访问OpenCV CV_8UC1 cv :: Mat的元素

Question

I have a cv::Mat of type CV_8UC1 (8-bit single channel image) and I would like to access elements using the at<> operator as follows: image.at<char>(row, column) . However, when casting to int : (int) image.at<char>(row, column) , some values become negative, eg, 255 becomes -1.

This might be a stupid question, but I can't tell why this happens and what would be a better way to convert the entries to int .

Thanks in advance!

Answer 1

你必须指定元素是unsigned char ，介于0和255之间，否则它们将是char（签名），从-128到127.转换将是这样的：

(int) image.at<uchar>(row,column);

Answer 2

In the matrix type CV_8 UC 1 stands for Unsigned Char.

So, you have to write

image.at<unsigned char>(row, column)