Install libwebp
You can download webp from
https://developers.google.com/speed/webp/community
To install webp, run
cd /usr/local/src git clone https://chromium.googlesource.com/webm/libwebp cd libwebp ./autogen.sh ./configure make make install
webp install following executable files
/usr/local/bin/cwebp /usr/local/bin/dwebp