Void stripping severity inspector

Determines the amount of pixel loss by void stripping on ETM+ images by SLC-off.

This function calculates the severity of the void stripping on ETM+ images caused by SLC-off. Input parameter is simply a grayscale image, while the output scalar value represents the severity. There is no matter for this function that the image contains void pixels around the boundary of the image tiles.

Return value of 0 means that there is no pixel loss by void stripping, while it is 1 when the whole image is filled with void pixels (e.g., zeros).