SHADOW DETECTION AND REMOVAL FROM SATELLITE CAPTURE IMAGES USING SUCCESSIVE THRESHOLDING ALGORITHM

Recently, Tsai presented an efficient algorithm which uses the ratio value of the hue over the intensity to construct the ratio map for detecting shadows of colour aerial images. Instead of only using the global thresholding process in Tsai's algorithm, this paper presents a novel successive thresholding scheme (STS) to detect shadows more accurately. In our proposed STS, the modified ratio map, which is obtained by applying the exponential function to the ratio map proposed by Tsai, is presented to stretch the gap between the ratio values of shadow and non-shadow pixels. By performing the global thresholding process on the modified ratio map, a coarse-shadow map is constructed to classify the input colour aerial image into the candidate shadow pixels and the non-shadow pixels.