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openlayers

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Build tools and sources for developing OpenLayers based mapping applications

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goog.provide('ol.math'); goog.require('ol'); goog.require('ol.asserts'); /** * Takes a number and clamps it to within the provided bounds. * @param {number} value The input number. * @param {number} min The minimum value to return. * @param {number} max The maximum value to return. * @return {number} The input number if it is within bounds, or the nearest * number within the bounds. */ ol.math.clamp = function(value, min, max) { return Math.min(Math.max(value, min), max); }; /** * Return the hyperbolic cosine of a given number. The method will use the * native `Math.cosh` function if it is available, otherwise the hyperbolic * cosine will be calculated via the reference implementation of the Mozilla * developer network. * * @param {number} x X. * @return {number} Hyperbolic cosine of x. */ ol.math.cosh = (function() { // Wrapped in a iife, to save the overhead of checking for the native // implementation on every invocation. var cosh; if ('cosh' in Math) { // The environment supports the native Math.cosh function, use it… cosh = Math.cosh; } else { // … else, use the reference implementation of MDN: cosh = function(x) { var y = Math.exp(x); return (y + 1 / y) / 2; }; } return cosh; }()); /** * @param {number} x X. * @return {number} The smallest power of two greater than or equal to x. */ ol.math.roundUpToPowerOfTwo = function(x) { ol.asserts.assert(0 < x, 29); // `x` must be greater than `0` return Math.pow(2, Math.ceil(Math.log(x) / Math.LN2)); }; /** * Returns the square of the closest distance between the point (x, y) and the * line segment (x1, y1) to (x2, y2). * @param {number} x X. * @param {number} y Y. * @param {number} x1 X1. * @param {number} y1 Y1. * @param {number} x2 X2. * @param {number} y2 Y2. * @return {number} Squared distance. */ ol.math.squaredSegmentDistance = function(x, y, x1, y1, x2, y2) { var dx = x2 - x1; var dy = y2 - y1; if (dx !== 0 || dy !== 0) { var t = ((x - x1) * dx + (y - y1) * dy) / (dx * dx + dy * dy); if (t > 1) { x1 = x2; y1 = y2; } else if (t > 0) { x1 += dx * t; y1 += dy * t; } } return ol.math.squaredDistance(x, y, x1, y1); }; /** * Returns the square of the distance between the points (x1, y1) and (x2, y2). * @param {number} x1 X1. * @param {number} y1 Y1. * @param {number} x2 X2. * @param {number} y2 Y2. * @return {number} Squared distance. */ ol.math.squaredDistance = function(x1, y1, x2, y2) { var dx = x2 - x1; var dy = y2 - y1; return dx * dx + dy * dy; }; /** * Solves system of linear equations using Gaussian elimination method. * * @param {Array.<Array.<number>>} mat Augmented matrix (n x n + 1 column) * in row-major order. * @return {Array.<number>} The resulting vector. */ ol.math.solveLinearSystem = function(mat) { var n = mat.length; if (ol.DEBUG) { for (var row = 0; row < n; row++) { console.assert(mat[row].length == n + 1, 'every row should have correct number of columns'); } } for (var i = 0; i < n; i++) { // Find max in the i-th column (ignoring i - 1 first rows) var maxRow = i; var maxEl = Math.abs(mat[i][i]); for (var r = i + 1; r < n; r++) { var absValue = Math.abs(mat[r][i]); if (absValue > maxEl) { maxEl = absValue; maxRow = r; } } if (maxEl === 0) { return null; // matrix is singular } // Swap max row with i-th (current) row var tmp = mat[maxRow]; mat[maxRow] = mat[i]; mat[i] = tmp; // Subtract the i-th row to make all the remaining rows 0 in the i-th column for (var j = i + 1; j < n; j++) { var coef = -mat[j][i] / mat[i][i]; for (var k = i; k < n + 1; k++) { if (i == k) { mat[j][k] = 0; } else { mat[j][k] += coef * mat[i][k]; } } } } // Solve Ax=b for upper triangular matrix A (mat) var x = new Array(n); for (var l = n - 1; l >= 0; l--) { x[l] = mat[l][n] / mat[l][l]; for (var m = l - 1; m >= 0; m--) { mat[m][n] -= mat[m][l] * x[l]; } } return x; }; /** * Converts radians to to degrees. * * @param {number} angleInRadians Angle in radians. * @return {number} Angle in degrees. */ ol.math.toDegrees = function(angleInRadians) { return angleInRadians * 180 / Math.PI; }; /** * Converts degrees to radians. * * @param {number} angleInDegrees Angle in degrees. * @return {number} Angle in radians. */ ol.math.toRadians = function(angleInDegrees) { return angleInDegrees * Math.PI / 180; }; /** * Returns the modulo of a / b, depending on the sign of b. * * @param {number} a Dividend. * @param {number} b Divisor. * @return {number} Modulo. */ ol.math.modulo = function(a, b) { var r = a % b; return r * b < 0 ? r + b : r; }; /** * Calculates the linearly interpolated value of x between a and b. * * @param {number} a Number * @param {number} b Number * @param {number} x Value to be interpolated. * @return {number} Interpolated value. */ ol.math.lerp = function(a, b, x) { return a + x * (b - a); };