Matlab Interp2函数行为与OpenCV Remap相比有所不同

问题描述

我正在尝试为interp2寻找等效的OpenCV函数，并且我参考此海报以在OpenCV中使用重映射函数.

I am trying to look for an equivalent OpenCV function for interp2 and I refer to this poster to use remap function in OpenCV.

cv :: remap(在opencv中)和interp2(matlab)

但是，我意识到这两个函数之间的输出存在显着差异.这是我的Matlab代码

However, I realized that there is a significant difference of the output between these two functions. Here is my Matlab Code

U = [0.1 0.1 0.1; 0.2 0.2 0.2; 0.3 0.3 0.3];
X = [0 0 0; 0.5 0.5 0.5; 1 1 1];
Y = [0 0.5 1;0 0.5 1;0 0.5 1];
V = interp2(U,X,Y,'linear',NaN)

我得到的输出V矩阵为

   NaN       NaN       NaN
   NaN       NaN       NaN
   NaN       NaN    0.1000

这是我的OpenCV代码

This is my OpenCV code

#include "highgui.h"
#include "cv.h"
using namespace cv;
using namespace std;

int main(int argc, char** argv)
{
    //generate flowmap model
    CvFileStorage* fx = cvOpenFileStorage("result.txt", 0, CV_STORAGE_WRITE);//ask storage for save file
    Mat xmesh = cvCreateMat(3, 3, 5);
    Mat ymesh = cvCreateMat(3, 3, 5);

    for (int i = 0; i < xmesh.rows; i++)
        for (int j = 0; j < xmesh.cols; j++)
        {
            xmesh.at<float>(i, j) = i*0.5;
            ymesh.at<float>(i, j) = j*0.5;
        }

    //generate optical flow folder
    Mat u = cvCreateMat(3, 3, 5);

    for (int i = 0; i <u.rows; i++)
        for (int j = 0; j < u.cols; j++)
        {
            u.at<float>(i, j) = (i + 1)*0.1;
        }
    Mat v = Mat::zeros(u.size(), u.type());

    remap(u, v, xmesh, ymesh, INTER_LINEAR, 0, cvScalarAll(0));

    //convert mat to Iplimage
    IplImage* xmesh_a = cvCloneImage(&(IplImage)xmesh);
    IplImage* ymesh_a = cvCloneImage(&(IplImage)ymesh);
    IplImage* u_a = cvCloneImage(&(IplImage)u);
    IplImage* v_a = cvCloneImage(&(IplImage)v);

    //save end to txt
    cvWrite(fx, "xmesh", xmesh_a, cvAttrList());
    cvWrite(fx, "ymesh", ymesh_a, cvAttrList());
    cvWrite(fx, "u", u_a, cvAttrList());
    cvWrite(fx, "v", v_a, cvAttrList());
    cvReleaseFileStorage(&fx);

    waitKey();

}

我得到的输出V矩阵是

1.00000001e-001, 1.50000006e-001, 2.00000003e-001,
1.00000001e-001, 1.50000006e-001, 2.00000003e-001,
1.00000001e-001, 1.50000006e-001, 2.00000003e-001

任何帮助将不胜感激.谢谢！

Any help will be appreciated. Thanks!

推荐答案

结果的差异与c ++和MATLAB的索引编制分别基于0和1的索引有关.

The difference in the results is related to difference in indexing between c++ and MATLAB that is 0-based and 1-based respectively.

interp2(U,X,Y,'linear',NaN)与interp2(1:3,1:3,U,X,Y,'linear',NaN)相同，将其更改为interp2(0:2,0:2,U,X,Y,'linear',NaN)，您将获得与OpenCV相同的结果.

interp2(U,X,Y,'linear',NaN) is the same as interp2(1:3,1:3,U,X,Y,'linear',NaN) changing it to interp2(0:2,0:2,U,X,Y,'linear',NaN) you will get the same result as OpenCV.

如果希望remap的结果与interp2的结果相同，则可以将xmesh和ymesh移回一步，并搜索负数位置以生成nan值.

If you want result of remap to be the same as that of interp2 you can shift the xmesh and ymesh one step back and search for negative locations to produce nan values.

#include <cmath>
//...
//...
for (int i = 0; i < xmesh.rows; i++)
    for (int j = 0; j < xmesh.cols; j++)
    {
        xmesh.at<float>(i, j) = i*0.5-1;
        ymesh.at<float>(i, j) = j*0.5-1;
    }
//...
//...
remap(u, v, xmesh, ymesh, INTER_LINEAR, 0, cvScalarAll(NAN));

结果:

nan nan nan
nan nan nan
nan nan 0.1

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