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// Copyright 2008 The Closure Library Authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS-IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
/**
* @fileoverview Represents a line in 2D space.
*
* @author robbyw@google.com (Robby Walker)
*/
goog.provide('goog.math.Line');
goog.require('goog.math');
goog.require('goog.math.Coordinate');
/**
* Object representing a line.
* @param {number} x0 X coordinate of the start point.
* @param {number} y0 Y coordinate of the start point.
* @param {number} x1 X coordinate of the end point.
* @param {number} y1 Y coordinate of the end point.
* @struct
* @constructor
* @final
*/
goog.math.Line = function(x0, y0, x1, y1) {
/**
* X coordinate of the first point.
* @type {number}
*/
this.x0 = x0;
/**
* Y coordinate of the first point.
* @type {number}
*/
this.y0 = y0;
/**
* X coordinate of the first control point.
* @type {number}
*/
this.x1 = x1;
/**
* Y coordinate of the first control point.
* @type {number}
*/
this.y1 = y1;
};
/**
* @return {!goog.math.Line} A copy of this line.
*/
goog.math.Line.prototype.clone = function() {
return new goog.math.Line(this.x0, this.y0, this.x1, this.y1);
};
/**
* Tests whether the given line is exactly the same as this one.
* @param {goog.math.Line} other The other line.
* @return {boolean} Whether the given line is the same as this one.
*/
goog.math.Line.prototype.equals = function(other) {
return this.x0 == other.x0 && this.y0 == other.y0 && this.x1 == other.x1 &&
this.y1 == other.y1;
};
/**
* @return {number} The squared length of the line segment used to define the
* line.
*/
goog.math.Line.prototype.getSegmentLengthSquared = function() {
var xdist = this.x1 - this.x0;
var ydist = this.y1 - this.y0;
return xdist * xdist + ydist * ydist;
};
/**
* @return {number} The length of the line segment used to define the line.
*/
goog.math.Line.prototype.getSegmentLength = function() {
return Math.sqrt(this.getSegmentLengthSquared());
};
/**
* Computes the interpolation parameter for the point on the line closest to
* a given point.
* @param {number|goog.math.Coordinate} x The x coordinate of the point, or
* a coordinate object.
* @param {number=} opt_y The y coordinate of the point - required if x is a
* number, ignored if x is a goog.math.Coordinate.
* @return {number} The interpolation parameter of the point on the line
* closest to the given point.
* @private
*/
goog.math.Line.prototype.getClosestLinearInterpolation_ = function(x, opt_y) {
var y;
if (x instanceof goog.math.Coordinate) {
y = x.y;
x = x.x;
} else {
y = opt_y;
}
var x0 = this.x0;
var y0 = this.y0;
var xChange = this.x1 - x0;
var yChange = this.y1 - y0;
return ((Number(x) - x0) * xChange + (Number(y) - y0) * yChange) /
this.getSegmentLengthSquared();
};
/**
* Returns the point on the line segment proportional to t, where for t = 0 we
* return the starting point and for t = 1 we return the end point. For t < 0
* or t > 1 we extrapolate along the line defined by the line segment.
* @param {number} t The interpolation parameter along the line segment.
* @return {!goog.math.Coordinate} The point on the line segment at t.
*/
goog.math.Line.prototype.getInterpolatedPoint = function(t) {
return new goog.math.Coordinate(
goog.math.lerp(this.x0, this.x1, t), goog.math.lerp(this.y0, this.y1, t));
};
/**
* Computes the point on the line closest to a given point. Note that a line
* in this case is defined as the infinite line going through the start and end
* points. To find the closest point on the line segment itself see
* {@see #getClosestSegmentPoint}.
* @param {number|goog.math.Coordinate} x The x coordinate of the point, or
* a coordinate object.
* @param {number=} opt_y The y coordinate of the point - required if x is a
* number, ignored if x is a goog.math.Coordinate.
* @return {!goog.math.Coordinate} The point on the line closest to the given
* point.
*/
goog.math.Line.prototype.getClosestPoint = function(x, opt_y) {
return this.getInterpolatedPoint(
this.getClosestLinearInterpolation_(x, opt_y));
};
/**
* Computes the point on the line segment closest to a given point.
* @param {number|goog.math.Coordinate} x The x coordinate of the point, or
* a coordinate object.
* @param {number=} opt_y The y coordinate of the point - required if x is a
* number, ignored if x is a goog.math.Coordinate.
* @return {!goog.math.Coordinate} The point on the line segment closest to the
* given point.
*/
goog.math.Line.prototype.getClosestSegmentPoint = function(x, opt_y) {
return this.getInterpolatedPoint(
goog.math.clamp(this.getClosestLinearInterpolation_(x, opt_y), 0, 1));
};
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