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CanvasBlocker/test/webGL-Test.html

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<!DOCTYPE html>
<html>
<head>
<title>Test</title>
</head>
<body>
<canvas id="canvas" width="10" height="10"></canvas>
<span id="output"></span>
<script>
(function(){
var canvas = document.getElementById('canvas');
var gl = canvas.getContext('webgl');
var pixels = new Uint8Array(gl.drawingBufferWidth * gl.drawingBufferHeight * 4);
gl.readPixels(0, 0, gl.drawingBufferWidth, gl.drawingBufferHeight, gl.RGBA, gl.UNSIGNED_BYTE, pixels);
var values = [];
for (var i = 0; i < pixels.length; i += 1){
values[pixels[i]] = (values[pixels[i]] || 0) + 1;
}
document.getElementById("output").textContent = JSON.stringify(values);
}());
</script>
</body></html>