| Popis: |
In four color printing, gray component replacement is a useful technique of replacing the achromatic part of a mixture of chromatic inks (CMY) with a corresponding amount of the black ink (K). It reduces ink consumption, which is beneficial in commercial and environmental sense. Many papers describe various approaches to gray component replacement (GCR). They are mainly focused on the methods of calculating CMYK solutions for a fixed K amount, but pay little attention to determination of K amount, i.e. black generation. Black generation is a procedure of determining the amount of black ink corresponding to the amount of gray component in a CMY mixture that we wish to replace. Due to imperfections of printing inks and printing processes, black generation is a challenging task. If the amount of gray component in a given CMY mixture is overestimated, the new GCR solution will not match the original color. This paper compares the efficiency of three black generation algorithms in terms of colorimetric accuracy and achieved ink savings in digital images. Regarding the colorimetric accuracy, it was found that the examined algorithms do not significantly differ in central tendency error measures. However, they do differ in 90th percentile error as some are more prone to overestimating the amount of gray component for a small subset of device inputs. It was also found that they differ in the ability to maintain colorimetric accuracy at higher replacement rates, i.e. at higher ink savings. |
