Convert opencv 3 code to opencv 4

1

Hi, I have some opencv 3 code as below, how can I conver them to opencv 4? THanks a lot

 CvMat * PW0 = cvCreateMat(3, 3, CV_64F);

  double pw0tpw0[3 * 3], dc[3], uct[3 * 3];
  CvMat PW0tPW0 = cvMat(3, 3, CV_64F, pw0tpw0);
  CvMat DC      = cvMat(3, 1, CV_64F, dc);
  CvMat UCt     = cvMat(3, 3, CV_64F, uct);

  for(int i = 0; i < number_of_correspondences; i++)
    for(int j = 0; j < 3; j++)
      PW0->data.db[3 * i + j] = pws[3 * i + j] - cws[0][j];

  cvMulTransposed(PW0, &PW0tPW0, 1);
  cvSVD(&PW0tPW0, &DC, &UCt, 0, CV_SVD_MODIFY_A | CV_SVD_U_T);

  cvReleaseMat(&PW0);
2

that’s not opencv3 code, but friggin 1.0 c-api (dead since A LONG TIME)

3

@berak . THanks. Could you please show me how to change the code to opencv 4?

4

https://docs.opencv.org/master/de/d7a/tutorial_table_of_content_core.html

6

I’m sure you can translate that stuff adequately.

docs for that old stuff should be in the docs to v2.4.

it’s just a few Mats. use regular Mat constructors that use their own memory. get rid of the double arrays.

pws and cws aren’t shown so only you know what they contain.

7

How about SVD? I could not find CV_SVD_U_T in opencv 4…

8

SVD is still there. it’s a class now.

9

it’s not even in the 2.4 docs

questions:

  • what does this code try to achieve ?
  • what are the inputs, and what are you doing with the result ?
  • why is there no V ?
  • why does it want to transpose U (instead of V)?
  • CV_SVD_U_T was defined as 2, which would be SVD_NO_UV today (meaning, it only calculates singular W values, not U at all)

maybe you can run the original c code with some random dummy values, and show the output (& compare it to the c++ version) ? you probably have to skip the flag, and transpose U manually (but this is just a guess)

found some older docs

10

2.x docs don’t list it, 3.x docs do…
https://docs.opencv.org/3.4/d2/df8/group__core__c.html#ga6593e7074d83a1586b43e5385495dfd6

11

I have found the full original code was there,
it’s solver from ORB_SLAM2.