Can I change the appearance of an html image during hover without a second image?

Question

Is there a way to change the appearance of an icon (ie. contrast / luminosity) when I hover the cursor, without requiring a second image file (or without requiring a hidden portion of the image)?

Answer 1

Here's some good information about image opacity and transparency with CSS.

So to make an image with opacity 50%, you'd do this:

<img src="image.png" style="opacity: 0.5; filter: alpha(opacity=50)" />

The opacity: part is how Firefox does it, and it's a value between 0.0 and 1.0. filter: is how IE does it, and it's a value from 0 to 100.