1. A method of forming a screened image comprising: providing a contone image; providing a screening tile structure of M by N cells; providing a dither magnitude curve; providing a spot function for each of the cells in the screening tile; providing a displacement vector for each of the cells in the screening tile; constructing threshold values for each of the cells by displacing the center of each cell spot function according to the displacement vectors and according to the dither curve; constructing a halftone image from the contone image and the screening tile by comparing value of each pixel from the contone image to a corresponding threshold value from the screening tile; and if the pixel value exceeds the threshold value set a corresponding pixel in the halftone image to one otherwise set the corresponding pixel in the halftone image to zero.