How to put transparent rolloever images on image maps?

[Quin]

I made an image map with several hotspots using rollever images (mouseover). The original image is 100kb and I cannot go any less and it is 800x600 pixels. The rollover images are also 800x600 but it is only a small element in the picture that is highlighted/altered using photoshop. I don;t really want several 100kb images so I made the background of each rollover image transparent which then brought the memory dont to 30kb. Now, the problem is when I test it by moving the mouse over the hotspot, the rollover image appears but the transparent background in there is white color. I wanted the original image to show through the areas that aree transparent in the rollover image. Is there a way to do it? Or is there a way for the image over the hotspot a smaller dimension lets say 100x100 instead?

Edited April 8, 2013 by Quin

[newseed]

I may not totally understand what you are trying to do here but I will give it a shot. You have a image that has hotspot links in various places. You have a rollover image(s) that uses a background image on hover for each hotspot. Your issue is that the rollover image is appearing white when on hover. First thing I would change is to make sure your image is transparent. Save it as a gif format. If you require to use a png format then make sure it's saved as png-24 and NOT png-8. If your rollover image is indeed transparent then you need to determine your css background color to make sure it's set to transparent. Now I do not know what your coding is and so I am guessing here but maybe you can supply a url so we can look and see what you have in order to server you better in finding a solution.