OpenLayers示例代码：测量
OpenLayers示例代码：测量
<!DOCTYPE html>
<html>
<head>
<title>Measure</title>
<link rel="stylesheet" href="https://openlayers.org/en/v4.0.1/css/ol.css" type="text/css">
<!-- The line below is only needed for old environments like Internet Explorer and Android 4.x -->
<script src="https://cdn.polyfill.io/v2/polyfill.min.js?features=requestAnimationFrame,Element.prototype.classList,URL"></script>
<script src="https://openlayers.org/en/v4.0.1/build/ol.js"></script>
<style>
.tooltip {
position: relative;
background: rgba(0, 0, 0, 0.5);
border-radius: 4px;
color: white;
padding: 4px 8px;
opacity: 0.7;
white-space: nowrap;
}
.tooltip-measure {
opacity: 1;
font-weight: bold;
}
.tooltip-static {
background-color: #ffcc33;
color: black;
border: 1px solid white;
}
.tooltip-measure:before,
.tooltip-static:before {
border-top: 6px solid rgba(0, 0, 0, 0.5);
border-right: 6px solid transparent;
border-left: 6px solid transparent;
content: "";
position: absolute;
bottom: -6px;
margin-left: -7px;
left: 50%;
}
.tooltip-static:before {
border-top-color: #ffcc33;
} </style>
</head>
<body>
<div id="map" class="map"></div>
<form class="form-inline">
<label>Measurement type </label>
<select id="type">
<option value="length">Length (LineString)</option>
<option value="area">Area (Polygon)</option>
</select>
<label class="checkbox">
<input type="checkbox" id="geodesic">
use geodesic measures
</label>
</form>
<script>
var wgs84Sphere = new ol.Sphere(6378137);
var raster = new ol.layer.Tile({
source: new ol.source.OSM()
});
var source = new ol.source.Vector();
var vector = new ol.layer.Vector({
source: source,
style: new ol.style.Style({
fill: new ol.style.Fill({
color: 'rgba(255, 255, 255, 0.2)'
}),
stroke: new ol.style.Stroke({
color: '#ffcc33',
width: 2
}),
image: new ol.style.Circle({
radius: 7,
fill: new ol.style.Fill({
color: '#ffcc33'
})
})
})
});
/**
* Currently drawn feature.
* @type {ol.Feature}
*/
var sketch;
/**
* The help tooltip element.
* @type {Element}
*/
var helpTooltipElement;
/**
* Overlay to show the help messages.
* @type {ol.Overlay}
*/
var helpTooltip;
/**
* The measure tooltip element.
* @type {Element}
*/
var measureTooltipElement;
/**
* Overlay to show the measurement.
* @type {ol.Overlay}
*/
var measureTooltip;
/**
* Message to show when the user is drawing a polygon.
* @type {string}
*/
var continuePolygonMsg = 'Click to continue drawing the polygon';
/**
* Message to show when the user is drawing a line.
* @type {string}
*/
var continueLineMsg = 'Click to continue drawing the line';
/**
* Handle pointer move.
* @param {ol.MapBrowserEvent} evt The event.
*/
var pointerMoveHandler = function(evt) {
if (evt.dragging) {
return;
}
/** @type {string} */
var helpMsg = 'Click to start drawing';
if (sketch) {
var geom = (sketch.getGeometry());
if (geom instanceof ol.geom.Polygon) {
helpMsg = continuePolygonMsg;
} else if (geom instanceof ol.geom.LineString) {
helpMsg = continueLineMsg;
}
}
helpTooltipElement.innerHTML = helpMsg;
helpTooltip.setPosition(evt.coordinate);
helpTooltipElement.classList.remove('hidden');
};
var map = new ol.Map({
layers: [raster, vector],
target: 'map',
view: new ol.View({
center: [-11000000, 4600000],
zoom: 15
})
});
map.on('pointermove', pointerMoveHandler);
map.getViewport().addEventListener('mouseout', function() {
helpTooltipElement.classList.add('hidden');
});
var typeSelect = document.getElementById('type');
var geodesicCheckbox = document.getElementById('geodesic');
var draw; // global so we can remove it later
/**
* Format length output.
* @param {ol.geom.LineString} line The line.
* @return {string} The formatted length.
*/
var formatLength = function(line) {
var length;
if (geodesicCheckbox.checked) {
var coordinates = line.getCoordinates();
length = 0;
var sourceProj = map.getView().getProjection();
for (var i = 0, ii = coordinates.length - 1; i < ii; ++i) {
var c1 = ol.proj.transform(coordinates[i], sourceProj, 'EPSG:4326');
var c2 = ol.proj.transform(coordinates[i + 1], sourceProj, 'EPSG:4326');
length += wgs84Sphere.haversineDistance(c1, c2);
}
} else {
length = Math.round(line.getLength() * 100) / 100;
}
var output;
if (length > 100) {
output = (Math.round(length / 1000 * 100) / 100) +
' ' + 'km';
} else {
output = (Math.round(length * 100) / 100) +
' ' + 'm';
}
return output;
};
/**
* Format area output.
* @param {ol.geom.Polygon} polygon The polygon.
* @return {string} Formatted area.
*/
var formatArea = function(polygon) {
var area;
if (geodesicCheckbox.checked) {
var sourceProj = map.getView().getProjection();
var geom = /** @type {ol.geom.Polygon} */(polygon.clone().transform(
sourceProj, 'EPSG:4326'));
var coordinates = geom.getLinearRing(0).getCoordinates();
area = Math.abs(wgs84Sphere.geodesicArea(coordinates));
} else {
area = polygon.getArea();
}
var output;
if (area > 10000) {
output = (Math.round(area / 1000000 * 100) / 100) +
' ' + 'km<sup>2</sup>';
} else {
output = (Math.round(area * 100) / 100) +
' ' + 'm<sup>2</sup>';
}
return output;
};
function addInteraction() {
var type = (typeSelect.value == 'area' ? 'Polygon' : 'LineString');
draw = new ol.interaction.Draw({
source: source,
type: /** @type {ol.geom.GeometryType} */ (type),
style: new ol.style.Style({
fill: new ol.style.Fill({
color: 'rgba(255, 255, 255, 0.2)'
}),
stroke: new ol.style.Stroke({
color: 'rgba(0, 0, 0, 0.5)',
lineDash: [10, 10],
width: 2
}),
image: new ol.style.Circle({
radius: 5,
stroke: new ol.style.Stroke({
color: 'rgba(0, 0, 0, 0.7)'
}),
fill: new ol.style.Fill({
color: 'rgba(255, 255, 255, 0.2)'
})
})
})
});
map.addInteraction(draw);
createMeasureTooltip();
createHelpTooltip();
var listener;
draw.on('drawstart',
function(evt) {
// set sketch
sketch = evt.feature;
/** @type {ol.Coordinate|undefined} */
var tooltipCoord = evt.coordinate;
listener = sketch.getGeometry().on('change', function(evt) {
var geom = evt.target;
var output;
if (geom instanceof ol.geom.Polygon) {
output = formatArea(geom);
tooltipCoord = geom.getInteriorPoint().getCoordinates();
} else if (geom instanceof ol.geom.LineString) {
output = formatLength(geom);
tooltipCoord = geom.getLastCoordinate();
}
measureTooltipElement.innerHTML = output;
measureTooltip.setPosition(tooltipCoord);
});
}, this);
draw.on('drawend',
function() {
measureTooltipElement.className = 'tooltip tooltip-static';
measureTooltip.setOffset([0, -7]);
// unset sketch
sketch = null;
// unset tooltip so that a new one can be created
measureTooltipElement = null;
createMeasureTooltip();
ol.Observable.unByKey(listener);
}, this);
}
/**
* Creates a new help tooltip
*/
function createHelpTooltip() {
if (helpTooltipElement) {
helpTooltipElement.parentNode.removeChild(helpTooltipElement);
}
helpTooltipElement = document.createElement('div');
helpTooltipElement.className = 'tooltip hidden';
helpTooltip = new ol.Overlay({
element: helpTooltipElement,
offset: [15, 0],
positioning: 'center-left'
});
map.addOverlay(helpTooltip);
}
/**
* Creates a new measure tooltip
*/
function createMeasureTooltip() {
if (measureTooltipElement) {
measureTooltipElement.parentNode.removeChild(measureTooltipElement);
}
measureTooltipElement = document.createElement('div');
measureTooltipElement.className = 'tooltip tooltip-measure';
measureTooltip = new ol.Overlay({
element: measureTooltipElement,
offset: [0, -15],
positioning: 'bottom-center'
});
map.addOverlay(measureTooltip);
}
/**
* Let user change the geometry type.
*/
typeSelect.onchange = function() {
map.removeInteraction(draw);
addInteraction();
};
addInteraction();
</script>
</body>
</html>
说明：
OpenLayers示例代码：测量
