/**********************************************************
Problem Definition:- Draw a 4x4 chessboard
rotated 45
degrees with horizontal axis. Use bresenham
algorithm
to draw all the lines. Use seed fill
algorithm to fill
black spaces of chessboard.
**********************************************************/
#include<stdio.h>
#include<math.h>
#include<GL/gl.h>
#include<stdlib.h>
#include<GL/glu.h>
#include<GL/glut.h>
float trans[3][3],ans[20][3],mat[20][3];
int tx,ty;
float X,Y;
typedef struct pixel
{
GLubyte
r;
GLubyte
g;
GLubyte
b;
}pixel;
pixel b_clr,f_clr;
void initialize()
{
float
X1,Y1;
printf("Enter
x coordinate:- ");
scanf("%f",&X);
printf("Enter
y coordinate:- ");
scanf("%f",&Y);
X1=X;
Y1=Y;
for(int
i=0;i<10;i+=2)
{
mat[i][0]=X;
mat[i][1]=Y;
mat[i][2]=1;
mat[i+1][0]=X+120;
mat[i+1][1]=Y;
mat[i+1][2]=1;
Y+=30;
}
Y=Y1;
for(int
i=10;i<20;i+=2)
{
mat[i][0]=X;
mat[i][1]=Y;
mat[i][2]=1;
mat[i+1][0]=X;
mat[i+1][1]=Y+120;
mat[i+1][2]=1;
X+=30;
}
float
root2 = 1/(sqrt(2));
trans[0][0]=trans[0][1]=trans[1][1]=root2;
trans[1][0]=-root2;
trans[0][2]=trans[1][2]=0;
tx=mat[0][0];
ty=mat[0][1];
trans[2][0]=((ty-tx)*root2)
+ tx;
trans[2][1]=((-ty-tx)*root2)
+ ty;
trans[2][2]=1;
for(int
i=0;i<20;i++)
{
for(int
j=0;j<3;j++)
{
ans[i][j]=0;
for(int
k=0;k<3;k++)
ans[i][j]+=mat[i][k]
* trans[k][j];
}
}
X=X1;
Y=Y1;
}
void plot(int x,int y) //FUNCTION TO
PLOT A POINT
{
glBegin(GL_POINTS);
glVertex2i(x,y);
glEnd();
glFlush();
}
void
Brezenham(int x1,int y1,int x2,int y2)
{
int
incx,incy,inc1,inc2,p,x,y;
//INITIALIZATION
int
dy=y2-y1;
int
dx=x2-x1;
if(dx<0)
dx=-dx;
if(dy<0)
dy=-dy;
incx=1;
incy=1;
if(x2<x1) //IF
FINAL CO-ORDINATE IS LESS THAN INITIAL THE INCREMENT ID NEGATIVE
incx=-1;
if(y2<y1)
incy=-1;
x=x1;
y=y1;
if(dx>dy)
//TOTAL NUMBER OF STEPS IS DX IF IT IS GREATER THAN DY
{
plot(x,y);
p=2*dy-dx;
inc1=2*(dy-dx);
inc2=2*dy;
for(int i=0;i<dx;i++)
{
if(p>0)
{
y+=incy;
p+=inc1;
}
else
p+=inc2;
x+=incx;
plot(x,y);
}
}
else
//TOTAL NUMBER OF STEPS IS DY IF IT IS GREATER THAN DX
{
plot(x,y);
p=2*dx-dy;
inc1=2*(dx-dy);
inc2=2*dx;
for(int
i=0;i<dy;i++)
{
if(p>0)
{
x+=incx;
p+=inc1;
}
else
{
p+=inc2;
}
y+=incy;
plot(x,y);
}
}
}
void boundary_fill(float x,float y)
{
pixel
c;
glReadPixels(x,y,1,1,GL_RGB,GL_UNSIGNED_BYTE,&c);
if((c.r!=b_clr.r
|| c.g!=b_clr.g || c.b!=b_clr.b)
&& (c.r!=f_clr.r || c.g!=f_clr.g || c.b!=f_clr.b))
{
glBegin(GL_POINTS);
glVertex2d(x,y);
glColor3ub(f_clr.r,f_clr.g,f_clr.b);
glEnd();
glFlush();
boundary_fill(x,y+1);
boundary_fill(x-1,y);
boundary_fill(x,y-1);
boundary_fill(x+1,y);
}
}
void init(void)
{
glClearColor(1.0,
1.0, 1.0, 0.0);
glColor3i(0,0,0);
glClear(GL_COLOR_BUFFER_BIT);
gluOrtho2D(0,750,0,750);
}
void draw()
{
glClear(GL_COLOR_BUFFER_BIT);
int
i;
for(i=0;i<20;i+=2)
Brezenham(ans[i][0],ans[i][1],ans[i+1][0],ans[i+1][1]);
float
factor=60/(sqrt(2));
float
add=30/sqrt(2);
Y=Y+add;
boundary_fill(X,Y);
for(int
i=2;i<=6;i++)
boundary_fill(X,Y+i*add);
Y=Y+factor;
boundary_fill(X+factor,Y);
boundary_fill(X+factor,Y+factor);
boundary_fill(X-factor,Y);
boundary_fill(X-factor,Y+factor);
glEnd();
glFlush();
}
int main(int argc,char **argv)
{
initialize();
b_clr.r=0;
b_clr.g=0;
b_clr.b=0;
f_clr.r=150;
f_clr.g=150;
f_clr.b=150;
glutInit(&argc,argv);
glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
glutInitWindowPosition(0,0);
glutInitWindowSize(750,750);
glutCreateWindow("Assignment 4");
init();
glutDisplayFunc(draw);
glutMainLoop();
}
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