1.  Scaling about the origin followed by translation.
2.  Scaling with reference to an arbitrary point.
3. Reflect about the line y = mx + c.

INPUT

#include <stdio.h>
#include <graphics.h>
#include <stdlib.h>
#include <math.h>
#include <conio.h>

void reset (int h[][2])
{
int val[9][2] = {
{ 50, 50 },{ 75, 50 },{ 75, 75 },{ 100, 75 },
{ 100, 50 },{ 125, 50 },{ 125, 100 },{ 87, 125 },{ 50, 100 }
};
int i;
for (i=0; i<9; i++)
{
h[i][0] = val[i][0]-50;
h[i][1] = val[i][1]-50;
}
}
void draw (int h[][2])
{
int i;
setlinestyle (DOTTED_LINE, 0, 1);
line (320, 0, 320, 480);
line (0, 240, 640, 240);
setlinestyle (SOLID_LINE, 0, 1);
for (i=0; i<8; i++)
line (320+h[i][0], 240-h[i][1], 320+h[i+1][0], 240-h[i+1][1]);
line (320+h[0][0], 240-h[0][1], 320+h[8][0], 240-h[8][1]);
}
void rotate (int h[][2], float angle)
{
int i;
for (i=0; i<9; i++)
{
int xnew, ynew;
xnew = h[i][0] * cos (angle) - h[i][1] * sin (angle);
ynew = h[i][0] * sin (angle) + h[i][1] * cos (angle);
h[i][0] = xnew; h[i][1] = ynew;
}
}
void scale (int h[][2], int sx, int sy)
{
int i;
for (i=0; i<9; i++)
{
h[i][0] *= sx;
h[i][1] *= sy;
}
}
void translate (int h[][2], int dx, int dy)
{
int i;
for (i=0; i<9; i++)
{
h[i][0] += dx;
h[i][1] += dy;
}
}
void reflect (int h[][2], int m, int c)
{
int i;
float angle;
for (i=0; i<9; i++)
h[i][1] -= c;
angle = M_PI/2 - atan (m);
rotate (h, angle);
for (i=0; i<9; i++)
h[i][0] = -h[i][0];
angle = -angle;
rotate (h, angle);
for (i=0; i<9; i++)
h[i][1] += c;
}

void ini()
{
int gd=DETECT,gm;
initgraph(&gd,&gm,"..\\bgi");
}
void dini()
{
getch();
closegraph();
}
void main()
{

int h[9][2],sx,sy,x,y,m,c,choice;
do
{
clrscr();
printf("1. Scaling about the origin.\n");
printf("2. Scaling about an arbitrary point.\n");
printf("3. Reflection about the line y = mx + c.\n");
printf("4. Exit\n");
printf("Enter the choice: ");
scanf("%d",&choice);
switch(choice)
{
case 1: printf ("Enter the x- and y-scaling factors: ");
scanf ("%d%d", &sx, &sy);
ini();
reset (h);
draw (h);getch();
scale (h, sx, sy);
cleardevice();
draw (h);
dini();
break;

case 2: printf ("Enter the x- and y-scaling factors: ");
scanf ("%d%d", &sx, &sy);
printf ("Enter the x- and y-coordinates of the point: ");
scanf ("%d%d", &x, &y);
ini();
reset (h);
translate (h, x, y);// Go to arbitrary point
draw(h); getch();//Show its arbitrary position
cleardevice();
translate(h,-x,-y);//Take it back to origin
draw(h);
getch();
cleardevice();
scale (h, sx, sy);//Now Scale it
draw(h);
getch();
translate (h, x, y);//Back to Arbitrary point
cleardevice();
draw (h);
putpixel (320+x, 240-y, WHITE);
dini();
break;
case 3: printf ("Enter the values of m and c: ");
scanf ("%d%d", &m, &c);
ini();
reset (h);
draw (h); getch();
reflect (h, m, c);
cleardevice();
draw (h);
dini();
break;
case 4: exit(0);
}
}while(choice!=4);
}

OUTPUT



1. Scaling about the origin followed by translation.


2. Scaling with reference to an arbitrary point.



3. Reflect about the line y = mx + c.