Assign array to initialized Mat object in OpenCV C++

Question

I'm working with OpenCV (3.3.1) in C++. I have an initialized Mat object and an array

Mat mat(2, 3, CV_32F, Scalar::all(0.5));
float arr[6] = {1,2,3,4,5,6};

I would like to assign the data from the array to the Mat object after the latter has been initialized. How can one do this efficiently?

I know that I can initialize the Mat object with the array using Mat mat(2, 3, CV_32F, arr); but I want to do the assignment after the initialization.

Humam Helfawi · Accepted Answer · 2017-11-30 21:01:47Z

2

One option could be:

std::memcpy(mat.data, arr, mat.rows*mat.cols*sizeof(float));

Another option (maybe no suitable for you since maybe you need to keep some part of the old header):

mat = Mat(2, 3, CV_32F, arr)

answered Nov 30, 2017 at 21:01

Humam Helfawi

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3 Comments

Daniel P Over a year ago

The first method looks good, but is it the most efficient way even when working with large arrays?

Humam Helfawi Over a year ago

@DanielP I am not sure. However, if you do not really need to copy the data, you should try to change your design and accept the array in the initializing stage. Show us your original problem, someone could find you a better solution

Daniel P Over a year ago

Yes, if I didn't need to copy the data, the second option you mentioned would work. For copying the first option seems to work well! Thank you!

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