is a format developed by the International Digital Publishing Forum. It is characterized by the XML- and XHTM-based optional use of CSS styling. The main feature of this format is the use of reflowable text (word wrap) which makes it possible to adapt the image to different device displays. The ePub file is a zip-archive with an .epub extension.
This format has the same color structure as RGB, but it includes an alpha channel that is used to display various levels of transparency. The transparency value is set from 0 to 1, where 1 corresponds to opacity. It is described using the CSS3 programming language.