A method and system is provided for processing scanned data representative of a document image for classifying portions of the data into contone, low frequency halftone or high frequency halftone regions. The method comprises identifying an image data value of an original pixel within a portion of a document image. Average pixel values are calculated for the plurality of image regions. First and second halftone noise energy values are computed relative to the original pixel value for the plurality of image regions. The noise values are compared against preselected standards and based upon the comparing, the region can be classified as high frequency halftone, low frequency halftone or contone. Portions of image of data which may introduce unwanted biases in the measurements such as edge portions, all black or all white portions are excluded from the energy level calculations.