计算图像骨骼_图片骨骼算法理解-优快云博客

本文链接：https://blog.youkuaiyun.com/abc20002929/article/details/17841975

http://en.wikipedia.org/wiki/Topological_skeleton

计算图像骨骼方法

1 形态学http://felix.abecassis.me/2011/09/opencv-morphological-skeleton/

2 straight skeletons

3 Voronoi diagram

1)中轴medial 与 voronoi顶点的位置

2)voronoi顶点收敛至中轴

3)形成骨骼

4 Zhang-Suen algorithm

Zhang-Suen thinning steps:

While points are deleted do
For all pixels p(i,j) do
if (a) 2 ≤ B(P1) ≤ 6
(b) A(P1) = 1
(c) Apply one of the following:
1. P2 x P4 x P6 = 0 in odd iterations
2. P2 x P4 x P8 = 0 in even iterations
(d) Apply one of the following:
1. P4 x P6 x P8 = 0 in odd iterations
2. P2 x P6 x P8 = 0 in even iterations
then
Delete pixel p(i,j)
end if
end for
end while

/**
 * Code for thinning a binary image using Zhang-Suen algorithm.
 */
#include <opencv2/imgproc/imgproc.hpp>
#include <opencv2/highgui/highgui.hpp>

/**
 * Perform one thinning iteration.
 * Normally you wouldn't call this function directly from your code.
 *
 * @param  im    Binary image with range = 0-1
 * @param  iter  0=even, 1=odd
 */
void thinningIteration(cv::Mat& im, int iter)
{
    cv::Mat marker = cv::Mat::zeros(im.size(), CV_8UC1);

    for (int i = 1; i < im.rows-1; i++)
    {
        for (int j = 1; j < im.cols-1; j++)
        {
            uchar p2 = im.at<uchar>(i-1, j);
            uchar p3 = im.at<uchar>(i-1, j+1);
            uchar p4 = im.at<uchar>(i, j+1);
            uchar p5 = im.at<uchar>(i+1, j+1);
            uchar p6 = im.at<uchar>(i+1, j);
            uchar p7 = im.at<uchar>(i+1, j-1);
            uchar p8 = im.at<uchar>(i, j-1);
            uchar p9 = im.at<uchar>(i-1, j-1);

            int A  = (p2 == 0 && p3 == 1) + (p3 == 0 && p4 == 1) + 
                     (p4 == 0 && p5 == 1) + (p5 == 0 && p6 == 1) + 
                     (p6 == 0 && p7 == 1) + (p7 == 0 && p8 == 1) +
                     (p8 == 0 && p9 == 1) + (p9 == 0 && p2 == 1);
            int B  = p2 + p3 + p4 + p5 + p6 + p7 + p8 + p9;
            int m1 = iter == 0 ? (p2 * p4 * p6) : (p2 * p4 * p8);
            int m2 = iter == 0 ? (p4 * p6 * p8) : (p2 * p6 * p8);

            if (A == 1 && (B >= 2 && B <= 6) && m1 == 0 && m2 == 0)
                marker.at<uchar>(i,j) = 1;
        }
    }

    im &= ~marker;
}

/**
 * Function for thinning the given binary image
 *
 * @param  im  Binary image with range = 0-255
 */
void thinning(cv::Mat& im)
{
    im /= 255;

    cv::Mat prev = cv::Mat::zeros(im.size(), CV_8UC1);
    cv::Mat diff;

    do {
        thinningIteration(im, 0);
        thinningIteration(im, 1);
        cv::absdiff(im, prev, diff);
        im.copyTo(prev);
    } 
    while (cv::countNonZero(diff) > 0);

    im *= 255;
}

/**
 * This is an example on how to call the thinning function above.
 */
int main()
{
    cv::Mat src = cv::imread("test_image.png");
    if (src.empty())
        return -1;

    cv::Mat bw;
    cv::cvtColor(src, bw, CV_BGR2GRAY);
    cv::threshold(bw, bw, 10, 255, CV_THRESH_BINARY);

    thinning(bw);

    cv::imshow("src", src);
    cv::imshow("dst", bw);
    cv::waitKey(0);

    return 0;
}