我正在寻找允许拥有this effect on a canvas’ stroke的代码.
我已经有了一个动画圆形笔画,我只需要获得ANGLE渐变,而不是线性而不是径向.我只有3种颜色.
现有的is available here(评价等级)
解决方法:
上下文strokeStyle可以是一个渐变：
// create a gradient
gradient = ctx.createLinearGradient(xStart, yStart, xEnd, yEnd);
gradient.addColorStop(0.0,"blue");
gradient.addColorStop(1.0,"purple");
// stroke using that gradient
ctx.strokeStyle = gradient;
示例代码和使用渐变strokeStyle的演示：http://jsfiddle.net/m1erickson/w46ps/
<!doctype html>
<html>
<head>
<link rel="stylesheet" type="text/css" media="all" href="css/reset.css" /> <!-- reset css -->
<script type="text/javascript" src="http://code.jquery.com/jquery.min.js"></script>
<style>
body{ background-color: ivory; }
#canvas{border:1px solid red;}
</style>
<script>
$(function(){
var canvas=document.getElementById("canvas");
var ctx=canvas.getContext("2d");
function drawMultiRadiantCircle(xc, yc, r, radientColors) {
var partLength = (2 * Math.PI) / radientColors.length;
var start = 0;
var gradient = null;
var startColor = null,
endColor = null;
for (var i = 0; i < radientColors.length; i++) {
startColor = radientColors[i];
endColor = radientColors[(i + 1) % radientColors.length];
// x start / end of the next arc to draw
var xStart = xc + Math.cos(start) * r;
var xEnd = xc + Math.cos(start + partLength) * r;
// y start / end of the next arc to draw
var yStart = yc + Math.sin(start) * r;
var yEnd = yc + Math.sin(start + partLength) * r;
ctx.beginPath();
gradient = ctx.createLinearGradient(xStart, yStart, xEnd, yEnd);
gradient.addColorStop(0, startColor);
gradient.addColorStop(1.0, endColor);
ctx.strokeStyle = gradient;
ctx.arc(xc, yc, r, start, start + partLength);
ctx.lineWidth = 30;
ctx.stroke();
ctx.closePath();
start += partLength;
}
}
var someColors = [];
someColors.push('#0F0');
someColors.push('#0FF');
someColors.push('#F00');
someColors.push('#FF0');
someColors.push('#F0F');
drawMultiRadiantCircle(150, 150, 120, someColors);
}); // end $(function(){});
</script>
</head>
<body>
<canvas id="canvas" width=300 height=300></canvas>
</body>
</html>