An html5 canvas element in the background of my page?
Is it possible to have a full screen canvas element in the background of a webpage and "normal" markup elements like a table in front of it?
like the following snippet (if it wouldn't be used as alternative content):
<canvas id="imageView" width="100%" height="100%">
开发者_高级运维 <table>...</table>
</canvas>
You could try setting a CSS style on the canvas where it has a position: fixed (or absolute as appropriate), and then any content that follows it (as opposed to container content as you've given in your example) should sit on top of it.
<html>
<style>
body {
margin:0;
padding:0;
}
canvas{
position:absolute;
left:0;
top:0;
z-index:-1;
}
div{
position:absolute;
z-index:0;
left:12px;
top:10px;
}
</style>
<body>
<canvas id="myCanvas" width="600" height="600" style="border:1px solid #c3c3c3;">
Your browser does not support the canvas element.
</canvas>
<div>hello is floating div</div>
<script type="text/javascript">
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
var grd = ctx.createLinearGradient(0, 0, 600, 600);
grd.addColorStop(0, "#FF0000");
grd.addColorStop(1, "#00FF00");
ctx.fillStyle = grd;
ctx.fillRect(0, 0, 600, 600);
</script>
</body>
</html>I tried it for you with the following code. The div gets placed on top of the canvas element just as Matthew describes it. So should work for you:
<!DOCTYPE HTML>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Canvas demo</title>
<style type="text/css">
#canvasSection{ position:fixed;}
</style>
<script type="text/javascript">
function draw()
{
//paint the text
var canvas = document.getElementById('canvasSection');
var context = canvas.getContext('2d');
context.fillStyle = '#00f';
context.font = 'italic 30px sans-serif';
context.textBaseline = 'top';
context.font = 'bold 30px sans-serif';
context.strokeText('Your Text!!', 0, 0);
//paint the square
var canvasSquare = document.getElementById('canvasSquare');
var ctxSquare = canvas.getContext('2d');
ctxSquare.fillStyle='#FF0000';
ctxSquare.fillRect(0, 100,50,100);
}
</script>
</head>
<body onLoad="draw()">
<canvas id="canvasSection">Error, canvas is not supported</canvas>
<div>TestText</div>
</body>
</html>You can use toDataURL() to have it in pure JS separated from HTML
var c = document.createElement('canvas'),
ctx = c.getContext('2d'),
size = c.width = c.height = 50;
for( var x = 0; x < size; x++ ){
for( var y = 0; y < size; y++ ){
ctx.fillStyle = 'hsl(0, 0%, ' + ( 100 - ( Math.random() * 15 ) ) + '%)';
ctx.fillRect(x, y, 1, 1);
}
}
document.body.style.background = 'url(' + c.toDataURL() + ')';HTML on <b>canvas background</b>Based on this CodePen
加载中,请稍侯......
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