canvas裁剪clip()函数的具体使用

2024-09-05 07:22:23

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在canvas中，可以使用clip()函数裁剪区域，设定裁剪区域后，只有在区域内的图像才能显示，其余部分会被屏蔽掉

未使用裁剪绘制一个圆

<!DOCTYPE html>  <html lang="en">  <head>      <meta charset="UTF-8">      <title></title>      <style>          *{margin:0; padding:0;}          html, body{width:100%; height:100%; overflow:hidden; background-color:#AFAFAF;}      </style>  </head>  <body>      <canvas id="canvas"></canvas>      <script>          var canvas = document.getElementById('canvas'),              context = canvas.getContext('2d');          canvas.width = document.body.clientWidth;          canvas.height = document.body.clientHeight;          context.lineWidth = 3;          context.strokeStyle = 'red';          context.beginPath();          context.arc(200, 200, 100, (Math.PI / 180) * 0, (Math.PI / 180) * 360, false);          context.stroke();          context.closePath();      </script>  </body>  </html>

效果

使用clip()裁剪区域

<!DOCTYPE html>  <html lang="en">  <head>      <meta charset="UTF-8">      <title></title>      <style>          *{margin:0; padding:0;}          html, body{width:100%; height:100%; overflow:hidden; background-color:#AFAFAF;}      </style>  </head>  <body>      <canvas id="canvas"></canvas>      <script>          var canvas = document.getElementById('canvas'),              context = canvas.getContext('2d');          canvas.width = document.body.clientWidth;          canvas.height = document.body.clientHeight;          context.lineWidth = 3;          context.strokeStyle = 'red';          context.rect(0, 0, 200, 200);          context.clip();          context.beginPath();          context.arc(200, 200, 100, (Math.PI / 180) * 0, (Math.PI / 180) * 360, false);          context.stroke();          context.closePath();      </script>  </body>  </html>

效果

也可以使用arc绘制圆形的剪裁区域

<!DOCTYPE html>  <html lang="en">  <head>      <meta charset="UTF-8">      <title></title>      <style>          *{margin:0; padding:0;}          html, body{width:100%; height:100%; overflow:hidden; background-color:#AFAFAF;}      </style>  </head>  <body>      <canvas id="canvas"></canvas>      <script>          var canvas = document.getElementById('canvas'),              context = canvas.getContext('2d');          canvas.width = document.body.clientWidth;          canvas.height = document.body.clientHeight;          context.lineWidth = 3;          context.strokeStyle = 'red';          context.arc(100, 100, 150, (Math.PI / 180) * 0, (Math.PI / 180) * 360, false);          context.clip();          context.beginPath();          context.arc(200, 200, 100, (Math.PI / 180) * 0, (Math.PI / 180) * 360, false);          context.stroke();          context.closePath();      </script>  </body>  </html>

效果

使用save和restore实现只裁剪单个路径

<!DOCTYPE html>  <html lang="en">  <head>      <meta charset="UTF-8">      <title></title>      <style>          *{margin:0; padding:0;}          html, body{width:100%; height:100%; overflow:hidden; background-color:#AFAFAF;}      </style>  </head>  <body>      <canvas id="canvas"></canvas>      <script>          var canvas = document.getElementById('canvas'),              context = canvas.getContext('2d');          canvas.width = document.body.clientWidth;          canvas.height = document.body.clientHeight;          context.lineWidth = 3;          context.strokeStyle = 'red';          context.save();          context.rect(0, 0, 200, 200);          context.clip();          context.beginPath();          context.arc(200, 200, 100, (Math.PI / 180) * 0, (Math.PI / 180) * 360, false);          context.stroke();          context.closePath();          context.restore();          context.beginPath();          context.arc(250, 250, 100, (Math.PI / 180) * 0, (Math.PI / 180) * 360, false);          context.stroke();          context.closePath();      </script>  </body>  </html>

效果