Image Alpha transparency with GD2 library

[ahayes1ic]

Can anyone tell me if it is possible to change an images' alpha transparency with the php GD2 library?

My aim is to upload an image (jpg, bmp, gif, png) to the webserver and fade it to 50% transparency and save it to a folder on the server as a gif or png image file.

[rulian]

you have to convert all images to PNG and you can set alpha transparancies. But it's probably easier and safer to do it via CSS and javascripting depending on how/what you are using it for

[ahayes1ic]

rulian wrote:

you have to convert all images to PNG and you can set alpha transparancies. But it's probably easier and safer to do it via CSS and javascripting depending on how/what you are using it for

The image is intended to be displayed in the background with css repeated and an image in the foreground in an img tag.

The foreground and background images are dynamic based on database results with the foreground image to stand out from the background which is why I want to fade the alpha of the background image.

Can you give me an example of some code to alter the png's transparency?

The only examples I can get a hold of are for merging images.

Cheers