On Mon, 7 Aug 2000, clemensF wrote:
> many of you will not like to read this, as it is a set of newbie questions
> of the most repelling sort.
> some will hope to read the answers later...

That's why this list is here?

> 1.  what is an alpha [channel]?

It's basically the transperence of the image. Usually this is implemented
as a grayscale layer (256 shades), where black is transparent, and white
is opaque, grey will therefore be translucent.

If you for example paint a filled circle on a completely transparent
layer, if you could see the alpha channel, it would get a full-white

Orinarily, gimp itself maintins the alpha channel, but using the tool "Add
Alpha channel", you can kindof "hardcode" it, on your own selecting which
parts of a layer should be transparent, opaque, or gradients thereof.

"Alpha", as I've read somewhere, is just because it in the beginning
symbolized a coefficent for how much of each pixel that should show...

> 2.  what's the difference between layers, channels and paths?

Layers are the ordinary stuff you paint on.

Channels are 256-color grayscale layers which are used for masks, input to
filters, saving away selections etc. To give a 3d-effect to an shape, you
could for example put a copy of its alpha channel to a layer, blur it a
little, and then use this channel for a bump map.

Paths are mathematically stored bezier-shapes which can be conveniently
reshaped and converted to selections.

Each of these three have their own dialog, and what I'm now missing in
gimp is some way to quick-load stuff, for example have a shortcut for
"convert channel 4 to selection"...

> 3.  is there a reasonable functional complement regarding vectors?
>     reasonable is available on freebsd or some other unix, and functional
>               complement means:  if i want to specify objects and motion using
>               vectors, can i make and render pretty surfaces in a jiffy with the
>               gimp?  or have it cooperate in 2d?

I don't really know, this is not my gebiet...Maybe would the simple
"sketch" do the job for you, maybe not...

> (4. how do i make use of histograms?

Is in the "levels"-dialog? There you can see how much there is of a
certain colour-value, and do stuff like "this gray is supposed to show as
black"...can be very useful instead of using the crude Contrast/Brightness

>  5. is there anything one can /not/ do with adequately defined brushes?
>     i'd like a broad, but memorable overview over defining and using brushes)

Sorry, can't help you on that one.

Hope I could help you some anyway.


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