Saving a map can produce two files:
- A mandatory
.ivlfile, containing all information about the map and all map objects (unless only the theme is saved, see Saving and reloading a map). - An
.imgfile, containing the map raster data in a proprietary format for fast access when reloading. This file is not produced if the map does not contain an image.
The .ivl file
The
.ivl
format is the standard Rogue Wave® JViews file format used to
save an
IlvManager
object, see Saving and reading in The
Essential JViews
Framework
. The file basically contains:
- The IlvManagerLayers of the manager, which themselves contain all of the graphic objects.
- All additional IlvNamedProperty objects attached to the IlvManagerLayers.
For example, in JViews
Maps 8.1, the entire map model, and all related information, is
stored in the
IlvManager
as named properties, see Map-specific manager properties, and saved
in the
.ivl
file.
The .img File
To deliver the map reload performance currently achieved by JViews Maps, raster data
for image objects is not saved in the
.ivl
file because this would slow down the
.ivl
file read time. Instead, all raster data is saved in a separate
.img
file. When reloading the map, this file can be mapped directly in
memory (if allowed by the operating system) for fast access and
virtually no parsing time.
Note that if the map does not contain an image, no
.img
file is generated with the
.ivl
file.
Finally, the
.ivl
and
.img
file extensions are defined by the Map Builder, but you are free
to use the API to give any filename you want to the map you are
saving. It is up to you to be consistent between the saving and
loading processes.