  This chapter presents a framework for detecting fake regions by using various
methods including watermarking technique and blind approaches. In particular,
we describe current categories on blind approaches which can be divided into
five: pixel-based techniques, format-based techniques, camera-based techniques,
physically-based techniques and geometric-based techniques. Then we take a
second look on the geometric-based techniques and further categorize them in
detail. In the following section, the state-of-the-art methods involved in the
geometric technique are elaborated.
