Canvas实现保存图片到本地的示例代码

//canvas绘制部分代码

var picurl = "http://wx.qlogo./mmopen/OicsrgN57fqDxImI3iMeSXRfVUQRueHcxRRuWG0O1Ea1bNyBPKKKLeq5FiaXFWOdsltVe1R1PtJ2EtsDHYDjHgQ/0";
   var img = new Image,
    canvas = document.createElement("canvas"),
    ctx = canvas.getContext("2d"),
      //后台nigix代理 参见问题2
      src = picurl.replace("http://wx.qlogo.","//wq.jd.");
      //解决 canvas 跨域 toDataURL不能读取问题 参见问题1
      img.crossOrigin = "Anonymous";
      //图片资源的预加载
       img.onload = function() {
             canvas.width = img.width;
            canvas.height = img.height;
             ctx.drawImage( img, 0, 0 );
            //将画好的base64图片
             localStorage.setItem( "savedImageData", canvas.toDataURL("image/png") );
      }
       img.src = src;

// 上传图片 参见问题3
$.ajax({
    type: 'POST',
    url:  loadJs.addToken('http://wq.jd./activetmp/promotepic/promoteaddpic', "j132"),
    data: {
        filename: new Date().getTime()+''+Math.floor(Math.random()10000) + '.jpg',
        content: base64pic,
        active: "shotpic20160901"
    },
    dataType: 'json',
    xhrFields: { withCredentials: true },
    suess: function(data) {
                           if (picdata.id == 1 && picdata.msg) {
                                    //图片路径 此前缀路径的图片最清晰 参见问题4
                                    var imgPre = 'http://img10.360buyimg./promotepic/';
                                    //图片地址拼接的完整地址链接
                                    var photo = imgPre + picdata.msg;
                                    $("#cardImg")[0].onload = function() {
                                             //to do 业务逻辑
                                    };
                                    $("#cardImg").attr("src",photo);
                           }
    },
    error:function(data){
    }
});