LocalResizeIMG.js

    /**
     * 获得base64
     * @param {Object} obj
     * @param {Number} [obj.width] 图片需要压缩的宽度，高度会跟随调整
     * @param {Number} [obj.quality=0.8] 压缩质量，不压缩为1
     * @param {Function} [obj.before(this, blob, file)] 处理前函数,this指向的是input:file
     * @param {Function} obj.success(obj) 处理后函数
     * @example
     *
     */
    $.fn.localResizeIMG = function (obj) {
        this.on('change', function () {
            var file = this.files[0];
            var URL = URL || webkitURL;
            var blob = URL.createObjectURL(file);

            // 执行前函数
            if($.isFunction(obj.before)) { obj.before(this, blob, file) };

            _create(blob, file);
            this.value = '';   // 清空临时数据
        });

        /**
         * 生成base64
         * @param blob 通过file获得的二进制
         */
        function _create(blob) {
            var img = new Image();
            img.src = blob;

            img.onload = function () {
                var _this = this;

                //生成比例
                var w = _this.width,
                    h = _this.width,
                    scale = w / h;
                w = obj.width || w;
                h = w / scale;

                //生成canvas
                var canvas = document.createElement('canvas');
                var ctx = canvas.getContext('2d');
                $(canvas).attr({width : w, height : h});
                ctx.drawImage(_this, 0, 0, w, h);

                /**
                 * 生成base64
                 * 兼容修复移动设备需要引入mobileBUGFix.js
                 */
                var base64 = canvas.toDataURL('image/jpeg', obj.quality || 0.8 );

                // 修复IOS
                if( navigator.userAgent.match(/iphone/i) ) {
                    var mpImg = new MegaPixImage(img);
                    mpImg.render(canvas, { maxWidth: w, maxHeight: h, quality: obj.quality || 0.8, orientation: 6 });
                    base64 = canvas.toDataURL('image/jpeg', obj.quality || 0.8 );
                }

                // 修复android
                if( navigator.userAgent.match(/Android/i) ) {
                    var encoder = new JPEGEncoder();
                    base64 = encoder.encode(ctx.getImageData(0,0,w,h), obj.quality * 100 || 80 );
                }

                // 生成结果
                var result = {
                    blob: blob,
                    base64 : base64,
                    clearBase64: base64.substr( base64.indexOf(',') + 1 )
                };

                // 执行后函数
                obj.success(result);
            };
        }
    };


    // 例子
/*
    $('input:file').localResizeIMG({
        width: 100,
        quality: 0.1,
        //before: function (_this, blob) {},
        success: function (result) {
            var img = new Image();
            img.src = result.base64;

            $('body').append(img);
            console.log(result);
        }
    });
*/