A method is described of generating a vector description of a color gradient in an image. The image comprises an array of pixels, each pixel having one or more associated color values. The image has at least one gradient area in which at least one of the color values varies between neighboring pixels. In each gradient area, a path is generated (step 210) comprising pixels having substantially the same color. Linear paths (403) and circular paths (501) are described. One or more control points are determined (step 220, 230) defining a line substantially perpendicular to the path. Representative color values are calculated at points along the line and a piecewise-linear color function is generated from the representative color values (step 240). The one or more control points and the piecewise-linear color function form a vector description of the color gradient in the gradient area.