弧线
如图所示，在Arcgis地图绘制弧线。
arcgis Api中提供了点，折线，多边形，圆绘制，但并没有弧线绘制，因公司有此需求，就研究了一下。刚好看到http://www.jianshu.com/p/4a0fdf10d55e，这篇文章讲述了如何绘制贝塞尔曲线，如此。便借用该段代码来实现地球上的弧线绘制。
define([
"esri/geometry/Polyline",
"esri/geometry/Point",
"esri/geometry/Polygon"
], function (Polyline, Point, Polygon) {
/* eslint-disable */
var Spline = function (options) {
this.points = options.points || [];
this.duration = options.duration || 100000;
this.sharpness = options.sharpness || 0.85;
this.centers = [];
this.controls = [];
this.stepLength = options.stepLength || 60;
this.length = this.points.length;
this.delay = 0;
// this is to ensure compatibility with the 2d version
for (var i = 0; i < this.length; i++) this.points[i][2] = this.points[i][2] || 0;
for (var i = 0; i < this.length - 1; i++) {
var p1 = this.points[i];
var p2 = this.points[i + 1];
this.centers.push({
x: (p1[0] + p2[0]) / 2,
y: (p1[1] + p2[1]) / 2,
z: (p1[2] + p2[2]) / 2
});
}
this.controls.push([this.points[0], this.points[0]]);
for (var i = 0; i < this.centers.length - 1; i++) {
var p1 = this.centers[i];
var p2 = this.centers[i + 1];
var dx = this.points[i + 1][0] - (this.centers[i].x + this.centers[i + 1].x) / 2;
var dy = this.points[i + 1][1]- (this.centers[i].y + this.centers[i + 1].y) / 2;
var dz = this.points[i + 1][2] - (this.centers[i].y + this.centers[i + 1].z) / 2;
this.controls.push([[
(1.0 - this.sharpness) * this.points[i + 1][0] + this.sharpness * (this.centers[i].x + dx),
(1.0 - this.sharpness) * this.points[i + 1][1] + this.sharpness * (this.centers[i].y + dy),
(1.0 - this.sharpness) * this.points[i + 1][2] + this.sharpness * (this.centers[i].z + dz)
],
[
(1.0 - this.sharpness) * this.points[i + 1][0] + this.sharpness * (this.centers[i + 1].x + dx),
(1.0 - this.sharpness) * this.points[i + 1][1] + this.sharpness * (this.centers[i + 1].y+ dy),
(1.0 - this.sharpness) * this.points[i + 1][2] + this.sharpness * (this.centers[i + 1].z + dz)
]]);
}
this.controls.push([this.points[this.length - 1], this.points[this.length - 1]]);
this.steps = this.cacheSteps(this.stepLength);
console.log("-----------this.controls-------------");
console.log(this.controls)
return this;
};
/*
Caches an array of equidistant (more or less) points on the curve.
*/
Spline.prototype.cacheSteps = function (mindist) {
var steps = [];
var laststep = this.pos(0);
steps.push(0);
for (var t = 0; t < this.duration; t += 10) {
var step = this.pos(t);
var dist = Math.sqrt((step.x - laststep.x) * (step.x - laststep.x) + (step.y - laststep.y) * (step.y - laststep.y) + (step.z - laststep.z) * (step.z - laststep.z));
if (dist > mindist) {
steps.push(t);
laststep = step;
}
}
return steps;
};
/*
returns angle and speed in the given point in the curve
*/
Spline.prototype.vector = function (t) {
var p1 = this.pos(t + 10);
var p2 = this.pos(t - 10);
return {
angle: 180 * Math.atan2(p1.y - p2.y, p1.x - p2.x) / 3.14,
speed: Math.sqrt((p2.x - p1.x) * (p2.x - p1.x) + (p2.y - p1.y) * (p2.y - p1.y) + (p2.z - p1.z) * (p2.z - p1.z))
};
};
/*
Gets the position of the point, given time.
WARNING: The speed is not constant. The time it takes between control points is constant.
For constant speed, use Spline.steps[i];
*/
Spline.prototype.pos = function (time) {
function bezier(t, p1, c1, c2, p2) {
if(time<10){
/* console.log("==============bez2222ier============");
console.log(t);
console.log(p1);
console.log(c1);
console.log(c2);
console.log(p2);*/
}
var B = function (t) {
var t2 = t * t, t3 = t2 * t;
return [(t3), (3 * t2 * (1 - t)), (3 * t * (1 - t) * (1 - t)), ((1 - t) * (1 - t) * (1 - t))];
};
var b = B(t);
if(time<10){
/*console.log("========b=====")
console.log(b)*/
}
var pos = {
x: p2[0] * b[0] + c2[0] * b[1] + c1[0] * b[2] + p1[0] * b[3],
y: p2[1] * b[0] + c2[1] * b[1] + c1[1] * b[2] + p1[1] * b[3],
z: p2[2] * b[0] + c2[2] * b[1] + c1[2] * b[2] + p1[2] * b[3]
};
return pos;
}
var t = time - this.delay;
if (t < 0) t = 0;
if (t > this.duration) t = this.duration - 1;
//t = t-this.delay;
var t2 = (t) / this.duration;
if (t2 >= 1) return this.points[this.length - 1];
var n = Math.floor((this.points.length - 1) * t2);
var t1 = (this.length - 1) * t2 - n;
if(time<10){
/*console.log("==============bezier============");
console.log(t);
console.log(t1);
console.log(t2);
console.log(this.points);
console.log(this.controls);*/
}
return bezier(t1, this.points[n], this.controls[n][1], this.controls[n + 1][0], this.points[n + 1]);
};
var customLib = {
getBesselLine: function (points, mapView, params) {
var coords = [];
var spline = new Spline(dojo.mixin({
points: points
}, params || {}));
console.log("------------spline---------------");
console.log(spline);
for (var i = 0; i < spline.duration; i += 10) {
var pos = spline.pos(i);
if(i<10){
console.log("-------------pos------------");
console.log(pos);
}
if (Math.floor(i / 100) % 2 === 0) {
coords.push([pos.x, pos.y,pos.z]);
}
}
var polyline = {
type: "polyline", // autocasts as new Polyline()
paths: [coords]
};
/* var line = new Polyline({
paths: [coords],
spatialReference: { wkid: 4326 }
});*/
return polyline
},
getBesselCenterPoint: function (p1, p2, mapView, L) {
L || (L = 30);
var point1 = mapView.toScreen(p1);
var point2 = mapView.toScreen(p2);
var a = point1.x, b = point1.y, c = point2.x, d = point2.y;
var e = (point1.x + point2.x) / 2;
var f = (point1.y + point2.y) / 2;
var g = Math.pow(a - e, 2) + Math.pow(b - f, 2) + Math.pow(L, 2);
var h = 2 * e - 2 * a;
var i = 2 * f - 2 * b;
var j = Math.pow(a, 2) - Math.pow(e, 2) + Math.pow(b, 2) - Math.pow(f, 2) + Math.pow(L, 2) - g;
var k = 1 + Math.pow(h / i, 2);
var m = (2 * b * h) / i - 2 * a + (2 * h * j) / Math.pow(i, 2);
var n = Math.pow(a, 2) + Math.pow(j / i, 2) + (2 * b * j) / i + Math.pow(b, 2) - g;
var x = (-m + Math.sqrt(Math.pow(m, 2) - 4 * k * n)) / (2 * k);
var y = -(h / i) * x - j / i;
var value = (a - x) * (d - y) - (b - y) * (c - x);
if (value < 0) {
x = (-m - Math.sqrt(Math.pow(m, 2) - 4 * k * n)) / (2 * k);
y = -(h / i) * x - j / i;
}
console.log('ddd', value)
var np = mapView.toMap({
x: x, y: y
});
return new Point({
x: np.x,
y: np.y,
spatialReference: mapView.spatialReference
});
},
getInterPointFromRing: function (ring, mapView) {
var i, ii, x, x1, x2, y1, y2;
var polygon = new Polygon({
"rings": [ring]
});
var extentCenter = polygon.extent.center;
var y = extentCenter.y;
var intersections = [];
var flatCoordinates = [];
for (var i = 0, len = ring.length; i < len; i++) {
flatCoordinates.push(ring[i][0], ring[i][1]);
}
var end = flatCoordinates.length;
x1 = flatCoordinates[end - 2];
y1 = flatCoordinates[end - 2 + 1];
for (i = 0; i < end; i += 2) {
x2 = flatCoordinates[i];
y2 = flatCoordinates[i + 1];
if ((y <= y1 && y2 <= y) || (y1 <= y && y <= y2)) {
x = (y - y1) / (y2 - y1) * (x2 - x1) + x1;
intersections.push(x);
}
x1 = x2;
y1 = y2;
}
var pointX = NaN;
var maxSegmentLength = -Infinity;
intersections.sort(function (a, b) {
return a - b;
});
x1 = intersections[0];
var xs = [];
for (i = 1, ii = intersections.length; i < ii; ++i) {
x2 = intersections[i];
var segmentLength = Math.abs(x2 - x1);
if (segmentLength > maxSegmentLength) {
x = (x1 + x2) / 2;
if (this._judgeCoordinates(
flatCoordinates, 0, end, 2, x, y)) {
pointX = x;
maxSegmentLength = segmentLength;
xs.push(x);
}
}
x1 = x2;
}
if (isNaN(pointX)) {
pointX = extentCenter.x;
}
return new Point({
x: pointX,
y: y,
spatialReference: mapView.spatialReference
});
},
_judgeCoordinates: function (flatCoordinates, offset, end, stride, x, y) {
var wn = 0;
var x1 = flatCoordinates[end - stride];
var y1 = flatCoordinates[end - stride + 1];
for (; offset < end; offset += stride) {
var x2 = flatCoordinates[offset];
var y2 = flatCoordinates[offset + 1];
if (y1 <= y) {
if (y2 > y && ((x2 - x1) * (y - y1)) - ((x - x1) * (y2 - y1)) > 0) {
wn++;
}
} else if (y2 <= y && ((x2 - x1) * (y - y1)) - ((x - x1) * (y2 - y1)) < 0) {
wn--;
}
x1 = x2;
y1 = y2;
}
var result = (wn !== 0);
if (!result) {
return false;
}
return true;
}
};
return customLib;
});
以上是修改过后的文件（其实就改了几个属性），将上述代码保存放置于项目下（我的放置在js文件夹下，重命名为curve.js），
require([
"esri/Graphic",
"../js/curve.js",
"dojo/domReady!"
],
function (Graphic, Curve) {});
仿照以上引入使用即可。
下来回归正题，图中所示分为两个部分，一部分是在地球表面绘制点，其次就是在地球上方绘制一条两点之间有一定弧度高度的线，就是上方的贝塞尔曲线的代码部分了。
绘制点。如下所示：传入参数为多个点坐标，即
[{
type: "point",
longitude:150.32,
latitude: 45.23
},{.....}]
symbol的url换为自己的图片地址即可。
drawPoint: function (points) {
require([
"esri/Graphic",
"dojo/domReady!"
],
function (Graphic) {
points.forEach(function (point) {
var symbol = {
type: "picture-marker", // autocasts as new PictureMarkerSymbol()
url: "../img/route.png",
width: "50px",
height: "50px"
};
var pop={ // autocasts as new PopupTemplate()
title: item['name'],
// Set content elements in the order to display.
// The first element displayed here is the fieldInfos.
content: [ {
// You can also set a descriptive text element. This element
// uses an attribute from the featurelayer which displays a
// sentence giving the total amount of trees value within a
// specified census block. Text elements can only be set within the content.
type: "text",
text: "There are {Point_Count} trees within census block {BLOCKCE10}"
},]
};
var graphic = new Graphic({
geometry: point,
symbol: symbol,
popupTemplate:pop
});
ArcMap.v.graphicsLayer.add(graphic);
});
});
}
绘制弧线。如下所示：传入参数为多条线坐标，即：
[
[{
type:'point',
longitude:142.23,
latitude:35.65
},{
type:'point',
longitude:15.25,
latitude:35.25
}],[.....]
]
线为两个点组成，即起始点与终止点，在drawLine中，会根据两点计算出中间点的经纬度和高度，将此三点传入上述贝塞尔曲线中，进行绘制即可。中间点的坐标可依据自己实际情况进行修改。
drawLine: function (lines) {
require([
"esri/Graphic",
"../js/curve.js",
"dojo/domReady!"
],
function (Graphic, Curve) {
lines.forEach(function (line) {
var sub1 = Math.abs(line[0].longitude - line[1].longitude);
var sub2 = Math.abs(line[0].latitude - line[1].latitude);
var height = (sub1 + sub2) * 5000;
var curve = [];
var curve1 = [line[0].longitude, line[0].latitude, 0];
var curve2 = [line[1].longitude, line[1].latitude, 0];
var curve3 = [(line[0].longitude + line[1].longitude) / 2, (line[0].latitude + line[1].latitude) /2, height];
curve.push(curve1);
curve.push(curve3);
curve.push(curve2);
var curveLine = Curve.getBesselLine(curve, ArcMap.v.view);
console.log("--------------------curveLine------------------------");
console.log(curveLine);
var lineSymbol = {
type: "simple-line", // autocasts as SimpleLineSymbol()
color: '#FFFF00',
width: 3
};
var pop={ // autocasts as new PopupTemplate()
title: item[0]['name']+'---'+item[1]['name'],
// Set content elements in the order to display.
// The first element displayed here is the fieldInfos.
content: [ {
// You can also set a descriptive text element. This element
// uses an attribute from the featurelayer which displays a
// sentence giving the total amount of trees value within a
// specified census block. Text elements can only be set within the content.
type: "text",
text: "There are {Point_Count} trees within census block {BLOCKCE10}"
},]
};
var polylineGraphic = new Graphic({
geometry: curveLine,
symbol: lineSymbol,
popupTemplate:pop
});
ArcMap.v.graphicsLayer.add(polylineGraphic);
});
});
}
也是初学，记录一下，如有bug，请不吝指出……
