html5 canvas绘画时钟

2023-08-11 21:17:22

本示例使用HTML5 canvas，模拟显示了一个时钟，请使用支持HTML5的浏览器预览效果：

HTML部分：

<!DOCTYPE html>

<html lang="en">

<head>

    <meta charset="UTF-8">

    <meta name="viewport" content="width=device-width, initial-scale=1.0,minimum-scale=1.0,maximum-scale=1.0">

    <title>canvas绘图</title>

</head>

<body onload="init()">

<canvas id="canvas" width="200px" height="200px"></canvas>

</body>

</html>

JavaScript部分：

function init(){

    var canvas = document.getElementById("canvas"),

        context = canvas.getContext("2d");

    setInterval(function(){draw(canvas, context)},1000);

}

function draw(canvas, context){

    var x = canvas.width,

        y = canvas.height,

        r = Math.min(x/2, y/2);

    context.clearRect(0, 0, x, y); //清除绘画历史

    //绘画钟框

    context.fillStyle = "#f1f1f1";

    drawCircle(context, x, y, r);

    //绘画文字

    var tx = x/2,ty = y/2,tr = 0.8*r;

    context.font = "bold 12px 微软雅黑";

    context.fillStyle = "#000";

    drawText(context, "1", tx + 0.5*tr,ty - 0.866*tr);

    drawText(context, "2", tx + 0.866*tr, ty - 0.5*tr);

    drawText(context, "3", tx + tr, ty);

    drawText(context, "4", tx + 0.866*tr, ty + 0.5*tr);

    drawText(context, "5", tx + 0.5*tr, ty + 0.866*tr);

    drawText(context, "6", tx, ty + tr);

    drawText(context, "7", tx - 0.5*tr, ty + 0.866*tr);

    drawText(context, "8", tx - 0.866*tr, ty + 0.5*tr);

    drawText(context, "9", tx - tr, ty);

    drawText(context, "10", tx - 0.866*tr, ty - 0.5*tr);

    drawText(context, "11", tx - 0.5*tr, ty - 0.866*tr);

    drawText(context, "12", tx, ty - tr);

    //获取当前时间

    var date = new Date(),

        h = date.getHours(),

        m = date.getMinutes(),

        s = date.getSeconds(),

        angleH = (360/12)*Math.PI/180,

        angleM = (360/60)*Math.PI/180

    context.strokeSyle = "#000";

     //绘制时刻度

    drawScale(context, x, y, r, angleH, -0.88*r, -0.96*r, 3, 12);

     //绘制分刻度

    drawScale(context, x, y, r, angleM, -0.93*r, -0.96*r, 1, 60);

    //绘画时分秒针

    drawCircle(context, x, y, 3);

    drawNeedle(context, x, y, r, h*angleH + m*angleM/12, -0.5*r);

    drawNeedle(context, x, y, r, m*angleM + s*angleM/60, -0.6*r);

    drawNeedle(context, x, y, r, s*angleM, -0.75*r);

}

//绘画圆

function drawCircle(context, x, y, r){

    context.save();

    context.beginPath();

    context.arc(x/2, y/2, r, 0, Math.PI*2, 0);

    context.fill();

    context.closePath();

    context.restore();

}

//绘画文字方法

function drawText(context, text, x, y){

    context.save();

    x -= (context.measureText(text).width/2);

    y += 4;

    context.translate(x, y);

    context.fillText(text, 0, 0);

    context.restore();

}

//绘制刻度方法

function drawScale(context, x, y, r, rotate, start, end, lineWidth, loop){

    context.save();

    context.beginPath();

    context.translate(x/2,y/2);

    context.lineWidth = lineWidth;

    for (var i = 0; i < loop; i++) {

        context.rotate(rotate);

        context.moveTo(0, start);

        context.lineTo(0, end);

    }

    context.closePath();

    context.stroke();

    context.restore();

}

//绘画时分秒针方法

function drawNeedle(context, x, y, r, rotate, line){

    context.save();

    context.translate(x/2,y/2);

    context.beginPath();

    context.rotate(rotate);

    context.moveTo(0, 0.1*r);

    context.lineTo(0, line);

    context.closePath();

    context.stroke();

    context.restore();

}

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