Abstract: Prior to printing work, the operator of the printing machine selectively inputs a kind of the printing paper (such as one of coated paper, mat-coated paper, and non-coated paper and so on) through a paper-type input portion 17. A CPU 11 controls the supply of ink according to the type of printing paper to be used as a result of controlling one of the operation of ink fountain keys, an ink fountain roller, and an ink ductor roller using an ink fountain key controller 21, an ink fountain roller controller 22, and an ink ductor roller controller 23.

Abstract: Solid-patches 11, 12, and 13 each printed with color-inks of cyan, magenta, yellow, and a gray patch 14 included in a color bar 15 are printed on a printed-matter 10. A measuring and calculation device 4 measures actual ink densities at each of the solid-patches and gray patches in the color bars 15 and obtains differential values between the actual ink densities and target ink densities at the gray patch 14. Then, both the amount of the primary-color-component and that of the color-impurity-component at the solid patches 11, 12, and 13 are respectively substituted into equations at every detection of the differential values and that of the gray patches. In this way, ink supply volume is adjusted as a result of converting the differential values into primary-color-component differential amount in each of the color-inks.