Modification of Pixel-swapping Algorithm with Initialization from a Sub-pixel/pixel Spatial Attraction Model

Pixel-swapping algorithm is a simple and efficient technique for sub-pixel mapping (Atkinson, 2001 and 2005). It was initially applied in shoreline and rural land-cover mapping but has been expanded to other land-cover mapping. However, due to its random initializing process, this algorithm must swap a large number of sub-pixels, and therefore it is computation intensive. This computing power consumption intensifies when the scale factor is large. A new, modified pixel-swapping algorithm (MPS) is presented in this paper to reduce the computation time, as well as to improve sub-pixel mapping accuracy. The MPS algorithm replaces the original random initializing process with a process based on a sub-pixel/pixel spatial attraction model. The new algorithm was used to allocate multiple land-covers at the subpixel level. The results showed that the MPS algorithm outperformed the original algorithm both in sub-pixel mapping accuracy and computational time. The improvement is especially significant in the case of large scale factors. Furthermore, the MPS is less sensitive to the size of neighboring sub-pixels and can still result in increased accuracy even if the size of neighbors is small. The MPS was also much less time consuming, as it reduced both the iterations and total amount of swapping needed.