CODEWITHSUNDEEP
c++opencvmatrix
John bracciano
John bracciano

Reputation: 81

OpenCV: Accessing elements of 5D Matrix

I have a problem accessing elements of a 5D Matrix in OpenCV. I create my Matrix using

int sizes[5] = { height_, width_, range_, range_, range_ };
Mat w_i_ = Mat(2 + channels, sizes, CV_16UC(channels), Scalar(0));

where channels = 3. Then I'm trying to access and modify the matrix elements using for loops:

for (UINT Y = 0; Y < height; ++Y) {
    for (UINT X = 0; X < width; ++X) {

        // a) Compute the homogeneous vector (wi,w)
        Vec3b wi = image.at<Vec3b>(Y, X);

        // b) Compute the downsampled coordinates
        UINT y = round(Y / sigmaSpatial);
        UINT x = round(X / sigmaSpatial);
        Vec3b zeta = round( (image.at<Vec3b>(Y, X) - min) / sigmaRange);
                       // round() here is overloaded for vectors

        // c) Update the downsampled S×R space
        int idx[5] = { y, x, zeta[0], zeta[1], zeta[2] };
        w_i_.at<Vec3b>(idx) = wi;
    }
}

I am getting an assertion failed error produced by Mat::at() when I run the code. Specifically the message I get is:

OpenCV Error: Assertion failed (elemSize() == (((((DataType<_Tp>::type) & ((512 - 1) << 3)) >> 3) + 1) << ((((sizeof(size_t)/4+1)*16384|0x3a50) >> ((DataType<_Tp>::type) & ((1 << 3) - 1))*2) & 3))) in cv::Mat::at, file c:\opencv\build\include\opencv2\core\mat.inl.hpp, line 1003

I have searched the web but I can't seem to find any topics on 5D Matrices (similar topics proved of no help).

Thanks in advance

Upvotes: 1

Views: 266

Answers (1)

Viktor Latypov
Viktor Latypov

Reputation: 14467

You initialize the zeta variable and do not check its values. Most likely you get an out-of-range value for zeta[0], zeta[1] and zeta[2] indices and thus the internal range checking in at() function fails.

To prevent such crashes at least add some manual range checking before calling at():

for(int i = 0 ; i < 3 ; i++)
   if(zeta[i] < 0 || zeta[i] >= _range)
      continue;

Upvotes: 0

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