Patent ID: 7245400

Claim:
A method of proofing screened printing data while maintaining raster information having binary tonal values, the method comprising: providing screened printing data; and filtering the screened printing data, wherein filtering comprises softening using a softening radius R that maintains the raster information and produces intermediate tonal values, wherein the softening radius R is determined by: a) calculating of a frequency distribution P(f) of a percentage area coverage f(0≦P≦1, 0≦f≦100%) for a predefined softening radius R=R 0 ; b) determining a percentage area coverage f 0 at which P(f) is maximum; c) determining of a maximum value f 1 and of a minimum value f 2 with f 1 <f 0 <f 2 , for which P(f 1 )<P′ and P(f 2 )<P′(0<P′<1); d) if f 2 −f 1 ≧Δf′(0<Δf′<100%), then calculating of the frequency distribution P(f) for a softening radius increased by a predefined value ΔR; e) repeating of the steps b)-d) to determine the softening radius R at which f 2 −f 1 <Δf′; wherein the intermediate tonal values are configured such that, by means of a colour space transformation, at least one of transformed tonal values and intermediate tonal values are formed which represent a true-to-colour proof.