Method and apparatus for intensifying contrast in printing formats

摘要

A method and apparatus for intensifying contrast during the recording of masters in electronic image processing wherein a master is scanned opto-electronically and an image signal is produced as well as two unsharp masking signals by scanning a first unsharp masking area and an enlarged second unsharp masking area around the current image point. Differential signals are generated from the image signal and each of the two unsharp masking signals and the two differential signals thus formed are mixed together in a selected ratio. The mixed signal is divided into positive and negative correction components which can be differently amplified and after comparison to threshold signals are combined to form a correction signal which has an effective width which depends on the mixing ratio. The mixing ratio may for example, be dependent on the gradient and/or the contrast of a master contour. The correction signal thus formed is then superimposed on the image signal so as to provide contrasted intensification and the contrast enhancement can be matched to the properties of the master by controlling the effective width of the correction signal.