Calculate Rotation Parameter

[Akshara.T.G]

I am having two images. One is base image and other is rotated version (in clockwise or anti clockwise) of the first image.
I want to calculate the rotation angle of the second image with respect to first image.

[Andrey_Dmitriev]

You can use Fourier-Mellin transform for recovering angle.
See link below for starting point.

www.cs.brown.edu/people/morgan/papers/ (McGuire98)RecoveringRotationTranslationAndScale.ppt

[BruceAmmons]

I see a couple of possibilities.

If the center of rotation is known, you can extract a circle of pixels around the center in each image. Using FFT analysis, you can use correlation to determine the shift between the two sets of pixels, which will give you the angle of rotation.

Another possibility is to select a portion of the original image and use pattern matching to locate it in the second image. This will give you the rotation within a fraction of a degree if you set up the parameters correctly.

Bruce

[gregstoll]

Akshara -

I think the IMAQ Rotation Detect VI should do what you want.

Greg Stoll
IMAQ R&D
National Instruments