# Code coverage report for src/geometry/LineUtil.js

## Statements: 100% (81 / 81) Branches: 94% (47 / 50) Functions: 100% (11 / 11) Lines: 100% (81 / 81)

All files » src/geometry/ » LineUtil.js

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     /*
     * L.LineUtil contains different utility functions for line segments
     * and polylines (clipping, simplification, distances, etc.)
     */

    /*jshint bitwise:false */ // allow bitwise oprations for this file

    L.LineUtil = {

    	// Simplify polyline with vertex reduction and Douglas-Peucker simplification.
    	// Improves rendering performance dramatically by lessening the number of points to draw.

    	simplify: function (/*Point[]*/ points, /*Number*/ tolerance) {
    		if (!tolerance || !points.length) {
    			return points.slice();
    		}

    		var sqTolerance = tolerance * tolerance;

    		// stage 1: vertex reduction
    		points = this._reducePoints(points, sqTolerance);

    		// stage 2: Douglas-Peucker simplification
    		points = this._simplifyDP(points, sqTolerance);

    		return points;
    	},

    	// distance from a point to a segment between two points
    	pointToSegmentDistance:  function (/*Point*/ p, /*Point*/ p1, /*Point*/ p2) {
    		return Math.sqrt(this._sqClosestPointOnSegment(p, p1, p2, true));
    	},

    	closestPointOnSegment: function (/*Point*/ p, /*Point*/ p1, /*Point*/ p2) {
    		return this._sqClosestPointOnSegment(p, p1, p2);
    	},

    	// Douglas-Peucker simplification, see http://en.wikipedia.org/wiki/Douglas-Peucker_algorithm
    	_simplifyDP: function (points, sqTolerance) {

    		var len = points.length,
    		    ArrayConstructor = typeof Uint8Array !== undefined + '' ? Uint8Array : Array,
    		    markers = new ArrayConstructor(len);

    		markers[0] = markers[len - 1] = 1;

    		this._simplifyDPStep(points, markers, sqTolerance, 0, len - 1);

    		var i,
    		    newPoints = [];

    		for (i = 0; i < len; i++) {
    			if (markers[i]) {
    				newPoints.push(points[i]);
    			}
    		}

    		return newPoints;
    	},

    	_simplifyDPStep: function (points, markers, sqTolerance, first, last) {

    		var maxSqDist = 0,
    		    index, i, sqDist;

    		for (i = first + 1; i <= last - 1; i++) {
    			sqDist = this._sqClosestPointOnSegment(points[i], points[first], points[last], true);

    			if (sqDist > maxSqDist) {
    				index = i;
    				maxSqDist = sqDist;
    			}
    		}

    		if (maxSqDist > sqTolerance) {
    			markers[index] = 1;

    			this._simplifyDPStep(points, markers, sqTolerance, first, index);
    			this._simplifyDPStep(points, markers, sqTolerance, index, last);
    		}
    	},

    	// reduce points that are too close to each other to a single point
    	_reducePoints: function (points, sqTolerance) {
    		var reducedPoints = [points[0]];

    		for (var i = 1, prev = 0, len = points.length; i < len; i++) {
    			if (this._sqDist(points[i], points[prev]) > sqTolerance) {
    				reducedPoints.push(points[i]);
    				prev = i;
    			}
    		}
    		if (prev < len - 1) {
    			reducedPoints.push(points[len - 1]);
    		}
    		return reducedPoints;
    	},

    	// Cohen-Sutherland line clipping algorithm.
    	// Used to avoid rendering parts of a polyline that are not currently visible.

    	clipSegment: function (a, b, bounds, useLastCode) {
    		var codeA = useLastCode ? this._lastCode : this._getBitCode(a, bounds),
    		    codeB = this._getBitCode(b, bounds),

    		    codeOut, p, newCode;

    		// save 2nd code to avoid calculating it on the next segment
    		this._lastCode = codeB;

    		while (true) {
    			// if a,b is inside the clip window (trivial accept)
    			if (!(codeA | codeB)) {
    				return [a, b];
    			// if a,b is outside the clip window (trivial reject)
    			} else if (codeA & codeB) {
    				return false;
    			// other cases
    			} else {
    				codeOut = codeA || codeB,
    				p = this._getEdgeIntersection(a, b, codeOut, bounds),
    				newCode = this._getBitCode(p, bounds);

    				if (codeOut === codeA) {
    					a = p;
    					codeA = newCode;
    				} else {
    					b = p;
    					codeB = newCode;
    				}
    			}
    		}
    	},

    	_getEdgeIntersection: function (a, b, code, bounds) {
    		var dx = b.x - a.x,
    		    dy = b.y - a.y,
    		    min = bounds.min,
    		    max = bounds.max;

    		if (code & 8) { // top
    			return new L.Point(a.x + dx * (max.y - a.y) / dy, max.y);
    		} else if (code & 4) { // bottom
    			return new L.Point(a.x + dx * (min.y - a.y) / dy, min.y);
    		} else if (code & 2) { // right
    			return new L.Point(max.x, a.y + dy * (max.x - a.x) / dx);
    		} else Eif (code & 1) { // left
    			return new L.Point(min.x, a.y + dy * (min.x - a.x) / dx);
    		}
    	},

    	_getBitCode: function (/*Point*/ p, bounds) {
    		var code = 0;

    		if (p.x < bounds.min.x) { // left
    			code |= 1;
    		} else if (p.x > bounds.max.x) { // right
    			code |= 2;
    		}
    		if (p.y < bounds.min.y) { // bottom
    			code |= 4;
    		} else if (p.y > bounds.max.y) { // top
    			code |= 8;
    		}

    		return code;
    	},

    	// square distance (to avoid unnecessary Math.sqrt calls)
    	_sqDist: function (p1, p2) {
    		var dx = p2.x - p1.x,
    		    dy = p2.y - p1.y;
    		return dx * dx + dy * dy;
    	},

    	// return closest point on segment or distance to that point
    	_sqClosestPointOnSegment: function (p, p1, p2, sqDist) {
    		var x = p1.x,
    		    y = p1.y,
    		    dx = p2.x - x,
    		    dy = p2.y - y,
    		    dot = dx * dx + dy * dy,
    		    t;

    		Eif (dot > 0) {
    			t = ((p.x - x) * dx + (p.y - y) * dy) / dot;

    			if (t > 1) {
    				x = p2.x;
    				y = p2.y;
    			} else if (t > 0) {
    				x += dx * t;
    				y += dy * t;
    			}
    		}

    		dx = p.x - x;
    		dy = p.y - y;

    		return sqDist ? dx * dx + dy * dy : new L.Point(x, y);
    	}
    };