Fish length is very important to the fishery research to identify fish population. In many fisheries, sample of fish length is a main parameter to identify fish reproduction, recruitment, growth and mortality. Currently in Malaysia, researchers have to measure the fish length one by one using measurement tools. This method is highly cost as we require buying fish first for measuring purposed. Moreover, manually measurement of fish length is time-consuming. Therefore, a method to measure the length of a fish automatically using image processing and formula optic is greatly needed to solve these problems. In this paper, we will discuss on the details of FLUDI framework. The FLUDI framework is a combination between Hsiu’s method and Serkan’s method. The accuracy of measuring the fish length was 99.81%.