IMAGE ENHANCEMENT METHOD FOR UNDERWATER IMAGES BASED ON DISCRETE COSINE EIGENBASIS TRANSFORMATION

This paper proposes a novel image enhancement method for underwater images based on discrete cosine eigenbasis transformation (DCET). Since underwater images have a global strong dominant color, their colorfulness and contrast are often degraded. Typical color correction methods for natural images, i.e., computational color constancy, achromatize the colored illuminant of input images by dividing with an estimated illuminant color. However, this procedure produces unwanted color artifacts for underwater images. To solve this problem, we introduce a novel assumption that achromatic illuminant images should have the DCT basis vectors as their principal component vectors, which is termed as discrete cosine eigenbasis (DCE). According to the assumption, we achromatize underwater images by using a DCET that transforms the input image to the images having the DCE. By incorporating post image enhancement techniques, the proposed method provides sharper and brighter visual quality than conventional color correction and image enhancement methods.