Compute the affine transformation parameters from a homogeneous 2D transformation matrix.

hom_mat2d_to_affine_par computes the affine transformation parameters corresponding to the homogeneous 2D transformation matrix HomMat2D. The parameters Sx and Sy determine how the transformation scales the original x- and y-axes, respectively. The two scaling factors are always positive. The angle Theta determines how the transformed coordinate axes deviate from orthogonality. For Theta = 0, the two coordinate axes are orthogonal. If Theta > pi/2 the transformation contains a reflection. The angle Phi determines the rotation of the transformed x-axis with respect to the original x-axis. The parameters Tx and Ty determine the translation of the two coordinate systems. The Matrix HomMat2D can be constructed from the six transformation parameters by the following operator sequence:

  hom_mat2d_identity (HomMat2DIdentity)
  hom_mat2d_scale (HomMat2DIdentity, Sx, Sy, 0, 0, HomMat2DScale)
  hom_mat2d_slant (HomMat2DScale, Theta, 'y', 0, 0, HomMat2DSlant)
  hom_mat2d_rotate (HomMat2DSlant, Phi, 0, 0, HomMat2DRotate)
  hom_mat2d_translate (HomMat2DRotate, Tx, Ty, HomMat2D)

If the matrix HomMat2D is non-degenerate, hom_mat2d_to_affine_par returns 2 (H_MSG_TRUE). Otherwise, an exception is raised.

vector_to_hom_mat2d, vector_to_rigid, vector_to_similarity

hom_mat2d_identity, hom_mat2d_translate, hom_mat2d_scale, hom_mat2d_rotate, hom_mat2d_slant

Basic operators