CSS滤镜效果属性filter

img{
-webkit-filter: grayscale(100%);
    -moz-filter: grayscale(100%);
    -ms-filter: grayscale(100%);
    -o-filter: grayscale(100%);
    filter: grayscale(100%);
}

http://www.runoob.com/cssref/css3-pr-filter.html