How can I convert an image into a 1d vector in c++?

edit

• you probably want to convert to grayscale, when reading: cv::imread(fileName, cv::IMREAD_GRAYSCALE)

• imread() returns uchar images, you cannot just cast it to float and expect to get the pointer arithm right. also, try to avoid messing with internal datastart,dataend members.

• why do you think, you need a std::vector<float> ? opencv's ml algorithms work on cv::Mat
• Mat flat = img.reshape(1,1); is probably, what you want. maybe you need a convertTo(CV_32F), too.

May be like this :

Mat mg = Mat::zeros(40,2,CV_32FC1);
cout << mg.size() << "\n";

std::vector<float> array;
if (mg.isContinuous())
{
array.assign((float*)mg.ptr(0),(float*)(mg.ptr(mg.rows-1))+mg.cols);
cout <<array.size()<<"\n";
}

@berak: I created the whole neural networks library, its not vectorized yet and I am experimenting the differences, thats why I am not allowed to use opencvs ml algorithms at the moment. By the way doing : cv::Mat mat = cv::imread(fileName, cv::IMREAD_GRAYSCALE);

mat.convertTo(mat,CV_32F);

std::vector<float> array(mat.data);

fails as well, complains about the conversion from uchar* to const std::allocator<_Ty>&.