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; estimating a color count of color pixels in device independent space and determining if the image data of the document is substantially neutral or color; converting the plurality of pixels of the image data in device independent space into a plurality of pixels in device dependent space; determining a pixel count of color pixels in the image data in the device dependent space; determining a billable pixel count of color pixels for marking and outputting the image data in device dependent space, and determining the billing structure for the image data of the document based on the billable pixel count, wherein the determined billable pixel count of color pixels is based on at least both of the estimated color count in device independent space and the determined pixel count in device dependent space.