### Floyd–Steinberg dithering

This implementation zig-zags to reduce some artifact patterns.

I couldn't solid-fill the drawing area. Even at 0.1 step size there were gaps.

```// Floyd-Steinberg dithering.  Implemented by @imakerobots

Canvas.setpenopacity(1);

// Global code will be evaluated once.
const turtle = new Turtle();
const level_of_detail=2;  // min=1.5, max=20, step=0.5

turtle.penup();
turtle.goto(-100,-100);
const stepSize = level_of_detail/10.0;
const stepsPerLine = Math.floor(200.0/stepSize);
stepsRemaining=stepsPerLine*stepsPerLine;
dx=1;

error1 = new Array(stepsPerLine);
error2 = new Array(stepsPerLine);
for(i=0;i<error1.length;++i) {
error1[i] = error2[i] = 0;
}

function newLine() {
for(var i=0;i<stepsPerLine;++i) {
error1[i] = error2[i];
error2[i] = 0;
}
}

function get_pixel(x,y) {
return error1[x] + y/stepsPerLine;
}

function find_closest_palette_color(oldpixel) {
return oldpixel>0.5?1.0:0.0;
}

function walk(i) {
var x=turtle.x()/stepSize+stepsPerLine/2;
var y=turtle.y()/stepSize+stepsPerLine/2;
if(x<0) x=0;
if(x>=stepsPerLine) x=stepsPerLine-1;
x=Math.floor(x);

var oldpixel = get_pixel(x,y);
var newpixel = find_closest_palette_color(oldpixel);
var quant_error = oldpixel - newpixel;
var xP1 = x+dx;
var xM1 = x-dx;
if(xP1>=0 && xP1<stepsPerLine) error1[xP1] += quant_error * 7.0/16.0;
if(xM1>=0 && xM1<stepsPerLine) error2[xM1] += quant_error * 3.0/16.0;
error2[x  ] += quant_error * 5.0/16.0;
if(xP1>=0 && xP1<stepsPerLine) error2[xP1] += quant_error * 1.0/16.0;

if(newpixel>0.5) {
turtle.penup();
} else {
turtle.pendown();
}

turtle.forward(stepSize);
if(turtle.x()>=100) {
turtle.right(90);
turtle.forward(stepSize);
turtle.right(90);
dx=-dx;
newLine();
} else if(turtle.x()<=-100) {
turtle.left(90);
turtle.forward(stepSize);
turtle.left(90);
dx=-dx;
newLine();
}

return turtle.y()<100 && turtle.y()>=-100;//stepsRemaining-- > 0;
}```