steps in bresenham line drawing algorithm code example

Example 1: bresenham line drawing algorithm code

#include<iostream.h>
#include<graphics.h>
 
void drawline(int x0, int y0, int x1, int y1)
{
    int dx, dy, p, x, y;
 
	dx=x1-x0;
	dy=y1-y0;
 
	x=x0;
	y=y0;
 
	p=2*dy-dx;
 
	while(x<x1)
	{
		if(p>=0)
		{
			putpixel(x,y,7);
			y=y+1;
			p=p+2*dy-2*dx;
		}
		else
		{
			putpixel(x,y,7);
			p=p+2*dy;
		}
		x=x+1;
	}
}
 
int main()
{
	int gdriver=DETECT, gmode, error, x0, y0, x1, y1;
	initgraph(&gdriver, &gmode, "c:\\turboc3\\bgi");
 
	cout<<"Enter co-ordinates of first point: ";
	cin>>x0>>y0;
 
	cout<<"Enter co-ordinates of second point: ";
	cin>>x1>>y1;
	drawline(x0, y0, x1, y1);
 
	return 0;
}

Example 2: Bresenham's line algorithm

static void bresenham(int x1, int y1, int x2, int y2) 
    { 
        int m_new = 2 * (y2 - y1); 
        int slope_error_new = m_new - (x2 - x1); 
      
        for (int x = x1, y = y1; x <= x2; x++) 
        { 
            System.out.print("(" +x + "," + y + ")\n"); 
  
            // Add slope to increment angle formed 
            slope_error_new += m_new; 
  
            // Slope error reached limit, time to 
            // increment y and update slope error. 
            if (slope_error_new >= 0) 
            { 
                y++; 
                slope_error_new -= 2 * (x2 - x1); 
            } 
        } 
    }