Method and device for proofing raster print data while maintaining the raster information
View Patent ↗The screened printing data are subjected to a filtering method, the raster information being maintained. Intermediate tonal values are produced by the filtering method, using the binary tonal values, the intermediate tonal values being configured in such a way that, by means of a color space transformation, transformed tonal values and/or intermediate tonal values can be formed which represent a true-to-color proof.
1. 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.
2. The method according to claim 1 wherein Δf′ lies in a range from 20%-30%.
3. The method according to claim 1 wherein P′ lies in a range between 0.15 and 0.25.
4. The method according to claim 1 wherein the filtering comprises scaling.
5. The method according to claim 4 wherein the scaling comprises bicubic scaling or bilinear scaling.
6. The method according to claim 1 wherein at least one of the transformed tonal value and the intermediate tonal value is a luminance value and a chrominance value, respectively.
7. The method according to claim 1 wherein the raster information is at least one of a screen resolution, a screen angle and a dot shape of the screen.
8. A device for proofing screened printing data while maintaining the raster information having binary tonal values, the device comprising:
a processor programmed to filter screened printing data while maintaining raster information, wherein an intermediate tonal value is produced by the filtering using a binary tonal value, and wherein the intermediate tonal value is such that, by means of a colour space transformation, at least one of a transformed tonal value and an intermediate tonal value is formed which represent a true-to-colour proof, and wherein the processor filters the screened printing data by softening the screened data using a softening radius R, which 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′.