I want to convert a float matrix to an unsigned char matrix with the same number of channels.
cv::Mat imgA(3, 3, CV_32FC(5));
// image is filled with something
cv::Mat imgB;
imgA.convertTo(imgB, CV_8UC(imgA.channels()));
How can the additional channels of a CV_8UC image be accessed? The following gives a segmentation fault.
std::cout << (int) imgB.at<uchar>(0,0,1) << "\n";
convertTo only changes the depth of the image, not the channels, so rather call it like:
imgA.convertTo(imgB, CV_8U);
if you need to access single pixels, you can add a new type for this:
typedef Vec<uchar,5> Vec5b;
for (int r=0; r<imgB.rows; r++) {
for (int c=0; c<imgB.cols; c++) {
Vec5b &pix = imgB.at<Vec5b>(r,c);
cout << int(pix[0]) << ","; // without the cast, cout would try to print ascii bytes ;(
cout << int(pix[1]) << ","
cout << int(pix[2]) << ","
cout << int(pix[3]) << ","
cout << int(pix[4]) << ";";
}
cout << endl;
}
but again, you also could simply print the whole Mat:
cout << imgB << endl;
Asked: 2016-12-28 05:03:03 -0600
Seen: 1,187 times
Last updated: Dec 28 '16