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Re: Map transparent image [message #35680 is a reply to message #35679]

Tue, 01 July 2003 12:49

Haje Korth
Messages: 651
Registered: May 1997

Senior Member

Michael,
this is a neat formula and I will print it for safe-keeping. I am fiddling
with the object graphics alpha blending and it works nicely. I knew this
could be reduced to one line of code, I just couldn't figure it out!

Thanks,
Haje

"Michael A. Miller" <mmiller3@iupui.edu> wrote in message
news:87vfumnjbh.fsf@lumen.indyrad.iupui.edu...
>>>> >> "Haje" == Haje Korth <haje.korth@jhuapl.edu> writes:
>
>> I am trying to overlay a grey-shaded mask over an image to
>> indicate areas where sample data are less
>> reliable. However, I want the grey shaded area to be
>> transparent so that I can still see the underlying data
>> points.
> ...
>> Does anyone know, how the mask can be worked into the image
>> prior to display? What is the math that one would apply?
>
> One method that you might like is alpha blending. If you have
> two images with two different colors (from two color maps say),
> calculate a new color map like
>
> RGB = BYTE( alpha * FLOAT(baseRGB) + (1.0 - alpha) *
FLOAT(overlayRGB) )
>
> where the *RGB are RGB 3-tuples. You can do this by hand, so to
> speak, in your own code if you are using direct graphics, or you
> can use the alpha blending that is built into object graphics.
>
> Mike
>
> --
> Michael A. Miller mmiller3@iupui.edu
> Imaging Sciences, Department of Radiology, IU School of Medicine

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[Message index]

		Re: Map transparent image By: Haje Korth on Tue, 01 July 2003 12:50
		Re: Map transparent image By: Haje Korth on Tue, 01 July 2003 12:49
		Re: Map transparent image By: Haje Korth on Tue, 01 July 2003 12:43
		Re: Map transparent image By: David Fanning on Tue, 01 July 2003 12:51
		Re: Map transparent image By: mmiller3 on Tue, 01 July 2003 12:22
		Re: Map transparent image By: Andy Loughe ( remove on Tue, 01 July 2003 07:46
		Re: Map transparent image By: David Fanning on Tue, 01 July 2003 11:12
		Re: Map transparent image By: Haje Korth on Tue, 01 July 2003 10:45
		Re: Map transparent image By: David Fanning on Tue, 01 July 2003 08:26
		Re: Map transparent image By: Haje Korth on Tue, 01 July 2003 08:04
		Re: Map transparent image By: David Fanning on Tue, 01 July 2003 06:24

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