1. A method for detecting heights of a mechanical object, the method comprising the steps of: creating from an image of the mechanical object, a feature histogram of each of a plurality of selected features of the object, by a processor of a computing device, each selected feature corresponding to one or more of the heights of the mechanical object along an axis perpendicular to a plane of the image of the object, the image captured along the axis, such that the heights of the object are not measured, where the feature histograms of the selected features contain brightness information of the object at the heights of the selected features; a) calculating a mean value for each of the feature histograms created, by the processor of the computing device; b) calculating an average value of the plurality of calculated mean values, by the processor of the computing device; c) determining from the average value, a range of values according to predetermined criteria, by the processor of the computing device; d) determining whether each calculated mean value is within the range of values, by the processor of the computing device, to determine whether the heights are within a predetermined range without having to measure the heights of the object.