exporting alpha chanels in Photoshop CS3

gwolf

I am attempting to export some file that have alpha channels to a program that will only accept GIF format.
When i try to save the file in Photoshop it will only allow me to save it as a copy, unlike photoshop 7 and when i export the file the alpha chanel does not export making the transparency solid white
Is there any way that you know to either save the picture in native GIF and not a copy or export the transparency?
I am kind of new to PS and i would appreciate the help

Matt · VIP

Hi there
You can export straight into the GIF format by going to the File menu and selecting to 'save for web and devices'. You can change the format to GIF with transparancy.
Hope this helps

gwolf · Posted: Sun Feb 03, 2008 7:32 am Post subject:

gwolf · Posted: Mon Feb 04, 2008 11:53 am Post subject:

Matt i made a mistake in the question put GIF format for the export whereas it was TGA i tried your suggestion but it only apply to GIF can you still help?
Thank you
Gwolf

Matt · VIP

gwolf
I haven't used the targa(.tga) format for a long long time. Are you sure you can't use a tiff or png file to import into your other application?

If you can't then here's how to save a targa file with an alpha channel representing transparency in Photoshop. Start off by creating the image and then load up the transparency mask by CTRL clicking the layer thumnail. Now you have all the transparency in the image selected switch over to the channels palette and press the little 'new channel' icon to create a new channel - this is going to be the alpha channel representing transparency. Go ahead and fill the selected area with white.

Now deselect the area (CTRL D) and go to File>Save. Choose the TGA format making sure the alpha channels option is ticked and click ok, now go ahead and select the 32 bits per pixel option and add no compression (although this will depend how you want to use the file).

Now if you open this back up inside photoshop you'll see no transparency represented by the familiar grey and white grid, however if you take a look at the alpha channel we created it's still intact - so why isn't it being represented in the image? Because that's not entirely how Photoshop reads transparency, just have a look at a PNG or TIFF for example.

The upshot is however, if you're working with another application that's asking specifically for targa files then it's likely that it'll be looking for an alpha channel representing your transparency. A video editing application like premiere for example can read transparency in this way and render the transparent pixels accordingly.

There's also an intersting article at the Adobe Support Centre regarding the different behavior of a TGA file between earlier and later versions of Photoshop. The article can be found here
http://www.adobe.com/support/downloads/detail.jsp?ftpID=1544
along with a revised plugin that's said to address the issue.
Hope this helps

gwolf · Posted: Tue Feb 05, 2008 10:36 pm Post subject:

Matt you are wealth of information.
thank you for being patient and detailed with your instructions
gwolf

jmlc73 · Posted: Mon Mar 30, 2009 7:29 pm Post subject: For those searching for this

To get PS CS3 to behave with alpha as PS7, just copy the file

C:\Program Files\Adobe\Photoshop 7.0\Plug-Ins\File Formats\Targa.8BI

into the same folder for PS CS3, that way it will handle the Targa files alpha as in PS 7

Good luck.
PS
Always remember to copy the original file to another location, just in case. Big Grin

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