Small object detection algorithm for sonar image based on pixel hierarchy

In view of the unclear outline of the object characteristics and the complexity of the background noise in sonar images, an object detection algorithm is proposed based on pixel hierarchy. According to the characteristics of depth map, "depth information" is inserted into different layers of the sonar image to describe the “depth” of each layer. Due to the higher gray values of the objects, and the lower gray values of the background, the sonar image is layered according to different gray-levels. The high gray values of sonar image are divided into several areas and then the areas are marked. Using the high gray value characteristics of the object pixels in each image layers, a coefficient for characterizing the possibility of containing the object pixels in each image layer is defined so that the final object segmentation is made easier. Experimental results show that the object segmentation algorithm is accurate and fast.