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 Post subject: A quick guide for alpha channels
 Post Posted: Tue Jan 18, 2011 1:15 pm 
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Joined: Fri Jul 02, 2010 4:50 am
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Location: Paris - France
For example: a nice plastic.

> First, draw your plastic.
> Second, new layer, select all, fill in black,
> Third, new layer and fill with white the area wich couldn't be transparent.
These two layers are the mask for alpha channels.

> Now: uncheck these two layers, select all, copy merged, create a new file then paste.
> Then: check the two layers (and uncheck the others). You must have only black and white. Select all, copy merged. Go on your new file. On your infos window (F7), select "channels", create a new channel, select it then paste.
> Now, you have to save your file as targa file.

It seems difficult but it's easy, more easy to do than explain or read...
But, some pics in order to explain visually the thing...

You draw your plastic Image

You create your black and white mask Image

You cut paste in a new file your plastic Image

You cut your mask and create a new channel in your new file Image

You paste your mask Image

You save the file as targa Image

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 Post subject: Re: A quick guide for alpha channels
 Post Posted: Sun Feb 13, 2011 9:55 pm 
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Joined: Sun Sep 19, 2010 3:37 am
Posts: 39
Ok so i created a new layer and filled it black, created another new layer and filled it black, so how do you fill white the part you want transparent? i used the pen tool to draw around it but couldnt fill it in with ant color.


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 Post subject: Re: A quick guide for alpha channels
 Post Posted: Mon Feb 14, 2011 6:27 am 
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Joined: Fri Oct 01, 2010 5:50 am
Posts: 59
If it is the phothoshop we are talking about. The quickest way for me is:

1. Draw the plastic
2. select the transparent part e.g. with magic wand
3. menu selection: invert selection
4. menu selection: save selection as new chanel
5. Save the file as 32bit tga

READY.


If you drew the plastic on one layer, instead of points 2&3 just alt-click magic wand on the layer icon and proceed to point 4.


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 Post subject: Re: A quick guide for alpha channels
 Post Posted: Sun Jun 05, 2011 11:33 am 
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Joined: Sun May 08, 2011 4:57 pm
Posts: 1071
Location: Turin-ITALY
Dear Popotte your tutorial is perfect....... only for who use Photoshop. :D
I known to use "Paint Shop Pro 8" or "Gimp 2.6" and "Inkscape 0.47" for work in svg.
Well. I can create a picture to B/w to be used as a mask to break through the design of the translite.
With the programs I use, I'm lost......... :( :(
it is true that I could use a color as a mask ,but it seems inelegant. ;)
Thanks in advance and greetings to all


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 Post subject: Re: A quick guide for alpha channels
 Post Posted: Sun Jun 05, 2011 11:49 am 
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Joined: Thu Jul 01, 2010 1:57 am
Posts: 1564
Here is where you can find the alpha channel in GIMP
The steps by Popotte are accurate, just apply the same rule
to GIMP.

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 Post subject: Re: A quick guide for alpha channels
 Post Posted: Sun Jun 05, 2011 12:10 pm 
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Joined: Sun May 08, 2011 4:57 pm
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Location: Turin-ITALY
fast response..... thanks...... now I do the tests......


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 Post subject: Re: A quick guide for alpha channels
 Post Posted: Mon Jun 06, 2011 1:05 pm 
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Joined: Sun May 08, 2011 4:57 pm
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Location: Turin-ITALY
Found a way to create the alpha channel , but I do not understand the following points:
1- "UNCHECK" for check/uncheck I have to pick the eye?
2- "MERGED" before copy I must merge the two levels?
3- "SELECT ALL" not all but only B&W ?
sorry but old age advances....... :roll: :shock: :?


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 Post subject: Re: A quick guide for alpha channels
 Post Posted: Mon Jun 06, 2011 4:45 pm 
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Joined: Thu Jul 01, 2010 1:57 am
Posts: 1564
once you understand the concept everything goes By itself. The alpha channel is an extra channel with additional Data. When working in RGB color mode or if you prefer Monitor color, you have usually 3 channels : Red Green and Blue.

If you want transparency, you need to create a Mask. THis mask is "embeded" in the images with the addition of a fourth channel : the alpha.

The alpha should be made out of Black and white. The white part will be opaque in your image while the black is completely transparent. Everything in between will be a gradient transitionning from opaque to transparent.


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 Post subject: Re: A quick guide for alpha channels
 Post Posted: Wed Jun 08, 2011 1:45 pm 
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Joined: Sun May 08, 2011 4:57 pm
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Sorry but I'm still here. I decided to use "Photoshop" to avoid problems, but........
pic 1-2 is how are the channels and layers when I save. I see the red 50% of the alpha channel on my picture.
pic 3 when reloading my image's alpha channel is not selected. My picture is without transparence.....


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 Post subject: Re: A quick guide for alpha channels
 Post Posted: Wed Jun 08, 2011 2:17 pm 
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Joined: Fri Jul 02, 2010 4:50 am
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Location: Paris - France
Just select the channel...

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Les cons ça ose tout. C'est même à  ça qu'on les reconnaît.
My tables avalaible at http://www.pinsimdb.org/fpreleases/ and http://www.irpinball.org/
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Le prix s'oublie, la qualité reste


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