OpenCV学习笔记（10）CvMat 与 STL vector 的格式转换与数据读写

用STL vector来进行数组的数据读写非常方便，可以动态调整数组大小，不过在OpenCV里使用vector时，要保存vector数组的数据，就需要转换为 CvMat 格式。
比如有一个双通道数组：

vector<cvpoint2d32f> points[2]; </cvpoint2d32f>

可以按如下方式来保存数据：

int len = points[0].size();
CvMat* pts = cvCreateMat(2,len,CV_32FC2);
for (i=0;i2;i++)
    for (j=0;jlen;j++)
    {
        ((float*)(pts->data.ptr + pts->step*i))[j*2] = points[i][j].x;
        ((float*)(pts->data.ptr + pts->step*i))[j*2+1] = points[i][j].y;
    }
CvFileStorage* fs = cvOpenFileStorage( "data.xml", 0, 
                    CV_STORAGE_WRITE);
cvWrite(fs, "points_matrix", pts);
cvReleaseFileStorage(&fs); 

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反之，从本地xml文件中读入CvMat数组，再转换为 vector 格式，方式如下：

CvFileStorage* fs = cvOpenFileStorage( "data.xml", 0, 
                    CV_STORAGE_READ);
CvMat* pts = (CvMat*)cvReadByName(fs, 0, "points_matrix");
CvSize pts_size = cvGetSize(pts);
points[0].resize(pts_size.width);
points[1].resize(pts_size.width);
for (i=0;i2;i++)
    for (j=0;jpts_size.width;j++)
    {
         points[i][j].x = ((float*)(pts->data.ptr + pts->step*i))[j*2];
         points[i][j].y = ((float*)(pts->data.ptr + pts->step*i))[j*2+1];
    }
cvReleaseFileStorage(&fs);

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