知识库

html
<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    html, 
    body {
      width: 100vw;
      height: 100vh;
      display: flex;
      flex-direction: column;
      justify-content: center;
      align-items: center;
    }
  </style>
</head>
<body>
  <canvas id="canvas"></canvas>
  <img src="" alt="">

  <script>
    const img = document.querySelector('img')
    const canvas = document.getElementById('canvas')
    const context = canvas.getContext('2d')

    canvas.style.backgroundColor = '#ddd'
    // 离屏
    canvas.style.display = 'none'

    context.fillStyle = 'red'
    context.font = '32px Arial'
    context.fillText('Hello Canvas', 0, 50)

    // 反映离屏 canvas 内容的图像
    img.src = canvas.toDataURL()
  </script>
</body>
</html>