JavaScript html5 canvas draws clock effect_javascript skills-JS Tutorial-php.cn

JavaScript html5 canvas draws clock effect_javascript skills

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Release： 2016-05-16 15:12:34

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The example in this article describes the JavaScript+html5 canvas drawing clock effect. Share it with everyone for your reference, the details are as follows:

HTML part:

<!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>

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JavaScript part:

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);
  //绘制分刻度
  drawScale(context, x, y, r, angleM, -0.93*r, -0.96*r, 1);
 //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){
 context.save();
 context.beginPath();
 context.translate(x/2,y/2);
 context.lineWidth = lineWidth;
 for (var i = 0; i < 60; 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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I hope this article will be helpful to everyone in JavaScript programming.