ChrisHurst

MyWebsiteAdvisor

This plugin allows you to Automatically displays a watermark on images which have been hotlinked as they are viewed on the Hotlinkers Website. 
The plugin uses PNG watermark images with transparency for precise control over the appearance of the watermarks. 
This plugin also supports simple text watermarks with adjustable color, size and transparency. 
The user friendly settings page allows for control over the appearance of your watermark. 
The watermark preview feature allows for easy testing of the plugin settings. 
The watermark size is controlled as a percentage of the target image, 50% means the watermark will be half the width of the target image. 
Watermarks are non-permenant, original images are not edited, the plugin maintains a cached copy of the watermarked image, which can be cleared and regenerated at any time!
<a href="http://MyWebsiteAdvisor.com/tools/wordpress-plugins/watermark-hotlink-protection/" rel="nofollow ugc">Upgrade to Watermark Hotlink Protection Ultra</a> for advanced 
watermark features including:
<ul>
<li>Fully Adjustable Image Watermark Position</li>
<li>Fully Adjustable Text Watermark Position</li>
<li>Adjustable JPEG Image Output Quality</li>
<li>Highest Quality Watermarks using Image Re-sampling rather than Re-sizing</li>
<li>Lifetime Priority Support and Update License</li>
</ul>
Developer Website: http://MyWebsiteAdvisor.com/
Plugin Support: http://MyWebsiteAdvisor.com/support/
Plugin Page: http://MyWebsiteAdvisor.com/tools/wordpress-plugins/watermark-hotlink-protection/
Requirements:
<ul>
<li>PHP v5.0+</li>
<li>WordPress v3.3+</li>
<li>GD extension for PHP</li>
<li>FreeType extension for PHP</li>
</ul>
To-do:

Watermark Hotlink Protection

Displays a watermark on images which have been hotlinked

8MediaCentral

Watermark WP Image Protect allows you to watermark all the images on your site. Unlike other watermarking techniques and plugins, the original images are unaffected and you do not need to edit or re-upload the images, it is done automatically for you on-the-fly.
Out of the box WP Image Protect has all these capabilities:
<ul>
<li>Apply text watermarks to all of your site in seconds (new and existing uploads) </li>
<li>Set the text, font, colour, size and background of the Watermark</li>
<li>Specify threshold to apply watermarks (to exclude thumbnails as required)</li>
<li>Exclude individual images from Watermarking with the media library</li>
<li>Alter, reposition or remove all Watermarks in seconds through your WordPress administration panel</li>
<li>View Image Statistics (goto Media > Library)</li>
</ul>
Please raise any support queries on the support forum.
<a href="http://8mediacentral.com/developments/wp-image-protect-watermark-wordpress-images-plugin/" rel="nofollow ugc">Add the WP Image Protect Premium Pack</a> for even more powerful features such as:
<ul>
<li>Images as Watermarks</li>
<li>Watermark Transparency</li>
<li>Hotlink Prevention</li>
<li>Supercharged Performance</li>
<li>Variable Text Watermarks</li>
<li>Additional Fonts</li>
<li>Premium Support</li>
</ul>
Video Demonstration
A short video showing how to get started with Watermark WP Image Protect:
<iframe loading="lazy" class="youtube-player" width="750" height="422" src="https://www.youtube.com/embed/ElAJo-ojvIc?version=3&rel=1&showsearch=0&showinfo=1&iv_load_policy=1&fs=1&hl=en-US&autohide=2&wmode=transparent" allowfullscreen="true" style="border:0;" sandbox="allow-scripts allow-same-origin allow-popups allow-presentation allow-popups-to-escape-sandbox"></iframe>
Some of the features included in the premium pack:
<iframe loading="lazy" class="youtube-player" width="750" height="422" src="https://www.youtube.com/embed/sZcToOC96CE?version=3&rel=1&showsearch=0&showinfo=1&iv_load_policy=1&fs=1&hl=en-US&autohide=2&wmode=transparent" allowfullscreen="true" style="border:0;" sandbox="allow-scripts allow-same-origin allow-popups allow-presentation allow-popups-to-escape-sandbox"></iframe>

Watermark WP Image Protect

Watermark WP Image Protect is an on-the-fly image watermarking plugin for WordPress.

Watermark Hotlink Protection vs Watermark WP Image Protect