a simple slider by jquery, get all img in a container then make slider with this. How to perfect it, please!

gistfile1.js

(function($){
	$.fn.rb_slider = function(i) {
		if( i ){
			this.rb_slider_zoom_in(!i);
		}else{
			this.rb_slider_zoom_out(!i);
		}
		
	}

	$.fn.rb_slider_zoom_in = function(i){
		obj = this;
		image = this.find('img').last();
		$(image).css( { 'width':'120%','height':'120%','left':'-10%','top':'-10%' });

		$(image).animate({ width : '100%', height: '100%',left : '0%', top : '0%' },5000,function(){
			obj.rb_slider_continue( $(this),i );
		});
	}

	$.fn.rb_slider_zoom_out = function(i){
		obj = this;
		image = this.find('img').last();
		$(image).css( { 'width':'100%','height':'100%', 'left' : 0, 'top' : 0 });

		$(image).animate({ width : '120%', height: '120%',left : '-10%', top : '-10%' },5000,function(){
			obj.rb_slider_continue( $(this),i );
		});
	}

	$.fn.rb_slider_continue = function(img, i){
		obj = this;
		$this = $(img);
		$this.animate({ opacity : 0 },2000,function(){
			obj.prepend($this);
			if( i ){
				obj.find('img').first().css( {'display':'block', 'opacity' : 1, 'width':'120%','height':'120%','left':'-10%','top':'-10%' });
			}else{
				obj.find('img').first().css( {'display':'block', 'opacity' : 1,'width':'100%','height':'100%', 'left': 0, 'top' : 0 });
			}
			obj.rb_slider(i);
		});
	}

})(jQuery);