var block = new cc.Sprite(params.texture);

            block.setBBoxOffsetTop = function(offset) {
                block.offsetTop = offset;
            };
            block.setBBoxOffsetBottom = function(offset) {
                block.offsetBottom = offset;
            };
            block.setBBoxOffsetLeft = function (offset) {
                block.offsetLeft = offset;
            };
            block.setBBoxOffsetRight = function (offset) {
                block.offsetRight = offset;
            };

            block.getBBox = function () {
                var left = block.offsetLeft || 0;
                var right = block.offsetRight || 0;
                var top = block.offsetTop || 0;
                var bottom = block.offsetBottom || 0;

                return cc.rect(this.getPositionX() - this.getContentSize().width/2 + left,
                               this.getPositionY() - this.getContentSize().height/2 + bottom,
                               this.getContentSize().width - left - right, this.getContentSize().height - top - bottom);
            };