Method and device for the freely selectable substitution of the uncoloured component in multicolour printing by black printing ink

摘要

This is a method for the freely selectable substitution of the uncoloured component in multicolour printing by black printing ink on the basis of a spectrophotometrically scanned original, reference points in a colour space being obtained during the spectrophotometric scanning of the original. In accordance with a preselected degree, the uncoloured component or the complementary colour component of the colours of a printing colour space, constructed in a multicolour fashion, is substituted by black printing ink. Reference point data are registered photometrically from a colour scale which is specific to the printing process. The printing colour space is classified in a colour model (HSL model, Fig. 1) which is independent of printing colour and is represented in this model. A two-dimensional, nonlinear darkening field is formed using lightness values (Fig. 2) and a two-dimensional nonlinear desaturation field is formed with saturation values (Fig. 3), both of which are taken from the original, and the substitution of the uncoloured component by black printing ink is undertaken by means of iterative searching within the darkening field and the desaturation field. <IMAGE>