Image Watermark的作者是dFactory,目前有60,000+个有效安装。已经Tested with 5.3.3版本的wordpress。
Image Watermark allows you to automatically watermark images uploaded to the WordPress Media Library and bulk watermark previously uploaded images.
For more information, check out plugin page at dFactory, documentation page or plugin support forum.
Features include:

Bulk watermark – Apply watermark option in Media Library actions
Watermark images already uploaded to Media Library
GD LIbrary and ImageMagic support
Image backup functionality
Option to remove watermark
Flexible watermark position
Watermark image preview
Set watermark offset
Select post types where watermark will be aplied to uploaded images or select adding watermark during any image upload
Select from 3 methods of aplying watermark size: original, custom or scaled
Set watermark transparency / opacity
Select image format (baseline or progressive)
Set image quality
Protect your images from copying via drag&drop
Disable right mouse click on images
Disable image protection for logged-in users
.pot file for translations included