canvas-图片翻转

图片90度翻转

在canvas中插入图片需先加载图片（利用Image对象）;加载完成后再执行操作drawImage(obj,x,y,w,h) 插入图片的坐标宽高等值

 

<!DOCTYPE html>
<html>
    <head>
        <meta charset="UTF-8">
        <title></title>
        <link rel="stylesheet" type="text/css" href="../css/public.css"/>
        <style type="text/css">
            body{background: black;}
            canvas{background: #fff;display: block;margin: 20px auto;}
            button{width: 100px;height: 40px;line-height: 40px;text-align: center;}
        </style>
        <script type="text/javascript">
            window.onload=function(){
                var oBtn=document.getElementsByTagName('button');
                var oImg=document.getElementById("img");
                var oDiv=document.getElementsByTagName('div')[0];
                var num=0;
                //在canvas中插入图片需要等图片加载完毕
                var aImg=new Image();
                aImg.src=oImg.src;
                aImg.onload=function(){
                    draw(oImg);
                }
                function draw(obj){
                    var oC=document.createElement('canvas');
                    var oG=oC.getContext("2d");
                    oC.width=obj.width;
                    oC.height=obj.height;
                    oDiv.replaceChild(oC,oImg);
                    oG.drawImage(obj,0,0);
                    oBtn[0].onclick=function(){
                        num--;
                        if(num<0){
                            num=3;
                        }
                        toChange();
                    }
                    oBtn[1].onclick=function(){
                        num++;
                        toChange();
                    }
                    function toChange(){
                        switch(num%4){
                            case 0:
                                oC.width=obj.width;
                                oC.height=obj.height;
                                oG.rotate(0*Math.PI/180);
                                oG.drawImage(obj,0,0);
                                break;
                            case 1:
                                oC.width=obj.height;
                                oC.height=obj.width;
                                oG.rotate(90*Math.PI/180);
                                oG.drawImage(obj,0,-obj.height);
                                break;
                            case 2:
                                oC.width=obj.width;
                                oC.height=obj.height;
                                oG.rotate(180*Math.PI/180);
                                oG.drawImage(obj,-obj.width,-obj.height);
                                break;
                            case 3:
                                oC.width=obj.height;
                                oC.height=obj.width;
                                oG.rotate(270*Math.PI/180);
                                oG.drawImage(obj,-obj.width,0);
                                break;
                        }
                    }
                }
            }
        </script>
    </head>
    <body>
        <button id="right"><</button>
        <button id="left">></button>
        <div>
            <img src="../img/x.jpg" id="img"/>
        </div>
    </body>
</html>

 

posted @ 2016-12-17 21:33  rain92  阅读(321)  评论(0)  编辑  收藏  举报