Tone.js/Tone/signal/WaveShaper.ts

import { ToneAudioNodeOptions } from "../core/context/ToneAudioNode";
import { optionsFromArguments } from "../core/util/Defaults";
import { isArray, isFunction, isUndef } from "../core/util/TypeCheck";
import { Signal, SignalOptions } from "./Signal";
import { SignalOperator } from "./SignalOperator";

type WaveShaperMappingFn = (value: number, index?: number) => number;

type WaveShaperMapping =  WaveShaperMappingFn | number[] | Float32Array;

interface WaveShaperOptions extends ToneAudioNodeOptions {
	mapping?: WaveShaperMapping;
	length: number;
	curve?: number[] | Float32Array;
}

/**
 * Wraps the native Web Audio API
 * [WaveShaperNode](http://webaudio.github.io/web-audio-api/#the-waveshapernode-interface).
 *
 *  @param mapping The function used to define the values.
 *                 The mapping function should take two arguments:
 *                 the first is the value at the current position
 *                 and the second is the array position.
 *                 If the argument is an array, that array will be
 *                 set as the wave shaping function. The input
 *                 signal is an AudioRange [-1, 1] value and the output
 *                 signal can take on any numerical values.
 *
 *  @param bufferLen The length of the WaveShaperNode buffer.
 *  @example
 * var timesTwo = new WaveShaper(function(val){
 * 	return val * 2;
 * }, 2048);
 *  @example
 * //a waveshaper can also be constructed with an array of values
 * var invert = new WaveShaper([1, -1]);
 */
export class WaveShaper extends SignalOperator<WaveShaperOptions> {

	name = "WaveShaper";

	/**
	 *  the waveshaper node
	 */
	private _shaper: WaveShaperNode = this.context.createWaveShaper();

	/**
	 * The input to the waveshaper node.
	 */
	input = this._shaper;

	/**
	 * The output from the waveshaper node
	 */
	output = this._shaper;

	protected _internalChannels = [this._shaper];

	constructor(options?: Partial<WaveShaperOptions>);
	constructor(mapping?: WaveShaperMapping , length?: number);
	constructor() {
		super(Object.assign(optionsFromArguments(WaveShaper.getDefaults(), arguments, ["mapping", "length"])));
		const options = optionsFromArguments(WaveShaper.getDefaults(), arguments, ["mapping", "length"]);

		if (isArray(options.mapping) || options.mapping instanceof Float32Array) {
			this.curve = Float32Array.from(options.mapping);
		} else if (isFunction(options.mapping)) {
			this.setMap(options.mapping, options.length);
		}
	}

	static getDefaults(): WaveShaperOptions {
		return Object.assign(Signal.getDefaults(), {
			length: 1024,
		});
	}

	/**
	 *  Uses a mapping function to set the value of the curve.
	 *  @param mapping The function used to define the values.
	 *                 The mapping function take two arguments:
	 *                 the first is the value at the current position
	 *                 which goes from -1 to 1 over the number of elements
	 *                 in the curve array. The second argument is the array position.
	 * @example
	 * //map the input signal from [-1, 1] to [0, 10]
	 * shaper.setMap(function(val, index){
	 * 	return (val + 1) * 5;
	 * })
	 */
	setMap(mapping: WaveShaperMappingFn, length: number = 1024): this {
		const array = new Float32Array(length);
		for (let i = 0, len = length; i < len; i++) {
			const normalized = (i / (len - 1)) * 2 - 1;
			array[i] = mapping(normalized, i);
		}
		this.curve = array;
		return this;
	}

	/**
	 * The array to set as the waveshaper curve. For linear curves
	 * array length does not make much difference, but for complex curves
	 * longer arrays will provide smoother interpolation.
	 */
	get curve(): Float32Array | null {
		return this._shaper.curve;
	}

	set curve(mapping: Float32Array | null) {
		this._shaper.curve = mapping;
	}

	/**
	 * Specifies what type of oversampling (if any) should be used when
	 * applying the shaping curve. Can either be "none", "2x" or "4x".
	 */
	get oversample(): OverSampleType {
		return this._shaper.oversample;
	}

	set oversample(oversampling: OverSampleType) {
		const isOverSampleType = ["none", "2x", "4x"].some(str => str.includes(oversampling));
		this.assert(isOverSampleType, "oversampling must be either 'none', '2x', or '4x'");
		this._shaper.oversample = oversampling;
	}

	/**
	 *  Clean up.
	 */
	dispose(): this {
		super.dispose();
		this._shaper.disconnect();
		return this;
	}
}