canvas裁剪clip()函数的具体使用

时间：2021-05-08

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

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