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最新推荐文章于 2025-05-12 18:44:46 发布

原创最新推荐文章于 2025-05-12 18:44:46 发布 · 637 阅读

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本文介绍了一种使用HTML canvas元素动态绘制圆环的方法，通过调整起点和终点的角度，实现圆环的平滑过渡和动画效果。

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var canvas = document.getElementById("myCanvas");
var context = canvas.getContext("2d");
var startP = [0 , 0.67 , 1.34 ];
var endP = [0.3 , 0.97 , 1.64];
var n = 0.01;
var animate;
window.onload = initPage;

function initPage() {
    var speed = document.getElementsByTagName("select")[0].value;
    window.clearInterval(animate);
    animate = setInterval("show()",speed);
}

function show() {
    context.clearRect(0,0,500,500);
    for(var i = 0 ; i<3 ; i++) {
	startP[i] += n;
	endP[i] += n;
	if(startP[i] == 2) {
	    startP[i] = 0;
	}
	if(endP[i] == 2) {
	    endP[i] = 0;
	}
    }
    context.beginPath();
    context.rect(0,0,500,500);
    context.lineWidth = 1;
    context.fillStyle = "#F2CA07";
    context.fill();
    context.stroke();

    context.beginPath();
    context.arc(250, 250, 10, 0, 2 * Math.PI, false);
    context.lineWidth = 1;
    context.fillStyle = "#333";
    context.fill();
    context.stroke();

    context.beginPath();
    context.arc(250, 250, 100, startP[0] * Math.PI, endP[0] * Math.PI, false);
    context.lineWidth = 160;
    context.strokeStyle = "#333";
    context.stroke();

    context.beginPath();
    context.arc(250, 250, 100, startP[1] * Math.PI, endP[1] * Math.PI, false);
    context.lineWidth = 160;
    context.strokeStyle = "#333";
    context.stroke();

    context.beginPath();
    context.arc(250, 250, 100, startP[2] * Math.PI, endP[2] * Math.PI, false);
    context.lineWidth = 160;
    context.strokeStyle = "#333";
    context.stroke();
}

Demo