Possible documentation error: minMaxIdx() on single-column matrix (Bug #2081)

Added by Frankie Fong over 12 years ago. Updated over 12 years ago.

Status:Cancelled Start date:2012-06-25
Priority:Normal Due date:
Assignee:Vadim Pisarevsky % Done:

0%
Category:documentation
Target version:2.4.2
Affected version: Operating System:
Difficulty: HW Platform:
Pull request:

Description

I noticed there is a difference in the results from minMaxIdx() going from OpenCV 2.2 to OpenCV 2.4.1.

I have a single-column-matrix 1x32. I call minMaxIdx() to retrieve the max-idx with a 'int maxBin[2] array.

OpenCV 2.2: the result is (0, 12)
OpenCV 2.4.1: the result is (12, 0)

According to the minMaxIdx() documentation, I should expect (0, 12); But if the ofs2Idx() performs according to the indexing convention of Mat class. I should expect (12, 0) because matrix element indexing begins with higher-dimension (rows).

Could you help clarify this?

Thanks!

Associated revisions

Revision 31395b07
Added by Vadim Pisarevsky over 12 years ago

added check for false bug report #2081

Revision a1bc11c4
Added by Vadim Pisarevsky over 12 years ago

fixed typo in minMaxIdx description (ticket #2081)

Revision 4a6c2ce3
Added by Andrey Pavlenko about 11 years ago

Merge pull request #2081 from ilya-lavrenov:tapi_perf

History

#1
Updated by Vadim Pisarevsky over 12 years ago

It works properly. 1x32 is single-row, not single-column.
Here is the test code

        Mat A(1, 32, CV_32F), B;
        for( int i = 0; i < A.cols; i++ )
            A.at<float>(i) = (float)(i <= 12 ? i : 24 - i);
        transpose(A, B);

        int minidx[2] = {0, 0}, maxidx[2] = {0, 0};
        double minval = 0, maxval = 0;
        minMaxIdx(A, &minval, &maxval, minidx, maxidx);

        CV_Assert(minidx[0] == 0 && minidx[1] == 31 && maxidx[0] == 0 && maxidx[1] == 12 &&
                  minval == -7 && maxval == 12);

        minMaxIdx(B, &minval, &maxval, minidx, maxidx);

        CV_Assert(minidx[0] == 31 && minidx[1] == 0 && maxidx[0] == 12 && maxidx[1] == 0 &&
              minval == -7 && maxval == 12);

  • Status changed from Open to Cancelled

#2
Updated by Frankie Fong over 12 years ago

Thanks for clarifying. What I am saying is it is changed since OpenCV 2.2. And the documentation is not updated. Quoting here:
..., i.e. single-row matrix is Mx1 matrix (and therefore minIdx/maxIdx will be (i1,0)/(i2,0)) and single-column matrix is 1xN matrix (and therefore minIdx/maxIdx will be (0,j1)/(0,j2)).....

#3
Updated by Andrey Kamaev over 12 years ago

  • Target version set to 2.4.2

#4
Updated by Vadim Pisarevsky over 12 years ago

thanks! it was obviously a bug in documentation: "single-column" and "single-row" should be exchanged. It was fixed in r8898

#5
Updated by Andrey Kamaev over 12 years ago

  • Status changed from Cancelled to Done

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