# include <iostream.h>
# include <conio.h>
# include <graphics.h>
# include <math.h>

char IncFlag;
int PolygonPoints[4][2] =
    {{10,10},{10,100},{100,100},{100,10}};

float Sx=0.5;
float Sy=2.0;

int RefX=55;
int RefY=55;
void PolyLine()
{
    int iCnt;
    cleardevice();
    line(0,240,640,240);
    line(320,0,320,480);
    for (iCnt=0; iCnt<4; iCnt++)
    {
        line(320+PolygonPoints[iCnt][0],240-PolygonPoints[iCnt][1],
          320+PolygonPoints[(iCnt+1)%4][0],240-PolygonPoints[(iCnt+1)%4][1]);
    }
}

void Scale()
{
    int iCnt;
    int Tx,Ty;
    cout<<endl;
    for (iCnt=0; iCnt<4; iCnt++)
    {
        PolygonPoints[iCnt][0] *= Sx;
        PolygonPoints[iCnt][0] += (1-Sx)*RefX;
        PolygonPoints[iCnt][1] *= Sy;
        PolygonPoints[iCnt][1] += (1-Sy)*RefY;
    }
}

void main()
{
    int gDriver = DETECT, gMode;
    int iCnt;
    initgraph(&gDriver, &gMode, "C:\\TC\\BGI");
    PolyLine();
    getch();
    Scale();
    PolyLine();
    getch();
}