Katsushi Kawamori

<h4>Compress PNG files</h4>
<ul>
<li>Compress PNG files when adding PNG files in Media Library. </li>
<li>Quality can be specified.</li>
<li>Compress can be specified.</li>
</ul>
<h4>Note</h4>
<p>This has no effect on files compressed with TinyPNG. Also, you can’t expect to get the excellent compression and image quality that TinyPNG provides.</p>


Png Compress

tpaksu

<p>This plugin uses CSS technique to fix the png image transparency issue and jQuery to apply this script to all of png images shown in the page.<br />
This doesn’t work for positioned and tiled png background images. Maybe in next versions.</p>


WP pngfix

Plugin that fixes the png image transparency issue on IE.

Png Compress vs WP pngfix