File storage


    There is four OpenPanorama file format:
- "OpenPanorama Panorama" with file extension .opp
- "OpenPanorama Image" with file extension .opi
- "OpenPanorama Lensflare" with file extension .opl
- "OpenPanorama Visit" with file extension .opv

    These extensions are very usefull to know which sort of file it is, and to associate a specific icon for each one.  

    There is two ways to use each of these file formats:
- as is
- in a zipped file


 I. Using XML files as is
 
You can use OpenPanorama XML files as is.
You can replace normal .xml extension with the OpenPanorama one (opp, opi, opl, opv) to open it and find it more easily.
If in the file, you use an external file (eg. an image), the viewer will look for this file in the local folder of the XML file.
It's better to use zipped file, to be sure that two different files don't use the same name in the same folder.


 II. Using XML files in a zipped file
 
You can use OpenPanorama XML files in a zipped file. You can replace normal .zip extension with the OpenPanorama one (opp, opi, opl, opv). When the viewer load a zipped file, it looks for the table of content (TOC) file which is call toc.xml first to know the folders which are in the zip and know which OpenPanorama file of the zip to open first.

A. The Table of content file
    The table of content file is an XML schema which is everytime call "toc.xml". This file have to be the first of the zip to allow software to open the panorama more quickly.
The toc.xml file looks like that:

<?xml version="1.0" encoding="utf-8" ?>
<!-- - first parameter is the filename of the openpanorama file to open first. it's optionnal.
If it's not set, the viewer will try to open first a .opv file, then .opp then .opl,
 then .opi, then the first .xml
The file in "first" don't have to be in the child elements of toc element.
-->
<
toc first="panorama.opp" xmlns="http://www.openpanorama.org/toc">
<!-- file is a file present in the zip. Files in the toc have to be listed in
the same order they are stored in the zip.
this element can be used zero or more times.
- src is the filename of the file. It's required.
-->
<file src="image.opi"/>
<file src="pano2.jpg"/>
<file src="lensflare.opl"/>
</toc>

OpenPanorama will provide some free software for diffrent sort of computers and OS to easily manage this sort of packages.

A. Storage and file access

You can store all external files used by the XML in the zipped file and/or in the folder of it..
When there is a request for an external file (eg. an image), the viewer will look first for this file in its zipped file, then in the mother zipped files until there is one (if the zipped file is in an other zipped file), then in the local folder of the last mother zipped file if not found.
Therefore, an openPanorama zipped file can store other zipped files which can store other zipped files, etc.....

Examples:
You can create a zipped lensflare.opl with the following file:
- mask.jpg
- lensflare.opl

You can create a zipped image.opi with the following files
- image.jpg
- mask.gif
- image.opi

Now you can use the two previous file in a zipped panorama.opp file with the following files in:
- pano.jpg
- lensflare.opl (zipped)
- image.opi (not zipped)
- image.jpg
- mask.gif
- panorama.opp
This example shows you that you can use zipped and non-zipped files in a same zipped file.

Now you can use the previouse file in a visit.opv zipped file with the followinf files:
- panorama.opp
- panorama2.opp
- panorama3.opp
- visit.opv

To allow a fast or progressive display of the panorama, you have to store the files in the zip in order of priority.



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