使用FFmpeg生成高清gif图，降低网格和噪点

加上参数 -vf "split[s0][s1];[s0]palettegen[p];[s1][p]paletteuse"

ffmpeg -i input.gif -vf "split[s0][s1];[s0]palettegen[p];[s1][p]paletteuse" out.gif

参考自：
https://blog.youkuaiyun.com/qq_40212938/article/details/113060064
https://blog.youkuaiyun.com/TracelessLe/article/details/109104953