mryuanshu

WppaoImage图片增强插件，来自Wppao团队缘殊开发，只为完成网站运营时必须要的几个图片处理功能，如远程图片本地化，图片加水印等功能。
目前支持的功能： 
* 图片文字水印功能 
* 图片文字水印字体自选 
* 图片文字水印尺寸自选 
* 图片文字水印颜色自选 
* 图片使用图片水印功能 
* 水印位置自选

Wppao Image

Wordpress图片增强插件，可以将远程图片获取到本地，并且可以对文章的图片打水印。

MyWebsiteAdvisor

ChrisHurst

This plugin allows you to Automatically add a watermark to all images as they are uploaded to the WordPress Media Library. 
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 now removable with the new backup system, any images watermarked while the new backup system is enabled are able to be restored to the original image.
<a href="http://MyWebsiteAdvisor.com/plugins/transparent-image-watermark/" rel="nofollow ugc">Upgrade to Transparent Watermark Ultra</a> for advanced 
watermark features including:
<ul>
<li>Manually Apply Watermarks to Images Previously Uploaded</li>
<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>
Check out the <a href="http://www.youtube.com/watch?v=fEhZK1U8W94" rel="nofollow ugc">Transparent Image Watermark for WordPress video</a>:
<iframe loading="lazy" class="youtube-player" width="750" height="422" src="https://www.youtube.com/embed/fEhZK1U8W94?version=3&rel=1&showsearch=0&showinfo=1&iv_load_policy=1&fs=1&hl=en-US&autohide=2&hd=1&wmode=transparent" allowfullscreen="true" style="border:0;" sandbox="allow-scripts allow-same-origin allow-popups allow-presentation allow-popups-to-escape-sandbox"></iframe>
Developer Website: http://MyWebsiteAdvisor.com/
Plugin Support: http://MyWebsiteAdvisor.com/support/
Plugin Page: http://MyWebsiteAdvisor.com/plugins/transparent-image-watermark/
Compare Watermark Plugins: http://MyWebsiteAdvisor.com/tools/wordpress-plugins/watermark-plugins-for-wordpress/
Video Tutorial: http://mywebsiteadvisor.com/learning/video-tutorials/transparent-image-watermark-tutorial/
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:

Transparent Image Watermark

Automatically watermark images as they are uploaded to the WordPress Media Library.

Wppao Image vs Transparent Image Watermark