OpenLayers示例代码：地形阴影
OpenLayers示例代码：地形阴影
<!DOCTYPE html>
<html>
<head>
<title>Shaded Relief</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>
table.controls td {
text-align: center;
padding: 2px 5px;
}
</style>
</head>
<body>
<div id="map" class="map"></div>
<table class="controls">
<tr>
<td>vertical exaggeration: <span id="vertOut"></span>x</td>
<td><input id="vert" type="range" min="1" max="5" value="1"/></td>
</tr>
<tr>
<td>sun elevation: <span id="sunElOut"></span>°</td>
<td><input id="sunEl" type="range" min="0" max="90" value="45"/></td>
</tr>
<tr>
<td>sun azimuth: <span id="sunAzOut"></span>°</td>
<td><input id="sunAz" type="range" min="0" max="360" value="45"/></td>
</tr>
</table>
<script>
/**
* Generates a shaded relief image given elevation data. Uses a 3x3
* neighborhood for determining slope and aspect.
* @param {Array.<ImageData>} inputs Array of input images.
* @param {Object} data Data added in the "beforeoperations" event.
* @return {ImageData} Output image.
*/
function shade(inputs, data) {
var elevationImage = inputs[0];
var width = elevationImage.width;
var height = elevationImage.height;
var elevationData = elevationImage.data;
var shadeData = new Uint8ClampedArray(elevationData.length);
var dp = data.resolution * 2;
var maxX = width - 1;
var maxY = height - 1;
var pixel = [0, 0, 0, 0];
var twoPi = 2 * Math.PI;
var halfPi = Math.PI / 2;
var sunEl = Math.PI * data.sunEl / 180;
var sunAz = Math.PI * data.sunAz / 180;
var cosSunEl = Math.cos(sunEl);
var sinSunEl = Math.sin(sunEl);
var pixelX, pixelY, x0, x1, y0, y1, offset,
z0, z1, dzdx, dzdy, slope, aspect, cosIncidence, scaled;
for (pixelY = 0; pixelY <= maxY; ++pixelY) {
y0 = pixelY === 0 ? 0 : pixelY - 1;
y1 = pixelY === maxY ? maxY : pixelY + 1;
for (pixelX = 0; pixelX <= maxX; ++pixelX) {
x0 = pixelX === 0 ? 0 : pixelX - 1;
x1 = pixelX === maxX ? maxX : pixelX + 1;
// determine elevation for (x0, pixelY)
offset = (pixelY * width + x0) * 4;
pixel[0] = elevationData[offset];
pixel[1] = elevationData[offset + 1];
pixel[2] = elevationData[offset + 2];
pixel[3] = elevationData[offset + 3];
z0 = data.vert * (pixel[0] + pixel[1] * 2 + pixel[2] * 3);
// determine elevation for (x1, pixelY)
offset = (pixelY * width + x1) * 4;
pixel[0] = elevationData[offset];
pixel[1] = elevationData[offset + 1];
pixel[2] = elevationData[offset + 2];
pixel[3] = elevationData[offset + 3];
z1 = data.vert * (pixel[0] + pixel[1] * 2 + pixel[2] * 3);
dzdx = (z1 - z0) / dp;
// determine elevation for (pixelX, y0)
offset = (y0 * width + pixelX) * 4;
pixel[0] = elevationData[offset];
pixel[1] = elevationData[offset + 1];
pixel[2] = elevationData[offset + 2];
pixel[3] = elevationData[offset + 3];
z0 = data.vert * (pixel[0] + pixel[1] * 2 + pixel[2] * 3);
// determine elevation for (pixelX, y1)
offset = (y1 * width + pixelX) * 4;
pixel[0] = elevationData[offset];
pixel[1] = elevationData[offset + 1];
pixel[2] = elevationData[offset + 2];
pixel[3] = elevationData[offset + 3];
z1 = data.vert * (pixel[0] + pixel[1] * 2 + pixel[2] * 3);
dzdy = (z1 - z0) / dp;
slope = Math.atan(Math.sqrt(dzdx * dzdx + dzdy * dzdy));
aspect = Math.atan2(dzdy, -dzdx);
if (aspect < 0) {
aspect = halfPi - aspect;
} else if (aspect > halfPi) {
aspect = twoPi - aspect + halfPi;
} else {
aspect = halfPi - aspect;
}
cosIncidence = sinSunEl * Math.cos(slope) +
cosSunEl * Math.sin(slope) * Math.cos(sunAz - aspect);
offset = (pixelY * width + pixelX) * 4;
scaled = 255 * cosIncidence;
shadeData[offset] = scaled;
shadeData[offset + 1] = scaled;
shadeData[offset + 2] = scaled;
shadeData[offset + 3] = elevationData[offset + 3];
}
}
return {data: shadeData, width: width, height: height};
}
var elevation = new ol.source.XYZ({
url: 'https://{a-d}.tiles.mapbox.com/v3/aj.sf-dem/{z}/{x}/{y}.png',
crossOrigin: 'anonymous'
});
var raster = new ol.source.Raster({
sources: [elevation],
operationType: 'image',
operation: shade
});
var map = new ol.Map({
target: 'map',
layers: [
new ol.layer.Tile({
source: new ol.source.OSM()
}),
new ol.layer.Image({
opacity: 0.3,
source: raster
})
],
view: new ol.View({
extent: [-13675026, 4439648, -13580856, 4580292],
center: [-13615645, 4497969],
minZoom: 10,
maxZoom: 16,
zoom: 13
})
});
var controlIds = ['vert', 'sunEl', 'sunAz'];
var controls = {};
controlIds.forEach(function(id) {
var control = document.getElementById(id);
var output = document.getElementById(id + 'Out');
control.addEventListener('input', function() {
output.innerText = control.value;
raster.changed();
});
output.innerText = control.value;
controls[id] = control;
});
raster.on('beforeoperations', function(event) {
// the event.data object will be passed to operations
var data = event.data;
data.resolution = event.resolution;
for (var id in controls) {
data[id] = Number(controls[id].value);
}
});
</script>
</body>
</html>
说明：
OpenLayers示例代码：地形阴影
