<div class="box"><img src="upimg/comm.png"/><div class="innerBox"><div class="inner"></div></div>
</div>

*{padding:0;margin: 0;
}
.box{width: 300px;height: 300px;background: skyblue;float: left;position: relative;overflow: hidden;margin:10px 10px 0 0;
}
.innerBox{position: absolute;bottom: 0;left: 0;width: 100%;height: 40px;
}
img{width: 100%;
}
.inner{position: absolute;top:40px;left: 0;width: 100%;height: 40px;background: red;
}

$('.box').hover(function(e){getIn($(this),e)
},function(e){getOut($(this),e)
})//获取在第几区域
function getdirection(obj,e){var bleft=obj.offset().left;//距离左部的大小var btop=obj.offset().top;//距离顶部的大小var li_w=obj.width();//每个图片的宽度var li_h=obj.height();//每个图片的高度var evt=e||window.event;var x=evt.pageX-bleft;//鼠标在该图片中的x坐标var y=evt.pageY-btop;//鼠标在该图片中的y坐标x=Math.abs(x);//这里是防止移出的时候，x的值为负（bleft的值大于pageX）y=Math.abs(y);//与上同理if(x>li_w){x=li_w-(x-li_w);//这里是防止在第四部分移出的时候，pageX的值大于图片的长度，所以需要用到长度减去多余的部分就是在第四区域的对称位置
    }var Alltan=Math.atan(li_h/li_w);//这是αvar leftTan=Math.atan(y/x);//这是βvar rightTan=Math.atan(y/(li_w-x));//这是θif(0<=leftTan&&leftTan<=Alltan&&0<=rightTan&&rightTan<=Alltan){console.log("在第一部分")return 1;}else if(Alltan<=leftTan&&leftTan<=Math.asin(1)&&0<=rightTan&&rightTan<=Alltan){console.log("在第二部分");return 2;}else if(Alltan<=leftTan&&leftTan<=Math.asin(1)&&Alltan<=rightTan&&rightTan<=Math.asin(1)){console.log("在第三部分");return 3;}else if(0<=leftTan&&leftTan<=Alltan&&Alltan<=rightTan&&rightTan<=Math.asin(1)){console.log("在第四部分");return 4;}
}//移入
function getIn(obj,e){var statu=getdirection(obj,e);var li_w=obj.width();var that=obj.find('.inner');var child_h=that.height();if(statu===1){that.css({"left":0,"top":-child_h}).stop().animate({"top":0},200)}else if(statu===2){that.css({"left":-li_w,"top":0}).stop().animate({"left":0},200)}else if(statu===3){that.stop().animate({"top":0},200)}else if(statu===4){that.css({"left":li_w,"top":0}).stop().animate({"left":0},200)}
}//移出
function getOut(obj,e){var statu=getdirection(obj,e);var li_w=obj.width();var that=obj.find('.inner');var child_h=that.height();if(statu===1){that.stop().animate({"top":-child_h},200,function(){$(this).css({"left":0,"top":child_h})})}else if(statu===2){that.stop().animate({"left":-li_w},200,function(){$(this).css({"left":0,"top":child_h})})}else if(statu===3){that.stop().animate({"top":child_h},200)}else if(statu===4){that.stop().animate({"left":li_w},200,function(){$(this).css({"left":0,"top":child_h})})}
}