CSS3的filter属性
（版权归原作者所有）
http://www.jianshu.com/p/ca7a2bdcc1e7/comments/4956985
filter: blur(5px);
filter: brightness(0.4);
filter: contrast(200%);
filter: drop-shadow(16px 16px 20px blue);
filter: grayscale(50%);
filter: hue-rotate(90deg);
filter: invert(75%);
filter: opacity(25%);
filter: saturate(30%);
filter: sepia(60%);
/* Apply multiple filters */
filter: contrast(175%) brightness(3%);
/* Global values */
filter: inherit;
filter: initial;
filter: unset;