Accuracy of leaf area measurement technique is depends on how accurate leaf and known object are detected. In this paper image is segmented using threshold technique. Threshold is applied on „L‟ component of CIELAB color space. Threshold is calculated using OTSU‟s method [10]. Segmented image is binary image in which leaf and known object are segmented as same color and background is segmented as different color. This segmented image is inverted in color. There may be some cuts and spots on leaf because of diseases and insects. In segmented binary image background and these spots are in same color. Leaf area can‟t be measured accurately without filling these spots. These holes are filled using region filling