放到<head></head>里面
<style>:-webkit-full-screen {-webkit-filter:grayscale(1);filter:grayscale(1)}:-ms-fullscreen {filter:grayscale(1)}:fullscreen {-webkit-filter:grayscale(1);filter:grayscale(1)}html {-webkit-filter:grayscale(1);filter:grayscale(1)}</style>