Processing.org. ImageJ. Marvin Image Processing Framework. Commons Sanselan - Commons. Commons Imaging: a Pure-Java Image Library Apache Commons Imaging, previously known as Apache Commons Sanselan, is a library that reads and writes a variety of image formats, including fast parsing of image info (size, color space, ICC profile, etc.) and metadata.
This library is pure Java. It's slower, consequently, but perfectly portable. It's easier to use than ImageIO/JAI/Toolkit (Sun/Java's image support), supports more formats (and supports them more correctly). It also provides easy access to metadata.