{
const context = DOM.context2d(width, width);
context.translate(width / 2, width / 2);
let m = 100;
let s = -1;
while (true) {
yield Promises.delay(10).then(() => {
context.clearRect(-width / 2, -width / 2, width, width);
const c = [0, 0, r];
circle(c, context, { fill: false });
if (m < -turnAfter || m > turnAfter) s *= -1;
m += s;
for (let i = startR; i < endR; i += stepR) {
const sq = square(r + i, m);
drawSquareAndInverted(sq, c, context);
}
return context.canvas;
});
}
}
function drawSquareAndInverted([p1, p2, p3, p4], c, context) {
const cr = 1.5;
const BLACK = circleSprite('black', cr * 2);
const RED = circleSprite('red', cr * 2);
for (let x = p2[0]; x <= p1[0]; x += step) {
[p1, p3].forEach(p => {
BLACK.draw(context, x, p[1]);
RED.draw(context, ...invertOnCircle(c, [x, p[1], cr]));
});
}
for (let y = p3[1]; y <= p2[1]; y += step) {
[p3, p4].forEach(p => {
const c_i = [p[0], y, cr];
BLACK.draw(context, p[0], y);
RED.draw(context, ...invertOnCircle(c, [p[0], y, cr]));
});
}
}
function circleSprite(color, size, pad = 1) {
const s = Math.ceil(size + pad * 2), r = size / 2, m = s / 2;
const c = DOM.context2d(s, s, 1);
c.fillStyle = color;
c.moveTo(m + r, m);
c.arc(m, m, r, 0, Math.PI * 2);
c.fill();
c.canvas.draw = (context, x, y) => {
context.drawImage(c.canvas, x - m, y - m);
}
return c.canvas;
}
function square(r, m) {
const p1 = [r + m, r + m];
const p2 = [-r - m, r + m];
const p3 = [r + m, -r - m];
const p4 = [-r - m, -r - m];
return [p1, p2, p3, p4];
}
function invertOnCircle([x, y, r], [px, py]) {
const d = dist2D([x, y], [px, py]);
const lenP = (r * r) / d;
return pointOnLine([[x, y], [px, py]], lenP / d);
}
One platform to build and deploy the best data apps
Experiment and prototype by building visualizations in live JavaScript notebooks. Collaborate with your team and decide which concepts to build out.
Use Observable Framework to build data apps locally. Use data loaders to build in any language or library, including Python, SQL, and R.
Seamlessly deploy to Observable. Test before you ship, use automatic deploy-on-commit, and ensure your projects are always up-to-date.