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