Читать книгу Multimedia Security, Volume 1 - William Puech - Страница 28

White balance increases the intensity range of the image. Since the weights are different for each color channel, as mentioned in section 1.2.3, the three noise curves are less correlated after this step. Then, gamma correction greatly increases the noise and the dynamic range of the image, due to the power law function. Furthermore, the noise curves are no longer monotonically increasing after this step. Indeed, if we denote γ the function applied during the gamma correction step, the asymptotic expansion around the intensity u yields γ(u + n) = γ(u) + γ′(u)n, where n is the noise at the intensity u.