Question

The book by Foley et al. presents a version of the Bresenham algorithm, that works for lines with slope m such that 0 ≤ m ≤ 1. Below, the algorithm follows:

void MidPointLine(int x0, int y0, // line start point

                              int x1, int y1) { // line final poin

   int dx = x1 - x0;

int dy = y1 - y0;

int d = 2 * dy - dx;

int incrE = 2 * dy;

int incrNE = 2 * (dy - dx);

int x = x0;

int y = y0;

PutPixel(x, y); // firs pixel of the line

while (x

if (d<=0) {

d += incrE;

x++;

    } else {

d += incrNE;

x++;

y++;

}

      PutPixel(x, y);

}

}

Assuming that the function above was invoked with the MidPointLine parameters (0,0,5,3): list the coordinate pairs (x, y) of all pixels that will be painted as a result of this call. Note: the first pixel to be painted will be the coordinates (0,0).

Answer 1

#include <stdio.h>
void MidPointLine(int x0, int y0, int x1, int y1)
{
    int dx = x1 - x0;
    int dy = y1 - y0;
    int d = 2 * dy - dx;
    int incrE = 2 * dy;
    int incrNE = 2 * (dy - dx);
    int x = x0;
    int y = y0;
    printf("(%d, %d)\n", x, y);
    while (x < x1)
    {
        if (d <= 0)
        {
            d += incrE;
            x++;
        }
        else
        {
            d += incrNE;
            x++;
            y++;
        }
        printf("(%d, %d)\n", x, y);
    }
}

int main()
{
    MidPointLine(0, 0, 5, 3);
    return 0;
}

Output:

(0, 0)
(1, 1)
(2, 1)
(3, 2)
(4, 2)
(5, 3)