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amc.drey -> [Guide][GIMP] Lock alpha channel (6/6/2010 23:42:32)
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What is this all about?
A simple and quick guide and hoping to add something to your knowledge.
Alpha Channel is a broad topic but this guide is all about locking the alpha channel
and it's advantages.
Alpha Channel?
An 8-bit layer in a graphics file format that is used for expressing translucency.
The additional eight bits per pixel serve as a mask and represent 256 translucency l
evels from entirely clear (0) to opaque (255), with levels in between representing the degree of haziness.
Doesn't help much? It's all about transparency!
How to lock the Alpha Channel?
[image]http://i752.photobucket.com/albums/xx168/Droscove/asdasdasdasd.png[/image]
When you click that, the alpha channel will be lock in every layer.
Why lock the Alpha Channel?
This works great if your working on a .PNG (Portable Network Graphics) or an image with a transparent part or
mostly the background is transparent. When you lock the alpha channel, everything that you will do
will NOT affect the transparent areas, only the OPAQUE ares. Didn't get the point? Here's an example,
Here, I made a rectangular selection then applied a black color fill in a transparent background -
[image]http://i752.photobucket.com/albums/xx168/Droscove/img2.png[/image] [image]http://i752.photobucket.com/albums/xx168/Droscove/img3.png[/image]
Then I applied a gradient map -
[image]http://i752.photobucket.com/albums/xx168/Droscove/img4.png[/image] [image]http://i752.photobucket.com/albums/xx168/Droscove/img5.png[/image]
Then I repeated the process, applying a gradient map but with the alpha channel being LOCKED.
[image]http://i752.photobucket.com/albums/xx168/Droscove/img6.png[/image] [image]http://i752.photobucket.com/albums/xx168/Droscove/img7.png[/image]
What happened?
The gradient map only affected the opaque areas of the canvas.
Conclusion?
We can say that this work similar to alpha to selection but in a easier way or works even better!
Applications?
For example, you got a stick figure with a transparent background -
[image]http://i752.photobucket.com/albums/xx168/Droscove/image2.png[/image]
And you wanted to change it to red, just lock alpha channel
[image]http://i752.photobucket.com/albums/xx168/Droscove/image3.png[/image]
and brush everywhere, the background won't be a mess, easy as pie!
Progress -
[image]http://i752.photobucket.com/albums/xx168/Droscove/image4.png[/image]
And when your done -
[image]http://i752.photobucket.com/albums/xx168/Droscove/image5.png[/image]
A neat result.
The END
Thanks for reading, :) In the future, I'm willing to add more guides about alpha channel if everyone likes it,
this forum will have a guide covering everything about Alpha Channels and that is my current goal!
Credits
PCmag encyclopedia for the definition of alpha channel.
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