1. A non-invasive method of identifying contours with complex structures having an error recognition rate tending towards zero, comprising the steps of: distinguishing and identifying contours of a slaughtered animal body; utilizing, on a basis of a characteristic piece of said slaughtered animal body by means of image processing, measurement values of individual sections, partial sections, averaged sections and areas with a reference to progression of said contours for calculating a muscle-meat percentage, a trade classification and an associated trade value and a market value; rating a quality of slaughtered animal bodies with further characteristic image information, wherein during error recognition of said contours of said slaughtered animal body, said contours having complex structures to be distinguished and identified, an operator at a workstation comprising a personal computer utilizes the personal computer to provide indications relating to an unidentified or incorrectly identified contour to be sought and; employing an image reproduction device to set at least one support point, in each case, set in an illustration of an image of a region of interest of said slaughtered animal body containing one or more regions, wherein data identifying said contours is to be determined from measurements.