Using the clip() function to crop in canvas

小云云
Release: 2018-03-03 10:13:50
Original
1865 people have browsed it

In canvas, you can use the clip() function to crop the area. After setting the cropping area, only the image within the area can be displayed, and the rest will be blocked. This article mainly introduces you to the relevant information on the specific use of the canvas clipping () function. I hope it can help you.

Draw a circle without clipping


<!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(&#39;canvas&#39;),  
            context = canvas.getContext(&#39;2d&#39;);  
        canvas.width = document.body.clientWidth;  
        canvas.height = document.body.clientHeight;  
        context.lineWidth = 3;  
        context.strokeStyle = &#39;red&#39;;  
        context.beginPath();  
        context.arc(200, 200, 100, (Math.PI / 180) * 0, (Math.PI / 180) * 360, false);  
        context.stroke();  
        context.closePath();  
    </script>  
</body>  
</html>
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Effect

Use clip() to crop the area


##

<!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(&#39;canvas&#39;),  
            context = canvas.getContext(&#39;2d&#39;);  
        canvas.width = document.body.clientWidth;  
        canvas.height = document.body.clientHeight;  
        context.lineWidth = 3;  
        context.strokeStyle = &#39;red&#39;;  
        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>
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Effect

can also be used arc draws a circular clipping area


<!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(&#39;canvas&#39;),  
            context = canvas.getContext(&#39;2d&#39;);  
        canvas.width = document.body.clientWidth;  
        canvas.height = document.body.clientHeight;  
        context.lineWidth = 3;  
        context.strokeStyle = &#39;red&#39;;  
        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>
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Effect

Use save and restore to achieve Only crop a single path


<!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(&#39;canvas&#39;),  
            context = canvas.getContext(&#39;2d&#39;);  
        canvas.width = document.body.clientWidth;  
        canvas.height = document.body.clientHeight;  
        context.lineWidth = 3;  
        context.strokeStyle = &#39;red&#39;;  
        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>
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Effect

Related recommendations:


Use the clip() method in the HTML5 Canvas API to crop an area image code example

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