Program to draw a square of side 100 units at the center of the screen and scale it such that it enlarges to a square of side 150 units without using OpenGL function for scaling
Written by Munia Balayil
#include<stdio.h>
#include<GL/glut.h>
int i;
float scalex, scaley, a[10], b[10], x, y, square_side;
void line(float x, float y, float a, float b)
{
glBegin(GL_LINES);
glVertex2f(x, y);
glVertex2f(a, b);
glEnd();
}
void display_square()
{
for(i = 0; i < 4; i++)
{
if(i != 3)
line(a[i], b[i], a[i+1], b[i+1]);
else
line(a[i], b[i], a[0], b[0]);
}
}
void Init()
{
/* Set clear color to white */
glClearColor(1.0, 1.0, 1.0, 0);
/* Set fill color to black */
glColor3f(0.0, 0.0, 0.0);
gluOrtho2D(0.0 , 640.0 , 0.0 , 480.0);
}
void scale()
{
// Find the translated rectangle vertices
for(i = 0; i < 4; i++)
{
a[i] = a[i] * scalex; b[i] = b[i] * scaley;
}
}
void draw()
{
glClear(GL_COLOR_BUFFER_BIT);
// Find the original square vertices
// (x, y) represents the upper left point
x = 270.0; y = 290.0;
a[0] = x; b[0] = y;
a[1] = x + square_side; b[1] = y;
a[2] = x + square_side; b[2] = y - square_side;
a[3] = x; b[3] = y - square_side;
// Draw original square
display_square();
// Perform scaling
scale();
// Draw scaled square using dotted lines
glEnable(GL_LINE_STIPPLE);
glLineStipple(1, 0xF0F0);
display_square();
glDisable(GL_LINE_STIPPLE);
glFlush();
}
void main(int argc, char **argv)
{
square_side = 100;
printf("\n************************************************\n");
printf("Length of the side of the square: %f\n", square_side);
scalex = 1.5;
scaley = 1.5;
printf("\n************************************************\n");
printf("Scaling factor along both directions: %f\n", scalex);
printf("\n************************************************\n");
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
glutInitWindowPosition(0, 0);
glutInitWindowSize(640, 480);
glutCreateWindow("Scaling");
Init();
glutDisplayFunc(draw);
glutMainLoop();
}
Written by Munia Balayil
