JavaScript html5 canvas绘制时钟效果_javascript技巧-js教程

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();}