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RGB and alpha channel value

 
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johannes



Joined: 21 Jan 2011
Posts: 65
Location: Leimen, Germany

PostPosted: Wed Oct 10, 2012 2:10 pm    Post subject: RGB and alpha channel value Reply with quote

Hi all,
bmp files can not only hold the (3) RGB values of a pixel, but also a fourth number, the 'alpha' value (see http://en.wikipedia.org/wiki/Alpha_compositing).

Question: is there a way to extract this number pixel by pixel with FTN95/clearwin ?

johannes
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PaulLaidler
Site Admin


Joined: 21 Feb 2005
Posts: 7916
Location: Salford, UK

PostPosted: Wed Oct 10, 2012 8:19 pm    Post subject: Reply with quote

I guess that it would depend on the context but as far as I know, ClearWin+ only uses 24 bit bitmaps. For a "drawing surface", GET_POINT@ gets the bit value at a given point but I would expect this to be only 24 bit.
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johannes



Joined: 21 Jan 2011
Posts: 65
Location: Leimen, Germany

PostPosted: Thu Oct 11, 2012 9:25 am    Post subject: Reply with quote

Hi Paul,
I checked my bmp file and indeed found that it is a 32 bit one. Thanks for the hint.
When I try to process it with my current FTN95 code (which works fine for <24 bit bmp), the result is just black. So I think you are right in saying that ClearWin can process only up to 24 bit.

Q to forum: Has anyone else experience with 32 bit bmps? A test file could be provided.

johannes
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