Graphics Interchange Format (GIF)

Most common formats of GIF are supported for reading by GDB including GIF87A and GIF89A files. As well, export to GIF format is supported. GIF format is a popular file format originally produced by CompuServe (tm). It is one of two formats (along with JPEG) common used on the World Wide Web.

GIF files are always represented as one raster channel, with a pseudocolor table. GIF files do not have any inherent concept of georeferencing. Comments, and other extensions to the GIF format are ignored. However if user provides a mapinfo TAB file with georeferencing information in it, GDB can support reading GIF with georeferencing through mapinfo TAB file.

Export of GIF files is supported. These files are exported with a type of "GIF". The exported image can only have one channel, and a pseudocolor table. If no pseudocolor table is provided during the export then a linear grayscale table will be used. Georeferencing, and metadata will be saved in an associated .pox file, but this will only be used by other PCI applications.

GIF format does not have any options at this time. At this time it is not possible to produce "interlaced", or progressively displayed GIF files.

In order to save a 24-bit image to a GIF file it is necessary to first convert the image to an 8-bit pseudocolor image. Within EASI, this can be accomplished using the CMPRSS8 or related programs.

PCI would like to thank John Bradley, author of the XV image viewer, from which the GIF translator was derived. PCI would also like to thank Patrick J. Naughton, Michael Mauldin, David Rowley, Spencer W. Thomas, Jim McKie, Steve Davies, Ken Turkowski, James A Woods, and Joe Orost who contributed to the GIF translator within XV.