Images uploaded using version 4.7 or less use the old filesystem. Images uploading using version 4.8 or later use the new filesystem.
The old filesystem stored images in numbered folders. The first 100 images were stored in a folder named 1-100, and the next 100 images uploaded were put in a folder called 101-200. The folders looked like this:
This old filesystem lets you copy galleries without using extra server space. But the images can be hard to locate, because there is not 1 folder for each gallery
The new filesystem creates 1 folder for each gallery. It looks like this:
If you uploaded images with version 4.7 or below, then upgraded to version 4.8 and uploaded images, you will have images using both the old and new filesystem, like this:
The gallery will work with images in the old and new filesys. You do not need to migrate the images. You might want to migrate the images so they are easier to find.
Version 4.8.1 of the gallery and above have a migration script that will move the images to the new filesystem, and delete the old folders. To migrate the images, please follow these steps:
1) Upgrade the gallery to version 4.8.1 or above.
2) Go to the Joomla administration, and go to the ignite gallery component. The url will have "administrator/index.php?option=com_igallery" in it. Edit the url, and add "&view=migrate" to the end of the url:
3) Follow the instructions on this page to complete the migration.
***please note, after migrating, the images will have new file paths on the server. If you have manually inserted a gallery image into a Joomla article using the Joomla editor, you will need to fix the path to the image.