acv-tonecurve/lib/MonotonicCubicSpline.js

Reads Photoshop acv files.

"use strict";
/*
 * ACV-TONECURVE licensed under the MIT (http://www.opensource.org/licenses/mit-license.php) licenses.
 *
 * @author Nagi Fuyumi [StellarCapital]
 * @version 1.0
 */
Object.defineProperty(exports, "__esModule", { value: true });
class MonotonicCubicSpline {
    constructor(x, y) {
        this.interpolate = (x) => {
            let _ref;
            let i;
            for (i = _ref = this.x.length - 2; _ref <= 0 ? i <= 0 : i >= 0; _ref <= 0 ? (i += 1) : (i -= 1)) {
                if (this.x[i] <= x) {
                    break;
                }
            }
            const h = this.x[i + 1] - this.x[i];
            const t = (x - this.x[i]) / h;
            const t2 = Math.pow(t, 2);
            const t3 = Math.pow(t, 3);
            const h00 = 2 * t3 - 3 * t2 + 1;
            const h10 = t3 - 2 * t2 + t;
            const h01 = -2 * t3 + 3 * t2;
            const h11 = t3 - t2;
            return (h00 * this.y[i] +
                h10 * h * this.m[i] +
                h01 * this.y[i + 1] +
                h11 * h * this.m[i + 1]);
        };
        const n = x.length;
        const delta = [];
        const m = [];
        const alpha = [];
        const beta = [];
        const dist = [];
        const tau = [];
        for (let i = 0, _ref = n - 1; 0 <= _ref ? i < _ref : i > _ref; 0 <= _ref ? (i += 1) : (i -= 1)) {
            delta[i] = (y[i + 1] - y[i]) / (x[i + 1] - x[i]);
            if (i > 0) {
                m[i] = (delta[i - 1] + delta[i]) / 2;
            }
        }
        m[0] = delta[0];
        m[n - 1] = delta[n - 2];
        const to_fix = [];
        for (let i = 0, _ref2 = n - 1; 0 <= _ref2 ? i < _ref2 : i > _ref2; 0 <= _ref2 ? (i += 1) : (i -= 1)) {
            if (delta[i] === 0) {
                to_fix.push(i);
            }
        }
        for (let _i = 0, _len = to_fix.length; _i < _len; _i++) {
            const i = to_fix[_i];
            m[i] = m[i + 1] = 0;
        }
        for (let i = 0, _ref3 = n - 1; 0 <= _ref3 ? i < _ref3 : i > _ref3; 0 <= _ref3 ? (i += 1) : (i -= 1)) {
            alpha[i] = m[i] / delta[i];
            beta[i] = m[i + 1] / delta[i];
            dist[i] = Math.pow(alpha[i], 2) + Math.pow(beta[i], 2);
            tau[i] = 3 / Math.sqrt(dist[i]);
        }
        const to_fix_2 = [];
        for (let i = 0, _ref4 = n - 1; 0 <= _ref4 ? i < _ref4 : i > _ref4; 0 <= _ref4 ? (i += 1) : (i -= 1)) {
            if (dist[i] > 9) {
                to_fix_2.push(i);
            }
        }
        for (let _j = 0, _len2 = to_fix.length; _j < _len2; _j++) {
            const i = to_fix_2[_j];
            m[i] = tau[i] * alpha[i] * delta[i];
            m[i + 1] = tau[i] * beta[i] * delta[i];
        }
        this.x = x.slice(0, n);
        this.y = y.slice(0, n);
        this.m = m;
    }
}
exports.default = MonotonicCubicSpline;