Deep Copy cv::StereoBM 深度拷贝

在使用OpenCV的三维立体重建的库时，一个重要的步骤就是生成左右视图的差异图Disparity，而控制生成disparity的参数的类是cv::StereoBM，我们有时候需要拷贝一份cv::StereoBM，然后改变其中的参数值，但是如果用默认的等号‘=’来进行拷贝，其实是浅拷贝，如果改变拷贝项的参数值，原来的参数值也会跟着改变，所以我们需要自己写一个深拷贝的函数，如下所示：

/**
 * Deep copy cv::StereoBM bm1 to bm2
 */
void copy_bm(const cv::StereoBM &bm1, cv::StereoBM &bm2) {
    if (!bm1.state) {
        return;
    }
    bm2.init(CV_STEREO_BM_NORMALIZED_RESPONSE, 0, 21);
    bm2.state->preFilterSize = bm1.state->preFilterSize;
    bm2.state->preFilterCap = bm1.state->preFilterCap;
    bm2.state->SADWindowSize = bm1.state->SADWindowSize;
    bm2.state->minDisparity = bm1.state->minDisparity;
    bm2.state->numberOfDisparities = bm1.state->numberOfDisparities;
    bm2.state->textureThreshold = bm1.state->textureThreshold;
    bm2.state->uniquenessRatio = bm1.state->uniquenessRatio;
    bm2.state->speckleWindowSize = bm1.state->speckleWindowSize;
    bm2.state->speckleRange = bm1.state->speckleRange;
}