A method for processing an image to increase sharpness of the image without changing hue characteristics. The method includes performing a transformation process to transform an original image signal into CIE XYZ colorimetric channels, forming a luminance channel Y, applying a filter on the luminance channel Y to obtain a processed luminance channel Y'', computing processed colorimetric channels X'' and Z'' based on the processed luminance channel Y'', and performing an inverse transformation process to transform the processed colorimetric channels X''Y''Z'' into a processed image signal.