Pixel force field is a novel image representation where at each pixel a two-dimensional vector is defined for representing the circumstance of the pixel. The vector is oriented to the center of the region composed of vectors having the same qualitative property, such as color and gray-scale level. Using the pixel force field, that is, the orientation and the magnitude of the vector, many fundamental and specific image processing tasks can be solved. As examples of the tasks, the force field is applied to color image thinning, color image segmentation, and color map vectorisation.