Coherence-Enhancing Shock Filters（附源码）

小鱼儿 2022-08-10 09:42 15阅读 0赞

## 引言 ##

这篇博客是基于对Joachim Weickert的文章《Coherence-Enhancing Shock Filters》的实现。但是我并没有阅读原文，参考了OpenCV的python源码改写而成。嗯，我真是一个勤劳的代码翻译工。  
python源码可以在OpenCV 300里面的目录

> XXX(OpenCV的安装目录)\\sources\\samples\\python2\\coherence.py

先来看一下效果，

![这里写图片描述][20151119204603573]

## 代码 ##

### Python代码 ###

Coherence-enhancing filtering example
    =====================================
    inspired by
      Joachim Weickert "Coherence-Enhancing Shock Filters"
      http://www.mia.uni-saarland.de/Publications/weickert-dagm03.pdf
    
    import numpy as np
    import cv2
    
    def coherence_filter(img, sigma = 11, str_sigma = 11, blend = 0.5, iter_n = 4):
        h, w = img.shape[:2]
    
        for i in xrange(iter_n):
            print i,
    
            gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
            eigen = cv2.cornerEigenValsAndVecs(gray, str_sigma, 3)
            eigen = eigen.reshape(h, w, 3, 2)  # [[e1, e2], v1, v2]
            x, y = eigen[:,:,1,0], eigen[:,:,1,1]
    
            gxx = cv2.Sobel(gray, cv2.CV_32F, 2, 0, ksize=sigma)
            gxy = cv2.Sobel(gray, cv2.CV_32F, 1, 1, ksize=sigma)
            gyy = cv2.Sobel(gray, cv2.CV_32F, 0, 2, ksize=sigma)
            gvv = x*x*gxx + 2*x*y*gxy + y*y*gyy
            m = gvv < 0
    
            ero = cv2.erode(img, None)
            dil = cv2.dilate(img, None)
            img1 = ero
            img1[m] = dil[m]
            img = np.uint8(img*(1.0 - blend) + img1*blend)
        print 'done'
        return img
    
    
    if __name__ == '__main__':
        import sys
        try:
            fn = sys.argv[1]
        except:
            fn = '../data/lena.jpg'
    
        src = cv2.imread(fn)
    
        def nothing(*argv):
            pass
    
        def update():
            sigma = cv2.getTrackbarPos('sigma', 'control')*2+1
            str_sigma = cv2.getTrackbarPos('str_sigma', 'control')*2+1
            blend = cv2.getTrackbarPos('blend', 'control') / 10.0
            print 'sigma: %d  str_sigma: %d  blend_coef: %f' % (sigma, str_sigma, blend)
            dst = coherence_filter(src, sigma=sigma, str_sigma = str_sigma, blend = blend)
            cv2.imshow('dst', dst)
    
        cv2.namedWindow('control', 0)
        cv2.createTrackbar('sigma', 'control', 9, 15, nothing)
        cv2.createTrackbar('blend', 'control', 7, 10, nothing)
        cv2.createTrackbar('str_sigma', 'control', 9, 15, nothing)
    
    
        print 'Press SPACE to update the image\n'
    
        cv2.imshow('src', src)
        update()
        while True:
            ch = 0xFF & cv2.waitKey()
            if ch == ord(' '):
                update()
            if ch == 27:
                break
        cv2.destroyAllWindows()

### C++代码 ###

/* ==============================================
    *   Coherence-Enhancing Shock Filters
    *  Author:WinCoder@qq.com
    *  inspired by
    *  Joachim Weickert "Coherence-Enhancing Shock Filters"
    *  http://www.mia.uni-saarland.de/Publications/weickert-dagm03.pdf
    *  
    *   Paras:
    *   @img        : input image ranging value from 0 to 255.
    *   @sigma      : sobel kernel size.
    *   @str_sigma  : neighborhood size,see detail in reference[2]
    *   @belnd      : blending coefficient.default value 0.5.
    *   @iter       : number of iteration.
    *    
    *   Example:
    *   Mat dst = CoherenceFilter(I,11,11,0.5,4);
    *   imshow("shock filter",dst);
    */
    Mat CoherenceFilter(Mat img,int sigma, int str_sigma, float blend, int iter)
    {
        Mat I = img.clone();
        int height = I.rows;
        int width  = I.cols;
    
        for(int i = 0;i <iter; i++)
        {
            Mat gray;
            cvtColor(I,gray,COLOR_BGR2GRAY);
            Mat eigen;
            cornerEigenValsAndVecs(gray,eigen,str_sigma,3);
    
            vector<Mat> vec;
            split(eigen,vec);
    
            Mat x,y;
            x = vec[2];
            y = vec[3];
    
            Mat gxx,gxy,gyy;
            Sobel(gray,gxx,CV_32F,2,0,sigma);
            Sobel(gray,gxy,CV_32F,1,1,sigma);
            Sobel(gray,gyy,CV_32F,0,2,sigma);
    
            Mat ero;
            Mat dil;
            erode(I,ero,Mat());
            dilate(I,dil,Mat());
    
            Mat img1 = ero;
            for(int nY = 0;nY<height;nY++)
            {
                for(int nX = 0;nX<width;nX++)
                {
                    if(x.at<float>(nY,nX)* x.at<float>(nY,nX)* gxx.at<float>(nY,nX)
                        + 2*x.at<float>(nY,nX)* y.at<float>(nY,nX)* gxy.at<float>(nY,nX)
                        + y.at<float>(nY,nX)* y.at<float>(nY,nX)* gyy.at<float>(nY,nX)<0)
                    {
                            img1.at<Vec3b>(nY,nX) = dil.at<Vec3b>(nY,nX);
                    }
                }
            }
            I = I*(1.0-blend)+img1*blend;
        }
        return I;
    }

## 效果 ##

整体效果看起来有一种艺术动漫效果风格。调节各种参数，自行体会。

![这里写图片描述][20151119150552138] ![这里写图片描述][20151119150607171]

## 可执行程序下载 ##

新浪网盘点此[下载][Link 1]  
CSDN资源[下载][Link 2]

## 参考文献 ##

[Coherence-Enhancing Shock Filters，Joachim Weickert][Coherence-Enhancing Shock Filters_Joachim Weickert]  
[OpenCV官方文档][OpenCV]

## 转载请保留以下信息 ##

<table> 
 <thead> 
  <tr> 
   <th>作者</th> 
   <th align="center">日期</th> 
   <th align="right">联系方式</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>风吹夏天</td> 
   <td align="center">2015年11月19日</td> 
   <td align="right">wincoder@qq.com</td> 
  </tr> 
 </tbody> 
</table>

[20151119204603573]: /images/20220731/f238fd97e70d4f978b6c318d1689447e.png
[20151119150552138]: https://img-blog.csdn.net/20151119150552138
[20151119150607171]: /images/20220731/bfb5e1ff2c5d448c89e3b96b7ef7b2ae.png
[Link 1]: http://vdisk.weibo.com/s/zHHOG8a9dwn6R
[Link 2]: http://download.csdn.net/detail/bluecol/9377137
[Coherence-Enhancing Shock Filters_Joachim Weickert]: http://www.mia.uni-saarland.de/Publications/weickert-dagm03.pdf
[OpenCV]: http://www.opencv.org.cn/opencvdoc/2.3.2/html/modules/imgproc/doc/feature_detection.html?highlight=cornereigenvalsandvecs#cv.CornerEigenValsAndVecs