Computer Graphics with Photoshop - Photoshop and transparency in the TGA file format

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Photoshop and transparency in the TGA file format

john@do.not.spam.me.please.com

2006-02-22, 6:14 pm

Hello,
in Photoshop CS2, if I have an image with transparency, and I save it
in PNG format, when I reload it I will get again transparency.
But if I save it in TGA, I won't. Even if I selected 32bit. Is there
any way to make it save and load transparency using 32bit TGAs? Please
note that I even tried to create an alpha channel from transparency
(using Image/Calculations..) but, while the newly created alpha channel
will be saved in the TGA file, it won't be reloaded. But, even worse,
the saved alpha/transparency IS NOT PERFECT. The edges look bad then.

But if I save e.g. in PNG, and then import the PNG into Artgem and
resave it in TGA, it works. Even when I reload it.

Does this mean that Artgem supports TGA in the right, proper way, while
PS support of TGA is bad/crippled?

And here we're talking about PS 9.0, not 1.0 beta.. how's it possible?

Thanks,
John

Nicholas Sherlock

2006-02-22, 6:14 pm

john@do.not.spam.me.please.com wrote:
> in Photoshop CS2, if I have an image with transparency, and I save it
> in PNG format, when I reload it I will get again transparency.
> But if I save it in TGA, I won't. Even if I selected 32bit. Is there
> any way to make it save and load transparency using 32bit TGAs?

Right click on the thumbnail of your layer, click "Select layer
transparency". Click the Select menu, "Save Selection...". Save it as a
new channel in your image. Then make sure "Alpha channels" is ticked
when saving your image.

Cheers,
Nicholas Sherlock

john@do.not.spam.me.please.com

2006-02-24, 10:10 am

Hello Nicholas Sherlock, you wrote:
>j...@do.not.spam.me.please.com wrote:
>
>Right click on the thumbnail of your layer, click "Select layer
>transparency". Click the Select menu, "Save Selection...". Save it as a
>new channel in your image. Then make sure "Alpha channels" is ticked
>when saving your image.
>
>Cheers,
>Nicholas Sherloc

Thank you Nicholas, now transparency is saved correctly to the bit, I
verifyed. However, there's a halo around the image (on the edges where
there was *semi*transparency).
Since the transparent parts are saved with white RGB values, I tried
to use a black background to fill transparent pixels but it won't give
the proper results. I think it's a "matte" problem, i.e. those pixels
that are semi-transparent will be saved against a wrong background by
Photoshop.
How could I solve this problem? To sum it all, now Photoshop will save
the correct alpha, but RGB will be correct only for opaque pixels, semi-
transparent ones will have RGB "matted" towards a wrong background color.

Moreover, is there *any* way in Photoshop to LOAD transparency from an
alpha channel? Imagine I have a solid image, I want to make the pixels
more or less opaque by using a mask. Is it possible? Cutting works only
for the pixels that I want to make completely transparent, and anyway
I'd like to have a pixel by pixel precise control.

Thanks again a lot,
John

Tom Nelson

2006-02-24, 10:14 pm

If you've saved transparency as an alpha channel...
1. Within the SAME image: select>load selection
2. From ANOTHER image (which must be open as well) select>load
selection and choose from the Document pop-up.

Tom Nelson
Tom Nelson Photography

In article <43fec291$0$28065$4fafbaef@reader1.news.tin.it>,
<john@do.not.spam.me.please.com> wrote:

> is there *any* way in Photoshop to LOAD transparency from an
> alpha channel?