I’ve been working off and on with my wall plotter project, and found that it was really difficult to find a good implentation of Bresenham’s line-drawing algorithm done in Arduino. The original code I found following a link from Wikipedia, pointing to implementations in a number of languages. This is modified from the original C code. http://rosettacode.org/wiki/Bitmap/Bresenham’s_line_algorithm#C

Note that I’m using suspension steppers, so my movement code is somewhat custom. Just replace those sections (noted with comments) to meet whatever movement method you prefer.

The function is called with x,y pairs. For my purposes, the first pair is always the current location and the second is the destination.

```
void line(int x0, int y0, int x1, int y1) { /// Bresenham's Line Algorithm
int md1, md2, s_s1, s_s2, ox, oy;
int dx = abs(x1-x0), sx = x0<x1 ? 1 : -1;
int dy = abs(y1-y0), sy = y0<y1 ? 1 : -1;
int err = (dx>dy ? dx : -dy)/2, e2;
for(;;){
ox=x0;
oy=y0;
if (x0==x1 && y0==y1) break;
e2 = err;
if (e2 >-dx) {
err -= dy;
x0 += sx;
}
if (e2 < dy) {
err += dx;
y0 += sy;
}
s_s1=s1;
s_s2=s2;
if (y0 < oy) { // Move UP, replace s1/s2 with your own code
s1=s1-1;
s2=s2-1;
};
if (y0 > oy) { // DOWN, replace s1/s2 with your own code
s1=s1+1;
s2=s2+1;
};
if (x0 < ox) { //LEFT, replace s1/s2 with your own code
s1=s1-1;
s2=s2+1;
};
if (x0 > ox) { //RIGHT, replace s1/s2 with your own code
s1=s1+1;
s2=s2-1;
};
md1=s1-s_s1;
md2=s2-s_s2;
stepper1.step(md1); //now do the actual move.
stepper2.step(md2);
delay(10); //delay for settling
}
}
```