Preserved Topic: Alpha channel (Page 1 of 1)

How do I save an image containing alphachannels for the web?

HI Mac.olsen .. welcome to the nut-house!

Can you be a bit more specific with your question.. as far as I am aware, normally images for the web are compressed into either .gif or .jpg formats. This method of compression does not support alpha channels. I think that the .tiff format does support alpha channels but I am not sure if browsers can display .tiff images?

Post back with details!

well, everyone seems to have different methods, but here's teh basic approach:

jpg: go to File >> Save a Copy, and specify JPG as the file type.

gif: again go File >> Save a Copy, but specify PSD as the file type (this way you keep the version with the layers and channels intact so you can edit it later if you want). Then on the copy version:

go to Image >> Mode and specify Indexed.

it will ask if you want to flatten the image...click yes.

Specify your color depth settings in the box that comes up.

Go to File >> Export >> gif89a and tell it if you want it interlaced and waht color(s) you may want to be transparent.

I use 5.0, and there are options in 5.5 and 6.0 that 5.0 doesn't have...so they may be easier than what I do

Tnx for the reply, I'll try to be more specific:
I've made an image with one alpha channel. (Stripes and stuff, like the asylum logo)
And I want to use it on my upcoming webpage. But when I convert it, the alpha channel stripes ect. don't show up. I've already converted it to tiff, but the browser can't display this format. That's really it, my, kind of anoying, problem!

-mac.olsen-

Posted at the same time!

But, over to the hard reality:
I found a kind of a solution on my problem, very original...
I did a print-screen and cut out the image, it worked.

But I don't think I'm doing it that way anymore...
Are there other ways of getting transparecy??

Tnx for your replys.

I'm baffled by the question. How is it that stripes contained in an alpha even show up on a tiff? Beyond the 4 basic channels (composite, R, G, B), any subsequent alphas are for storing selections. These don't show up when you view the graphic. In any file format.

If the "stripes" define transparency, you can utilize the alpha in gif89a to define the transparent parts of the image. It's not antialiased though - jaggies will be an issue. Convert the image with the alpha to indexed color. File>export>gif89a. Select the alpha for transparency. The resulting file won't have an alpha channel, but it will use that info to define transparent.

As far as I know, the only web file format that does support alphas and partial transparency is png, which is a way cool graphics format so badly supported by most browsers it is basically useless. Bummer. It's potential is awesome.

ooh..I get to nod and smile by following the PhotoGod again.

The man's got it there mac. Export using gif89a and select alpha channel for your transparency.

Bing...Bang...Boom.

Peter





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