Topic: getting binary alpha channel from png

hi guys,

i have a png file with pixels in different alpha values. some completely opaque, some completely transparent, some in between.
since it's a png it doesnt show an extra alpha channel in the channel list.

what i want to do now, is to remove all those "in between" alpha values.
say the alpha channel runs from 0 to 1, i want all pixels with alpha 0 < 0.5 set to alpha 0 and all others set to alpha 1.

usually i would do this with the image->adjust->threshold, but as i said, pngs dont show up their alpha channel. :/

thanks a lot!



(Edited by GRUMBLE on 09-20-2006 19:03)

Open your png
In the Layers toolbar: Ctrl click on the layer, Add Layer mask, alt click on the mask, posterize it to 2. ( alt+i, a , p, 2, enter )

To get rid of the last transparent pixels, delete and apply the mask, then duplicate and merge the layer a zillion times ( ctrl+j, ctrl+e )


Is it what you want ?



(Edited by poi on 09-20-2006 19:36)

yeah, thanks poi!

You're welcome.
Btw I figured that you can click on the mask instead of alt-click

Oh and for the zillion copies it's faster to bash ctrl+j many times, then ctrl+shift+e



(Edited by poi on 09-20-2006 20:15)