How to add 2 Mat objects of different type?

edit

I think it impossible using + operator. You can:

• Use convert to float

 
const Mat A( 10, 20, CV_32FC1, Scalar::all(CV_PI) );
const Mat B( A.size(), CV_8UC1, Scalar::all(10) );
Mat E(A.size(), A.type());
B.convertTo(E, CV_32FC1);
Mat C( A.size(), A.type() );
C = E+A;

• Per-element sum

const Mat A( 10, 20, CV_32FC1, Scalar::all(CV_PI) );
const Mat B( A.size(), CV_8UC1, Scalar::all(10) );
Mat C(A.size(), A.type());
for (int i = 0; i < A.rows; i++)
{
    for (int j = 0; j < A.cols; j++)
    {
        C.at<float>(i,j) = A.at<float>(i,j)+B.at<uchar>(i,j);
    }
}

or

const Mat A( 10, 20, CV_32FC1, Scalar::all(CV_PI) );
const Mat B( A.size(), CV_8UC1, Scalar::all(10) );
Mat C(A.size(), A.type());
for (int i = 0; i < A.rows; i++)
{
    const float* Aptr = reinterpret_cast< const float*>(A.ptr(i));
    const uchar* Bptr = reinterpret_cast< const uchar*>(B.ptr(i));
    float* Cptr = reinterpret_cast< float*>(C.ptr(i));
    for (int j = 0; j < A.cols; j++)
    {
        Cptr[j] = Aptr[j]+Bptr[j];
    }
}