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Add ol.geom.flat.lineStringInterpolate

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This commit is contained in:
Tom Payne
2013-11-26 16:26:53 +01:00
parent d45734634a
commit 321837f157
2 changed files with 104 additions and 0 deletions
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62
src/ol/geom/flatgeom.js
View File

@@ -1,5 +1,6 @@
goog.provide('ol.geom.flat');
goog.require('goog.array');
goog.require('goog.asserts');
goog.require('goog.vec.Mat4');
@@ -154,6 +155,7 @@ ol.geom.flat.lineStringLength = function(flatCoordinates, offset, end, stride) {
var x1 = flatCoordinates[offset];
var y1 = flatCoordinates[offset + 1];
var length = 0;
var i;
for (i = offset + stride; i < end; i += stride) {
var x2 = flatCoordinates[i];
var y2 = flatCoordinates[i + 1];
@@ -166,6 +168,66 @@ ol.geom.flat.lineStringLength = function(flatCoordinates, offset, end, stride) {
/**
* @param {Array.<number>} flatCoordinates Flat coordinates.
* @param {number} offset Offset.
* @param {number} end End.
* @param {number} stride Stride.
* @param {number} fraction Fraction.
* @param {ol.Coordinate=} opt_point Point.
* @return {ol.Coordinate} Point at fraction along the line string.
*/
ol.geom.flat.lineStringInterpolate =
function(flatCoordinates, offset, end, stride, fraction, opt_point) {
goog.asserts.assert(0 <= fraction && fraction <= 1);
var point = goog.isDef(opt_point) ? opt_point : [NaN, NaN];
var n = (end - offset) / stride;
if (n === 0) {
goog.asserts.fail();
} else if (n == 1) {
point[0] = flatCoordinates[offset];
point[1] = flatCoordinates[offset + 1];
} else if (n == 2) {
point[0] = (1 - fraction) * flatCoordinates[offset] +
fraction * flatCoordinates[offset + stride];
point[1] = (1 - fraction) * flatCoordinates[offset + 1] +
fraction * flatCoordinates[offset + stride + 1];
} else {
var x1 = flatCoordinates[offset];
var y1 = flatCoordinates[offset + 1];
var length = 0;
var cumulativeLengths = [0];
var i;
for (i = offset + stride; i < end; i += stride) {
var x2 = flatCoordinates[i];
var y2 = flatCoordinates[i + 1];
length += Math.sqrt((x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1));
cumulativeLengths.push(length);
x1 = x2;
y1 = y2;
}
var target = fraction * length;
var index = goog.array.binarySearch(cumulativeLengths, target);
if (index < 0) {
var t = (target - cumulativeLengths[-index - 2]) /
(cumulativeLengths[-index - 1] - cumulativeLengths[-index - 2]);
var o = offset + (-index - 2) * stride;
point[0] = (1 - t) * flatCoordinates[o] + t * flatCoordinates[o + stride];
point[1] = (1 - t) * flatCoordinates[o + 1] +
t * flatCoordinates[o + stride + 1];
} else {
point[0] = flatCoordinates[offset + index * stride];
point[1] = flatCoordinates[offset + index * stride + 1];
}
}
return point;
};
/**
* @param {Array.<number>} flatCoordinates Flat coordinates.
* @param {number} offset Offset.
* @param {number} end End.
* @param {number} stride Stride.
* @param {number} x X.
* @param {number} y Y.
* @return {boolean} Contains (x, y).

42
test/spec/ol/geom/flatgeom.test.js
View File

@@ -54,6 +54,48 @@ describe('ol.geom.flat', function() {
});
describe('ol.geom.flat.lineStringInterpolate', function() {
it('returns the expected value for single points', function() {
var flatCoordinates = [0, 1];
var point =
ol.geom.flat.lineStringInterpolate(flatCoordinates, 0, 2, 2, 0.5);
expect(point).to.eql([0, 1]);
});
it('returns the expected value for simple line segments', function() {
var flatCoordinates = [0, 1, 2, 3];
var point =
ol.geom.flat.lineStringInterpolate(flatCoordinates, 0, 4, 2, 0.5);
expect(point).to.eql([1, 2]);
});
it('returns the expected value when the mid point is an existing ' +
'coordinate', function() {
var flatCoordinates = [0, 1, 2, 3, 4, 5];
var point =
ol.geom.flat.lineStringInterpolate(flatCoordinates, 0, 6, 2, 0.5);
expect(point).to.eql([2, 3]);
});
it('returns the expected value when the midpoint falls halfway between ' +
'two existing coordinates', function() {
var flatCoordinates = [0, 1, 2, 3, 4, 5, 6, 7];
var point =
ol.geom.flat.lineStringInterpolate(flatCoordinates, 0, 8, 2, 0.5);
expect(point).to.eql([3, 4]);
});
it('returns the expected value when the coordinates are not evenly spaced',
function() {
var flatCoordinates = [0, 1, 2, 3, 6, 7];
var point =
ol.geom.flat.lineStringInterpolate(flatCoordinates, 0, 6, 2, 0.5);
expect(point).to.eql([3, 4]);
});
});
describe('ol.geom.flat.linearRingIsClockwise', function() {
it('identifies clockwise rings', function() {