See the FRAME command for the options for image file format with PyFerret.
GIF is a highly compressed format suitable for single images. (Ferret will not directly create GIF89 animations.) The procedure for creating a GIF image is nearly identical to the creation of a single frame of an HDF file. The modification is generally just to select a file name with the ".gif" extension; Ferret will automatically sense this as a request to create a GIF-formatted image file. Alternatively, any file name can be used if the GIF format is specified explicitly using
If a number of GIF images are created using the same file name Ferret will automatically rename subsequent versions with a version number. Thus a repeat loop can be used to generate many GIF images.
REPEAT/L=1:12(FILL sst; GO fland; FRAME/file=myimage.gif)
Note: In this mode of grabbing an image, Ferret creates a GIF file by requesting the image back from your screen (your X server). In order for Ferret to correctly grab the image, the X server should be configured to be running either in 8-bit PseudoColor mode (i.e. direct color) or 24-bit TrueColor mode (i.e. indexed color) with X server backing store enabled. If the X server is configured in 16-bit TrueColor (also indexed color) mode, Ferret will be unable to grab the GIF image from the X server.
An alternative approach to creating GIF's (which does not share this restriction) is to invoke Ferret with the -gif command line switch "ferret -gif".