6. Scan Fill Algorithm.cpp

/* 
Write C++ program to draw a concave polygon and fill it with desired color using scan fill algorithm.
*/



#include <conio.h>
#include <iostream>
#include <graphics.h>
#include <stdlib.h>
using namespace std;

class point
{
    public:
    int x,y;
};

class poly
{
    private:
        point p[20];
        int inter[20],x,y;
        int v,xmin,ymin,xmax,ymax;
    public:
        int c;
        void read();
        void calcs();
        void display();
        void ints(float);
        void sort(int);
};


void poly::read()
{
    int i;
    cout<<"\n\t SCAN_FILL ALGORITHM";
    cout<<"\n Enter the no of vertices of polygon:";
    cin>>v;
    if(v>2)
    {
        for(i=0;i<v; i++) 
        {
            cout<<"\nEnter the co-ordinate no.- "<<i+1<<" : ";
            cout<<"\n\tx"<<(i+1)<<"=";
            cin>>p[i].x;
            cout<<"\n\ty"<<(i+1)<<"=";
            cin>>p[i].y;
        }
        p[i].x=p[0].x;
        p[i].y=p[0].y;
        xmin=xmax=p[0].x;
        ymin=ymax=p[0].y;
    }
    else
        cout<<"\n Enter valid no. of vertices.";
}

void poly::calcs()
{ //MAX,MIN
    for(int i=0;i<v;i++)
    {
        if(xmin>p[i].x)
        xmin=p[i].x;
        if(xmax<p[i].x)
        xmax=p[i].x;
        if(ymin>p[i].y)
        ymin=p[i].y;
        if(ymax<p[i].y)
        ymax=p[i].y;
    }
}

void poly::display()
{
    int ch1;
    char ch='y';
    float s,s2;
    do
    {
        cout<<"\n\nMENU:";
        cout<<"\n\n\t1 . Scan line Fill ";
        cout<<"\n\n\t2 . Exit ";
        cout<<"\n\nEnter your choice:";
        cin>>ch1;
        switch(ch1)
        {
            case 1:
                s=ymin+0.01;
                delay(100);
                cleardevice();
                while(s<=ymax)
                {
                    ints(s);
                    sort(s);
                    s++;
                }
                break;
            case 2:
                exit(0);
        }

        cout<<"Do you want to continue?: ";
        cin>>ch;
    }while(ch=='y' || ch=='Y');
}

void poly::ints(float z) 
{
    int x1,x2,y1,y2,temp;
    c=0;
    for(int i=0;i<v;i++)
    {
        x1=p[i].x;
        y1=p[i].y;
        x2=p[i+1].x;
        y2=p[i+1].y;
        if(y2<y1)
        {
            temp=x1;
            x1=x2;
            x2=temp;
            temp=y1;
            y1=y2;
            y2=temp;
        }
        if(z<=y2&&z>=y1)
        {
            if((y1-y2)==0)
            x=x1;
            else 
            {
                x=((x2-x1)*(z-y1))/(y2-y1);
                x=x+x1;
            }
            if(x<=xmax && x>=xmin)
            inter[c++]=x;
        }
    }
}

void poly::sort(int z) 
{
    int temp,j,i;

        for(i=0;i<v;i++)
        {
            line(p[i].x,p[i].y,p[i+1].x,p[i+1].y); 
        }
        delay(100);
        for(i=0; i<c;i+=2)
        {
            delay(100);
            line(inter[i],z,inter[i+1],z);  
        }
}

int main() 
{
    int cl;
    initwindow(500,600);
    cleardevice();
    poly x;
    x.read();
    x.calcs();
    cleardevice();
    cout<<"\n\tEnter the colour u want:(0-15)->"; //Selecting colour
    cin>>cl;
    setcolor(cl);
    x.display();
    closegraph(); 
    getch();
    return 0;
}