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pythonopencvimage-processing

Decompose Homography matrix in opencv python

H = K[R|t] where H (3*3) is homographic matrix, R is Rotation matrix, K is matrix of camera's intrinsic parameters and t is translation vector.

I have calculated K using chess board pattern as follows

ret, K, dist, rvecs, tvecs = cv2.calibrateCamera(objpoints, imgpoints, chess_gray.shape[::-1],None,None)

Homograpy matrix H is calculated as

pts_src = np.float32(pts_src)
pts_dst = np.float32(pts_dst)
H, status = cv2.findHomography(pts_src, pts_dst)

How to decompose R and t from H and K using

cv2.decomposeHomograpyMat(H,K,....)

How to write other inputs and outputs of above functions?

Solution

  • Assuming H as homography matrix and K as camera matrix the Python code is:

    num, Rs, Ts, Ns  = cv2.decomposeHomographyMat(H, K)

    num possible solutions will be returned.

    Rs contains a list of the rotation matrix.
    Ts contains a list of the translation vector.
    Ns contains a list of the normal vector of the plane.

    For further informations take a look into the official documentation:
    OpenCV 3.4 - decomposeHomographyMat()