Notes

DDA Algorithm:
Step1: Start Algorithm
Step2: Declare x1,y1,x2,y2,dx,dy,x,y as integer variables.
Step3: Enter values of x1,y1,x2,y2.
Step4: Calculate dx = x2-x1
Step5: Calculate dy = y2-y1
Step6: If ABS (dx) > ABS (dy)
Then step = abs (dx)
Else
Step7: xinc=dx/step
yinc=dy/step
assign x = x1
assign y = y1
Step8: Set pixel (x, y)
Step9: x = x + xinc
y = y + yinc
Set pixels (Round (x), Round (y))
Step10: Repeat step 9 until x = x2
Step11: End Algorithm
Program:
#include <graphics.h>
#include <stdio.h>
#include <math.h>
int main( )
{
float x,y,x1,y1,x2,y2,dx,dy,pixel;
int i,gd,gm;
printf("Enter the value of x1 : ");
scanf("%f",&x1);
printf("Enter the value of y1 : ");
scanf("%f",&y1);
printf("Enter the value of x2 : ");
scanf("%f",&x2);
printf("Enter the value of y1 : ");
scanf("%f",&y2);
detectgraph(&gd,&gm);
initgraph(&gd,&gm,"");
dx=abs(x2-x1);
dy=abs(y2-y1);
if(dx>=dy)
pixel=dx;
else
pixel=dy;
dx=dx/pixel;
dy=dy/pixel;
x=x1;
y=y1;
i=1;
while(i<=pixel)
{
putpixel(x,y,1);
x=x+dx;
y=y+dy;
i=i+1;
delay(100);
}
getch();
closegraph();
}


Bresenham's Line Algorithm:
Step1: Start Algorithm
Step2: Declare variable x1,x2,y1,y2,d,i1,i2,dx,dy
Step3: Enter value of x1,y1,x2,y2
Where x1,y1are coordinates of starting point
And x2,y2 are coordinates of Ending point
Step4: Calculate dx = x2-x1
Calculate dy = y2-y1
Calculate i1=2*dy
Calculate i2=2*(dy-dx)
Calculate d=i1-dx
Step5: Consider (x, y) as starting point and xendas maximum possible
value of x.
If dx < 0
Then x = x2
y = y2
xend=x1
If dx > 0
Then x = x1
y = y1
xend=x2
Step6: Generate point at (x,y)coordinates.
Step7: Check if whole line is generated.
If x > = xend
Stop.
Step8: Calculate co-ordinates of the next pixel
If d < 0
Then d = d + i1
If d ≥ 0
Then d = d + i2
Increment y = y + 1
Step9: Increment x = x + 1
Step10: Draw a point of latest (x, y) coordinates
Step11: Go to step 7
Step12: End of Algorithm
Program:
#include <stdio.h>
#include <conio.h>
#include <graphics.h>
int main()
{
int x, y, x1, y1, x2, y2, dx, dy, p, i;
int gd = DETECT, gm;
printf("Enter first point:");
scanf("%d%d", &x1, &y1);
printf("Enter Second point:");
scanf("%d%d", &x2, &y2);
initgraph(&gd, &gm, (char *)"");
dx = x2 - x1;
dy = y2 - y1;
p = 2 * dy - dx;
x = x1;
y = y1;
i = 0;
while (i <= dx)
{
putpixel(x, y, WHITE);
if (p < 0)
{
x = x + 1;
p = p + 2 * dy;
}
else
{
x = x + 1;
y = y + 1;
p = p + 2 * dy - 2 * dx;
}
i++;
}
getch();
closegraph();
return 0;
}