1. A method for controlling image display, comprising: reading gray scales of all sub-pixels of a current frame image displayed by a display device; determining an ideal luminance corresponding to the gray scale according to a predetermined ideal corresponding relationship between the gray scales and the luminance of respective sub-pixels, respectively; determining an adjusted gray scale corresponding to the ideal luminance according to a predetermined original corresponding relationship between the gray scales and the luminance of respective sub-pixels, respectively; driving the display device to display the current frame image according to the adjusted gray scale; wherein, the ideal corresponding relationship between the gray scale and the luminance of respective sub-pixels is characterized by an ideal characteristic curve of the gray scales vs. the luminance, or characterized by an ideal corresponding relationship between the gray scales and the luminance stored in a table; and the original corresponding relationship between the gray scales and the luminance of respective sub-pixels is characterized by an original characteristic curve of the gray scales vs. the luminance, or characterized by an original corresponding relationship between the gray scales and the luminance stored in a table; wherein, the ideal characteristic curve of the gray scales vs. the luminance is particularly determined as follows: determining the ideal corresponding relationship of a plurality of gray scales vs. the luminance of each sub-pixel; making interpolation calculation on the ideal corresponding relationship between the plurality of gray scales and the luminance of each sub-pixel respectively, to obtain the ideal characteristic curve of the gray scales vs. the luminance of the sub-pixels; and wherein, the ideal corresponding relationship of the plurality of gray scales vs. the luminance of each sub-pixel is particularly determined as follows: selecting a plurality of different gray scales, driving the display device with the gray scales respectively to display images corresponding to the gray scales; measuring and recording the luminance of all the sub-pixels corresponding to each gray scale among the displayed images; summing and averaging the luminance of the plurality of sub-pixels corresponding to each gray scale respectively, obtaining the ideal luminance corresponding to the selected gray scales, and obtaining the ideal corresponding relationship between the plurality of selected gray scales and the luminance of each sub-pixel; wherein, assuming that there are k gray scales, the measured luminance of the gray scale G x corresponding to the sub-pixel in the i th row and j th column is the L ij,x , the measured luminance of the gray scale G x corresponding to all or part of the sub-pixels is åL ij,x , the ideal luminance of each sub-pixel under the gray scale G x is Lx, then Lx = å ⁢ ⁢ L ij , x n ( x = 1 , 2 , 3 , … ⁢ ⁢ k ) wherein, n denotes the number of the measured luminance participating in the summation, and the n can be the number of all or part of the sub-pixels.