jng

JNG, short for JPEG Network Graphics, is a graphics file format that was defined as part of the MNG (Multiple-image Network Graphics) specification. It was designed to store JPEG-encoded image data within a PNG-style container, enabling the combination of lossy JPEG compression with features associated with PNG such as an embedded alpha channel and support for multiple frames in a single file. The primary goal was to provide a single file format capable of efficiently storing photographic imagery while still offering transparency and other PNG-like capabilities.

Structure and data model: A JNG file encapsulates either JPEG-compressed image data or uncompressed image data, along with optional alpha information. It uses a chunk-based structure reminiscent of PNG, but with dedicated mechanisms for handling JPEG data streams and the associated alpha plane. This arrangement makes JNG suitable for photographic content where lossy compression is advantageous, while preserving the ability to represent transparency.

History and status: JNG was introduced in the context of the MNG format during the late 1990s and early 2000s. Despite the theoretical benefits, it failed to gain broad support among image editing tools and Web browsers. The broader MNG project itself did not achieve lasting adoption, and as a result, JNG remains a niche format with limited contemporary use. PNG and JPEG remain the dominant formats for lossless graphics and lossy photographic images, respectively.