用canvas制作简单的放大镜(选用高像素的图片哟)-原创手记-慕课网

<!DOCTYPE html>
<html>
    <head>
        <meta charset="UTF-8">
        <title>放大镜canvas版</title>
        <style type="text/css">
            *{
                margin: 0;
                padding: 0;
            }
            #canvas{
                display: block;
                margin: 0 auto;
                box-shadow: 2px 3px 10px 5px gray;
            }
        </style>
    </head>
    <body>
        <canvas id="canvas" width="477" height="476"></canvas>
    </body>
    <script type="text/javascript">
        var canvas = document.getElementById('canvas');
        var context = canvas.getContext('2d');
//      创建图片
        var img = new Image();
        img.src = 'img/4.jpg';
        img.onload = function(){
            context.drawImage(img,0,0);
        }
//      添加鼠标事件
        canvas.onmousedown = function(){
            canvas.onmousemove = function(e){
//          清除画布
                context.clearRect(0,0,canvas.width,canvas.height);
//              再次绘制图片到画布上
                context.drawImage(img,0,0);
                var event = window.event  e;
                var x = event.clientX - canvas.offsetLeft;
                var y = event.clientY - canvas.offsetTop;
//              开始绘制放大区域
                context.drawImage(img,x-50,y-50,100,100,x-70,y-70,140,140);
            }
        }
//      鼠标移出事件
        canvas.onmouseleave = function(){
//          清除鼠标移动事件
            canvas.onmousemove = null;
//          清除画布
            context.clearRect(0,0,canvas.width,canvas.height);
//          再次绘制图片到画布上
            context.drawImage(img,0,0);
        }
    </script>
</html>
用canvas制作简单的放大镜(选用高像素的图片哟)原创
