155 lines
2.6 KiB
C++
155 lines
2.6 KiB
C++
/* Define the structure to store the edges*/
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#include<iostream>
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#include<graphics.h>
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using namespace std;
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struct edge{
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int x1,y1,x2,y2,flag;
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};
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int main()
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{
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int gd=DETECT,gm,n,i,j,k;
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struct edge ed[10],temped;
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float dx,dy,m[10],x_int[10],inter_x[10];
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int x[10],y[10],ymax=0,ymin=480,yy,temp;
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initgraph(&gd,&gm,NULL);
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/*read the number of vertices of the polygon*/
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cout<<"Enter the no.of vertices of the graph :";
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cin>>n;
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/*read the vertices of the polygon and also find ymax and ymin*/
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cout<<"Enter the vertices";
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for(i=0;i<n;i++)
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{
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cin>>x[i];
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cin>>y[i];
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if(y[i]>ymax)
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ymax=y[i];
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if(y[i]<ymin)
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ymin=y[i];
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ed[i].x1=x[i];
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ed[i].y1=y[i];
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}
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/*store the edge information*/
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cout<<"\nEdge Information\n";
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for(i=0;i<n-1;i++)
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{
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ed[i].x2=ed[i+1].x1;
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ed[i].y2=ed[i+1].y1;
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ed[i].flag=0;
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cout<<"("<<ed[i].x1<<", "<<ed[i].y1<<") ("<<ed[i].x2<<", "<<ed[i].y2<<")"<<endl;
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}
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ed[i].x2=ed[0].x1;
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ed[i].y2=ed[0].y1;
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ed[i].flag=0;
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cout<<"("<<ed[i].x1<<", "<<ed[i].y1<<") ("<<ed[i].x2<<", "<<ed[i].y2<<")"<<endl;
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/*Check for y1>y2, if not interchnge y1 and y2 */
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cout<<"\nUpdated Edge Information\n";
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for(i=0;i<n;i++)
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{
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if(ed[i].y1 < ed[i].y2)
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{
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temp=ed[i].x1;
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ed[i].x1=ed[i].x2;
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ed[i].x2=temp;
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temp=ed[i].y1;
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ed[i].y1=ed[i].y2;
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ed[i].y2=temp;
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}
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cout<<"("<<ed[i].x1<<", "<<ed[i].y1<<") ("<<ed[i].x2<<", "<<ed[i].y2<<")"<<endl;
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}
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/*Draw the polygon*/
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for(i=0;i<n;i++)
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{
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line(ed[i].x1, ed[i].y1,ed[i].x2,ed[i].y2);
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}
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/*calculating 1/slope of each edge*/
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for(i=0;i<n;i++)
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{
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dx=ed[i].x2-ed[i].x1;
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dy=ed[i].y2-ed[i].y1;
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if(dy==0)
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{
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m[i]=0;
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}
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else
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{
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m[i]=dx/dy;
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}
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inter_x[i]=ed[i].x1;
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}
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yy=ymax;
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//Working with Active edges
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while(yy>ymin)
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{
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//cout<<"\n\t"<<yy;
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for(i=0;i<n;i++)
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{
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if(yy>ed[i].y2 && yy<=ed[i].y1)
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ed[i].flag=1; //Active edge
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else
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ed[i].flag=0; //not Active edge
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}
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j=0;
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for(i=0;i<n;i++)
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{
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if(ed[i].flag==1)
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{
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if(yy==ed[i].y1)
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{
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x_int[j]=ed[i].x1;
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j++;
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}
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else
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{
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x_int[j]=inter_x[i]+(-m[i]);
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inter_x[i]=x_int[j];
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j++;
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}
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}
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}
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/*sorting the x intersection*/
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for(i=0;i<j;i++)
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{
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for(k=0;k<j-1;k++)
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{
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if(x_int[k]>x_int[k+1])
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{
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temp=(int)x_int[k];
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x_int[k]=x_int[k+1];
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x_int[k+1]=temp;
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}
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}
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}
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/*extracting pairs of values to draw lilnes*/
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for(i=0;i<j;i=i+2)
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{ setcolor(GREEN);
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line((int)x_int[i],yy,(int)x_int[i+1],yy);
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}
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yy--;
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delay(50);
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}//while
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delay(10000);
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closegraph();
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}
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/*
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Enter the vertices 80 20 100 80 150 60 130 200 40 250
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*/
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