Patent ID: 7123379

Claim:
A color proofing apparatus for improving the color reproducibility of printed matter to be produced by a printing press in proof print produced by a proof press by the use of a computer, the color proofing apparatus comprising: a look-up table creating section for creating a look-up table including converted values of image data over the entire color space with respect to the proof press; a noise strength and distribution amount input section for setting the noise strength and distribution amount indicating the level of a variation of the color of the printing paper for the printing press; a paper color input section for specifying the color of the printing paper for the printing press; a look-up table correcting section for correcting the look-up table based on the color inputted to the paper color input section and a paper exposed area factor in the proof print; an image data converting section for changing the image data converted by the use of the look-up table corrected by the look-up table correcting section based on the noise strength and distribution amount inputted to the noise strength and distribution amount input section, to thus output the changed image data; in the case where the proof print is produced based on only area gradation and the colors of the printing paper for the printing press and a printing paper for the proof press are approximated to each other to such an extent as not to need to take the ink transmittance into account, the look-up table correcting section includes: a paper exposed area factor calculating section for determining a paper exposed area factor α in accordance with the following equation when arbitrary reference data P in the look-up table has color values (Cp, Mp, Yp, Bkp), each of which is N-bit data: α=(1 −Cp /(2 N −1))×(1 −Mp /(2 N −1))×(1 −Yp /(2 N −1))×(1 −Bkp /(2 N −1)), in contrast, determining the paper exposed area factor α in accordance with the following equation when the arbitrary reference data P in the look-up table has the color values (Cp, Mp, Yp, Bkp), each of which is percentage data: α=(1 −Cp /100)×(1 −Mp /100)×(1 −Yp /100)×(1 −Bkp /100); and a color corrected value calculating section for determining corrected values (Ci′, Mi′, Yi′, Bki′) of color values (Ci, Mi, Yi, Bki) of arbitrary reference data I in the look-up table in accordance with the following equations when color values (Ca, Ma, Ya, Bka) of the printing paper for the printing press are added to a part where a paper exposed area factor is 100%: Ci′=Ci+Ca×α, Mi′=Mi+Ma×α, Yi′=Yi+Ya ×α and Bki′=Bki+Bka×α, to thus replace the color values of the reference data with the corrected values.