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mri_fft_complex.c File Reference
#include "mrilib.h"Go to the source code of this file.
Functions | |
| void | mri_fft_complex (int mode, float taper, MRI_IMAGE *im) |
| float * | mri_setup_taper (int nx, float taper) |
Function Documentation
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Definition at line 19 of file mri_fft_complex.c. References cfft2d(), free, complex::i, MRI_IMAGE::kind, malloc, mri_data_pointer(), MRI_FATAL_ERROR, MRI_IS_2D, mri_setup_taper(), MRI_IMAGE::nx, MRI_IMAGE::ny, and complex::r.
00020 {
00021 float *rbuf , *ibuf , *xtap , *ytap ;
00022 complex *cxim ;
00023 int ii , jj , npix , jbase , nx,ny ;
00024
00025 if( im->kind != MRI_complex ){
00026 fprintf( stderr , "mri_fft_complex only works on complex images!\n" ) ;
00027 MRI_FATAL_ERROR ;
00028 }
00029
00030 if( ! MRI_IS_2D(im) ){
00031 fprintf(stderr,"mri_fft_complex only works on 2D images!\n") ;
00032 MRI_FATAL_ERROR ;
00033 }
00034
00035 /*** set up buffers ***/
00036
00037 npix = im->nx * im->ny ; /* number of pixels */
00038 rbuf = (float *)malloc( sizeof(float) * npix ) ; /* real and imag buffs */
00039 ibuf = (float *)malloc( sizeof(float) * npix ) ;
00040 cxim = mri_data_pointer( im ) ; /* easy acces to im */
00041
00042 for( ii=0 ; ii < npix ; ii++ ){
00043 rbuf[ii] = cxim[ii].r ;
00044 ibuf[ii] = cxim[ii].i ;
00045 }
00046
00047 /*** taper buffers, if desired ***/
00048
00049 if( taper > 0.0 && taper <= 1.0 ){
00050 nx = im->nx ;
00051 ny = im->ny ;
00052 xtap = mri_setup_taper( nx , taper ) ;
00053
00054 /***
00055 printf( "taper" ) ;
00056 for( ii=0 ; ii < nx ; ii++ ){
00057 if( (ii%5) == 0 ) printf("\n") ;
00058 printf( "%12.4e " , xtap[ii] ) ;
00059 }
00060 printf("\n") ;
00061 ***/
00062
00063 if( nx == ny ) ytap = xtap ;
00064 else ytap = mri_setup_taper( ny , taper ) ;
00065
00066 for( jj=0 ; jj < ny ; jj++ ){
00067 jbase = jj * nx ;
00068 for( ii=0 ; ii < nx ; ii++ ){
00069 rbuf[ii] *= xtap[ii] * ytap[jj] ;
00070 ibuf[ii] *= xtap[ii] * ytap[jj] ;
00071 }
00072 }
00073 free( xtap ) ;
00074 if( ytap != xtap ) free(ytap) ;
00075 }
00076
00077 /*** FFT buffers and copy them back to original image ***/
00078
00079 cfft2d( mode , im->nx , im->ny , rbuf,ibuf ) ;
00080
00081 for( ii=0 ; ii < npix ; ii++ ){
00082 cxim[ii].r = rbuf[ii] ;
00083 cxim[ii].i = ibuf[ii] ;
00084 }
00085
00086 return ;
00087 }
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Definition at line 91 of file mri_fft_complex.c. References malloc. Referenced by main(), mri_fft_complex(), and ts_to_ftime().
00092 {
00093 register int ii ;
00094 int ntap ;
00095 float *tap ;
00096 float phi ;
00097
00098 tap = (float *)malloc( sizeof(float) * nx ) ; /* make array */
00099
00100 for( ii=0 ; ii < nx ; ii++ ) tap[ii] = 1.0 ; /* default 1's */
00101
00102 ntap = (int) (nx * 0.5 * taper ) ; /* # pts on each end */
00103
00104 if( ntap == 0 ){ /* special case of no points: taper is tiny */
00105 tap[0] = tap[nx-1] = 0.5 ;
00106 return tap ;
00107 }
00108
00109 phi = PI / ntap ;
00110 for( ii=0 ; ii < ntap ; ii++ ){
00111 tap[ii] = 0.5 - 0.5 * cos( ii*phi ) ;
00112 tap[nx-1-ii] = tap[ii] ;
00113 }
00114
00115 return tap ;
00116 }
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