1. A processor-implemented method for determining a billing structure for outputting documents comprising at least one page 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; determining if the pixels in the image data in device independent space are neutral or non-neutral; converting the plurality of pixels in device independent space into a plurality of pixels in device dependent space; determining a billable pixel count of color pixels for the image data in device dependent space based on at least the determined non-neutral pixels in device independent space, and determining the billing structure for the image data of the document based on the billable pixel count.