dltjs/dist/dlt.js

A package for computing Direct Linear Transformation matrix.

'use strict';

Object.defineProperty(exports, "__esModule", {
    value: true
});

var _mathjs = require('mathjs');

var _mathjs2 = _interopRequireDefault(_mathjs);

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

/**
 * See this paper for more about DLT.
 * https://www.cs.ubc.ca/grads/resources/thesis/May09/Dubrofsky_Elan.pdf
 */

var dltjs = {

    /**
     * Create transformation matrix from given point pairs.
     * @param {array} p0 Original points. At least 4 points must be given.
     * @param {array} p1 Transformed points. At least 4 points must be given.
     */
    dlt2d: function dlt2d(p0, p1) {

        if (p0.length < 4 || p1.length < 4) {
            throw new Error('At least 4 point pairs must be given.');
        }

        var H = [],
            B = [];
        for (var i = 0; i < 4; i++) {
            var _ref = [p0[i][0], p0[i][1], p1[i][0], p1[i][1]],
                x = _ref[0],
                y = _ref[1],
                u = _ref[2],
                v = _ref[3];

            H.push([x, y, 1, 0, 0, 0, -x * u, -y * u]);
            H.push([0, 0, 0, x, y, 1, -x * v, -y * v]);
            B.push(u);
            B.push(v);
        }

        var M = _mathjs2.default.lusolve(H, B);
        M = _mathjs2.default.reshape(M, [8]);
        M.push(1);
        return _mathjs2.default.reshape(M, [3, 3]);
    },

    /**
     * Transform point p with matrix M.
     * @param {array} M 3x3 matrix.
     * @param {array} p point with format of [x, y].
     */
    transform2d: function transform2d(M, p) {

        if (M[2][2] !== 1) {
            M = _mathjs2.default.divide(M, M[2][2]);
        }

        var p0 = [p[0], p[1], 1];
        var p1 = _mathjs2.default.multiply(M, p0);
        p1 = _mathjs2.default.divide(p1, p1[2]);

        return [p1[0], p1[1]];
    }
};

exports.default = dltjs;