Abstract: In this digital world we come across many image processing software that produce doctored Images with high sophistication, which are manipulated in such a way that the tampering is not easily visible to naked eye. The authenticity of a digital image has become a challenging task due to the various tools present in the photo editing software packages. There are number of ways of tampering an Image, such as splicing two different images together, removal of objects from the image, addition of objects in the image, change of appearance of objects in the image or resizing the image. This Image authentication technique detects traces of demosaicing in the complete absence of any form of digital watermark or signature and is therefore referred as passive. So there is a need for developing techniques to distinguish the photographic image from the Photorealistic Computer Generated Image, the genuine ones from the doctored ones. Estimation of demosaicing parameters is not necessary ;rather ,detection of the demosaicing is important.

Keywords: photorealistic computer generated images (PRCG), photographic images (PIM), Demosaicing, Color Filter Array (CFA).