The GeoGateway JPEG support is based on the Independent JPEG Group's (IJG) version 4 code. A suite of public domain Unix tools for dealing with JPEG files is available by anonymous ftp from ftp.uu.net in the directory graphics/jpeg.
Export of JPEG JFIF files is supported. These files are exported with a type of "JPG".
JPEG files do not normally contain any auxiliary information such as georeferencing, LUTs, or PCTs; however, an .aux file is written upon export, and this will be honoured when reading PCI generated JPEG files.
Only one (greyscale) and three (RGB colour) bands may be exported to a jpeg file. There is an option to specify a numerical percent 'quality' of the resulting JPEG file. The default quality is 75. More quality implies a bigger image. The useful range of this parameter is approximately 15-90.
Note that JPEG is a lossy compression, and under no circumstances will the image be preserved exactly, even if the quality is 100.