Draw a Line : Bresenham’s Line Drawing Algorithm


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C Program

#include<stdio.h>
#include<conio.h>
#include<graphics.h>
#include<math.h>
void swap(int &x, int &y) {
	int k = x;
	x = y;
	y = k;
}
void main() {
	int gd = DETECT, gm = DETECT, x1, x2, y1, y2, dx, dy, p, k;
	float m = 0;
	clrscr();
	printf("Enter the sarting point x1 & y1\n");
	scanf("%d%d", &x1, &y1);
	printf("Enter the end point x2 & y2\n");
	scanf("%d%d", &x2, &y2);
	dx = abs(x2 - x1);
	dy = abs(y2 - y1);
	m = (float) (y2 - y1) / (x2 - x1);
	initgraph(&gd, &gm, "");
	cleardevice();
	if (fabs(m) > 1) {
		swap(x1, y1);
		swap(x2, y2);
		swap(dx, dy);
	}
	if ((x1 > x2)) {
		x1 = x2;
		y1 = y2;
	}
	p = 2 * dy - dx;
	for (k = 0; k < abs(dx); k++) {
		if (p < 0) {
			p = p + 2 * dy;
		} else {
			if (m < 0)
					y1--; else
					y1++;
			p = p + (2 * dy) - (2 * dx);
		}
		if (fabs(m) <= 1)
			    putpixel(x1++, y1, 15); else
			    putpixel(y1, x1++, 15);
	}
	getch();
}





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