Paint-doctored JPEG image forensics based on blocking artifacts

In today´s digital era, because of the advent of image editing and processing tools it is conceivable to alter digital images very easily without leaving any obvious tampering traces. Thus, image forgery has become very easy and authenticity of digital images has been severely threatened, resulting in a need for reliable and robust image forensic techniques. Image painting is one of the commonly used methods to conceal unwanted portions of an image. In this paper, a passive method for detecting painted areas on widely used JPEG images is proposed. The block processing during JPEG compression presents horizontal and vertical breaks into images, which is recognized as block artifact grids (BAGs). The detection technique is based on the fact that BAGs usually disarrange after performing painting operations. Experimental results demonstrate the validity and effectiveness of the proposed approach.