liang-barsky

#include<opencv2/core/core.hpp>
#include<opencv2/imgproc/imgproc.hpp>
#include<opencv2/highgui/highgui.hpp>
#include<opencv2/opencv.hpp>
#include<stdio.h>
#include <string>
#define For(i,a,b) for(int i=a;i<=b;++i)

using namespace cv;
 
Mat src;
Mat dst;
Point old_pt;
Point new_pt;
double xmin,xmax,ymin,ymax;
int flag;

void liang(Point pre_pt, Point cur_pt){
    flag=0;
    double l,r,L,R;
    double x1=pre_pt.x,x2=cur_pt.x;
    double y1=pre_pt.y,y2=cur_pt.y;
    double p[6],q[6];

    p[1] = -(x2 - x1);
    p[2] = -p[1];
    p[3] = -(y2 - y1);
    p[4] = -p[3];

    q[1] = x1 - xmin;
    q[2] = xmax - x1;
    q[3] = y1 - ymin;
    q[4] = ymax - y1;
    
    if(p[1]<0){
        l=q[1]/p[1];
        r=q[2]/p[2];
    }
    if(p[1]>0){
        r=q[1]/p[1];
        l=q[2]/p[2];
    }
    if(p[1]==0){
        l=0;
        r=1;
    }
    
    if(p[3]<0){
        L=q[3]/p[3];
        R=q[4]/p[4];
    }
    if(p[3]>0){
        R=q[3]/p[3];
        L=q[4]/p[4];
    }
    if(p[3]==0){
        L=0;
        R=1;
    }
    
    l=max((double)0,l);
    r=min((double)1,r);
    L=max((double)0,L);
    R=min((double)1,R);
    l=max(l,L);
    r=min(r,R);

    if(l<r){
        old_pt.x=x1+l*p[2];
        old_pt.y=y1+l*p[4];
        new_pt.x=x1+r*p[2];
        new_pt.y=y1+r*p[4];
        flag=1;
    }
}

void on_mouse(int event, int x, int y, int flags, void* ustc){
    static Point pre_pt ;
    static Point cur_pt ;
    char temp_1[20];
    char temp_2[20];
    if (event == EVENT_LBUTTONDOWN){
        dst.copyTo(src);
        pre_pt = Point(x, y);
        circle(src, pre_pt, 0.5, Scalar(255, 0, 0), FILLED, 0);
        imshow("liang-barsky", src);
    }
    else if (event == EVENT_MOUSEMOVE && (flags & EVENT_FLAG_LBUTTON)){
        dst.copyTo(src);
        cur_pt = Point(x, y);

        sprintf(temp_2,"x:%d,y:%d",pre_pt.x,pre_pt.y);
        sprintf(temp_1,"x:%d,y:%d",x,y);

        putText(src,temp_2,Point(pre_pt.x,pre_pt.y),FONT_HERSHEY_SIMPLEX,0.8,Scalar(0,255,255));
        putText(src,temp_1,Point(x,y),FONT_HERSHEY_SIMPLEX,0.8,Scalar(0,255,255));

        circle(src, pre_pt, 3, Scalar(255,0, 0), FILLED, 0);
        circle(src, cur_pt, 3, Scalar(255,0, 0), FILLED, 0);

        line(src, pre_pt, cur_pt, Scalar(0, 255,0), 2, 8 ,0);
        imshow("liang-barsky", src);
    }
    else if (event == EVENT_LBUTTONUP){
        dst.copyTo(src);
        cur_pt = Point(x, y);

        sprintf(temp_2,"x:%d,y:%d",pre_pt.x,pre_pt.y);
        sprintf(temp_1,"x:%d,y:%d",x,y);
        
        putText(src,temp_2,Point(pre_pt.x,pre_pt.y),FONT_HERSHEY_SIMPLEX,0.8,Scalar(0,255,255));
        putText(src,temp_1,Point(x,y),FONT_HERSHEY_SIMPLEX,0.8,Scalar(0,255,255));
        
        circle(src, pre_pt, 3, Scalar(255,0, 0), FILLED, 0);
        circle(src, cur_pt, 3, Scalar(255,0, 0), FILLED, 0);

        liang(pre_pt,cur_pt);

        if(flag){
            line(src, pre_pt, old_pt, Scalar(0, 255,0), 2, 8, 0);
            line(src, old_pt, new_pt, Scalar(255, 0, 0), 4, 8, 0);
            line(src, new_pt, cur_pt, Scalar(0, 255,0), 2, 8, 0);
        }
        else{
            line(src, pre_pt, cur_pt, Scalar(0, 255,0), 2, 8, 0);
        }
        imshow("liang-barsky", src);
    }
}
 
int main(){
    namedWindow("liang-barsky", WINDOW_AUTOSIZE);
    src=Mat(1000, 1000, CV_8UC3, Scalar(0));
    xmax=ymax=600;
    xmin=ymin=200;
    rectangle(src,Rect(200,200,400,400),Scalar(255,255,255),2,1,0);
    src.copyTo(dst);
    setMouseCallback("liang-barsky", on_mouse, 0);
    imshow("liang-barsky", src);
    waitKey(0);
    return 0;
}