Graphics practical lab manual

Shri Rawatpura Sarkar Institute of Technology-II, New Raipur

CHHATTISGARH SWAMI VIVEKANAND TECHNICAL UNIVERSITY, BHILAI (C.G.)Semester – VI Branch – Computer Science And EngineeringSubject: Computer Graphics Lab Code – 322622 (22)Total Practical Periods – 40Total Marks in end semester examination – 40

List of Experiments:

1. Write a program to draw the line using DDA algorithm.

2. Write a program to draw the line using Bresenham’s algorithm.

3. Write a program to draw circle using Bresenham’s algorithm.

4. Write a program to draw circle using mid-point algorithm.

5. Write a program to demonstrate draw ellipse using midpoint algorithm.

6. Write a program Rotation of Triangle.

7. Write a program Translation of Line.

8. Write a program to perform scaling of line.

9. Write a program shearing of Rectangle.

10. Write a program to implement boundary –fill algorithm.

11. Write a program to implement flood –fill algorithm.

12. Write a program to implement Bezier curve using four control points.

13. Write a program to implement CohenSutherland line clipping algorithm.

14. Write a program to implement Liang Barsky line clipping algorithm.

15. Write a program to implement face of a cartoon.

Book Reference:-

1. Computer Graphics & Multimedia- G. S. Baluja -Dhanpat Rai & CO.

2. Computer Graphics Donald Hearn & M Pauline Baker-Pearson Pvt.Ltd

CSE/6th/CG Lab/Prepared by Toran Lal Sahu


EXPERIMENT-11. Write a program to draw the line using DDA algorithm.

Digital Differential Analyzer (DDA) is used for linear interpolation of variables over an interval between start and end point of a line. Simplest implementation the DDA algorithm interpolates values in interval [(xstart, ystart), (xend, yend)] by computing for each xi the equations xi = xi−1+1, yi = yi−1 + Δy/Δx, Where Δx = xend − xstart and Δy = yend − ystart. CODING: #include <graphics.h>/* include the necessary header files*/ #include <stdlib.h>#include <stdio.h>#include <conio.h>void draw(int xa,int ya,int xb,int yb); void main() { int xa,ya,xb,yb; clrscr(); printf("Line DDA algorithm"); printf("\n Enter the value of xa, ya:"); scanf("%d%d",&xa,&ya); printf("\n Enter the value of xb, yb:"); scanf("%d%d",&xb,&yb); draw(xa,ya,xb,yb); } void draw(int xa,int ya,int xb,int yb) { int xin,yin,x,y,dx,dy,steps,k; /* request auto detection */ int gdriver=DETECT,gmode,errorcode; /* initialize graphics and local variables */ initgraph(&gdriver,&gmode, "c:\\tc\\bgi") /* read result of initialization */ errorcode=graphresult(); /* an error occurred */ if (errorcode!=grOk) { printf("Graphics error: %s\n", grapherrormsg(errorcode)); printf("Press any key to halt:"); getch(); exit(1); } dx=xb-xa; dy=yb-ya; if(abs(dx)>abs(dy)) /* if the condition is satisfied */ { /* calculate the value of the condition variable*/ steps=abs(dx); } else { steps=abs(dy);



} xin=dx/steps; yin=dy/steps; x=xa; y=ya; putpixel(x,y,1); /* draw the first pixel for the line*/ for(k=1;k<=steps;k++) /* for each value of the condition variable, */ { x=x+xin; /* calculate the values of (x,y) and draw the pixel*/ y=y+yin; putpixel(x,y,1); } /* clean up */ getch(); closegraph(); }



EXPERIMENT-2

2. Write a program to draw the line using Bresenham’s algorithm.

The Bresenham line algorithm is an algorithm which determines which points in an n-dimensional raster should be plotted in order to form a close approximation to a straight line between two given points. The endpoints of the line are the pixels at (x0, y0) and (x1, y1), where the first coordinate of the pair is the column and the second is the row. CODING: #include <graphics.h>/* include the necessary header files*/ #include <stdlib.h>#include <stdio.h>#include <conio.h>void draw(int xa, int ya, int xb, int yb); void main() { int xa, ya, xb, yb; clrscr(); printf("Bresenhnams algorithm"); /* get the coordinates of the line*/ printf("\n Enter the value of xa, ya:"); scanf("%d%d",&xa,&ya); printf("\n Enter the value of xb, yb:"); scanf("%d%d",&xb,&yb); draw(xa,ya,xb,yb); } void draw(int xa, int ya, int xb, int yb) { int x,y,dx,dy,xend,p; /* request auto detection */ int gdriver=DETECT,gmode,errorcode; /* initialize graphics and local variables */

initgraph(&gdriver,&gmode,"c:\\tc\\bgi"); /* read result of initialization */ errorcode=graphresult(); /* an error occurred */

if(errorcode!=grOk) { printf("Graphics error: %s\n", grapherrormsg(errorcode)); printf("Press any key to halt:"); getch(); exit(1); } dx=xb-xa; dy=yb-ya; p=2*dy-dx; /* calculate the value of the condition variable*/ if(xa>xb) /* depending on the position of the coordinates*/ { x=xb; /* assign the values for (x,y)*/ y=yb;



xend=xa; } else if(xb>xa) { x=xa; y=ya; xend=xb; } putpixel(x,y,1); /* draw the pixel on the screen*/ while(x<xend) /* depending on the control condition draw the pixels*/ { x=x+1; if(p<0) { p=p+2*dy; } else { y=y+1; p=p+2*dy; } putpixel(x,y,1); } /* clean up */ getch(); closegraph(); }



EXPERIMENT-3

3. Write a program to draw circle using mid-point algorithm.

The MidPoint Circle Algorithm is an algorithm used to determine the points needed for drawing a circle. The algorithm is a variant of Bresenham's line algorithm, and is thus sometimes known as Bresenham's circle algorithm. Which starts accordingly with the circle equation x2 + y2 = r2. And with the center of the circle is located at (0, 0) CODING: #include<stdio.h>/* include the necessary header files*/ #include<conio.h>#include<math.h>#include<graphics.h>main() { int gd=DETECT,gin; int xcenter,ycenter,radius; int p,x,y,twox,twoy; /*request auto detect*/ initgraph(&gd,&gin,"C:\\tc\\bgi"); x=0; printf("\nEnter the radius value:"); /* get the value of the radius and center values*/ scanf("%d",&radius); printf("Enter the center values:"); scanf("%d %d",&xcenter,&ycenter); plotpoints(xcenter,ycenter,x,y); /* call the plotpoints function*/ y=radius; p=1-radius; twox=2*x; twoy=2*y; printf("\np\tx\ty\t2x\t2y\n"); printf("\n%d\t%d\t%d\t%d\t%d\n",p,x,y,twox,twoy);

while(x<y) /* in the conditional loop compute the value of the x and y values*/ { if(p<0) x=x+1; else { x=x+1; y=y-1; } if(p<0) p=p+2*x+1; else p=p+2*(x-y)+1; twox=2*x; twoy=2*y;



printf("\n%d\t%d\t%d\t%d\t%d\n",p,x,y,twox,twoy); plotpoints(xcenter,ycenter,x,y); } getch(); return 0; } int plotpoints(int xcenter, int ycenter,int x,int y) /* plot the points of the circle as per the procedure*/ { putpixel(xcenter+x,ycenter+y,1); putpixel(xcenter-x,ycenter+y,1); putpixel(xcenter+x,ycenter-y,1); putpixel(xcenter-x,ycenter-y,1); putpixel(xcenter+y,ycenter+x,1); putpixel(xcenter-y,ycenter+x,1); putpixel(xcenter+y,ycenter-x,1); putpixel(xcenter-y,ycenter-x,1); }



EXPERIMENT-4

4. Write a program to draw ellipse using mid-point algorithm.

The Midpoint Ellipse Algorithm is a method for drawing ellipses in computer graphics this method is modified from Bresenham’s which starts accordingly with the ellipse equation b2x2 + a2y2 – a2b2 = 0 where a is the horizontal radius and b is the vertical radius CODING: #include<stdio.h>/* include the necessary header files*/ #include<conio.h>#include<graphics.h>include<math.h>#include<stdlib.h>void plotpoints(int,int,int,int); void main() { int gd=DETECT,gm; int xcenter,ycenter,rx,ry; int p,x,y,px,py,rx1,ry1,rx2,ry2; initgraph(&gd,&gm,"C:\\TC\\BGI"); /* request auto detect*/ printf("\n Enter the radius :"); /* get the radius and the center values*/ scanf("%d %d",&rx,&ry); printf("\n Enter the xcenter and ycenter values :"); scanf("%d %d",&xcenter,&ycenter); ry1=ry*ry; rx1=rx*rx; ry2=2*ry1; rx2=2*rx1; /* Region 1 */ x=0; y=ry; plotpoints(xcenter,ycenter,x,y); /* for the first region calculate the condition parameter*/ p=(ry1-rx1*ry+(0.25*rx1)); px=0; py=rx2*y; printf("\nx\ty\tp\tpx\tpy\n"); printf("\n%d\t%d\t%d\t%d\t%d",x,y,p,px,py); while(px<py) /* if this condition is true, compute values of x and y*/ { x=x+1; px=px+ry2; if(p>=0) { y=y-1; py=py-rx2;



p=p+ry1+px-py; } else p=p+ry1+px; plotpoints(xcenter,ycenter,x,y); /* call the plotpoints function*/ printf("\n%d\t%d\t%d\t%d\t%d",x,y,p,px,py); } /* Region 2 */ printf("\n%d\t%d\t%d\t%d\t%d",x,y,p,px,py); printf("\n\nRegion 2\n"); printf("\nx\ty\tp\tpx\tpy\n"); /* for region 2 recalculate the condition variables*/ p=(ry1*(x+0.5)*(x+0.5)+rx1*(y-1)*(y-1)-rx1*ry1); while(y>0) { y=y-1; py=py-rx2; if(p<=0) { x=x+1; px=px+ry2; } if(p>0) p=p+rx1-py; else p=p+rx1-py+px; plotpoints(xcenter,ycenter,x,y); /* draw the pixels for region 2*/ printf("\n%d\t%d\t%d\t%d\t%d",x,y,p,px,py); } getch(); closegraph(); } void plotpoints(int xcenter,int ycenter,int x,int y) /* plot the points of the circle as per the procedure*/ { putpixel(xcenter+x,ycenter+y,6); putpixel(xcenter-x,ycenter+y,6); putpixel(xcenter+x,ycenter-y,6); putpixel(xcenter-x,ycenter-y,6); }



EXPERIMENT-5

5. Write a program Rotation of Triangle.A transformation is any operation on a point in space (x, y) that maps the point's coordinates into a new set of coordinates (x1, y1).The Two Dimensional transformations has five operations such as Translation, Rotation, Reflection, Scaling and Shearing. CODING: #include<graphics.h>#include<stdlib.h>#include<stdio.h>#include<conio.h>int x1,x2,x3,y1,y2,y3,t,tx,sx,sy,shx,shy,ch; float rx1,rx2,rx3,ry1,ry2,ry3; float ang,theta; int main(void) { int gdriver = DETECT, gmode, errorcode; initgraph(&gdriver, &gmode,"C:\\TC\\BGI"); /* request for auto detection*/ errorcode = graphresult(); if(errorcode != grOk) /* if error occours*/ { printf("Graphics error: %s\n", grapherrormsg(errorcode)); printf("Press any key to halt:"); getch(); exit(1); } else { do{ printf("\n1.Translation\n2.Reflection\n3.Rotation\n4.Scaling\n5.Shearing\n"); printf("\nEnter Your choice"); /* get the choice from the user*/ scanf("%d",&ch); switch(ch) { printf("\n Enter all coordinates values :"); scanf("%d %d %d %d %d %d",&x1,&y1,&x2,&y2,&x3,&y3); printf("\n Before Rotation "); /* get the original coordinates*/ line(x1,y1,x2,y2); line(rx2,ry2,rx3,ry3); line(rx3,ry3,rx1,ry1); } getch(); closegraph(); /* close the graph*/ return 0; }



EXPERIMENT-6

6.Write a program to implement boundary –fill algorithm

include<graphics.h>

#include<dos.h>

void fill_right(int x,int y);

void fill_left(int x,int y);

void main()

{

int gd=DETECT,gm,x,y,n,i;

clrscr();

initgraph(&gd,&gm,"c:\\turboc3\\bgi");

printf("*** Boundary Fill algorithm ***");

line (50,50,200,50);

line (200,50,200,300);

line (200,300,50,300);

line (50,300,50,50);

x=100; y=100;

fill_right(x,y);

fill_left(x-1,y);

getch();

}

void fill_right(int x,int y)

{

{

if((getpixel(x,y) != WHITE)&&(getpixel(x,y) != RED)

{

putpixel(x,y,RED);



fill_right(++x,y); x=x-1;

fill_right(x,y-1);

fill_right(x,y+1);

}

delay(1);

}

void fill_left(int x,int y)

{

if((getpixel(x,y) != WHITE)&&(getpixel(x,y) != RED))

{

putpixel(x,y,RED);

fill_left(--x,y); x=x+1;

fill_left(x,y-1);

fill_left(x,y+1);

}

delay(1);

}



EXPERIMENT-7

7. Write a program to implement boundary –fill algorithm.#include<stdio.h>

#include<conio.h>

#include<graphics.h>

void boundfill(int xc,int yc,int r,int b)

{

int cur;

cur=getpixel(xc,yc);

if(cur!=b && cur!=r)

{

putpixel(xc,yc,r);

delay(1);

boundfill(xc+1,yc,r,b);

boundfill(xc-1,yc,r,b);

boundfill(xc,yc+1,r,b);

boundfill(xc,yc-1,r,b);

}

}

void main()

{

int gd=DETECT,gm;

initgraph(&gd,&gm,"..\\bgi");

rectangle(100,100,300,300);

boundfill(105,105,4,WHITE);



getch();

closegraph();

}

getch();

}



EXPERIMENT-8

8. Write a program to implement Bezier curve using four control points.#include <stdio.h>

#include <stdlib.h>

#include <graphics.h>

#include <math.h>

void bezier (int x[4], int y[4])

{

int gd = DETECT, gm; int i;

double t;

initgraph (&gd, &gm, "..\\bgi");

for (t = 0.0; t < 1.0; t += 0.0005)

{

double xt = pow (1-t, 3) * x[0] + 3 * t * pow (1-t, 2) * x[1] + 3 * pow (t, 2) * (1-t) * x[2] + pow (t, 3) * x[3];

double yt = pow (1-t, 3) * y[0] + 3 * t * pow (1-t, 2) * y[1] + 3 * pow (t, 2) * (1-t) * y[2] + pow (t, 3) * y[3];

putpixel (xt, yt, WHITE);

}

for (i=0; i<4; i++)

putpixel (x[i], y[i], YELLOW);

getch();

closegraph();

return;

}

void main()

{

int x[4], y[4]; int i;



printf ("Enter the x- and y-coordinates of the four control points.\n");

for (i=0; i<4; i++) scanf ("%d%d", &x[i], &y[i]); bezier (x, y);

}

closegraph();

}

getch();

}



EXPERIMENT-9

9. Write a program to implement CohenSutherland line clipping algorithm.#include<stdio.h>

#include<conio.h>


#include<math.h>

void clip(float,float,float);

int i,j=0,n;

int rx1,rx2,ry1,ry2;

float x1[8],y1[8];

void main()

{

int gd=DETECT,gm;

int i,n;

float x[8],y[8],m;

clrscr();

initgraph(&gd,&gm,"");

printf("coordinates for rectangle : ");

scanf("%d%d%d%d",&rx1,&ry1,&rx2,&ry2);

printf("no. of sides for polygon : ");

scanf("%d",&n);

printf("coordinates : ");

for(i=0;i<n;i++)

{

scanf("%f%f",&x[i],&y[i]);



}

cleardevice();

outtextxy(10,10,"Before clipping");

outtextxy(10,470,"Press any key....");

rectangle(rx1,ry1,rx2,ry2);

for(i=0;i<n-1;i++)

line(x[i],y[i],x[i+1],y[i+1]);

line(x[i],y[i],x[0],y[0]);

getch();

cleardevice();

for(i=0;i<n-1;i++)

{

m=(y[i+1]-y[i])/(x[i+1]-x[i]);

clip(x[i],y[i],m);

}

clip(x[0],y[0],m);

outtextxy(10,10,"After clipping");

outtextxy(10,470,"Press any key....");

rectangle(rx1,ry1,rx2,ry2);

for(i=0;i<j-1;i++)

line(x1[i],y1[i],x1[i+1],y1[i+1]);

getch();

}

void clip(float e,float f,float m)

{



while(e<rx1 e>rx2 f<ry1 f>ry2)

{

if(e<rx1)

{

f+=m*(rx1-e);

e=rx1;

}

else if(e>rx2)

{

f+=m*(rx2-e);

e=rx1;

}

if(f<ry1)

{

e+=(ry1-f)/m;

f=ry1;

}

else if(f>ry2)

{

e+=(ry2-f)/m;

f=ry2;

}

x1[j]=e;

y1[j]=f;

j++;

}

}



EXPERIMENT-10

10. Write a program to implement Liang Barsky line clipping algorithm.

#include<stdio.h>

#include<conio.h>


#include<math.h>

Void main

{

float x1,y1,x2,y2,xmin,xmax,ymin,ymax,dx,dy;

float p[4],q[4],r[4];

float max,min,u1,u2;

float xi,xii,yi,yii;

int gd,gm,i;

gd=DETECT;

initgraph(&gd,&gm,"c:\\tc\\bgi");

clrscr();

printf("\n enter the line co-ordinates");

printf("\n enter 1st x=");

scanf("%f",&x1);

printf("\t 1st y=");

scanf("%f",&y1);

printf("\n enter 2nd x=");

scanf("%f",&x2);

printf("\t 2nd y=");

scanf("%f",&y2);

printf("\n enter window boundry");



printf("\n xmin=");

scanf("%f",&xmin);

printf("\n ymin=");

scanf("%f",&ymin);

printf("\n xmax=");

scanf("%f",&xmax);

printf("\n ymax=");

scanf("%f",&ymax)

dx=x2-x1;

dy=y2-y1;

cleardevice();

line(x1,y1,x2,y2);

rectangle(xmin,ymin,xmax,ymax);

p[0]=-dx;

q[0]=x1-xmin;

p[1]=dx;

q[1]=xmax-x1;

p[2]=-dy;

p[2]=-dy;

q[2]=y1-ymin;

p[3]=dy;

q[3]=ymax-y1;

for(i=0;i<4;i++)

{

if(p[i]==0 && q[i]<0)

{

printf("Line is outside the boundry,it is not a clipping candidate\n");

getch();



exit(0);

}

}

for(i=0;i<4;i++)

{

r[i]=q[i]/p[i];

printf("\n r[%d]=%f",i,r[i]);

}

max=0;min=1;

for(i=0;i<4;i++)

if(p[i]<0)

{

if(r[i]>max)

max=r[i];

}

else

{

if(r[i]<min)

min=r[i];

}

u1=max;

u2=min;

printf("\n u1=%f",u1);

printf("\n u2=%f",u2);

if(u1>u2)

{

printf("\n line is completely outside");



getch();

exit(0);

}

xi=x1+(u1*dx);

yi=y1+(u1*dy);

xii=x1+(u2*dx);

yii=y1+(u2*dy);

rectangle (xmin, ymin, xmax, ymax);

sector(5);

line(xi,yi,xii,yii);

getch();

closegraph();

}



EXPERIMENT-11

11. Write a program to implement face of a cartoon.

# include <graphics.h># include<conio.h>#include <stdlib.h>main(){int gd= DETECT, gm,area, temp1, temp2, left=25, top=75;void*p;initgraph(&gd, &gm,”C:\\TC\BGI”);

Setcolor(YELLOW);Circle(50, 100,25);Sefillstyle(SOLID__FILL,YELLOW);

floodfill(50,100, YELLOW);Setcolor(BLACK);

Sefillstyle(SOLID__FILL,BLACK);fillellipse(44, 85, 2, 6);

fillellipse(56, 85, 2, 6);ellipse(50, 100, 205, 335, 20,9);

ellipse(50, 100, 205, 335, 20,10);

ellipse(50, 100, 205, 335, 20,11);area= imagesize(left, top, left+ 50, top+50);p= malloc(area);setcolor(WHITE);settextstyle(SANS_SERIF_FONT, HORIZ_DIR,2);outtextxy(155, 451, “Smiling Face Animation”);setcolor(BLUE);rectangle(0,0 , 639,449);while(!kbhit()){Temp1= 1+ randam(588);{Temp1= 1+ randam(380);{

Getimage(left, top, left+ 50, top+ 50);putimage(left, top, p, XOR_PUT);putimage(temp1, temp2, p, XOR_PUT);delay(100);left= temp1;top = temp2;



}getch();closegraph();return();}
