I did some research and iProtect was the only plugin who offered what I was looking for - quick and simple post images overlay. I love it!
But there's an issue that is bugging me. It overlays the images even in the blog rss feed, which will be OK if working.
When I inspect the image element in Google Reader I see that the background-image property in the DIV is missing. But it's present in the feed contents, for example:
In RSS contents:
<div width="500" height="332" style="background-image:url(http://www.kulinarno-joana.com/wp-content/uploads/2010/06/DSC2775.jpg); background-repeat: no-repeat; background-position: center;"><img src="http://www.kulinarno-joana.com/wp-content/plugins/iprotect/trans.gif" title="Салата с кускус и черна леща" alt="" width="500" height="332" /></div>
In Google Reader - view source:
<div width="500" height="332" style="background-repeat:no-repeat"><img src="http://www.kulinarno-joana.com/wp-content/plugins/iprotect/trans.gif" title="Салата с кускус и черна леща" alt="" width="500" height="332"></div>
Well the original images are not rendered. They have to be in the DIV background. The same appears when I import the RSS feed in Microsoft Outlook 2007 - it shows only the text of the post and the trans.gif on top of empty DIVs.
Do you have any idea what is happening, what is stripping the background from the code?