canvas中使用clip()函数裁剪方法

来源：匠吉游戏

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。本文主要和大家介绍了canvas裁剪clip()函数的具体使用的相关资料,希望能帮助到大家。

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