OpenCV cvDFT 傅里叶变换

【原文：http://blog.csdn.net/u013777833/article/details/19926191】

 #include<cv.h>
 #include<highgui.h>
 #include<stdio.h>

 void fft2shift(IplImage *src, IplImage *dst)
 {
     IplImage *image_Re = 0, *image_Im = 0;
     int nRow, nCol, i, j, cy, cx;
     double scale, shift, tmp13, tmp24;
     image_Re = cvCreateImage(cvGetSize(src), IPL_DEPTH_64F, 1);
     //Imaginary part
     image_Im = cvCreateImage(cvGetSize(src), IPL_DEPTH_64F, 1);
     cvSplit( src, image_Re, image_Im, 0, 0 );
     //具体原理见冈萨雷斯数字图像处理p123
     // Compute the magnitude of the spectrum Mag = sqrt(Re^2 + Im^2)
     //计算傅里叶谱
     cvPow( image_Re, image_Re, 2.0);
     cvPow( image_Im, image_Im, 2.0);
     cvAdd( image_Re, image_Im, image_Re);
     cvPow( image_Re, image_Re, 0.5 );
     //对数变换以增强灰度级细节(这种变换使以窄带低灰度输入图像值映射
     //一宽带输出值，具体可见冈萨雷斯数字图像处理p62)
     // Compute log(1 + Mag);
     cvAddS( image_Re, cvScalar(1.0), image_Re ); // 1 + Mag
     cvLog( image_Re, image_Re ); // log(1 + Mag)

     //Rearrange the quadrants of Fourier image so that the origin is at the image center
     nRow = src->height;
     nCol = src->width;
     cy = nRow/2; // image center
     cx = nCol/2;
     //CV_IMAGE_ELEM为OpenCV定义的宏，用来读取图像的像素值，这一部分就是进行中心变换
     for( j = 0; j < cy; j++ ){
         for( i = 0; i < cx; i++ ){
             //中心化，将整体份成四块进行对角交换
             tmp13 = CV_IMAGE_ELEM( image_Re, double, j, i);
             CV_IMAGE_ELEM( image_Re, double, j, i) = CV_IMAGE_ELEM(
                 image_Re, double, j+cy, i+cx);
             CV_IMAGE_ELEM( image_Re, double, j+cy, i+cx) = tmp13;

             tmp24 = CV_IMAGE_ELEM( image_Re, double, j, i+cx);
             CV_IMAGE_ELEM( image_Re, double, j, i+cx) =
                 CV_IMAGE_ELEM( image_Re, double, j+cy, i);
             CV_IMAGE_ELEM( image_Re, double, j+cy, i) = tmp24;
         }
     }
     //归一化处理将矩阵的元素值归一为[0,255]
     //[(f(x,y)-minVal)/(maxVal-minVal)]*255
     double minVal = 0, maxVal = 0;
     // Localize minimum and maximum values
     cvMinMaxLoc( image_Re, &minVal, &maxVal );
     // Normalize image (0 - 255) to be observed as an u8 image
     scale = 255/(maxVal - minVal);
     shift = -minVal * scale;
     cvConvertScale(image_Re, dst, scale, shift);
     cvReleaseImage(&image_Re);
     cvReleaseImage(&image_Im);
 }
 int main(int argc, char* argv[])
 {
     IplImage *src ,*dst,*Invdst,*temp,*Im = 0,*Re,*FourierImage;

     temp = cvLoadImage("C:\\Users\\Lonely\\Desktop\\lena.jpg",0);
     //显示原图像
     cvNamedWindow("待变换图像",0);
     cvShowImage("待变换图像",temp);
     dst = cvCreateImage(cvGetSize(temp),temp->depth,1);
     FourierImage = cvCreateImage(cvGetSize(temp),temp->depth,1);
     Invdst = cvCreateImage(cvGetSize(temp),temp->depth,1);
     src = cvCreateImage(cvGetSize(temp),IPL_DEPTH_64F,2);
     Im = cvCreateImage(cvGetSize(temp),IPL_DEPTH_64F,1);
     Re = cvCreateImage(cvGetSize(temp),IPL_DEPTH_64F,1);

     //利用cvConcertScale转换数据类型
     cvConvertScale(temp,Re);
     //复数通道的灰度值设为0
     cvZero(Im);
     //傅里叶变换在复数域，在opencv中表示为二通道

     cvMerge(Re,Im,NULL,NULL,src);
     IplImage *Fourier = cvCreateImage(cvGetSize(temp),IPL_DEPTH_64F,2);
     IplImage *InvFourier = cvCreateImage(cvGetSize(temp),IPL_DEPTH_64F,2);

     //傅里叶变换
     cvDFT(src,Fourier,CV_DXT_FORWARD);
     cvDFT(Fourier,InvFourier,CV_DXT_INV_SCALE);
     cvSplit(Fourier,Re,Im,NULL,NULL);
     //利用cvConcertScale转换数据类型
     cvConvertScale(Re,dst);


     //显示傅里叶变换图像
     cvNamedWindow("傅里叶变换图像",0);
     cvShowImage("傅里叶变换图像",dst);

    //中心化
     fft2shift(Fourier,FourierImage);
     cvNamedWindow("中心化傅里叶变换图像",0);
     cvShowImage("中心化傅里叶变换图像",FourierImage);

     cvSplit(InvFourier,Re,Im,NULL,NULL);
     //利用cvConcertScale转换数据类型
     cvConvertScale(Re,Invdst);

     //显示傅里叶逆变换图像
     cvNamedWindow("傅里叶逆变换图像",0);
     cvShowImage("傅里叶逆变换图像",Invdst);

     cvWaitKey(0);

     //释放内存
     cvReleaseImage(&src);
     cvReleaseImage(&dst);
     cvReleaseImage(&Invdst);
     cvReleaseImage(&temp);
     cvReleaseImage(&Im);
     cvReleaseImage(&Re);
     cvReleaseImage(&Fourier);
     cvReleaseImage(&InvFourier);

     cvDestroyAllWindows();



 }

fft2shift来自http://blog.csdn.net/abcjennifer/article/details/7359952

结果：

OpenCV版本：2.4.4

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