Detecting photographic composites using shadows

Image compositing technology has become popular for tampering with digital photographies. We describe how such composites can be detected by enforcing the geometric and photometric constraints from shadows. In particular, we explore (i) the imaged shadow relations that are modeled by the planar homology, and (ii) the color characteristics of the shadows measured by the shadow matte. Our approach efficiently extracts these constraints from a single image and makes use of them for the digital forgery detection. Experimental results on visually plausible images demonstrate the performance of the proposed method.