Abstract: Image forgery is a manipulation process which hides some key information from the digital image. To avoid the traces of this manipulation, attackers use contrast enhancement. So, contrast enhancement can be used as an identifying feature for detecting an image forgery. In this paper, an algorithm to detect the global contrast enhancement applied to JPEG-compressed images is proposed. The histograms of the images are created and then the peak or gap bins present in the histogram are analyzed theoretically and distinguished by identifying the zero-height gap fingerprints. To verify the efficiency and effectiveness of the proposed technique, extensive experiments have verified.

Keywords: Composite image, contrast enhancement, digital forensics, image forgery.