Patent ID: 7515305

Claim:
A method for measuring spatial uniformity in an image, comprising: printing a test pattern from an image forming device including a plurality of strips and rows of fiducials proximal thereto; correcting for distortions in an image caused by printing and scanning artifacts; mapping from scanner coordinates to digital image coordinates; determining a gray level of each strip in said plurality of strips as a function of digital image cross process coordinate; filtering a profile of said each strip whereby said artifacts from a halftone screen are eliminated; wherein said rows of fiducials are selected for said correcting of said distortions; wherein said correcting of said distortions further includes: determining a process direction cross section of each fiducial in a selected row of fiducials; determining a process direction shift of said each fiducial in said selected row of fiducials; and, shifting a pixel column of said image to adjust said each fiducial in a horizontal orientation in said selected row of fiducials whereby said selected row of fiducials is adjusted to a substantially horizontal orientation; filtering a profile of said each fiducial in said selected row of fiducials including: analyzing each pixel column in a sequence starting from one side of said image and proceeding to the other side of said image including identifying a current process direction transition index where a transition from high scanner response to low scanner response occurs; comparing said current process direction transition index to a previous process direction transition index; identifying a next process direction transition index; identifying a phase of said profile of said each fiducial, said phase is determined at a period of twice a length of said each fiducial; and, converting said phase into a process direction displacement.