EarthMoonSystem/EarthMoonSystem.html at master · Makaite/EarthMoonSystem · GitHub

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<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <canvas id="tutorial" width="300" height="300">
    你的浏览器不兼容Canvas,请升级您的浏览器!
  </canvas>

  <script>
    window.onload = () => {
      let canvasEL = document.getElementById('tutorial')
      if(!canvasEL.getContext) {
        return
      }

      let ctx = canvasEL.getContext('2d')

      let sun = new Image()
      sun.src = '../images/canvas_sun.png'

      let earth = new Image()
      earth.src = '../images/canvas_earth.png'

      let moon = new Image()
      moon.src = '../images/canvas_moon.png'

      requestAnimationFrame(draw)

      function draw() {
        ctx.clearRect(0,0,300,300)
        ctx.save()

        ctx.save()
        ctx.drawImage(sun,0,0)
        ctx.translate(150,150)
        ctx.strokeStyle = 'rgba(0,153,255,0.4)'
        ctx.beginPath()
        ctx.arc(0,0,105,0,Math.PI * 2)
        ctx.stroke()
        ctx.restore()

        let time = new Date()
        let seconds = time.getSeconds()
        let milliseconds = time.getMilliseconds()

        ctx.save()
        ctx.translate(150,150)
        ctx.rotate(Math.PI * 2 / 60 * seconds + Math.PI * 2 / 60 /1000 * milliseconds)
        ctx.translate(105,0)
        ctx.drawImage(earth,-12,-12)

        ctx.save()
        ctx.rotate(Math.PI * 2 / 10 * seconds + Math.PI * 2 / 10 / 1000 * milliseconds)
        ctx.translate(0,28)
        ctx.drawImage(moon,-3.5,-3.5)
        ctx.restore()

        ctx.save()
        ctx.fillStyle = 'rgba(0, 0, 0, 0.4)'
        ctx.fillRect(0, -12, 40, 24)
        ctx.restore()


        ctx.restore()
        requestAnimationFrame(draw)
      }
    }
  </script>
</body>
</html>