Vertical line on HxW canvas of pixels
- by bobby williams
I searched and found nothing.
I'm trying to draw lines (simple y=mx+b ones) on a canvas of black pixels.
It works fine, but no line occurs when it is vertical. I'm not sure why. My first if statement checks if the denominator is zero, therefore m is undefined and no need for a line equation.
My second and third if statement check how steep it is and based on that, calculate the points in between.
I don't think there is a need for other classes, since I think there is a bug in my code or I'm just not translating the mathematics into code properly. If more is needed, I'll be happy to post more.
/**
* Returns an collection of points that connects p1 and p2
*/
public ArrayList getPoints()
{
ArrayList points = new ArrayList();
// checks to see if denominator in m is zero. if zero, undefined.
if ((p2.getX() - p1.getX()) == 0) {
for (int y = p1.getY(); y<p2.getY(); y++) {
points.add(new Point(p1.getX(), y, getColor()));
}
}
double m = (double)(p2.getY()-p1.getY())/(double)(p2.getX()-p1.getX());
int b = (int)(p1.getY() - (m * p1.getX()));
// checks to see if slope is steep.
if (m > -1 || m < 1) {
for (int x = p1.getX(); x<p2.getX(); x++) {
int y = (int) ((m*x)+b);
points.add(new Point(x, y, getColor()));
}
}
// checks to see if slope is not steep.
if (m <= -1 || m >= 1) {
for (int y = p1.getY(); y<p2.getY(); y++) {
int x = (int) ((y-b)/m);
points.add(new Point(x, y, getColor()));
}
}
return points;
}
