本实验为计算机科学与技术学院计算机专业大四上限选课，2023-2024-1年度课程实验，较以往实验内容发生较大变化

本实验使用vs2019，c++语言，需要提前安装opencv，具体方法请自行搜索。

 实验7：图像结构

快速距离变换

• 实现基于前向和逆向扫描的快速距离变换算法，并将距离场进行可视化显示，如下图所示。

#include <opencv2/opencv.hpp>
#include <iostream>
#include <cmath>
using namespace cv;
using namespace std;

Mat img, out;
double mmax = 0;

double Dmin(double a, double b)
{
    return a < b ? a : b;
}

void quickDistance(Mat src, Mat& dis)
{
    Mat tmp = src;
    double result = 0.0;
    double LeftTop = sqrt(2), Top = 1.0;
    double RightTop = LeftTop, Left = Top ;
    double LeftBottom = LeftTop, Bottom = Top;
    double RightBottom = LeftTop, Right = Top;
    for (int i = 1; i < src.rows - 1; i++)
    {
        for (int j = 1; j < src.cols - 1; j++)
        {
            result = Dmin((double)tmp.at<uchar>(i, j), LeftTop + (double)tmp.at<uchar>(i - 1, j - 1));
            result = Dmin(result, Top + (double)tmp.at<uchar>(i - 1, j));
            result = Dmin(result, Left + (double)tmp.at<uchar>(i, j - 1));
            result = Dmin(result, LeftBottom + (double)tmp.at<uchar>(i + 1, j - 1));
            tmp.at<uchar>(i, j) = (uchar)round(result);
        }
    }
    for (int i = src.rows - 2; i > 0; i--)
    {
        for (int j = src.cols - 2; j > 0; j--)
        {
            result = Dmin((double)tmp.at<uchar>(i, j), RightTop + (double)tmp.at<uchar>(i - 1, j + 1));
            result = Dmin(result, Right + (double)tmp.at<uchar>(i, j + 1));
            result = Dmin(result, RightBottom + (double)tmp.at<uchar>(i + 1, j + 1));
            result = Dmin(result, Bottom + (double)tmp.at<uchar>(i + 1, j));
            tmp.at<uchar>(i, j) = (uchar)round(result);
            mmax = max(mmax, result);
        }
    }
    dis = tmp;
}

int main()
{
    img = imread("C:/Users/13441/Desktop/数字图像/back8.png");
    //img = 255 - img;
    cvtColor(img, img, COLOR_RGB2GRAY);
    threshold(img, img, 190, 255, THRESH_BINARY);
    Mat vis = img;
    imshow("input", img);
    quickDistance(img, out);
    for (int i = 0; i < out.rows; i++) {
        for (int j = 0; j < out.cols; j++) {
            double value = (double)out.at<uchar>(i, j);
            int color_value = (int)(value*255 / mmax);
            vis.at<uchar>(i, j) = (uchar)max(0, (int)color_value);
        }
    }
    imshow("out2", vis);

    waitKey();

    return 0;
}

结果：