Ink jet printing system, ink jet printing method, and storage medium

An ink jet printing method of printing an image on a predetermined region of a print medium during a first number of times of scans of a print head comprising a first nozzle array for ejecting a first ink and a second nozzle array for ejecting a second ink having lightness lower than that of the first ink, the method comprising:

• generating first data for ejecting the first ink during a second number of times of scans included in the first number of times of the scans based on first mask patterns, and second data for ejecting the second ink during a third number of times of scans included in the first number of times of the scans based on second mask patterns, the second number of times of the scans including a final scan of the first number of times of the scans, the third number of times of the scans not including the final scan, and the number of printing allowed pixels each with a printing allowed pixel present adjacent thereto in the second mask patterns being smaller than that of the first mask patterns, and
• printing the image using the print head based on the first data and the second data.

A storage medium in which a computer readable program is stored, the program allowing a computer to function as a data generation apparatus that generates data allowing a print head to apply first and second inks to a predetermined region on a print medium during a first number of times of scans of the print head, the second ink having lightness lower than that of the first ink,

• wherein the function of the data generation apparatus is executed such that a first data allowing the print head to apply the first ink to the predetermined region during a second number of times of scans included in the first number of times of the scans is generated based on first mask patterns and a second data allowing the print head to apply the second ink to the predetermined region during a third number of times of scans included in the first number of times of the scans is generated based on second mask patterns in which the number of printing allowed pixels each with a printing allowed pixel present adjacent thereto is smaller than that of the first mask patterns, the second number of times of the scans including a final scan of the first number of scans, and the third number of times of the scans not including the final scan.