Patent ID: 8251482

Claim:
A printing apparatus including a roller for conveying a printing medium in a conveying direction, the roller being usable in an orientation with the longitudinal direction of the roller being the same as a direction crossing with the conveying direction, and being provided across the width of the printing medium, said apparatus comprising: a unit configured to cause said printing apparatus to form a plurality of test patterns along the longitudinal direction of the roller, the test patterns being used for detecting conveying errors at respective positions in the longitudinal direction of the roller, the conveying errors depending on an eccentricity of the roller and being made corresponding to angles of rotation of the roller, the test patterns corresponding respectively to the positions; and a determining unit configured to determine a correction function by using the plurality of test patterns, the correction function being used for correcting the conveying errors and having the angles of rotation of the roller from a reference position and correction values corresponding to each other, wherein said determining unit acquires the conveying errors for each of the plurality of test patterns that correspond respectively to the conveying errors, applies a correction using one correction function of a plurality of prepared correction functions to each of the acquired conveying errors, and determines one correction function to be the correction function used for correcting the respective conveying errors in the longitudinal direction, based on a result of the application of the correction to each of the acquired conveying errors.