- 從網址http://www.fftw.org/install/windows.html 上獲得FFTW的windows dll預編譯版本;
- 解壓縮文件,打開windows命令行窗口,就是那個cmd窗口。然後把當前目錄轉換到你解壓縮文件的目錄下。
- 執行以下3個指令
- 鏈接器 | 輸入 | 附加依賴項 加入libfftw3-3.lib,libfftw3f-3.lib,libfftw3l-3.lib
- libfftw3-3.dll,libfftw3f-3.dll,libfftw3l-3.dll放在當前工程目錄(或system32)或在vs屬性中的Debugging | Environment 中添加路徑(例:path=%path%;.\fftw\bin)
- 記得include“fftw3.h”
測試demo
#include "fftw3.h"
#include <stdio.h>
#define N 8
int main()
{
int i;
fftw_complex *din,*out;
fftw_plan p;
din = (fftw_complex*) fftw_malloc(sizeof(fftw_complex) * N);
out = (fftw_complex*) fftw_malloc(sizeof(fftw_complex) * N);
if((din==NULL)||(out==NULL))
{
printf("Error:insufficient available memory\n");
}
else
{
for(i=0; i<N; i++)/*測試數據*/
{
din[i][0] = i+1;
din[i][1] = 0;
}
}
p = fftw_plan_dft_1d(N, din, out, FFTW_FORWARD,FFTW_ESTIMATE);
fftw_execute(p); /* repeat as needed */
fftw_destroy_plan(p);
fftw_cleanup();
for(i=0;i<N;i++)/*OUTPUT*/
{
printf("%f,%fi\n",din[i][0],din[i][1]);
}
printf("\n");
for(i=0;i<N;i++)/*OUTPUT*/
{
printf("%f,%fi\n",out[i][0],out[i][1]);
}
if(din!=NULL) fftw_free(din);
if(out!=NULL) fftw_free(out);
getchar();
return 0;
}
結果輸出如下:
/* load original image */
IplImage *img_src = cvLoadImage("a.bmp", CV_LOAD_IMAGE_GRAYSCALE);
if (img_src == 0)
{
std::cout << "cannot load file" << std::endl;
return 0;
}
/* create new image for FFT & IFFT result */
IplImage *img_fft = cvCreateImage(cvSize(img_src->width, img_src->height), IPL_DEPTH_8U, 1);
IplImage *img_ifft = cvCreateImage(cvSize(img_src->width, img_src->height), IPL_DEPTH_8U, 1);
/* get image properties */
int width = img_src->width;
int height = img_src->height;
int step = img_src->widthStep;
uchar *img_src_data = (uchar *)img_src->imageData;
uchar *img_fft_data = (uchar *)img_fft->imageData;
uchar *img_ifft_data = (uchar *)img_ifft->imageData;
/* initialize arrays for fftw operations */
fftw_complex *data_in = (fftw_complex *)fftw_malloc(sizeof(fftw_complex) * width * height);
fftw_complex *fft = (fftw_complex *)fftw_malloc(sizeof(fftw_complex) * width * height);
fftw_complex *ifft = (fftw_complex *)fftw_malloc(sizeof(fftw_complex) * width * height);
/* create plans */
fftw_plan plan_f = fftw_plan_dft_2d(height, width, data_in, fft, FFTW_FORWARD, FFTW_ESTIMATE);
fftw_plan plan_b = fftw_plan_dft_2d(height, width, fft, ifft, FFTW_BACKWARD, FFTW_ESTIMATE);
int i, j, k;
/* load img_src's data to fftw input */
for (i = 0, k = 0; i < height; ++i)
{
for (j = 0; j < width; ++j)
{
// method 1: 輸入數據乘以(-1)^(i+j),即可中心化
data_in[k][0] = /*pow(-1, i + j) * */(double)img_src_data[i * step + j];
data_in[k][1] = 0.0;
k++;
}
}
/* perform FFT */
fftw_execute(plan_f);
/* perform IFFT */
fftw_execute(plan_b);
/* normalize FFT result */
double maxx = 0.0, minn = 10000000000.0;
for (i = 0; i < width * height; ++i)
{
fft[i][0] = log(sqrt(fft[i][0] * fft[i][0] + fft[i][1] * fft[i][1]));
maxx = fft[i][0] > maxx ? fft[i][0] : maxx;
minn = fft[i][0] < minn ? fft[i][0] : minn;
}
for (i = 0; i < width * height; ++i)
{
fft[i][0] = 255.0 * (fft[i][0] - minn) / (maxx - minn);
}
/* copy FFT result to img_fft's data */
int i0, j0;
for (i = 0, k = 0; i < height; ++i)
{
for (j = 0; j < width; ++j)
{
if (i < height / 2)
i0 = i + height / 2;
else
i0 = i - height / 2;
if (j < width / 2)
j0 = j + width / 2; // method 2
else
j0 = j - width / 2;
img_fft_data[i * step + j] = (uchar)fft[/*k++*/i0 * width + j0][0];
}
}
/* normalize IFFT result */
for (i = 0; i < width * height; ++i)
{
ifft[i][0] /= width * height;
}
/* copy IFFT result to img_ifft's data */
for (i = 0, k = 0; i < height; ++i)
{
for (j = 0; j < width; ++j)
{
img_ifft_data[i * step + j] = (uchar)ifft[k++][0];
}
}
/* display images */
cvNamedWindow("original_image", CV_WINDOW_AUTOSIZE);
cvNamedWindow("FFT", CV_WINDOW_AUTOSIZE);
cvNamedWindow("IFFT", CV_WINDOW_AUTOSIZE);
cvShowImage("original_image", img_src);
cvShowImage("FFT", img_fft);
cvShowImage("IFFT", img_ifft);
cvWaitKey(0);
/* free memory */
cvDestroyWindow("original_image");
cvDestroyWindow("FFT");
cvDestroyWindow("IFFT");
cvReleaseImage(&img_src);
cvReleaseImage(&img_fft);
cvReleaseImage(&img_ifft);
fftw_destroy_plan(plan_f);
fftw_destroy_plan(plan_b);
fftw_free(data_in);
fftw_free(fft);
fftw_free(ifft);