C ++ Opencv-对mat的任何更改，也要更改用于初始化mat的向量

Question

I have a vector data and I create a cv::mat :

cv::Mat HNorm(this->data.size(), 1, CV_32FC1, this->data.data());

Then I normalize HNorm 's values:

normalize(HNorm, HNorm, 0, 300, cv::NORM_MINMAX, -1, cv::Mat());

The thing is that the same normalization happens to data vector. What I want is to be able to work with HNorm without affecting data .

Answer 1

The particular constructor you use does not copy the data. It is designed this way for efficiency reasons. This basically just creates the Mat headers and changes the internal pointer to point to the supplied data array. If you want to not change the underlying data in subsequent operations without affecting the input data array, you need to copy it.

You could clone the Mat object and this will copy the underlying data. See the docs here:

http://docs.opencv.org/master/d3/d63/classcv_1_1Mat.html#ad1c9cc37d66c4e5bd05fae36f62d1cb4

So something like:

cv::Mat HNorm(this->data.size(), 1, CV_32FC1, this->data.data());
cv::Mat cloned = HNorm.clone();

// work on the cloned object now