http://java.freehep.org/vectorgraphics/Manual.html#ImageFormats
Remember that some formats do not support all graphics created from J-Express. Some features (such as pixel transparency) may be missing from the exported figure. Make sure to check that all features of an exported figure is present or change your format.
Vector Graphics Formats store the drawing as you make it. No rasterization takes place while outputting the format. Unlike Image formats, which do rasterize at the time of output, rasterization for vector formats happens in the viewer of the format. The output can be scaled, rotated and manipulated in many ways, without losing its precision. For most drawings Vector Formats should be preferred.
Computer Graphics Metafile (.cgm, .CGM)
The Computer Graphics Metafile format is used for electronic interchange. Although initially a vector format, it has been extended in two upwardly compatible extensions to include raster capabilities and provides a very useful format for combined raster and vector images. It can be used by many document applications, but is limited in functionality.
The Portable Document Format from Adobe is a multi-page format for electronic interchange as well as printing. It is a file that will look the same on the screen and in print, regardless of what kind of computer or printer someone is using and regardless of what software package was originally used to create it.
Scalable Vector Graphics is an XML based format for vector graphics on the Web.
Enhanced Meta File (.emf, .EMF)
The EMF format is a Windows specific format and can be used to import into Office applications (e.g. Word, PowerPoint, etc...).
PostScript (.ps, .PS)
The PostScript format from Adobe is a multi-page format for printing. Encapsulated PostScript(.eps) is a single page of PostScript which can be used for inclusion in another document (such as a LaTeX document).
Shock Wave Format / Macromedia Flash File Format (.swf, .SWF)
MacroMedia's Flash format is a format for animation, based on frames. Outputing to SWF produces one such frame.
VectorGraphics formats are preferred for most drawings, unless a lot of imaging is involved. Resizing of an image normally results in a degradation of the image. Resizing a VectorGraphics output will use all of the resolution available.
Portable Network Graphics Format (.png, .PNG)
The Portable Network Graphics (PNG) format is used because it is superior to many of the more commonly used image encoding algorithms such as GIF and JPEG. No information is lost while encoding in the PNG format, and the resulting files are often much smaller than files compressed in other formats. The number of colors available for display simultaneously is much greater and, importantly, the PNG encoding system is royalty free. PNG images can be displayed normally in any newer web browser. For more information on PNG visit:
http://www.libpng.org/pub/png/Joint Photographers Expert Group Format (.jpg, .JPG)
JPEG is a popular image format for continuous tone pictures (e.g. photographs).
Unix Portable PixMap (.ppm, .PPM)
Portable Pix Map is a format which allows you to convert your image to a variety of other image formats.