CODEWITHSUNDEEP
opencvmatrix
aranga
aranga

Reputation: 377

How to calculate the Absolute value of complex numbers in opencv

can any one help me about how to get the absolute value of a complex matrix.the matrix contains real value in one channel and imaginary value in another one channel.please help me if s possible means give me some example.

Thanks in advance Arangarajan

Upvotes: 2

Views: 3069

Answers (2)

user6745682
user6745682

Reputation:

If you look in the OpenCV phasecorr.cpp module, there's a function called magSpectrums that does this already and will handle conjugate symmetry-packed DFT results too. I don't think it's exposed by the header file, but it's easy enough to copy it. If you care about speed, make sure you compile with any available SIMD options turned on too because they can make a big difference with this calculation.

Upvotes: 1

Eric
Eric

Reputation: 2341

Let's assume you have 2 components: X and Y, two matrices of the same size and type. In your case it can be real/im values.

// n rows, m cols, type float; we assume the following matrices are filled 
cv::Mat X(n,m,CV_32F); 
cv::Mat Y(n,m,CV_32F);

You can compute the absolute value of each complex number like this:

// create a new matrix for storage
cv::Mat A(n,m,CV_32F,cv::Scalar(0.0));
for(int i=0;i<n;i++){
  // pointer to row(i) values
  const float* rowi_x = X.ptr<float>(i);
  const float* rowi_y = Y.ptr<float>(i); 
  float* rowi_a = A.ptr<float>(i); 
  for(int j=0;j<=m;j++){ 
     rowi_a[j] = sqrt(rowi_x[j]*rowi_x[j]+rowi_y[j]*rowi_y[j]);
  }
}

Upvotes: 4

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