Changing image on hover with CSS/HTML

I have this problem where I have set an image to display another image when the mouse hovers over, however the first image still appears and the new one doesn't change height and width and overlaps the other one. I'm still pretty new to HTML/CSS so I may have missed something simple. Here is the code:

<img src="LibraryTransparent.png" id="Library">

#Library {
    height: 70px;
    width: 120px;
}

#Library:hover {
    background-image: url('LibraryHoverTrans.png');
    height: 70px;
    width: 120px;
}

Solution 1:

Another option is to use JS:

<img src='LibraryTransparent.png' onmouseover="this.src='LibraryHoverTrans.png';" onmouseout="this.src='LibraryTransparent.png';" />

Solution 2:

One solution is to use also the first image as a background image like this:

<div id="Library"></div>

#Library {
   background-image: url('LibraryTransparent.png');
   height: 70px;
   width: 120px;
}

#Library:hover {
   background-image: url('LibraryHoverTrans.png');
}

If your hover image has a different size, you've got to set them like so:

#Library:hover {
   background-image: url('LibraryHoverTrans.png');
   width: [IMAGE_WIDTH_IN_PIXELS]px;
   height: [IMAGE_HEIGHT_IN_PIXELS]px;
}

Solution 3:

What I usually do is that I create a double image with both states, acting like kind of a two-frame film which I then use with as background for the original element so that the element has width / height set in pixels, resulting in showing only one half of the image. Then what the hover state defines is basically "move the film to show the other frame".

For example, imagine that the image has to be a gray Tux, that we need to change to colorful Tux on hover. And the "hosting" element is a span with id "tuxie".

1. I create 50 x 25 image with two Tuxes, one in color and other gray,
2. then assign the image as a background for a 25 x 25 span,
3. and finally set the hover to simply move the background 25px left.

The minimal code:

<style>
    #tuxie {
        width: 25px; height: 25px;
        background: url('images/tuxie.png') no-repeat left top;
    }
    #tuxie:hover { background-position: -25px 0px }
</style>

<div id="tuxie" />

and the image:

Advantages are:

• By putting both frames in one file, it's ensured that they are loaded at once. This avoids the ugly glitch on slower connections when the other frame never loads immediately, so first hover never works properly.

• It may be easier to manage your images this way since "paired" frames are never confused.

• With smart use of Javascript or CSS selector, one can extend this and include even more frames in one file.

  In theory you could put even multiple buttons in single file and govern their display by coordinates, although such approach could get quickly out of hand.

Note that this is built with background CSS property, so if you really need to use with <img />s, you must not set the src property since that overlaps the background. (Come to think that clever use of transparency here could lead to interesting results, but probably very dependent on quality of image as well as of the engine.).