Page 126 - Algorithms Notes for Professionals

/* A C program to implement Bresenham line drawing algorithm for |m|<1 */
#include<stdio.h>
#include<conio.h>
#include<graphics.h>
#include<math.h>

int main()
{
int gdriver=DETECT,gmode;
int x1,y1,x2,y2,delx,dely,p,i;
initgraph(&gdriver,&gmode,"c:\\TC\\BGI");

printf("Enter the intial points: ");
scanf("%d",&x1);
scanf("%d",&y1);
printf("Enter the end points: ");
scanf("%d",&x2);
scanf("%d",&y2);

putpixel(x1,y1,RED);

delx=fabs(x2-x1);
dely=fabs(y2-y1);
p=(2*dely)-delx;
for(i=0;i<delx;i++){
if(p<0)
{
x1=x1+1;
putpixel(x1,y1,RED);
p=p+(2*dely);
}
else
{
x1=x1+1;
y1=y1+1;
putpixel(x1,y1,RED);
p=p+(2*dely)-(2*delx);
}
}
getch();
closegraph();
return 0;
}

Algorithm for slope |m|>1:

1. Input two end points (x1,y1) and (x2,y2) of the line.
2. Plot the first point (x1,y1).
3. Calculate
Delx =| x2 – x1 |
Dely = | y2 – y1 |
4. Obtain the initial decision parameter as
P = 2 * delx – dely
5. For I = 0 to dely in step of 1

If p < 0 then
y1 = y1 + 1
Pot(x1,y1)

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