Re: [Gimp-user] Alpha channel and pixel transparency value

2009-04-15 Thread David Gowers
On Thu, Apr 16, 2009 at 9:50 AM, DJ delphit...@yahoo.com wrote:
 Hi Gimp-user,


 I'd like to know the transparency value of a pixel in Gimp. In PSP,
 when you run the cursor over a pixel it'll tell you the RGB and the
 alpha percentage.  Can I get this information in Gimp?

Have you looked at docs.gimp.org to find out the answer to some of
these questions?

Anyway, the 'Cursor' dockable does this.

David
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Re: [Gimp-user] Alpha channel and pixel transparency value

2009-04-15 Thread David Gowers
Hi DJ,

On Thu, Apr 16, 2009 at 10:28 AM, DJ delphit...@yahoo.com wrote:
 It may not appear like it, but yeh.  Sorry.

 I'm hitting PF1 all the time to get specific doc too.

 I do a google site search for terms too.

 I didn't quite know what you meant by Cursor dockable. So I checked
  Windows - Dockable Dialogs, and didn't see that terminology. A friend

Eh, maybe it is called 'Pointer' dockable. I don't use GIMP in the
English language, but Lojban.
The menu item in question appears after Undo History and before Sample
Points in the menu.

http://docs.gimp.org/en/gimp-windows-show-dock.html
http://docs.gimp.org/en/gimp-pointer-info-dialog.html

I noticed that pressing Shift+F1 over the 'Pointer' menu item only
gives the 'EEK! Missing help' page. This is probably a bug in the
docs, since the relevant page does actually exist.

  I scrolled across the image. That checkbox option eluded me...

Such an option is not available in GIMP. If you would like it, I
suggest making a mockup and submitting it to
gimp-brainstorm.blogspot.com.
However, the Pointer dockable works fine for me for this purpose, on
the rare occasions I need it.

Do you have a good reason for replying only to me rather than the
list? It makes the thread on the mailing list appear disjointed.
Here, I use 'Reply to All' to reply to messages from mailing lists,
and this is effective.

David
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Re: [Gimp-user] alpha channel computation

2008-07-24 Thread Sven Neumann
Hi,

On Thu, 2008-07-24 at 11:49 -0700, Nerius Landys wrote:
 Hello.  I have a TGA image that is fully opaque.  I want to introduce
 translucency to the image, making each pixel translucent according to
 how far away from black it is.  If a pixel is originally black, it
 becomes fully opaque.  If a pixel is originally white, it becomes
 fully transparent.  If a pixel is 0x7f7f7f (gray) or 0xff007f
 (approximately halfway in brighness between dark and light), it
 becomes somewhere around half transparent (computed using diagonal of
 color cube).
 
 Is there an easy way to do this in GIMP?

Easy. Just add a layer mask. In the dialog for creating the mask, choose
to initialize the mask with Grayscale copy of layer. Now you already
got almost what you want. You just need to invert the mask as you want
white to be transparent and black to be opaque. Colors-Invert will do
this. Now all you need to do is to apply the layer mask.


Sven



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Re: [Gimp-user] Alpha Channel

2005-04-13 Thread David Marrs
cedric wrote:
I wonder why, when Opening or creating a document, there are only 3
color channel and then, when creatin a layer, the alpha is coming. What
this stand for ?
Cedric
 

The bottom layer cannot be transparent, as far as I'm aware, so it does 
not have an alpha channel associated with it. You can still export 
transparent gifs and pngs though.

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Re: [Gimp-user] Alpha Channel

2005-04-13 Thread Jeffrey Brent McBeth
On Wed, Apr 13, 2005 at 03:57:56PM +0100, David Marrs wrote:
 cedric wrote:
 
 I wonder why, when Opening or creating a document, there are only 3
 color channel and then, when creatin a layer, the alpha is coming. What
 this stand for ?
 
 Cedric
  
 
 The bottom layer cannot be transparent, as far as I'm aware, so it does 
 not have an alpha channel associated with it. You can still export 
 transparent gifs and pngs though.

Err, unless I am misunderstanding you, you are wrong.  Bottom layers can
most definitely be transparent.  As noted previously in response to this
question, when you create a new image, what you fill the base layer with
changes whether or not it has an alpha channel.  At any point, you can add
an alpha channel by going to:

Layer - Transparency - Add Alpha Channel

At any point, you can remove an alpha channel by flattening the layer.

Jeff
-- 

Computer Science is as much about computers as astronomy is about telescopes
-- Edsger Wybe Dijkstra (1930-2002)



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Re: [Gimp-user] Alpha Channel

2005-04-13 Thread David Marrs
Jeffrey Brent McBeth wrote:
On Wed, Apr 13, 2005 at 03:57:56PM +0100, David Marrs wrote:
 

cedric wrote:
   

I wonder why, when Opening or creating a document, there are only 3
color channel and then, when creatin a layer, the alpha is coming. What
this stand for ?
Cedric
 

The bottom layer cannot be transparent, as far as I'm aware, so it does 
not have an alpha channel associated with it. You can still export 
transparent gifs and pngs though.
   

Err, unless I am misunderstanding you, you are wrong.
Yup, sorry. I should know that, having made bottom layers transparent in 
the past! (wtf?) I don't know where I got that from. Put it down to lack 
of coffee.

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Re: [Gimp-user] Alpha Channel

2005-04-12 Thread Malcolm Tredinnick
On Wed, 2005-04-13 at 01:47 +0200, cedric wrote:
 I wonder why, when Opening or creating a document, there are only 3
 color channel and then, when creatin a layer, the alpha is coming. What
 this stand for ?

The default setting for a new document is the RGB colorspace with the
document filled with the background color; no transparency is needed.
When you add a layer, if you change nothing, the layer will be
transparent, so an alpha channel is required at that point and one will
be added.

You can set up a new document to have the background filled with
transparency (under the advanced options tab in the new image dialog
box) and then you will have an alpha channel from the start. However, if
you create a new layer filled with the background or foreground color,
that will still add an alpha channel if you do not have one in the
image, because there are always transparency options available for
layers.

Cheers,
Malcolm

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Re: [Gimp-user] Alpha Channel

2003-12-13 Thread Sven Neumann
Hi,

Paulo S [EMAIL PROTECTED] writes:

 I am a novice user of GIMP and I would like to understand Alpha
 Channel. Could somebody here please help me?

Perhaps some of these links can help:

 http://kimihia.org.nz/how/gimpalpha/
 http://gug.sunsite.dk/faq.php?cat=1
 http://gimp-savvy.com/BOOK/node56.html


Sven
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Re: [Gimp-user] Alpha Channel

2003-12-13 Thread Paulo S
Perhaps some of these links can help:

 http://kimihia.org.nz/how/gimpalpha/
 http://gug.sunsite.dk/faq.php?cat=1
 http://gimp-savvy.com/BOOK/node56.html
Thanks a lot, Sven!

Paulo
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