JPEG 2000 (Photoshop optional plug-in)

JPEG 2000 is a file format that provides more options and greater flexibility than the standard JPEG (JPG) format. Using JPEG 2000, you can produce images with better compression and quality for both Web and print publishing. To save files in the JPEG 2000 format, the optional JPEG 2000 plug-in must be installed in Adobe Photoshop CS/Plug-Ins/Adobe Photoshop Only/File Formats. The optional JPEG 2000 format plug-in can be found on the Photoshop CS installation CD in Goodies/Optional Plug-Ins/Photoshop Only/File Formats.

Note: Currently, computers with the necessary plug-in can display your JPEG 2000 files on the Web.

Unlike traditional JPEG files, which are lossy, the JPEG 2000 format supports optional lossless compression. The JPEG 2000 format also supports 16-bit color or grayscale files, 8-bit transparency, and it can retain alpha channels and spot channels. Grayscale, RGB, CMYK, and Lab are the only modes supported by the JPEG 2000 format.

The JPEG 2000 format also supports using a Region of Interest (ROI) to minimize file size and preserve quality in critical regions of an image. By using an alpha channel, you can specify the area (ROI) where the most detail should be preserved, allowing greater compression and less detail in other regions. (See Creating alpha channels (Photoshop).)