A method of processing image data for displaying on an OLED display device comprising white W, red R, green G and blue B sub-pixels where a ratio of luminous efficacy is W:G:R:B=30:10:3:1, the method comprising the steps of: determining (S4) a first image region of the image data and a second image region of the image data, the first image region including an opaque fixed image that is not included in the second image region such that the first image region is more likely to cause a ghost image effect than the second image region, the image data being represented by first color components red R, green G and blue B; applying (S8) a first conversion algorithm to first pixel data (RGB) of the first image region to obtain first converted pixel data (W'R'G'B') represented by second color components, the number of which being larger than a number of the first color components, said second color components consisting of white W, red R, green G and blue B; and applying (S12) a second conversion algorithm to second pixel data of the second image region to obtain second converted pixel data (WRGB) represented by the second color components, wherein the first conversion algorithm increases a use rate of a first component W of the second color components and decreases a use rate of a second component B of the second color components relative to the second conversion algorithm, wherein said first W component has a higher luminous efficacy than said second B component, wherein the first conversion algorithm generates α times the use rate of said second B component and β times the use rate of said first W component relative to the second conversion algorithm, where α is less than 1, and β = 1 + 1/30 ∗ (1 - α). determining (S4) a first image region of the image data and a second image region of the image data, the first image region including an opaque fixed image that is not included in the second image region such that the first image region is more likely to cause a ghost image effect than the second image region, the image data being represented by first color components red R, green G and blue B; applying (S8) a first conversion algorithm to first pixel data (RGB) of the first image region to obtain first converted pixel data (W'R'G'B') represented by second color components, the number of which being larger than a number of the first color components, said second color components consisting of white W, red R, green G and blue B; and applying (S12) a second conversion algorithm to second pixel data of the second image region to obtain second converted pixel data (WRGB) represented by the second color components, wherein the first conversion algorithm increases a use rate of a first component W of the second color components and decreases a use rate of a second component B of the second color components relative to the second conversion algorithm, wherein said first W component has a higher luminous efficacy than said second B component, wherein the first conversion algorithm generates α times the use rate of said second B component and β times the use rate of said first W component relative to the second conversion algorithm, where α is less than 1, and β = 1 + 1/30 ∗ (1 - α). <EOS>