Draw the ouput of a webglearth canvas to a 2d canvas
Question
I am trying to copy the output of a canvas running webglearth ( http://www.webglearth.org/ ) to a standard 2d canvas. I followed the answer to this question, but I can only see the background colour of the canvas.
My code is:
<html>
<body>
<div id="earthDiv" style="background-color:rgba(255,0,255,0.5); width:500px; height: 500px;"></div>
<canvas id="canvas" style="background-color:rgba(0,255,0,0.5); width:500px; height: 500px;"></canvas>
<script src="http://www.webglearth.com/v2/api.js"></script>
<script type="text/javascript">
window.onload = function () {
var earth = new WE.map("earthDiv");
var earthCanvas = earth.canvas;
var earthContext = earthCanvas.getContext("webgl", {
preserveDrawingBuffer: true,
});
WE.tileLayer('http://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png', {}).addTo(earth);
var canvas = document.getElementById("canvas");
var context = canvas.getContext("2d");
setInterval(function () {
context.drawImage(earthContext.canvas, 0, 0);
}, 1000);
};
</script>
</body>
</html>
1 answers
solution1
0 ACCPTED 2018-10-16 11:05:11
Turns out this is an issue: https://github.com/webglearth/webglearth2/issues/104 , where the context for the canvas needs "preserveDrawingBuffer: true" when it is got for the first time.
It can be worked around by changing
Cesium.Scene({
canvas: this.canvas,
contextOptions: { webgl: { alpha: !0 !== c.sky } }
});
in http://www.webglearth.com/v2/api.js to
Cesium.Scene({
canvas: this.canvas,
contextOptions: { webgl: { alpha: !0 !== c.sky, preserveDrawingBuffer: true } }
});
(and then saving it and using it as a local file).
It can be worked around by getting a png image using
earth.getScreenshot(function(dataUrl) {...}))
(see https://github.com/webglearth/webglearth2/issues/60 )
However the png approach does not perform amazingly.
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