Fast Fourier Transformation

Functions

cpl_image * omega_gen_lowpass (int xs, int ys, double sigma_x, double sigma_y)
 Generate a low pass filter for FFT convolution .
cpl_image * omega_get_spatial_freq (cpl_image *flat, cpl_mask *bpm, double gausfilt, int mirrorx, int mirrory)
 Get low spatial frequency componenets from the flat field using the FFTW.
cpl_image * omega_mirror_edges (cpl_image *image, int dx, int dy)
 expand image by mirroring edges

Detailed Description

This module provides functions to do fast fourier transformations

Synopsis:
Functions to deal with fast fourier transformations
 #include "omega_bpm.h"
 #include "omega_utils.h"

Function Documentation

cpl_image* omega_gen_lowpass ( int  xs,
int  ys,
double  sigma_x,
double  sigma_y 
)

Generate a low pass filter for FFT convolution .

Parameters:
xs x size of the generated image.
ys y size of the generated image.
sigma_x Sigma for the gaussian distribution.
sigma_y Sigma for the gaussian distribution.
Returns:
1 newly allocated image.

This function generates an image of a 2d gaussian, modified in such a way that the different quadrants have a quadrants of the gaussian in the corner. This image is suitable for FFT convolution. Copied from eclipse, src/iproc/generate.c

The returned image must be deallocated.

Definition at line 84 of file omega_fftw.c.

Referenced by omega_get_spatial_freq().

cpl_image* omega_get_spatial_freq ( cpl_image *  flat,
cpl_mask *  bpm,
double  gausfilt,
int  mirrorx,
int  mirrory 
)

Get low spatial frequency componenets from the flat field using the FFTW.

Function to calculate the low spatial frequency

Parameters:
flat twilight or dome flat
bpm optonal bad pixels image
gausfilt Gaussian Fourier filter size
mirrorx for mirroring edges (ocfft continuity)
mirrory for mirroring edges (ocfft continuity)
medfilt for cleaning bad pixels
Returns:
1 newly allocated image.

Definition at line 171 of file omega_fftw.c.

References omega_gen_lowpass(), and omega_mirror_edges().

Referenced by omega_make_mflat().

cpl_image * omega_mirror_edges ( cpl_image *  image,
int  dx,
int  dy 
)

expand image by mirroring edges

Parameters:
image_in Image.
x_size the number of pixels in x to expand
y_size the number of pixels in y to expand

Definition at line 266 of file omega_fftw.c.

Referenced by omega_get_spatial_freq().


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