1. A processor-implemented method for processing image data using an image processing apparatus, the image processing apparatus comprising at least one processor for processing documents containing image data comprising a plurality of pixels, the method comprising the following acts implemented by the at least one processor: receiving image data of a document comprising a plurality of pixels; determining pixel classifications and counts of the pixels in the image data; classifying the image data into a category based on the determination of the pixel classifications and the counts, and determining a billing structure for the image data based on the classification of image data.