A DjVu file is a format used to store scanned documents, especially those that have a combination of text, images, and drawings. It is an open source alternative to Adobe's PDF format. DjVu file viewers and plugins are available for Windows and Mac computer systems. DjVu files are typically smaller than PDF files, making them a good choice for converting large volumes of text. A DjVu file is split into three images: background, foreground, and mask image. The mask image has a higher resolution, and the background and foreground can be heavily compressed to reduce file size. The DjVu file format was developed by several researchers in the late 1990s at the AT&T labs. A small sample of programs that can open DjVu documents include DjVuLibre DjView, MacDjView Desktop Viewer, WinDjView, and LizardTech Browser Plug In.