how to check whether two matrices are identical in OpenCV

Question

I have two instances of cv::Mat : m1 and m2. They are of the same numeric type and sizes. Is there any function in OpenCV that returns whether the matrices are identical (ha

Answer 1

As mentioned by Acme and Tim, you can use cv::compare. This is the code I use to compare my cv::Mat:

 bool matIsEqual(const cv::Mat mat1, const cv::Mat mat2){
    // treat two empty mat as identical as well
    if (mat1.empty() && mat2.empty()) {
        return true;
    }
    // if dimensionality of two mat is not identical, these two mat is not identical
    if (mat1.cols != mat2.cols || mat1.rows != mat2.rows || mat1.dims != mat2.dims) {
        return false;
    }
    cv::Mat diff;
    cv::compare(mat1, mat2, diff, cv::CMP_NE);
    int nz = cv::countNonZero(diff);
    return nz==0;
}

It is important to stand out that the function cv::countNonZero only works with cv::Mat of one channel, so if you need to compare two cv::Mat images, you need first to convert your cv::Mat in this way:

Mat gray1, gray2;
cvtColor(InputMat1, gray1, CV_BGR2GRAY);
cvtColor(InputMat2, gray2, CV_BGR2GRAY);

where InputMat1 and InputMat2 are the cv::Mat you want to compare. After that you can call the function:

bool equal = matsEqual(gray1, gray2);

I took this code of this site: OpenCV: compare whether two Mat is identical

I hope this help you.