Application of html5-image cropping renderings-H5 Tutorial-php.cn

Application of html5-image cropping renderings

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Release： 2017-04-27 15:25:07

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How to crop an image using HTML5? The graphics drawn later will use this cropping area. To cancel this cropping area, you need to use the save and restore state. Here are the screenshots of the

effect. :

#Code:

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>canvas</title>
<script>
    // 图像裁剪：context.clip()

    // context.clip()只绘制封闭路径区域内的图像，不绘制路径外部图像，用的时候

    // 先创建裁剪区域

    // 再绘制图像（之后绘制的图形都会采用这个裁剪区域，要取消这个裁剪区域就需要用到保存恢复状态，下面有讲）

    // 给出圆形和星形的裁剪代码
     function createCircleClip(context) {
        context.beginPath();
        context.arc(200, 170, 100, 0, Math.PI * 2, true);
        context.closePath();
        context.clip();
    }

    function create5StarClip(context) {
        var n = 0;
        var dx = 200;
        var dy = 150;
        var s = 150;
        context.beginPath();
        var x = Math.sin(0);
        var y = Math.cos(0);
        var dig = Math.PI / 5 * 4;
        for (var i = 0; i < 5; i++) {
           var x = Math.sin(i * dig);
           var y = Math.cos(i * dig);
           context.lineTo(dx + x * s, dy + y * s);
        }
        context.closePath();
        context.clip();
    } 

	function draw() {
        var canvas = document.getElementById("mycanvas");
        if (canvas == null)
         return false;

        var context = canvas.getContext("2d");

        context.fillStyle = "black";
        context.fillRect(0, 0, 400, 300);
        image = new Image();
        image.src = "Image/html5.jpg"

        image.onload = function () {
            //圆形裁剪区
            //createCircleClip(context)
            //星形裁剪区
            create5StarClip(context);
            context.drawImage(image,0,0);
        }
        
	} 		

	window.onload=draw;
</script>
</head>
<body>
  <p id="p1"></p>
  <canvas id="mycanvas" width="1000" height="800">当前浏览器不支持canvas</canvas>
</body>
</html>

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