“…According to Fig. 3, the statistical models of contourlet coefficients exhibit a sharp peak at zero amplitude and heavy tails to both sides of the peak, and normal inverse Gaussian model [21,22] can describe curves with any shape because of its four flexible parameters, so we choose normal inverse Gaussian model to describe the distribution of contourlet coefficients of image. For most images, two parameters in the four parameters of normal inverse Gaussian model are constant [23].…”