我在图像上应用渐变滤镜时遇到问题。我希望渐变从黑到完全透明，从上到下，从下到上。我已经为div定义了css并使用单色（background-color），但是对于图像（background-image），它已经赢了。
我的风格定义是：
#some_id{
background: -moz-linear-gradient(top, rgba(0,0,0,1) 0%, rgba(0,0,0,1) 8%, rgba(0,0,0,0) 100%),
-moz-linear-gradient(bottom, rgba(0,0,0,1) 0%, rgba(0,0,0,1) 8%, rgba(0,0,0,0) 100%); /* FF3.6+ */
background: -webkit-gradient(linear, left top, left bottom, color-stop(0%,rgba(0,0,0,1)), color-stop(8%,rgba(0,0,0,1)), color-stop(100%,rgba(0,0,0,0))),
-webkit-gradient(linear, left bottom, left top, color-stop(0%,rgba(0,0,0,1)), color-stop(8%,rgba(0,0,0,1)), color-stop(100%,rgba(0,0,0,0))); /* Chrome,Safari4+ */
background: -webkit-linear-gradient(top, rgba(0,0,0,1) 0%,rgba(0,0,0,1) 8%,rgba(0,0,0,0) 100%),
-webkit-linear-gradient(bottom, rgba(0,0,0,1) 0%,rgba(0,0,0,1) 8%,rgba(0,0,0,0) 100%); /* Chrome10+,Safari5.1+ */
background: -o-linear-gradient(top, rgba(0,0,0,1) 0%,rgba(0,0,0,1) 8%,rgba(0,0,0,0) 100%),
-o-linear-gradient(bottom, rgba(0,0,0,1) 0%,rgba(0,0,0,1) 8%,rgba(0,0,0,0) 100%); /* Opera 11.10+ */
background: -ms-linear-gradient(top, rgba(0,0,0,1) 0%,rgba(0,0,0,1) 8%,rgba(0,0,0,0) 100%),
-ms-linear-gradient(bottom, rgba(0,0,0,1) 0%,rgba(0,0,0,1) 8%,rgba(0,0,0,0) 100%); /* IE10+ */
background: linear-gradient(to bottom, rgba(0,0,0,1) 0%,rgba(0,0,0,1) 8%,rgba(0,0,0,0) 100%),
linear-gradient(to top, rgba(0,0,0,1) 0%,rgba(0,0,0,1) 8%,rgba(0,0,0,0) 100%); /* W3C */
background-image: url('../images/tla/tlo1.jpg');
}