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let _context;
function getContext() {
if (!_context) {
_context = new AudioContext();
}
return _context;
}
async function loadSample(url) {
const res = await fetch(url);
const buffer = await res.arrayBuffer();
return getContext().decodeAudioData(buffer);
}
function playSoundSample(sample, sampleNote, noteToPlay) {
const ctx = getContext();
const source = ctx.createBufferSource();
source.buffer = sample;
source.playbackRate.value = 2 ** ((noteToPlay - sampleNote) / 12);
source.connect(ctx.destination);
source.start(0);
}
function sigmoid(x) {
return 1 / (1 + Math.exp(-x));
}
function drawNoteLines(canvas) {
const ctx = canvas.getContext("2d");
let clicks = [];
function render() {
const W = 256;
const H = 512;
ctx.clearRect(0, 0, W, H);
const L = 1.0;
ctx.lineWidth = L;
ctx.strokeStyle = "#ccc";
for (let note = 0; note <= 12; note++) {
ctx.beginPath();
const y = (note / 12) * (H - L) + L / 2;
ctx.moveTo(0, y);
ctx.lineTo(W, y);
ctx.stroke();
}
let now = Date.now();
const R = 10.0;
for (const [x, y, t] of clicks) {
ctx.beginPath();
ctx.arc(x - R, y - R, 10, 0, 2 * Math.PI);
const tt = (now - t) / 1000; // [0, 1]
const alpha = sigmoid(5 - 10 * tt);
ctx.fillStyle = `rgb(0, 99, 228, ${alpha})`;
ctx.fill();
}
clicks = clicks.filter((o) => now < o[2] + 1_000);
if (clicks.length > 0) {
requestAnimationFrame(render);
}
}
render();
canvas.addEventListener("mousedown", (e) => {
const { layerX, layerY } = e;
clicks.push([layerX, layerY, Date.now()]);
render();
});
}
window.drawNoteLines = drawNoteLines;
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