So I'm trying to place an image into a scene using opencv. I can rotate it about its centre (z axis) using GetRotationMatrix2d and warpaffine. I'm wondering to I need to use a perspective transform? Or can I just create a 3d rotation matrix and plug it into warpaffine? And is there any getRotationMatrix equivalent for 3d? Thanks!
Edit: I found this post but it does not work for me.
My code is below And I have gotten it to rotate, although I'm not sure what focal length I should be using? everytime I rotate about a different angle I need to play around with the focal length to get it right. Say if I rotate my image 45' it looks like the pic below but that's clearly warped off in some way...
void rotateImage(const Mat &input, Mat &output, double alpha, double beta, double gamma, double dx, double dy, double dz, double f)
{
alpha = (alpha - 90.)*CV_PI/180.;
beta = (beta - 90.)*CV_PI/180.;
gamma = (gamma - 90.)*CV_PI/180.;
// get width and height for ease of use in matrices
double w = (double)input.cols;
double h = (double)input.rows;
// Projection 2D -> 3D matrix
Mat A1 = (Mat_<double>(4,3) <<
1, 0, -w/2,
0, 1, -h/2,
0, 0, 0,
0, 0, 1);
// Rotation matrices around the X, Y, and Z axis
Mat RX = (Mat_<double>(4, 4) <<
1, 0, 0, 0,
0, cos(alpha), -sin(alpha), 0,
0, sin(alpha), cos(alpha), 0,
0, 0, 0, 1);
Mat RY = (Mat_<double>(4, 4) <<
cos(beta), 0, -sin(beta), 0,
0, 1, 0, 0,
sin(beta), 0, cos(beta), 0,
0, 0, 0, 1);
Mat RZ = (Mat_<double>(4, 4) <<
cos(gamma), -sin(gamma), 0, 0,
sin(gamma), cos(gamma), 0, 0,
0, 0, 1, 0,
0, 0, 0, 1);
// Composed rotation matrix with (RX, RY, RZ)
Mat R = RX * RY * RZ;
// Translation matrix
Mat T = (Mat_<double>(4, 4) <<
1, 0, 0, dx,
0, 1, 0, dy,
0, 0, 1, dz,
0, 0, 0, 1);
// 3D -> 2D matrix
Mat A2 = (Mat_<double>(3,4) <<
f, 0, w/2, 0,
0, f, h/2, 0,
0, 0, 1, 0);
// Final transformation matrix
Mat trans = A2 * (T * (R * A1));
// Apply matrix transformation
warpPerspective(input, output, trans, input.size(), INTER_LANCZOS4);
}
