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List:       graphicsmagick-apis
Subject:    Re: [GM-apis] R: Re: R: Re:  understand  ImageType, ClassType and ColorspaceType
From:       Bob Friesenhahn <bfriesen () simple ! dallas ! tx ! us>
Date:       2013-04-12 14:00:10
Message-ID: alpine.GSO.2.01.1304120851430.2267 () freddy ! simplesystems ! org
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On Fri, 12 Apr 2013, maracas83@libero.it wrote:

> Thank you very much.
> Your help was very helpful. I still have some questions:
> 1) There is a project for the creation of tutorials, examples and
> documentation shared (like wiki)? If so, I'd like to give my contribution.

Due to the recent SourceForge project upgrade, GraphicsMagick now 
seems to have a Wiki.  I don't yet have any experience with it.

It is most useful if improvements make it into the project itself 
rather than a Wiki.  The web pages are mostly sourced from '.rst' text 
files under the 'www' subdirectory of the source tree.  For example 
the 'types' documentation comes from "www/api/types.rst".  Patches are 
appreciated.

> 2) I made ​​a test on a 32-bit bitmap where the alpha channel is equal to 255
> (FF hex), but the matte() method returns 0. How can I distinguish bitmap where
> the alpha channel is not ignored?

If you read from a file which has an alpha channel, then matte should 
be automatically enabled and return true.  If you create your own 
image (using the APIs) then you will need to enable it yourself (e.g. 
"image.matte(true)").  This can also be used to easily remove the 
opacity channel if you want to ignore it.

GraphicsMagick may strip the alpha channel when writing if it detects 
that the image is completely opaque.

Bob
-- 
Bob Friesenhahn
bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/

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