corresponding to a second display position, so as to form a 2x2 B pixel area; determining the logic values of first and second flag bits by comparing the value corresponding to the absolute difference between the data in each of the R and B pixel areas column by column to a preset threshold value, wherein, if a comparison value between the data in each column is less than the preset threshold value, the logic values of the first and second flag bits are determined as HIGH, whereas, if the comparison value is greater than the preset threshold value, the logic values of the first and second flag bits are determined as LOW; computing the sharpness of the corresponding display data using the difference between the data in each row of each of the R and B pixel areas and a preset level value in case the logic value of at least one of the first and second flag bits is HIGH, wherein the sharpness is obtained by dividing the sum of the differences between the data in each row of each of the R and B pixel areas by 2 and multiplying the level value to the result of the division, and wherein, if the logic value of at least one of the first and second flag bits is HIGH, the corresponding Rand B pixel areas are detected as a vertical edge for sharpness filtering, and then the number of bits of the data of the corresponding R/B pixel area is extended from M bits to N bits (N>M); computing the luminance of the display data by taking the average value of the data corresponding to the odd row of each of the R and B pixel areas; determining the gray scale value of output R data by adding the sharpness to the luminance of the R data, and determining the gray scale value of output B data by adding the sharpness to the luminance of the B data; and inverse-gamma-converting the output R and B data, and combining the inverse-gamma-converted R and B data and the input G data and then outputting the combined data according to the sub-pixel structure of the display panel. separating the R and B data and the G data from the input data; gamma-converting the separated R and B data, and loading data corresponding to respective odd rows of gamma-converted R and B data to a register, and storing data corresponding to respective even rows of the R and B data adjacent to the loaded odd rows; loading two R data of the even row, along with two R data of the odd row corresponding to a first display position, so as to form a 2x2 R pixel area, and loading two B data of the even row, along with two B data of the odd row corresponding to a second display position, so as to form a 2x2 B pixel area; determining the logic values of first and second flag bits by comparing the value corresponding to the absolute difference between the data in each of the R and B pixel areas column by column to a preset threshold value, wherein, if a comparison value between the data in each column is less than the preset threshold value, the logic values of the first and second flag bits are determined as HIGH, whereas, if the comparison value is greater than the preset threshold value, the logic values of the first and second flag bits are determined as LOW; computing the sharpness of the corresponding display data using the difference between the data in each row of each of the R and B pixel areas and a preset level value in case the logic value of at least one of the first and second flag bits is HIGH, wherein the sharpness is obtained by dividing the sum of the differences between the data in each row of each of the R and B pixel areas by 2 and multiplying the level value to the result of the division, and wherein, if the logic value of at least one of the first and second flag bits is HIGH, the corresponding Rand B pixel areas are detected as a vertical edge for sharpness filtering, and then the number of bits of the data of the corresponding R/B pixel area is extended from M bits to N bits (N>M); computing the luminance of the display data by taking the average value of the data corresponding to the odd row of each of the R and B pixel areas; determining the gray scale value of output R data by adding the sharpness to the luminance of the R data, and determining the gray scale value of output B data by adding the sharpness to the luminance of the B data; and inverse-gamma-converting the output R and B data, and combining the inverse-gamma-converted R and B data and the input G data and then outputting the combined data according to the sub-pixel structure of the display panel.