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ktxed
05-14-2005, 04:16 PM
how do i export alpha channels of any layer? for example i make a new transparent layer,i draw something and want it's alpha exported...i don't know how..
could you help?

I only managed to export my picture as a png file with only 8bit alpha.Is 8bit minimum for an alpha channel?(i guess not)

j_p
05-14-2005, 04:48 PM
so what is wrong with 8bit alpha?
do you really need 16bit? i believe pngs are able to contain 16bit per channel (RGBA) but usually its 8bit per channel....and 256 colors for the alpha should be enough for most stuff

and its not the minimum, gif for example uses a 1bit alpha channel...

if you would tell the world what you plan to do with that picture, someone might tell you if you need so many bits for that job...

is photoshop able to edit 16bit/channel?

i hope you are not mistaking 8bit pictures for 8bit/channel pictures or vice versa...

good luck
jan

ktxed
05-17-2005, 06:02 PM
256 colors are not enough...photoshop doesn't use 256 cols for a big gradient...i needed more than 8 bits for a game.

womanonfire
05-18-2005, 04:45 PM
do you need a .png? can you use .tga?
another way to make an alpha is to select the transparent area and go to the Channels palette and click the 'Create New Channel' button at the bottom. this will give you a new channel in black and white. this is an alpha channel. you can paint into it, add gradients, whatever. the black areas are masked and the white areas will be shown (or is it the opposite?, always get it confused.) when you save as a targa (and other formats too) you have the option to save as 24 bit alpha. hope this helps. hard for me to explain ;)

Nerv
05-19-2005, 05:11 AM
I'm havin the same prblem with tga. I have to copy the transparent layer to the alpha channel then only save it. I wish to know is there any way to make transparent area automaticaly export to alpha channel when the file is saved as tga?

womanonfire
05-19-2005, 10:11 AM
I wish to know is there any way to make transparent area automaticaly export to alpha channel when the file is saved as tga?

I don't think so.

ktxed
05-19-2005, 07:30 PM
i know how to create an alpha channel...
i don't know how to export it as a separate file...ex. my_alpha_channel.jpg ;) i was able to export the the alpha at only 8bits with Paint Shop Pro (from a png with 8bit alpha)
i don't think photoshop has only 8 bits for the alpha channel.

peez
09-13-2005, 09:13 AM
I'm havin the same prblem with tga. I have to copy the transparent layer to the alpha channel then only save it. I wish to know is there any way to make transparent area automaticaly export to alpha channel when the file is saved as tga?

Here's my workflow:
- Ctrl-click the layer with transparency (this selects the transparency)
- go to Channels
- click "Save selection as channel"
- now you have a alpha channel -> Save as TGA

Takes a second. Not automatic, but easiest I know.

Velk
09-13-2005, 03:57 PM
256 colors are not enough...photoshop doesn't use 256 cols for a big gradient...i needed more than 8 bits for a game.
8 bits is the bit depth per pixel - you really need more than that? PS just added 16 bit support recently - remember that this is per channel so an 8 bit document is really 24 bits, with an alpha it is 32 bits.

cinemastar
09-18-2005, 07:28 PM
this the only info of alpha channel ?

peez
09-19-2005, 09:07 AM
i don't think photoshop has only 8 bits for the alpha channel.

If you Save As PNG when in 16bit/ch mode in PS, and have a Alpha Channel present, you get 64 bit PNG. At least 3ds max recognises that as 64 bit image, meaning there are all four RGBA channels, all 16 bit. So there you have 16bit alpha.
I also tried to Save As TIFF, but at least max didn't find any alpha there. When opening that back in PS, alpha was there. So, that's another format supporting 16bit alpha.

I'm also wondering where should one need 16 bit alpha. Some high-end print work maybe..?

peez
09-19-2005, 09:14 AM
i know how to create an alpha channel...
i don't know how to export it as a separate file...ex. my_alpha_channel.jpg ;) i was able to export the the alpha at only 8bits with Paint Shop Pro (from a png with 8bit alpha)


One way to export Alpha only (in Photoshop):
- choose Alpha channel in Channels view
- Ctrl-A to select all
- Ctrl-C to copy
- Ctrl-N for new image (size is automatic when copy/paste)
- Ctrl-V to Paste
- save image in whatever format you like

Works in both 8/16 bit.

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