Which pixels should light up to draw a straight line? Drag the ends of the line, or click to move the nearer one. My 2011 version solves the basic case, lines going right and rising at most 45°, tracking the error between the true line (red) and the pixels with a floating-point number. The other seven directions are mirror images of it: swap the ends, flip it upside down, or swap x and y, draw it, and mirror the pixels back. Compare it as written, with the mirroring, and as the integer-only version that needs no mirroring.
/**
* Created by mihailod, Feb 15, 2011, 7:04:00 PM
*/
public class Bresenham {
public static void main(String[] args) {
final int x0 = 0; //Integer.parseInt(args[0]);
final int y0 = 0; //Integer.parseInt(args[1]);
final int x1 = 5; //Integer.parseInt(args[2]);
final int y1 = 2; //Integer.parseInt(args[3]);
line(x0, y0, x1, y1);
}
private static void line(final int x0, final int y0, final int x1, final int y1) {
int deltax = x1 - x0;
int deltay = y1 - y0;
double error = 0d;
double deltaErr = (double)deltay / (double)deltax;
int y = y0;
for(int x = x0; x <= x1; x++) {
plot(x,y);
error = error + deltaErr;
if (Math.abs(error) >= 0.5) {
y = y + 1;
error = error - 1.0;
}
}
}
private static void plot(final int x, final int y) {
System.out.print("(" + x + ", " + y + ") ");
}
}