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 Post subject: Contours [shaping the alpha channel with curves]
PostPosted: Fri Feb 22, 2013 10:05 pm  (#1) 
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In this tutorial i will show you how to use an effect called Contours.

A big thank you to Draconian who inspired me to research this technique and another thanks to saulgoode, who gave me a big revelation with his mini tutorial about how to shape the alpha channel of a gradient with the Curves Tool.

Lets begin:

The Curves Tool is under Colors → Curves.
For this technique to work, change the 'Channel' to Alpha !!!

Image


Our first example is a radial gradient: red to transparent, stroked from center to edge of the canvas on a TRANSPARENT layer !
Now drag the curve as in the screenshot below and see how the gradient changes.
This way we can tweak the gradient to our needs.

Image

Of course it works with a linear gradient just the same.

Image

For more examples look at this thread:
viewtopic.php?f=8&t=5789

But it doesnt stop here.
We can give our curve a much more complex shape, and tweak the appearance of the gradient like this:

Image

or this:

Image

or this:

Image

And from here we come to the Contours Effect, which is something borrowed from Photoshop Layer Styles.
In PS you have 12 Contours, and each one has a different name, which describes the effect.
These Contours can be displayed with little diagrams as in this chart and what you see is a cross chart of the final effect and at the same time, the shape of the curve.

Image

You dont have to give the curve the exact same shape, something similar is good enough to get the same effect and you can tweak your curve and the gradient by adding more anchors and playing with them.

Alternatively you can download the Contour Curves from this thread and save them to your presets:
viewtopic.php?f=12&t=5672&start=10#p79105

Also i recommend you to read the Gimp manual for the Curves Tool, in case you dont know how to work with the curve and anchors.
http://gimp.open-source-solution.org/ma ... urves.html

Now one way to use Contours is for texteffects.
Shaping Dropshadows, Inner and Outer Glows, the Satin-effect - everything that uses Gaussian Blurred pixels on a transparent layer.
To demonstrate i made text on a grey background and added an Outer Glow by alpha selecting the text, growing by 5 and then blurring by 20, like this.

Image

This is an Angular S-Curve and you can also use it to make rounded text.

Image

Image

Also, Contours are used for surface contours in Jon Stipe's layerfx script, which you can download here:
http://gimpscripts.com/2011/10/gimp-layer-effects/
or here:
http://registry.gimp.org/node/186

Im not quite sure how it works, probably with the Contours applied to the BumpMap, but it doesnt matter because the script does it all for you.
Here is one example:
Image


Last edited by Esper on Sat Feb 23, 2013 11:52 am, edited 7 times in total.

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 Post subject: Re: Contours [shaping the alpha channel with curves]
PostPosted: Fri Feb 22, 2013 10:49 pm  (#2) 
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Esper wrote:
Im not quite sure how it works, probably with the Contours applied to the BumpMap, but it doesnt matter because the script does it all for you.
just tried, it works exactly how i suspected

01. alpha select text
02. feather
03. fill with black
04. apply Contours
05. merge down with white layer
06. BumpMap
07. PROFIT !!!
Attachment:
ContouredBumpMap.png
ContouredBumpMap.png [ 103 KiB | Viewed 1294 times ]


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 Post subject: Re: Contours [shaping the alpha channel with curves]
PostPosted: Sat Feb 23, 2013 5:58 am  (#3) 
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I need try more times! :roll:
Thx Esper! :bigthup

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bbbbbbbbbbb Be patient, English is not my language.


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 Post subject: Re: Contours [shaping the alpha channel with curves]
PostPosted: Sat Feb 23, 2013 7:19 am  (#4) 
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Esper , Great tutorial. I have never seen this method before. I have used the filters for the effects but never looked at what is behind the filters.
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 Post subject: Re: Contours [shaping the alpha channel with curves]
PostPosted: Sat Feb 23, 2013 1:39 pm  (#5) 
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Some advanced stuff here, Esper!
Had it b-marked (and i don't do that very often) ;)

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 Post subject: Re: Contours [shaping the alpha channel with curves]
PostPosted: Sat Feb 23, 2013 2:07 pm  (#6) 
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you should a-mark it instead, K1te ! :bigthup


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 Post subject: Re: Contours [shaping the alpha channel with curves]
PostPosted: Sat Feb 23, 2013 2:11 pm  (#7) 
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Esper wrote:
you should a-mark it instead, K1te ! :bigthup



OK! :hehe Will send a feature request for that to GnuTux!

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 Post subject: Re: Contours [shaping the alpha channel with curves]
PostPosted: Sat Feb 23, 2013 2:14 pm  (#8) 
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you dont post as much as you used to :(
busy ?


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 Post subject: Re: Contours [shaping the alpha channel with curves]
PostPosted: Sat Feb 23, 2013 2:17 pm  (#9) 
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Was on vacation this week, stayed away from computers and mobile devices. Only books and the ocean beach walks.
I'm back with a bag of new ideas and recharged battery, lol.

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 Post subject: Re: Contours [shaping the alpha channel with curves]
PostPosted: Sat Feb 23, 2013 3:32 pm  (#10) 
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thanks Wbool !

Akros wrote:
I need try more times! :roll:
what seems to be the problem Akros ?


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