Canvas/46_canvas_判断点击区域.html

<!DOCTYPE html>
<html>

<head>
  <meta charset="utf-8" />
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <title>Page Title</title>
  <meta name="viewport" content="width=device-width, initial-scale=1">
</head>

<body>
  <canvas id="myCanvas" style="border:1px solid red;">
    当前浏览器不支持canvas，请更换浏览器后再试
  </canvas>
  <script>
    window.onload = function () {
      var canvas = document.getElementById('myCanvas')

      canvas.width = 800
      canvas.height = 800


      var ctx = canvas.getContext('2d')

      ctx.fillStyle = 'blue'

      ctx.rect(100, 100, 400, 400)

      ctx.fill()


      canvas.addEventListener('mouseup', function (e) {
        // 鼠标在canvas中的位置
        var x = e.clientX - canvas.getBoundingClientRect().left
        var y = e.clientY - canvas.getBoundingClientRect().top

        console.log(x, y)
        // ! 注意isPointInPath只能判断点是否在路径中，所以前面必须要有个能判断的路径，使用fillRect是不行的，因为他没有产生路径，可以使用rect产生一个路径
        console.log(ctx.isPointInPath(x, y))
        if (ctx.isPointInPath(x, y)) {

          ctx.fillStyle = 'red'

          ctx.rect(100, 100, 400, 400)

          ctx.fill()
        } else {
          ctx.fillStyle = 'blue'

          ctx.rect(100, 100, 400, 400)

          ctx.fill()
        }
      })
    }
  </script>
</body>

</html>