How to use mean.binaryproto with blobFromImage(s) ?

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I’m using dnn::readNetFromCaffe to load this model published in the caffe model zoo:

https://github.com/BVLC/caffe/wiki/Mo...

Apart from the standard .prototxt and .caffemodel files, a third file is provided: mean.binaryproto.

I know I should use it to perform the mean subtraction. But I couldn't figure out whether its a cv::subtract I should apply before invoking blobFromImage or is it something I'd use to somehow infer the mean and scalefactor parameters.

Mat mean = readMeanFromBinary(); // How to read a binaryproto into a Mat ?
Mat img = imread(imgFile);
// How to use mean ?
Mat inputBlob = blobFromImage(img, 1.0f, Size(227, 227), Scalar(), false);
net.setInput(inputBlob, "data");
Mat prob = age.forward("prob");

So I have basically two questions:

• How to read the mean.binaryproto file into a Mat ?
• Once I have the mean, can I use it with blobFromImage ?

thanks Fábio