utils.canvasMasking = function(img) {

    var deferred = $.Deferred();

    var newImg = document.createElement('img');

    newImg.setAttribute('crossOrigin', 'Anonymous'); //解决跨域问题

    newImg.src = img.src;

    //源图片加载失败

    newImg.onerror = function() {

        deferred.reject('源图片加载失败');

    };

    //源图片加载成功

    newImg.onload = function() {

        var imageWidth = img.width;

        var imageHeight = img.height;

        var mask = document.createElement('img');

        mask.setAttribute('crossOrigin', 'Anonymous');

        mask.src = img.getAttribute('data-mask');

        //遮罩图片加载失败

        mask.onerror = function() {

            deferred.reject('遮罩图片加载失败');

        };

        //遮罩图片加载成功

        mask.onload = function() {

            var maskCanvas = document.createElement('canvas');

            var maskContext = maskCanvas.getContext('2d');

            var maskWidth = mask.width;

            var maskHeight = mask.height;

            maskCanvas.width  = maskWidth;

            maskCanvas.height = maskHeight;

            /**

             * 合并mask与处理后的原始图

             */

            maskContext.drawImage(mask, 0, 0, maskWidth, maskHeight);

            //将一个源（新的）图像绘制到目标（已有）的图像上

            maskContext.globalCompositeOperation = 'source-in';

            maskContext.drawImage(img, 0, 0, maskWidth, maskHeight);

            img.src = maskCanvas.toDataURL();

            deferred.resolve(maskCanvas);

        };

    };

    return deferred.promise();

};