【OpenCV学习】DFT变换

【OpenCV学习】DFT变换

作者：gnuhpc 
出处：http://www.cnblogs.com/gnuhpc/

 #include "cv.h"
 #include "highgui.h"
 #include "cxcore.h"
 void cvShiftDFT(CvArr *src_arr,CvArr *dst_arr)
 {
     CvMat * tmp;
     CvMat q1stub,q2stub;
     CvMat q3stub,q4stub;
     CvMat d1stub,d2stub;
     CvMat d3stub,d4stub;
     CvMat *q1,*q2,*q3,*q4;
     CvMat *d1,*d2,*d3,*d4;
     CvSize size = cvGetSize(src_arr);
     CvSize dst_size = cvGetSize(dst_arr);
     int cx,cy;
     if ((dst_size.width!= size.width)||(dst_size.height!=size.height))
     {
         cvError(CV_StsUnmatchedSizes,"cvShiftDFT",
             "Source and Destination arrays must have the same sizes",
             __FILE__,__LINE__);
     }
     if (src_arr == dst_arr)
     {
         tmp = cvCreateMat(size.height/2,size.width/2,cvGetElemType(src_arr));
     }
     cx=size.width/2;//取出图像的原点
     cy=size.height/2;
     q1=cvGetSubRect(src_arr,&q1stub,cvRect(0,0,cx,cy));
     //取出图像的第一象限，由q1指针指向它
     q2=cvGetSubRect(src_arr,&q2stub,cvRect(cx,0,cx,cy));
     //取出图像的第二象限，由q2指针指向它
     q3=cvGetSubRect(src_arr,&q3stub,cvRect(cx,cy,cx,cy));
     //取出图像的第三象限，由q3指针指向它
     q4=cvGetSubRect(src_arr,&q4stub,cvRect(0,cy,cx,cy));
     //取出图像的第四象限，由q4指针指向它

     d1=cvGetSubRect(src_arr,&d1stub,cvRect(0,0,cx,cy));
     d2=cvGetSubRect(src_arr,&d2stub,cvRect(cx,0,cx,cy));
     d3=cvGetSubRect(src_arr,&d3stub,cvRect(cy,cy,cx,cy));
     d4=cvGetSubRect(src_arr,&d4stub,cvRect(0,cy,cx,cy));
     if (src_arr!=dst_arr)
     {
         if (!CV_ARE_TYPES_EQ(q1,d1))
         {
             cvError(CV_StsUnmatchedSizes,"cvShiftDFT",
                 "Source and Destination arrays must have the same sizes",
                 __FILE__,__LINE__);
         }
         //以图像中心为原点，调整傅里叶变换图像的四个象限区，
         //即第一与第三象限交换，第二与第四象限交换
         cvCopy(q3,d1,0);
         cvCopy(q4,d2,0);
         cvCopy(q1,d3,0);
         cvCopy(q2,d4,0);
     }
     else
     {//若源矩阵和目的矩阵相同则直接在源矩阵中进行操作
         cvCopy(q3,tmp,0);
         cvCopy(q1,q3,0);
         cvCopy(tmp,q1,0);
         cvCopy(q4,tmp,0);
         cvCopy(q2,q4,0);
         cvCopy(tmp,q2,0);
     }
 }
 int main(int argc,char ** argv)
 {
     const char* filename =(argc>=2?argv[1]:"lena.jpg");
     IplImage *im;
     IplImage *realInput,*imaginaryInput,*complexInput;
     IplImage *image_Re,*image_Im;
     int dft_M,dft_N;
     CvMat *dft_A;
     CvMat tmp;
     double m,M;
     im = cvLoadImage(filename, CV_LOAD_IMAGE_GRAYSCALE  );//加载图像
     if (!im)
     {
         return -1;
     }
     //分配空间
     realInput = cvCreateImage(cvGetSize(im),IPL_DEPTH_64F,1);//单通道
     imaginaryInput =cvCreateImage(cvGetSize(im),IPL_DEPTH_64F,1);//单通道
     complexInput = cvCreateImage(cvGetSize(im),IPL_DEPTH_64F,2);//双通道
     cvScale(im,realInput,1.0,0.0);
     //#define cvScale cvConvertScale=>readInput=im
     cvZero(imaginaryInput);
     //清空这个图像的内容
     cvMerge(realInput,imaginaryInput,NULL,NULL,complexInput);
     //混合这两个图像作为complexInput的两个通道
     /*得到最优DFT尺寸 */
     dft_M = cvGetOptimalDFTSize(im->height-1);
     dft_N = cvGetOptimalDFTSize(im->width-1);

     dft_A = cvCreateMat(dft_M,dft_N,CV_64FC2);
     image_Re = cvCreateImage(cvSize(dft_N,dft_M),IPL_DEPTH_64F,1);//实部
     image_Im = cvCreateImage(cvSize(dft_N,dft_M),IPL_DEPTH_64F,1);//虚部
     cvGetSubRect(dft_A,&tmp,cvRect(0,0,im->width,im->height));
     cvCopy(complexInput,&tmp,NULL);
     if( dft_A->cols > im->width )//若得到的最优DFT尺寸在宽度上大于原图，则重新取
     {
         cvGetSubRect(dft_A,&tmp,cvRect(im->width,0,dft_A->cols-im->width,im->height));
         cvZero(&tmp);
     }
     cvDFT(dft_A,dft_A,CV_DXT_FORWARD,complexInput->height);

     cvNamedWindow("win",0);
     cvNamedWindow("magnitude",0);
     cvShowImage("win",im);

     //分割出实部和虚部
     cvSplit(dft_A,image_Re,image_Im,0,0);

     //计算功率谱 Mag=sqrt(Re^2+Im^2)
     cvPow(image_Re,image_Re,2.0);
     cvPow(image_Im,image_Im,2.0);
     cvAdd(image_Re,image_Im,image_Re,NULL);//image_Re<=image_Re+image_Im
     cvPow(image_Re,image_Re,0.5);
     //计算log(1+Mag)
     cvAddS(image_Re,cvScalarAll(1.0),image_Re,NULL);
     cvLog(image_Re,image_Re);
     cvShiftDFT(image_Re,image_Re);
     cvMinMaxLoc(image_Re,&m,&M,NULL,NULL,NULL);
     cvScale(image_Re,image_Re,1.0/(M-m),1.0*(-m)/(M-m));
     cvShowImage("magnitude",image_Re);
     cvWaitKey(-1);
     return 0;
 }