Adds quantize() and tests

stephband · May 17, 2024 · a8e3249 · a8e3249
1 parent 5fd183a
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diff --git a/modules/quantize.js b/modules/quantize.js
@@ -0,0 +1,84 @@
+
+const assign = Object.assign;
+
+/**
+quantize()
+Quantize events into triplets and duplets.
+**/
+
+function collect(split, events, i) {
+    let n = i - 1;
+    while(events[++n] && events[n][0] < split);
+    return n > i ?
+        events.slice(i, n) :
+        undefined ;
+}
+
+function toBeat0(output, event) {
+    const e = Array.from(event);
+    e[0] = 0;
+    output.push(e);
+    return output;
+}
+
+function quantizeScale(events, scale = 1, output) {
+    let i = 0;
+
+    const events00 = collect(scale * 0.0972222222, events, i);
+    if (events00) {
+        i += events00.length;
+        events00.reduce(toBeat0, output);
+    }
+
+    const events25 = collect(scale * 0.2916666667, events, i);
+    if (events25) i += events25.length;
+    const events33 = collect(scale * 0.4305555556, events, i);
+    if (events33) i += events33.length;
+    const events50 = collect(scale * 0.5694444444, events, i);
+    if (events50) i += events50.length;
+    const events67 = collect(scale * 0.7083333333, events, i);
+    if (events67) i += events67.length;
+    const events75 = collect(scale * 0.9027777778, events, i);
+
+    // Quadruplets
+    if (events25 && events50
+        || events25 && events75
+        || events50 && events75
+        || events25 && events33
+        || events33 && events50
+        || events50 && events67
+        || events67 && events75
+    ) {
+        console.log('Quadruplets');
+        return;
+    }
+
+    if (events33) {
+        console.log('Triplets');
+        return events33.map((event) => assign([], event, { 0: 0.333333333 }));
+    }
+
+    // We already checked (events50 && events67) so this is exclusive OR. In
+    // english, that means there is only one event beat at 50% or 67% in this
+    // beat, and we want to fall through to looking at these events at 2x zoom
+    if (events50 || events67) {
+        console.log('Recurse at 2x');
+        return;
+    }
+
+    // Quadruplets
+    if (events25) {
+        return events25.map((event) => assign([], event, { 0: 0.25 }));
+    }
+
+    if (events75) {
+        return events75.map((event) => assign([], event, { 0: 0.75 }));
+    }
+
+    return output;
+}
+
+export default function quantize(events) {
+    const output = [];
+    return quantizeScale(events, 1, output);
+}
diff --git a/test/index.html b/test/index.html
@@ -0,0 +1,46 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+    <title>&lt;scribe-music&gt;</title>
+
+    <meta charset="utf-8" />
+    <meta name="author" content="@stephband" />
+    <meta name="description" content="" />
+    <meta name="viewport" content="width=device-width" />
+
+    <script title="debug">window.DEBUG = true;</script>
+</head>
+<body>
+    <script type="module">
+        import quantize from '../modules/quantize.js';
+        import test from '../lib/fn/modules/test.js';
+
+        const assign = Object.assign;
+
+        test('Quantize', [
+            [],
+            [[0,           'note', 'C4', 1, 1]],
+            [[0.25,        'note', 'C4', 1, 1]],
+            [[0.25,        'note', 'C4', 1, 1]],
+            [[0.333333333, 'note', 'C4', 1, 1]],
+            [[0.333333333, 'note', 'C4', 1, 1]],
+
+            [[0.75,        'note', 'C4', 1, 1]],
+            [[0.75,        'note', 'C4', 1, 1]]
+        ], (expect, done) => {
+            expect(quantize([]));
+            expect(quantize([[0.0, 'note', 'C4', 1, 1]]));
+            expect(quantize([[0.1, 'note', 'C4', 1, 1]]));
+            expect(quantize([[0.2, 'note', 'C4', 1, 1]]));
+            expect(quantize([[0.3, 'note', 'C4', 1, 1]]));
+            expect(quantize([[0.4, 'note', 'C4', 1, 1]]));
+            quantize([[0.5, 'note', 'C4', 1, 1]]);
+            quantize([[0.6, 'note', 'C4', 1, 1]]);
+            quantize([[0.7, 'note', 'C4', 1, 1]]);
+            expect(quantize([[0.8, 'note', 'C4', 1, 1]]));
+            expect(quantize([[0.9, 'note', 'C4', 1, 1]]));
+            done();
+        });
+    </script>
+</body>
+</html>