Shadow Detection in Arial Image Using Optimized Ratio Map

In image processing many algorithms get disturbed because of shadow. These problems can be avoided if the location of shadows is clear. This article presents a new optimized algorithm for extracting shadows from a single color aerial image. Most of similar works do this by using a suite color space. In this work two RGB and YCbCr color spaces are combined and a powerful ratio map has been created. Furthermore, in a new method, effect of sky blue color is determined that improves the ratio map. Candidate shadow and non-shadow regions are separated by applying Otsu’s thresholding method. Because of ratio map performance it is not necessary to analyze region by region and leads to decrease computation cost. So it can be used in online application. The experimental results demonstrate the advantage of the proposed algorithm.