读取TM波段3和波段4的图像，计算归一化植被指数NDVI，并用NDVI处理单波段图像，突出显示遥感影像的植被部分（输出后的图像上高亮的部分是植被区域）-Band 3 and band 4 images of a TM image are read and NDVI computed. Then a single band image is processed with the NDVI leading to the vegetation regions in the remote sensed