<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
<style type="text/css">
canvas{
border:1px solid #ccc;
}
</style>
</head>
<body>
<canvas width="600"height="500"></canvas>
<script>
var myCanvas=document.querySelector('canvas');
var ctx=myCanvas.getContext('2d');
// ctx.moveTo(100,100);
// ctx.lineTo(355,100);
ctx.lineWidth=30;
for( var i=0;i<255;i++){
ctx.beginPath();
ctx.moveTo(100+i-1,100);
ctx.lineTo(100+i,100);
ctx.strokeStyle='rgb('+i+','+i+','+i+')';
ctx.stroke();
}
</script>
</body>
</html>
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