1. A method of identifying a threat object of interest in X-ray image data, wherein the image data comprises a plurality of grey-scale or color pixel values, comprising: receiving the X-ray image data; and applying at least one predetermined bifurcation transform to the X-ray image data to effect divergence of the threat object of interest from other objects, wherein said at least one predetermined bifurcation transform is determined by applying at least one initial bifurcation transform to X-ray image data containing a known threat object that is substantially similar to said threat object of interest, and adjusting said at least one initial bifurcation transform so that the known threat object diverges from other objects in the X-ray image data once said predetermined bifurcation transform is applied to said X-ray image data.