A method and apparatus for determining the alignment of printing plate mounted on an imaging drum, and applying an image to a printing plate while maintaining registration and alignment between the image and a reference edge of the printing plate include mounting the printing plate on a plate making machine and then determining the locations of at least one point on the reference edge. The locations of two or more points are used to determine a transformation that is applied to image data to yield transformed image data. The transformed image data is used to image the printing plate.