FileManager Plus :

1.watermark
allow add watermark to special position when upload images.
2.max filesize upload
allow to set max upload filesize, not hardcode as 300000 by opencart.
3.Display Full Name
allow to display full image name in filemanager page.
4.Filter File By Name
in filemanager page toolbar, you can add input filter, then it will filter image by name.
5.File Sort
allow sort file list in filemanager page, you can sort by Name,Upload Date, FileSize.
6.Permison Control
you can control 'upload,delete,move,rename..' permission by different user group.

The fllowing is the screenshot of backend control:





This is the frontend change:
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