Patent ID: 7397580

Claim:
A printing control method of generating print data to be supplied to a print unit to print, the print unit capable of forming dots on a print medium by ejecting at least one type of colored ink containing a color material and a quality-enhancing ink for enhancing quality of a printed material, the printing control method comprising: (a) a color conversion step of converting pixel values into multiple gradation data of each ink, the pixel values representing color of each pixel of given image data, the multiple gradation data of each ink expressing the color of the pixel by using the colored ink and the quality-enhancing ink available in the print unit; and (b) a gradation-reduction step of generating at least part of colored dot data and transparent dot data by ordered dither method, according to the generated multiple gradation data of each ink by the color conversion, the colored dot data representing formation status of colored dots formed with the colored ink on each of printing pixels, the transparent dot data representing formation status of transparent dots formed with the quality-enhancing ink on each printing pixel; wherein the gradation-reduction step includes a step of generating the transparent dot data in succession with specific colored dot data using a quality-enhancing ink threshold value, the quality-enhancing ink threshold value having a value generated according to a value read from a specific dither matrix used for generating the specific colored dot data for a specific colored ink, and the quality-enhancing ink threshold value being a value stored in an element arranged in a position shifted for at least one of row and column in relation to an element used for generating the specific colored dot data within the specific dither matrix.