For one of my clients, I needed to take their logo, shrink it down and place it against a dark brown background... easy enough it seemed. Since their main logo was dark in color, I had them send me a light colored version. It was an Adobo Illustrator file with a transparent background and I thought, "great, I'll just shrink it down as a gif with a transparent background and voila!".
But it was not to be... no matter what I did, the logo came out jagged and the text was unreadable... I talk to a Graphic Designer friend and he mentions
anti-aliasing so I do my research and all becomes clear...
In order for an image to be anti-aliased, it needs to have a background color in order to blend it together with the other colors for the smoothing effect. With transparent GIFs, that can't happen as the software doesn't have a background color to blend.
And that's why most designers don't use transparent gifs much, they just don't look as good as a properly anti-aliased image... if you know the background color for the image, it's best to set that as the background in your image editing program and resize the image with that background.
Seems like opacity should be able to help out here... still more to learn...