Abstract: A method of adjusting process black and a driver thereof. The method includes converting a part of process black data into mono black data. Accordingly, a user can arbitrarily adjust a ratio of process black to obtain a more natural output image and print the output image in process black and mono black, thereby reducing the consumption of ink or a colorant contained in process black.

Abstract: A method of determining a time to replace developing solutions in a printer includes providing a reference card including sample patches of standard colors for predetermined colors of the developing solutions, sample patches of test colors into which the standard colors change due to contamination, and standard color differences &Dgr;E* calculated from standard color values Es* corresponding to the respective standard colors and measured standard contamination values Ec* corresponding to the respective test colors; inputting information about test patches for the predetermined colors into the printer and printing the test patches; and comparing the sample patches with the test patches to determine whether to replace the developing solutions. Since the reference card is provided together with a printer including information about test patches, a user can easily determine a time to replace a developing solution.

Abstract: A method of adjusting process black and a driver thereof. The method includes converting a part of process black data into mono black data. Accordingly, a user can arbitrarily adjust a ratio of process black to obtain a more natural output image and print the output image in process black and mono black, thereby reducing the consumption of ink or a colorant contained in process black.

Abstract: An image forming apparatus having a plurality of halftone tables to store a toner quantity value corresponding to a displacement of a gradation grade value of a pixel of image data in different patterns, respectively. The image forming apparatus also has a controller to output print image information by selecting any one of the halftone tables and by fetching a toner quantity value corresponding to a gradation grade value of each pixel of original image data in the selected halftone table, and an engine to print an image corresponding the print image information as output in the controller in recording media. Therefore, it is possible to enhance quality of the print image by extending a range of gradation representation in a desired region according to the characteristics of the printed image.

Abstract: A method of determining a time to replace a developing solution in a printer includes providing a reference card including sample patches of standard colors for predetermined colors of the developing solutions, sample patches of test colors into which the standard colors change due to contamination, and standard color differences &Dgr;E* calculated from standard color values Es* corresponding to the respective standard colors and measured standard contamination values Ec* corresponding to the respective test colors; inputting information about test patches for the predetermined colors into the printer and printing the test patches; and comparing the sample patches with the test patches to determine whether to replace the developing solutions. Since the reference card is provided together with a printer including information about test patches, a user can easily determine a time to replace a developing solution.