Image Noise Level Estimation by Principal Component Analysis

The problem of blind noise level estimation arises in many image processing applications, such as denoising, compression, and segmentation. In this article, we propose a new noise level estimation method based on principal component analysis of image blocks. We show that the noise variance can be estimated as the smallest eigenvalue of the image block covariance matrix. Compared with 13 existing methods, the proposed approach shows a good compromise between speed and accuracy. It is at least 15 times faster compared with the methods with similar accuracy; and it is at least 2 times more accurate than other methods. Our method does not assume the existence of homogeneous areas in the input image, hence it can successfully process images containing only textures.