Sine or Cosine of every element in Mat (c++)

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How precise do you need it?

You can get within a few percent with a third order polynomial. You need to:

1) transfer all matrix values to the range -pi/2 to pi/2 by adding whole multiples of pi. (I assume matrix values are in radians, if they are in degrees multiply by pi/180).

2) calculate Sin(x)=x-(x^3)/6

3) for Cosine calculate Sin(pi/2-x)

if you want better precision you can use higher order polynomials: sin(x) is exactly the infinite polynomial x-(x^3/3!)+(x^5/5!)-(x^7/7!) +.... (look up "Taylor series" for more info) but the accuracy increases pretty fast as you add terms.

I have not tried it, but I guarantee that this would be faster than an element by element sin function (which is probably implemented by a polynomial approximation anyway).

guy

This should be the fastest way of retrieving Mat elements

Size contSize = mat.size();
if (mat.isContinous())
{
    contSize.width *= contSize.height;
    contSize.height = 1;
}
for (int i = 0; i < contSize.height; ++i)
{
    T* ptr = mat.ptr<T>(y);
    for (int j = 0; j < contSize.width; ++j)
    {
        ptr[j] = ...;
    }
}

according to one of the core developers of OpenCV posted in this topic. Then inside the loop, do apply a sine or cosine on the value based on standard C++ functionality.

I haven't found such a function in the API, so I guess you need to loop over the Matrix yourself.