OpenCV: how to rotate IplImage?

Question

I need to rotate an image by very small angle, like 1-5 degrees. Does OpenCV provide simple way of doing that? From reading docs i can assume that getAffineTransform() should be involved, but there is no direct example of doing something like:

IplImage *rotateImage( IplImage *source, double angle);

Answer 1

Check my answer to a similar problem:

http://stackoverflow.com/questions/2278414/rotating-an-image-in-c-c/2278430#2278430

Essentially, use cvWarpAffine - I've described how to get the 2x3 transformation matrix from the angle in my previous answer.

Answer 2

If you use OpenCV 2.0 it is as easy as

using namespace cv;

Mat rotateImage(const Mat& source, double angle)
{
    Point2f src_center(source.cols/2.0F, source.rows/2.0F);
    Mat rot_mat = getRotationMatrix2D(src_center, angle, 1.0);
    Mat dst;
    warpAffine(source, dst, rot_mat, source.size());
    return dst;
}

Note: angle is in degrees, not radians.

See the C++ interface documentation for more details and adapt as you need:

• getRotationMatrix
• warpAffine