It is effectively a combination of the JPEG and zlib compression mechanisms. TightVNC uses so-called 'tight encoding' of areas, which improves performance over low bandwidth connection.
Constantin Kaplinsky developed TightVNC, using and extending the RFB protocol of Virtual Network Computing (VNC) to allow end-users to control another computer's screen remotely. A server for macOS is available under a commercial source code license only, without SDK or binary version provided. TightVNC is a free and open-source remote desktop software server and client application for Linux and Windows.
