C Program to draw a rectangle and perform the operations.

#include <stdio.h>
#include <graphics.h>
#include <stdlib.h>
#include <math.h>
 
void draw (int r[][2])
{
int i;
setlinestyle (DOTTED_LINE, 0, 1);
line (320, 0, 320, 480);
line (0, 240, 640, 240);
 
setlinestyle (SOLID_LINE, 0, 1);
line (320+r[0][0], 240-r[0][1], 320+r[1][0], 240-r[1][1]);
line (320+r[0][0], 240-r[0][1], 320+r[3][0], 240-r[3][1]);
line (320+r[1][0], 240-r[1][1], 320+r[2][0], 240-r[2][1]);
line (320+r[2][0], 240-r[2][1], 320+r[3][0], 240-r[3][1]);
}
 
void reset (int r[][2])
{
int i;
int val[4][2] = {
{ 0, 0 },{ 100, 0 },{ 100, 50 },{ 0, 50 }
};
for (i=0; i<4; i++)
{
r[i][0] = val[i][0];
r[i][1] = val[i][1];
}
}
 
void rotate (int r[][2], int angle)
{
int i;
double ang_rad = (angle * M_PI) / 180;
for (i=0; i<4; i++)
{
double xnew, ynew;
xnew = r[i][0] * cos (ang_rad) - r[i][1] * sin (ang_rad);
ynew = r[i][0] * sin (ang_rad) + r[i][1] * cos (ang_rad);
r[i][0] = xnew;
r[i][1] = ynew;
}
}
 
void shear (int r[][2], int sx, int sy)
{
int i;
for (i=0; i<4; i++)
{
int xnew, ynew;
xnew = r[i][0] + r[i][1] * sx;
ynew = r[i][1] + r[i][0] * sy;
r[i][0] = xnew;
r[i][1] = ynew;
}
}
 
void translate (int r[][2], int dx, int dy)
{
int i;
for (i=0; i<4; i++)
{
r[i][0] += dx;
r[i][1] += dy;
}
}
 
void ini()
{
int gd=DETECT,gm;
initgraph(&gd,&gm,"..//bgi");
}
void main()
{
 
int r[4][2],angle,dx,dy,x, y,choice;
 
do
{
clrscr();
printf("1.Rotation about the origin followed by translation\n");
printf("2.Rotation about an arbitrary point\n");
printf("3.Shear about the origin\n");
printf("4.Exit\n\n");
printf("Enter your choice: ");
scanf("%d",&choice);
switch(choice)
{
case 1: printf("Enter the rotation angle: ");
scanf("%d", &angle);
printf("Enter the x- and y-coordinates for translation: ");
scanf("%d%d",&dx,&dy);
ini();
cleardevice();
reset(r);
draw(r);getch();
rotate(r, angle);
cleardevice();
draw(r);getch();
translate(r,dx,dy);
cleardevice();
draw(r);getch();
closegraph();
break;
case 2: printf("Enter the rotation angle: ");
scanf("%d",&angle);
printf("Enter the x- and y-coordinates of the point: ");
scanf("%d%d",&x,&y);
ini();
cleardevice();
reset(r);
translate(r,x,y);
draw(r);
putpixel(320+x,240-y,WHITE);
getch();
translate(r,-x,-y);
draw(r);getch();
rotate(r,angle);
draw(r);getch();
translate(r,x,y);
cleardevice();
draw(r);
putpixel(320+x,240-y,WHITE);
getch();
closegraph();
break;
case 3: printf("Enter the x- and y-shears: ");
scanf("%d%d",&x,&y);
ini();
reset(r);
draw(r);getch();
shear(r, x, y);
cleardevice();
draw (r);getch();
closegraph();
break;
case 4: closegraph();
}
}while(choice!=4);
}