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[Bezzy]

I have some RGBA TGAs which I want to convert to PNG because of size (I have to upload to SVN using a fooking modem).

What's the best way to get the alpha map over to PNG (where transparency is part of the pixel color, rather than just an extra channel)? I'm guessing that I convert the Alpha Channel to a mask, and then press "delete" on the RGB to expose the background... problem is, I don't know how! Masks are the one thing I never really properly learned. Any tips?

[Dan MacDonald]

I believe you use the save for web option off the file menu and specify PNG-8 as the destination format. There may be some super cool way to do it, but from one self taught photoshop guy to another.. I think that will get the job done.

[nenad]

Transparency is always an extra channel it's just a matter of interpretation by the target application. But to keep it simple, here's a droolprof step-by-step recipe (I'm using photoshop6):

1) load tga
2) open layers palette, double click on "background" and rename it to "layer0"
3) open channels palette and ctrl+click on "Alpha1" channel. This should create a selection
4) invert the selection (Select>Inverse) and press "del"
5) save as png

If the background color in tgas was black and images were saved with premultiplied alpha you can do Layer>Matting>Remove Black Matte to get rid of the "black halo"

[Bezzy]

Thanks guys! I'll get on it tomorrow.

I won't let you down.

[Bezzy]

Thanks nenad. That worked. Didn't actually have to select->inverse for what I was doing.

[oNyx]

That ctrl+click way certainly works. However, if you want to convert lots of images try imagemagick.

mogrify -format png *.tga
(converts all *.tga files to png)

Note that the final file size may be equal or even bigger if you use png instead of tga. That's because png uses deflate (like zip), which is inferior to lzma (the compression scheme nsis/7z uses).

[Bezzy]

That ctrl+click way certainly works. However, if you want to convert lots of images try imagemagick.

mogrify -format png *.tga
(converts all *.tga files to png)

Note that the final file size may be equal or even bigger if you use png instead of tga. That's because png uses deflate (like zip), which is inferior to lzma (the compression scheme nsis/7z uses).

Does that convert the alpha, too?

And the reason I'm using png is just because of a lack of broadband. Just needed to have smaller image sizes without actually turning them into archieves (thus putting an extra step into any SVN updates you get) - we'll end up using a different compression method entirely, i'm sure, but this is the easiest short term solution for us right now.

Thanks for the tip!

[oNyx]

>Does that convert the alpha, too?

Yes. Otherwise I wouldn't have suggested that. (It also works fine the other way around.)