1. A method of generating a halftone image from a grey scale image by means of a dither matrix, the halftone image being represented by symbols printed by a printer, the halftone image, the grey scale image and the dither matrix each occupying an area, the three areas being substantially equal to each other, the halftone image and the grey scale image each having a plurality of pixels, each pixel having a value, and the dither matrix having a plurality of elements that are generated by a plurality of patterns, each pattern also having a plurality of elements, each element in each pattern occupying a position in the dither matrix area, each element having a value, the method comprising the steps of: comparing the value of each pixel of the grey scale image with the value of an element in the dither matrix; determining, based on the result of the comparison, the value of a corresponding pixel of the halftone image; and forming said half tone image with said printer by printing said symbols in accordance with the determined pixel values; wherein the dither matrix is generated by: selecting a model indicative of the symbols printed by the printer; generating an intermediate pattern having a plurality of elements, each element having either a maximum or a minimum value, the values of the elements being dependent on the model of the symbols, those elements having the maximum value being distributed substantially uniformly within the pattern; generating a plurality of other patterns, each pattern having a different number of elements of the maximum value than the intermediate pattern; and summing the intermediate pattern and the plurality of other patterns to get the dither matrix.