A method of preventing chromatic aliasing at an edge of an image displayed upon display system, said display system employing subpixel rendering of image data upon a display, the display consisting of subpixel repeating groups having the following arrangement: R G B W B W R G wherein R represents a red subpixel, G represents a green subpixel, B represents a blue subpixel and W represents a white subpixel, and wherein the display comprises a plurality of columns, each column comprising two subpixels, the steps of said method comprising: receiving source image data; for each source image data, detecting if it relates to a second column from a left edge of the display by counting the number of columns from the left edge, and, if so, calculating whether a value for the blue subpixel in the first column, B, is greater than a value for the blue subpixel in the second column B, and where B > B, subpixel rendering the source image data relating to the second column with a second image filter on a pixel by pixel basis which involves switching off the blue subpixel in the second column, otherwise subpixel rendering the source image data relating to the second column with a first image filter on a pixel by pixel basis, and for each source image data, detecting if it relates to a final column from a left edge of the display by counting the number of columns from the left edge, and, if so, calculating whether the value for the blue subpixel in the final column, B, is greater than the value for the blue subpixel in the immediately adjacent column, B[N-1], and where B > B[N-1], subpixel rendering the source image data relating to the final column with the second image filter on a pixel by pixel basis which involves switching on the blue subpixel in the final column, otherwise subpixel rendering the source image data relating to the final column with the first image filter on a pixel by pixel basis, for each source data which does not relate to a second column or a final column from the left edge of the display, subpixel rendering with a first image filter on a pixel by pixel basis. receiving source image data; for each source image data, detecting if it relates to a second column from a left edge of the display by counting the number of columns from the left edge, and, if so, calculating whether a value for the blue subpixel in the first column, B, is greater than a value for the blue subpixel in the second column B, and where B > B, subpixel rendering the source image data relating to the second column with a second image filter on a pixel by pixel basis which involves switching off the blue subpixel in the second column, otherwise subpixel rendering the source image data relating to the second column with a first image filter on a pixel by pixel basis, and for each source image data, detecting if it relates to a final column from a left edge of the display by counting the number of columns from the left edge, and, if so, calculating whether the value for the blue subpixel in the final column, B, is greater than the value for the blue subpixel in the immediately adjacent column, B[N-1], and where B > B[N-1], subpixel rendering the source image data relating to the final column with the second image filter on a pixel by pixel basis which involves switching on the blue subpixel in the final column, otherwise subpixel rendering the source image data relating to the final column with the first image filter on a pixel by pixel basis, for each source data which does not relate to a second column or a final column from the left edge of the display, subpixel rendering with a first image filter on a pixel by pixel basis.