Variables and Images:

The SIC image format is the equivalent for maps of the table format for columns. Images are regularly sampled 2-d, 3-d or 4-d data which require conversion formula for the coordinates along each axis. Data values are real (single precision) or double precision. Access time to SIC images is typically 20 times faster than the RGDATA format. GreG can read images using the SIC command DEFINE IMAGE (see the SIC manual for details). Images are then available as multi-dimensional variables, whose names can be specified as argument to a RGDATA/VARIABLE command. Any information about projection, coordinate system, etc...associated with the image is given to GreG to define astronomically correct plots. The GRAPHIC program, a superset of GreG, also incorporates an IMAGE command for similar purpose. GreG can write Images, by saving the Regular Grid array as an image (see WRITE IMAGE ). Header information (conversion formulae, projection information...) is written according to the current parameters defined by command SET.