interpolate.js

interpolate.js

/**
 * Modified from:
 * https://github.com/react-spring/react-spring/blob/master/src/animated/createInterpolator.ts
 */

function clamp(value, min, max) {
	return Math.max(min, Math.min(max, value));
}

export function findRange(input, inputRange) {
	for (var i = 1; i < inputRange.length - 1; ++i)
		if (inputRange[i] >= input) break;

	return i - 1;
}

function baseInterpolate(
	input = 0,
	inputMin = 0,
	inputMax = 1,
	outputMin = 0,
	outputMax = 1,
) {
	let result = input;

	if (outputMin === outputMax) return outputMin;
	if (inputMin === inputMax) return input <= inputMin ? outputMin : outputMax;

	// Input Range
	if (inputMin === -Infinity) result = -result;
	else if (inputMax === Infinity) result = result - inputMin;
	else result = (result - inputMin) / (inputMax - inputMin);

	// Output Range
	if (outputMin === -Infinity) result = -result;
	else if (outputMax === Infinity) result = result + outputMin;
	else result = result * (outputMax - outputMin) + outputMin;

	let clampMin = outputMin;
	let clampMax = outputMax;

	if (outputMax < outputMin) {
		clampMin = outputMax;
		clampMax = outputMin;
	}

	return clamp(result, clampMin, clampMax);
}

function interpolate(input = 0, inputRange = [0, 1], outputRange = [0, 1]) {
	const range = findRange(input, inputRange);

	return baseInterpolate(
		input,
		inputRange[range],
		inputRange[range + 1],
		outputRange[range],
		outputRange[range + 1],
	);
}