This is really interesting. Today while surfing I found an jQuery article which shows button on top of the image when user takes the mouse on the image and hides it when mouse is out. And I liked the idea. I was eager to find out that how this is done and let me tell you it was implemented with ease. The solution was very simple.
The solution is implemented using 2 different images. One image is the original image and other image is replica of first image but little blur and with a button. And using jQuery on mouse over hides the first image and show the second image and onmouseout does the opposite.