Not too clear what you mean.
An HTML image tag <img src="">does not have a link
<a href=""> </a> attribute. So, if you want viewer to click image instead of text for link, you wrap the image tag inside the link anchor tag. Like so
<a href="_"> <img src="___"> </a>
As far as text on top of an image is concerned, think you would be using Z-index. The element has to be "positioned" to apply a z-index.
It you have online link to your page, it might clarify things.
Sorry, missed your link above.