**Name**

**ridgrecpol** Get the polar frequency grid used to perform ridgelet decomposition

**Command Synopsis**

**ridgrecpol** [-I *input_im*] [-R *output_re*] [-C *output_im*] *input_re*

-Iinput_im: imaginary input of the 2D-FFT image

-Routput_re: real output (2D-FFT image in polar grid)

-Coutput_im: imaginary output (2D-FFT image in polar grid)

input_re: real input of the 2D-FFT image

**Function Summary**

void ridgrecpol (in_re , in_im , out_re , out_im )

Fimage in_re , in_im ;

Fimage out_re , out_im ;

**Description**

Recall that ridgelet transform is obtained as a wavelet transform in the Radon domain. To get the Radon transform, a 2D FFT is computed and the rectangular 2D-Fourier plane is interpolated on a polar grid that is, along lines going through the origin in the frequency plane.

The module `ridgrectpol` precisely performs this interpolation, using a
nearest-neighbor algorithm described in [SCD02].

**See Also**

**Version 1.0**

Last Modification date : Thu Apr 15 08:03:52 2004

**Author**

Guillaume Charpiat, Vincent Feuvrier