openpiv_cxx.windef.multipass_img_deform

openpiv_cxx.windef.multipass_img_deform(frame_a, frame_b, x_old, y_old, u_old, v_old, window_size, overlap, correlation_method='circular', deformation_method='symmetric', deformation_algorithm='taylor expansions', order=1, radius=2)

PIV with image deformation

Multi pass of the PIV evaluation. This function does the PIV evaluation of the second and other passes. It returns the coordinates of the interrogation window centres, the displacement u, v for each interrogation window as well as the signal to noise ratio array.

Parameters:

  • frame_a (ndarray) – A two dimensional array of integers containing grey levels of the first frame.

  • frame_b (ndarray) – A two dimensional array of integers containing grey levels of the second frame.

  • window_size (ints) – The size of the interrogation window.

  • overlap (ints) – The overlap of the interrogation window, e.g. window_size/2.

  • x_old (ndarray) – The x coordinates of the vector field of the previous pass.

  • y_old (ndarray) – The y coordinates of the vector field of the previous pass.

  • u_old (ndarray) – The u displacement of the vector field of the previous pass in case of the image mask - u_old and v_old are MaskedArrays.

  • v_old (ndarray) – The v displacement of the vector field of the previous pass.

  • correlation_method (str) – Type of correlation to use where linear is zero padded to 2N*2M (must remain power of 2 unless FFTW is used).

  • deformation_algorithm (str) – Type of deformation to use.

  • deformation_method (str) – Order/type of deformation to use.

  • order (scalar) – The order of the Taylor expansions interpolation kernel.

  • radius (scalar) – The radius of the Whittaker-Shannon interpolation kernel.

Returns:

  • x, y (ndarray) – Array containg the x coordinates of the interrogation window centres.

  • u, v (ndarray) – Array containing the u/v displacement for every interrogation window.

  • s2n (ndarray) – Array consisting of signal to noise ratio values.