1. A method for classifying an image block of a printed image into contone, halftone, or error diffusion classes, comprising: scanning the printed image; selecting an n by n block of pixels from the scanned image; calculating an array of DCT coefficients of the pixel block, wherein the calculated DCT coefficients are representative of spatial frequency and spatial orientation of the pixel block; inputting the array of DCT coefficients into a classifier which has been configured to classify printed images into contone, halftone and error diffusion classifications using DCT coefficients; and determining whether the image classification of the pixel block is contone, halftone or error diffusion based on input DCT coefficients.