Need only one edge in Canny edge algorithm

Question

When i use the canny edge algorithm, it produces the 2 edges opposite the thick colored line as expected, but i want only one edge to be displayed so as to make my line and curve detection algorithm much less complicated, any ideas on how i can make that happen ?

enter image description here

Here is the code :

bool CannyEdgeDetection(DataStructure& col)
{

Mat src, src_gray;
Mat dst, detected_edges, fin;
int WhiteCount = 0, BCount = 0;

char  szFil1[32] = "ocv.bmp";
char  szFil2[32] = "dst.bmp";
src = imread(szFil1);
dst = imread(szFil1);
blur( src_gray, detected_edges, Size(3,3) );
Canny( src, dst, 100, 200, 3 );
imwrite(szFil2, dst );

IplImage* img = cvLoadImage(szFil2);
int height    = img->height;
int width     = img->width;
int step      = img->widthStep;
int channels  = img->nChannels;
uchar * datau      = (uchar *)img->imageData;

for(int i=0;i<height;i++){
for(int j=0;j<width;j++){
for(int k=0;k<channels;k++){
datau[i*step+j*channels+k] = 255 - datau[i*step+j*channels+k];   
if (datau[i*step+j*channels+k]==0){
WhiteCount++;
col.pixel_col [i][j] = 2;
}
else{BCount++;
col.pixel_col[i][j] = 0;
}
}
}
}

cvSaveImage("img.bmp" ,img);

return 0;

}

This is not the original image but similar :

enter image description here

Which part do i comment out to be able to read black images in white backgrounds ? or any colored image ?

bool done;
do
{
  cv::morphologyEx(img, temp, cv::MORPH_OPEN, element);
  cv::bitwise_not(temp, temp);
  cv::bitwise_and(img, temp, temp);
  cv::bitwise_or(skel, temp, skel);
  cv::erode(img, img, element);

  double max;
  cv::minMaxLoc(img, 0, &max);
  done = (max == 0);
} while (!done);

What have you tried so far? Can you post some code? Or at least the input image? — dom
can you upload a link to your original image? May be other people can provide better methods. — Abid Rahman K
The dumb-simple method to do it is to resize the image - make it small enough that the edges will be 1-2 pixels. You will have both 1-pixel canny edges and an instant performance boost. — Sam

Abid Rahman K Abid Rahman K · Accepted Answer · 2012-07-15T14:08:25

That process is called skeletonization or thinning. You can google for that.

Here is a simple method for skeletonization : skeletonization OpenCV In C#

Below is the output I got when applied above method to your image ( Image is inverted before skeletonization because above method work for white images in black background, just opposite case of your input image).

enter image description here

Need only one edge in Canny edge algorithm

1 Answers