I have such code
Mat srcImage = imread("1.jpg", 0);
Mat planes[] = {Mat_<float>(srcImage), Mat::zeros(srcImage.size(), CV_32F)};
Mat complexI;
merge(planes, 2, complexI);
How to understand this Mat_<float>(srcImage)? I cannot search any useful information about it. Could help to understand it?
it's just a clever trick (maybe too clever, if it's hard to understand ...)
i guess, the context here is some dft analysis, which requires complex, float input.
normally, you would have to do:
Mat srcImage = imread("1.jpg", 0); // read the grayscale image. it's still uchar.
Mat realPart;
srcImage.convertTo(realPart, CV_32F); // manual conversion
Mat imPart = Mat::zeros(srcImage.size(), CV_32F);
Mat planes [] = { realPart, imPart };
merge(planes, 2, complexI);
the Mat_<float>(img) constructor does an internal, automatic conversion to float (it's a template object, it's type is determined at compile time, so it obviously cannot hold any other data type). it's a shortcut, saving some lines of code, simply.
those template Mat_'s also have some other, interesting properties:
since the type is already handled in the constructor, you no more need at<type> to access the elements, but can use a straightforward m(2,2)
then, it has an overloaded comma operator, so you can fill it like:
Mat_<float> T(3,3);
T << .2, .2, .4,
.1, .2, .1,
.2, .1, .3;
(which is quite useful for quickly setting up transformation Matrices, or filter kernels)
Asked: 2017-11-07 00:20:42 -0600
Seen: 523 times
Last updated: Nov 07 '17
