libretime/legacy/public/js/waveformplaylist/curves.js

72 lines
1.7 KiB
JavaScript

var Curves = {};
Curves.createLinearBuffer = function createLinearBuffer(length, rotation) {
var curve = new Float32Array(length),
i, x,
scale = length - 1;
for (i = 0; i < length; i++) {
x = i / scale;
if (rotation > 0) {
curve[i] = x;
}
else {
curve[i] = 1 - x;
}
}
return curve;
};
Curves.createExponentialBuffer = function createExponentialBuffer(length, rotation) {
var curve = new Float32Array(length),
i, x,
scale = length - 1,
index;
for (i = 0; i < length; i++) {
x = i / scale;
index = rotation > 0 ? i : length - 1 - i;
curve[index] = Math.exp(2 * x - 1) / Math.exp(1);
}
return curve;
};
//creating a curve to simulate an S-curve with setValueCurveAtTime.
Curves.createSCurveBuffer = function createSCurveBuffer(length, phase) {
var curve = new Float32Array(length),
i;
for (i = 0; i < length; ++i) {
curve[i] = (Math.sin((Math.PI * i / length) - phase)) /2 + 0.5;
}
return curve;
};
//creating a curve to simulate a logarithmic curve with setValueCurveAtTime.
Curves.createLogarithmicBuffer = function createLogarithmicBuffer(length, base, rotation) {
var curve = new Float32Array(length),
index,
key = ""+length+base+rotation,
store = [],
x = 0,
i;
if (store[key]) {
return store[key];
}
for (i = 0; i < length; i++) {
//index for the curve array.
index = rotation > 0 ? i : length - 1 - i;
x = i / length;
curve[index] = Math.log(1 + base*x) / Math.log(1 + base);
}
store[key] = curve;
return curve;
};