Alpha Channel Mask -translucent

Alpha Channel Mask -translucent

Post by Paul Furma » Fri, 01 Mar 2002 14:21:07



I want to save a tiff with a translucent alpha channel mask
for use in AutoCAD. Is this possible to make the image
translucent by erasing with a 30% opacity or even a halftone
pattern to make it see-through? If I do the translucent
erase, it doesn't help.

I really don't understand channels well so I may be missing
something obvious.

thanks,

--
Paul Furman
http://www.edgehill.net
san francisco native plants

 
 
 

Alpha Channel Mask -translucent

Post by Zimphir » Fri, 01 Mar 2002 15:25:40




Quote:> I want to save a tiff with a translucent alpha channel mask
> for use in AutoCAD. Is this possible to make the image
> translucent by erasing with a 30% opacity or even a halftone
> pattern to make it see-through? If I do the translucent
> erase, it doesn't help.

> I really don't understand channels well so I may be missing
> something obvious.

> thanks,

> --
> Paul Furman
> http://www.edgehill.net
> san francisco native plants

Make the alpha mask a lighter grey instead of Black.

--
Zimphire

 
 
 

Alpha Channel Mask -translucent

Post by Paul Furma » Fri, 01 Mar 2002 16:04:00


Quote:> > I want to save a tiff with a translucent alpha channel mask
> > for use in AutoCAD. Is this possible to make the image
> > translucent by erasing with a 30% opacity or even a halftone
> > pattern to make it see-through? If I do the translucent
> > erase, it doesn't help.

> Make the alpha mask a lighter grey instead of Black.

> --
> Zimphire

Hmmm, So this should work for placing art in illustrator or quark?
It doesn't seem to show up in autoCAD which doesn't suprise me. It
seems the deleting the foreground is necessary to have any impact
or else it all shows as white... Does that even make sense? It
doesn't quite to me. Maybe I don't understand how masks work.

<scratching head>

 
 
 

Alpha Channel Mask -translucent

Post by Zimphir » Fri, 01 Mar 2002 16:50:29




Quote:> > > I want to save a tiff with a translucent alpha channel mask
> > > for use in AutoCAD. Is this possible to make the image
> > > translucent by erasing with a 30% opacity or even a halftone
> > > pattern to make it see-through? If I do the translucent
> > > erase, it doesn't help.

> > Make the alpha mask a lighter grey instead of Black.

> > --
> > Zimphire

> Hmmm, So this should work for placing art in illustrator or quark?
> It doesn't seem to show up in autoCAD which doesn't suprise me. It
> seems the deleting the foreground is necessary to have any impact
> or else it all shows as white... Does that even make sense? It
> doesn't quite to me. Maybe I don't understand how masks work.

> <scratching head>

What exactly are you trying to do? There might be another way.

--
Zimphire

 
 
 

Alpha Channel Mask -translucent

Post by Paul Furma » Fri, 01 Mar 2002 17:01:02



> What exactly are you trying to do? There might be another way.

Trying to make translucent images in AutoCAD. I don't think it's able to
do that though. Normally only black & white images can be given a
transparent background but this alpha thing allows placing color images
with their backgrounds cropped out. I think it's on a pixel by pixel
basis though & can't actually be translucent.

I'm sure there is some way to do an "every other pixel" selection & have
half the pixels clear but that still wouldn't be quite the same. Might
be interesting though.

thanks,
Paul

 
 
 

Alpha Channel Mask -translucent

Post by John Ramplin » Fri, 01 Mar 2002 20:09:47


If I understand Alpha channels correctly, they are nothing more than
greyscale images.
They don't appear in your main image.
They become masks or selections when you choose to use them as such.
Black is 100% masked out, white is 0% . The question of transparency doesn't
come into it.

If I've understood this wrongly, I'm sure some kind person will correct me.

John

 
 
 

Alpha Channel Mask -translucent

Post by Taci » Sat, 02 Mar 2002 01:39:13


Quote:>I want to save a tiff with a translucent alpha channel mask
>for use in AutoCAD. Is this possible to make the image
>translucent by erasing with a 30% opacity or even a halftone
>pattern to make it see-through?

Assuming AutoCAD supports translucency in a TIFF (as opposed to a TGA), then
yes.

Make an alpha channel. Fill it with 30% black.

--
"Quand la morale triomphe, il se passe des choses tres vilaines."
Literature. Art. Photography. Forums. Shareware. Kink. Sex.
All at: http://www.xeromag.com/franklin.html

 
 
 

Alpha Channel Mask -translucent

Post by Jeremiah Spradli » Sat, 02 Mar 2002 03:12:45


Quote:

> > Make the alpha mask a lighter grey instead of Black.

> > --
> > Zimphire

> Hmmm, So this should work for placing art in illustrator or quark?
> It doesn't seem to show up in autoCAD which doesn't suprise me. It
> seems the deleting the foreground is necessary to have any impact
> or else it all shows as white... Does that even make sense? It
> doesn't quite to me. Maybe I don't understand how masks work.

> <scratching head>

Yes, you are using a "layer opacity mask" instead of the "alpha mask
channel".  The opacity slider on the right hand side controls the "layer
opacities", and will not affect the
final opacity of the image.

-
Jeremiah Spradlin

 
 
 

Alpha Channel Mask -translucent

Post by Ross » Sat, 02 Mar 2002 04:55:16


For page layout programs, you use a clipping path, but that is
all-or-nothing transparency, no translucency.

If AutoCAD supports an 8-bit alpha channel for defining 256 levels of
transparency, then you just need to know what file format it accepts.
Probably TIFF.

There are several ways to create an alpha channel in PS. If you need
an area to be 30% opaque, then one way would be to:

1. Create a new alpha channel in the Channels palette by clicking on
the "Create new channel" button. Depending on how you have things set
up, it will either be all black, or all white. You can double-click
the channel and change the "Color Indicates" option if you want.

Black "pixels" in an alpha channel, will mask out corresponding pixels
in the image, so the new channel filled with black, if used as a mask,
would hide everything. If you want the mask to reveal everything, just
fill the alpha channel with white.

2. Select the area in the image you want to be translucent using
whatever tool(s) or technique(s) would be appropriate. If you want the
whole image, just Select>All, or Ctrl-A.

3. With the selection active, fill the alpha channel with 70% gray.
(You'll first need to click on the channel in the palette.) That will
make the area 70% transparent (or 30% opaque) if the alpha channel is
used as a mask.

4. Save as TIF, and make sure "Alpha channels" is checked in the
dialog.

5. Open the TIF in AutoCAD. You'll need to look up how to apply the
alpha channel in that app, as it may not use it automatically.

Ross



Quote:>> > I want to save a tiff with a translucent alpha channel mask
>> > for use in AutoCAD. Is this possible to make the image
>> > translucent by erasing with a 30% opacity or even a halftone
>> > pattern to make it see-through? If I do the translucent
>> > erase, it doesn't help.

>> Make the alpha mask a lighter grey instead of Black.

>> --
>> Zimphire

>Hmmm, So this should work for placing art in illustrator or quark?
>It doesn't seem to show up in autoCAD which doesn't suprise me. It
>seems the deleting the foreground is necessary to have any impact
>or else it all shows as white... Does that even make sense? It
>doesn't quite to me. Maybe I don't understand how masks work.

><scratching head>

 
 
 

Alpha Channel Mask -translucent

Post by Paul Furma » Sat, 02 Mar 2002 14:38:58


Thanks, all for the tips. Interesting lesson! Unfortunately AutoCAD only
recognizes transparent masking, not translucency. That's a pretty cool trick in
itself and very useful.

> Assuming AutoCAD supports translucency in a TIFF (as opposed to a TGA)

 
 
 

1. alpha channels, alpha channels

Its not too often I'm intimidated by semantics, but this is one of those cases.
It sounds like a term Scotty would have used to explain why the teleporter
wasn't working that day, but its too important not to grasp, I've had enough.
Everything I've read describes what they do and I have definite ideas about
how I want to use them, but the only way I'll penetrate the kernel of
understanding is through a step-by-step tutorial.  All the learning material
seems to stop short right at that point.  I'd love to be able to create
seamless texturemaps and transparent masks but so far its been like,
"okay, so I've saved this black and white layer thing."  Could anyone
out there spin me around and point me in a direction?  As applied mainly
to Photoshop and 3DStudio at this point.

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