Butterworth filter

最新推荐文章于 2024-10-28 08:43:18 发布

super_zw

最新推荐文章于 2024-10-28 08:43:18 发布

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文章标签： filter im matrix function image dst

本文介绍了一种使用Butterworth滤波器进行图像处理的方法，包括低通和高通滤波器的设计与应用。通过对图像进行灰度转换、傅立叶变换及其逆变换等步骤，实现了对图像中特定频率成分的增强或抑制。

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Butterworth filter

// Butterworth filter
//fc = cut frequency
//n filter order
//type: if tipo <0, low pass, if >=0 high pass
//the image shoul be square

IplImage *cinza = cvCreateImage(cvSize(img->width,img->height),
IPL_DEPTH_8U, 1);
IplImage *re64 = cvCreateImage(cvSize(img->width,img->height),
IPL_DEPTH_64F, 1);
IplImage *im64 = cvCreateImage(cvSize(img->width,img->height),
IPL_DEPTH_64F, 1);

CvMat *mask = cvCreateMat( img->height,img->width, CV_64FC1 );

int Xmin = -img->width/2;
int Ymin = -img->height/2;
int i, j;

// function transferece filter matrix
for(i=0; iwidth; i++)
for(j=0; jheight; j++)
{
double dxy = sqrt(pow(Xmin+i,2)+pow(Ymin+j,2));
double H;
if(tipo < 0)
{ H = (1/(1 + pow(dxy/fc,2*n)));} //low pass

if(tipo >= 0)
{
if(dxy==0){ H=0;}
else
H = (1/(1 + pow(fc/dxy,2*n))); //high pass
}

cvSetReal2D(mask, j, i, H);
}

cvCvtColor(img, cinza, CV_BGR2GRAY);
cvCvtScale(cinza, re64,1./255);
cvSetZero(im64);

cvFftw(re64,im64,true); //fft

cvMul(re64, mask, re64, 1);
cvMul(im64, mask, im64, 1);

cvFftw(re64,im64,false); //ifft

cvCvtScale(re64,dst ,255.);

cvReleaseImage(&re64);
cvReleaseImage(&im64);
cvReleaseImage(&cinza);