调用了opencv中的cvFindHomography这个函数求出了空间平面与像平面间的单应矩阵再通过单应矩阵求出需测距的像点对应的实际点，进而完成测距.-In application of cvFindHomography of openCV to measure the distance through photos.

调用opencv的cvFindHomography函数求得H矩阵，再利用利用cvInvert求得H的逆矩阵，最后，选取图像上的像素点，利用cvMatMul(Ma, Mb, Mc)求出其结果矩阵。-The cvFindHomography call opencv function matrix H is obtained, and then use use cvInvert determined inverse matrix H, and