[Geoserver-users] transparent transparencies and IE/FFox

ok, this may seem convoluted, but I'm trying to do a somewhat dense GIS
visualization using GeoServer/OpenLayers, and am having problems with
transparency and browsers.

I want to display multiple layers on top of each other, so they will be
transparent, but each layer has an alpha channel (i.e. semi-transparent
features). Using PNG this works great in FireFox, but I can't find a
workable solution for IE, and I would like it to be available to all. this
is what I observe so far:

- Transparent PNG's work great in FireFox
- But they come up as the dreaded pink tile in IE
- JPG's look crappy and grainy regardless of which browser
- Transparent GIF's are find in IE and FireFox
- but GIF's dont seem to support opacity (i.e. the alpha channel) in the
image.

any thoughts?

thanks,
mike
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mfrumin ha scritto:

ok, this may seem convoluted, but I'm trying to do a somewhat dense GIS
visualization using GeoServer/OpenLayers, and am having problems with
transparency and browsers.

I want to display multiple layers on top of each other, so they will be
transparent, but each layer has an alpha channel (i.e. semi-transparent
features). Using PNG this works great in FireFox, but I can't find a
workable solution for IE, and I would like it to be available to all. this
is what I observe so far:

- Transparent PNG's work great in FireFox
- But they come up as the dreaded pink tile in IE
- JPG's look crappy and grainy regardless of which browser

We are investingating on how to make the compression level user tunable in fact.

- Transparent GIF's are find in IE and FireFox
- but GIF's dont seem to support opacity (i.e. the alpha channel) in the
image.

GIF do not support alpha channel as far as I know.
IE is known of not supporting properly translucent PNG's, here is a possible fix:
http://homepage.ntlworld.com/bobosola/
but be warned that afaik the fix slows down IE a lot.
Oh, there's a ton of material on this issue, just search "transparent png IE" with Google.

Apart from this, I don't know what to suggest... try asking on the
openlayers mailing list, since this is more a client side issue.
Or make up things so that you don't need multiple layers... (that
is, change your single layer definition on the fly instead of making
single layers visible/invisible).

Hope this helps
Cheers
Andrea