Write cv::Mat to binary files? [duplicate]

Question

I am using openCV and I have a 95,1 mat object of type CV_32F, which I would like to write to a binary file. I am using the code below however I cannot cast a 32F to an char type. Are there any suggestions? I also want to perform the reverse procedure of reading a binary file and storing the values into a mat object of the same type.

try{
    ofstream posBinary;
    posBinary.open("C:/Users/Dr.Mollica/Documents/TSR Datasets/signDatabasePublicFramesOnly/posSamps.bin", ios::out | ios::binary);
    posBinary.write((char *)featureVector, sizeof(featureVector);
}
catch (exception X){ cout << "Error! Could not write Binary file" << endl; }

Also to note, the reason I want to do it in a binary file is I will be writing a large number of these vectors to the file which will be read in to a machine learning algorithm. And from my understanding reading and writing to a binary file is the fastest way possible.

Answer 1

I recommend you to use OpenCV APIs to write cv::Mat to xml or yml files, which you can later read the cv::Mat back from them easily.

For example:

cv::Mat yourMatData;

// write Mat to file
cv::FileStorage fs("file.yml", cv::FileStorage::WRITE);
fs << "yourMat" << yourMatData;

// read Mat from file
cv::FileStorage fs2("file.yml", FileStorage::READ);
fs2["yourMat"] >> yourMatData;

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Updated: If you prefer to write/read them to/from binary files, you can first convert cv::Mat to array/vector. And then write the array/vector to files.

To read on, check out Convert Mat to Array/Vector in OpenCV.