1 #include<opencv2/opencv.hpp>
2 #include<iostream>
3 using namespace std ;
4 using namespace cv ;
5 Mat gaussianlbrf( Mat scr, float sigma);//高斯低通滤波器函数
6 Mat freqfilt( Mat scr, Mat blur);//频率域滤波函数
7 static void help(char* progName)
8 {
9 cout << endl
10 << "This program demonstrated the use of the discrete Fourier
11 transform (DFT). " << endl
12 << "The dft of an image is taken and it's power spectrum is
13 displayed." << endl
14 << "Usage:" << endl
15 << progName << " [image_name -- default ../data/lena.jpg] " << endl <<
16 endl ;
17 }
18 int main ()
19 {
20 const char* filename = "1.jpg";
21 Mat input = imread (filename, IMREAD_GRAYSCALE );
22 if (input. empty ())
23 return -1;
24 imshow ("input", input);//显示原图
25 int w = getOptimalDFTSize (input. cols ); //获取进行dtf的最优尺寸
26 int h = getOptimalDFTSize (input. rows ); //获取进行dtf的最优尺寸
27 Mat padded;
28 copyMakeBorder (input, padded, 0, h - input. rows , 0, w - input. cols ,
29 BORDER_CONSTANT , Scalar :: all (0));//边界填充
30 padded. convertTo (padded, CV_32FC1 ); //将图像转换为flaot型
31 Mat gaussianKernel = gaussianlbrf(padded, 45);//高斯低通滤波器
32 Mat out = freqfilt(padded, gaussianKernel);//频率域滤波
33 out = out( Rect (0, 0, input. cols , input. rows ));
34 imshow ("结果图 sigma=40", out);
35 waitKey (0);
36 return 0;
37 }
38 //*****************高斯低通滤波器***********************
39 Mat gaussianlbrf( Mat scr, float sigma)
40 {
41 Mat gaussianBlur(scr. size (), CV_32FC1 ); //,CV_32FC1
42 //高斯函数参数,越小,频率高斯滤波器越窄,滤除高频成分越多,图像就越平滑
43
44 float d0 = 2 * sigma*sigma;
45 for (int i = 0; i < scr. rows ; i++)
46 {
47 for (int j = 0; j < scr. cols ; j++)
48 {
49 float d = pow (float(i - scr. rows / 2), 2) + pow (float(j -
50 scr. cols / 2), 2);//分子,计算pow必须为float型
51 gaussianBlur. at <float>(i, j) = expf (-d / d0);//expf为以e为底求幂
52 (必须为float型)
53 }
54 }
55 imshow ("高斯低通滤波器", gaussianBlur);
56 return gaussianBlur;
57 }
58 //*****************频率域滤波*******************
59 Mat freqfilt( Mat scr, Mat blur)
60 {
61 //***********************DFT*******************
62 Mat plane[] = { scr, Mat :: zeros (scr. size () , CV_32FC1 ) }; //创建通道,存储 dft后的实部与虚部(CV_32F,必须为单通道数)
63 Mat complexIm;
64 merge (plane, 2, complexIm);//合并通道 (把两个矩阵合并为一个2通道的Mat类容
65 器)
66 dft (complexIm, complexIm);//进行傅立叶变换,结果保存在自身
67 //***************中心化********************
68 split (complexIm, plane);//分离通道(数组分离)
69 int cx = plane[0]. cols / 2; int cy = plane[0]. rows / 2;//以下的操作是移动
70 图像 (零频移到中心)
71 Mat part1_r(plane[0], Rect (0, 0, cx, cy));//元素坐标表示为(cx,cy)
72 Mat part2_r(plane[0], Rect (cx, 0, cx, cy));
73 Mat part3_r(plane[0], Rect (0, cy, cx, cy));
74 Mat part4_r(plane[0], Rect (cx, cy, cx, cy));
75 Mat temp;
76 part1_r. copyTo (temp);//左上与右下交换位置(实部)
77 part4_r. copyTo (part1_r);
78 temp. copyTo (part4_r);
79 part2_r. copyTo (temp);//右上与左下交换位置(实部)
80 part3_r. copyTo (part2_r);
81 temp. copyTo (part3_r);
82 Mat part1_i(plane[1], Rect (0, 0, cx, cy));//元素坐标(cx,cy)
83 Mat part2_i(plane[1], Rect (cx, 0, cx, cy));
84 Mat part3_i(plane[1], Rect (0, cy, cx, cy));
85 Mat part4_i(plane[1], Rect (cx, cy, cx, cy));
86 part1_i. copyTo (temp);//左上与右下交换位置(虚部)
87 part4_i. copyTo (part1_i);
88 temp. copyTo (part4_i);
89 part2_i. copyTo (temp);//右上与左下交换位置(虚部)
90 part3_i. copyTo (part2_i);
91 temp. copyTo (part3_i);
92 //*****************滤波器函数与DFT结果的乘积****************
93 Mat blur_r, blur_i, BLUR;
94 multiply (plane[0], blur, blur_r); //滤波(实部与滤波器模板对应元素相乘)
95 multiply (plane[1], blur, blur_i);//滤波(虚部与滤波器模板对应元素相乘)
96 Mat plane1[] = { blur_r, blur_i };
97 merge (plane1, 2, BLUR);//实部与虚部合并
98 //*********************得到原图频谱图***********************************
99 magnitude (plane[0], plane[1], plane[0]);//获取幅度图像,0通道为实部通道,1 为虚部,因为二维傅立叶变换结果是复数
100 plane[0] += Scalar :: all (1);//傅立叶变o换后的图片不好分析,进行对数处理,结
101 果比较好看
102 log (plane[0], plane[0]);// float型的灰度空间为[0,1])
103 normalize (plane[0], plane[0], 1, 0, CV_MINMAX );//归一化便于显示
104 imshow ("原图像频谱图", plane[0]);
105 //******************IDFT*******************************
106 /*
107 Mat part111(BLUR,Rect(0,0,cx,cy)); //元素坐标(cx,cy)
108 Mat part222(BLUR,Rect(cx,0,cx,cy));
109 Mat part333(BLUR,Rect(0,cy,cx,cy));
110 Mat part444(BLUR,Rect(cx,cy,cx,cy));
111 part111.copyTo(temp); //左上与右下交换位置(虚部)
112 part444.copyTo(part111);
113 temp.copyTo(part444);
114 part222.copyTo(temp); //右上与左下交换位置
115 part333.copyTo(part222);
116 temp.copyTo(part333);
117 */
118 idft (BLUR, BLUR);//idft结果也为复数
119 split (BLUR, plane);//分离通道,主要获取通道
120 magnitude (plane[0], plane[1], plane[0]);//求幅值(模)
121 normalize (plane[0], plane[0], 1, 0, CV_MINMAX );//归一化便于显示
122 return plane[0];//返回参数
123 }