Canvas绘制时钟

Posted 2022-12-03 一如年少模样

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<!DOCTYPE html>
<html>
    <head>
        <meta charset="utf-8" />
        <title>Canvas Clock</title>
        <style type="text/css">

            div
                text-align: center;
                margin-top: 250px;
            
            #clock

                border: 1px solid #ccc;
            
        </style>
    </head>
    <body>
        <div>
            <canvas id="clock" height="200px" width="200px"></canvas>
        </div>

        <script type="text/javascript" src="js/clock.js"></script>
    </body>
</html>

var dom=document.getElementById('clock');
var cxt=dom.getContext("2d");
var width=cxt.canvas.width;
var height=cxt.canvas.height;
var r=width/2;

function drawBackground()
    cxt.save();
    cxt.translate(r,r);
    cxt.beginPath();
    cxt.lineWidth=10;
    cxt.arc(0,0,r-5,0,2*Math.PI,false);
    cxt.stroke();
    cxt.font="18px Arial";
    cxt.textAlign='center'
    cxt.textBaseline='middle'
    var hourNums=[3,4,5,6,7,8,9,10,11,12,1,2];
    hourNums.forEach(function(number,i)

        var rad=2*Math.PI/12*i;
        var x=Math.cos(rad)*(r-30);
        var y=Math.sin(rad)*(r-30);
        cxt.fillText(number,x,y);

    );

    for(var i=0;i<60;i++)

        var rad=2*Math.PI/60*i;
        var x=Math.cos(rad)*(r-18);
        var y=Math.sin(rad)*(r-18);
        cxt.beginPath();
        if(i % 5===0)
            cxt.fillStyle="#000"
            cxt.arc(x,y,2,0,2*Math.PI,false);
        
        else
            cxt.fillStyle="#ccc"
            cxt.arc(x,y,2,0,2*Math.PI,false);
        
        cxt.fill(); 
    



function drawHour(hour,minute)
    cxt.save();
    cxt.beginPath();
    var rad=2*Math.PI/12*hour;
    var mrad=2*Math.PI/12/60*minute
    cxt.rotate(rad+mrad);
    cxt.lineWidth=6;
    cxt.lineCap='round'
    cxt.moveTo(0,10);
    cxt.lineTo(0,-r/2);
    cxt.stroke();
    cxt.restore();


function drawMinute(minute)
    cxt.save();
    cxt.beginPath();
    var rad=2*Math.PI/60*minute;
    cxt.rotate(rad);
    cxt.lineWidth=3;
    cxt.lineCap='round'
    cxt.moveTo(0,10);
    cxt.lineTo(0,-r+30);
    cxt.stroke();
    cxt.restore();


function drawSecond(second)
    cxt.save();
    cxt.beginPath();
    cxt.fillStyle='#c14543'
    var rad=2*Math.PI/60*second;
    cxt.rotate(rad);    
    cxt.moveTo(-2,20);
    cxt.lineTo(2,20);
    cxt.lineTo(1,-r+18);
    cxt.lineTo(-1,-r+18);
    cxt.fill();
    cxt.restore();


function drawDot()

    cxt.beginPath();
    cxt.fillStyle='#fff'
    cxt.arc(0,0,3,0,2*Math.PI,false);
    cxt.fill();


function draw()

    cxt.clearRect(0,0,width,height);
    var now=new Date();
    var hour=now.getHours();
    var minute=now.getMinutes();
    var second=now.getSeconds();
    drawBackground();
    drawHour(hour,minute);
    drawMinute(minute);
    drawSecond(second);
    drawDot();
    cxt.restore();

draw();
setInterval(draw,1000);

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