popmotion/lib/utils/interpolate.js

The animator's toolbox

import { progress } from './progress';
import { mix } from './mix';
import { mixColor } from './mix-color';
import { mixComplex, mixArray, mixObject } from './mix-complex';
import { color } from 'style-value-types';
import { clamp } from './clamp';
import { pipe } from './pipe';
import { invariant } from 'hey-listen';
var mixNumber = function (from, to) { return function (p) { return mix(from, to, p); }; };
function detectMixerFactory(v) {
    if (typeof v === 'number') {
        return mixNumber;
    }
    else if (typeof v === 'string') {
        if (color.test(v)) {
            return mixColor;
        }
        else {
            return mixComplex;
        }
    }
    else if (Array.isArray(v)) {
        return mixArray;
    }
    else if (typeof v === 'object') {
        return mixObject;
    }
}
function createMixers(output, ease, customMixer) {
    var mixers = [];
    var mixerFactory = customMixer || detectMixerFactory(output[0]);
    var numMixers = output.length - 1;
    for (var i = 0; i < numMixers; i++) {
        var mixer = mixerFactory(output[i], output[i + 1]);
        if (ease) {
            var easingFunction = Array.isArray(ease) ? ease[i] : ease;
            mixer = pipe(easingFunction, mixer);
        }
        mixers.push(mixer);
    }
    return mixers;
}
function fastInterpolate(_a, _b) {
    var from = _a[0], to = _a[1];
    var mixer = _b[0];
    return function (v) { return mixer(progress(from, to, v)); };
}
function slowInterpolate(input, mixers) {
    var inputLength = input.length;
    var lastInputIndex = inputLength - 1;
    return function (v) {
        var mixerIndex = 0;
        var foundMixerIndex = false;
        if (v <= input[0]) {
            foundMixerIndex = true;
        }
        else if (v >= input[lastInputIndex]) {
            mixerIndex = lastInputIndex - 1;
            foundMixerIndex = true;
        }
        if (!foundMixerIndex) {
            var i = 1;
            for (; i < inputLength; i++) {
                if (input[i] > v || i === lastInputIndex) {
                    break;
                }
            }
            mixerIndex = i - 1;
        }
        var progressInRange = progress(input[mixerIndex], input[mixerIndex + 1], v);
        return mixers[mixerIndex](progressInRange);
    };
}
export function interpolate(input, output, _a) {
    var _b = _a === void 0 ? {} : _a, _c = _b.clamp, isClamp = _c === void 0 ? true : _c, ease = _b.ease, mixer = _b.mixer;
    var inputLength = input.length;
    invariant(inputLength === output.length, 'Both input and output ranges must be the same length');
    invariant(!ease || !Array.isArray(ease) || ease.length === inputLength - 1, 'Array of easing functions must be of length `input.length - 1`, as it applies to the transitions **between** the defined values.');
    if (input[0] > input[inputLength - 1]) {
        input = [].concat(input);
        output = [].concat(output);
        input.reverse();
        output.reverse();
    }
    var mixers = createMixers(output, ease, mixer);
    var interpolator = inputLength === 2
        ? fastInterpolate(input, mixers)
        : slowInterpolate(input, mixers);
    return isClamp
        ? function (v) { return interpolator(clamp(input[0], input[inputLength - 1], v)); }
        : interpolator;
}
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