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Bitmaps

Posted on 1997-12-18
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Last Modified: 2013-12-03
I dont really know how to word this question, so I'll explain.  I have a bitmap (of a large key).  I wish to display this bitmap, but I want it to be transparent (around the key, not through it).  I want other application running under the key to be shown through it (including the desktop, explorer etc).

I am running Windows 95 with Delphi 3.0

Any help would be appreciated.
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Question by:SJohnson
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Expert Comment

by:StevenB
ID: 1354146
 If your picture is not too complicated then you might consider redrawing it as a Metafile, as this will handle the transparency.
  If this is not possible then you could either investigate the TImageList, which I believe has some transparency attributes, or search for a transparent image component on one of the component sites (Delphi Deli, Delphi Super Page).

  Steven.
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Expert Comment

by:altena
ID: 1354147
take a look at the "bitblt" function in the win32 API.

(and play around with the "dwRop" parameter.)

  Good Luck
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Author Comment

by:SJohnson
ID: 1354148
Maybe the question wasnt clear enough, I dunno.  Lets try again.  I have an image of a key (it would be impossible to make this a metafile).  I want to place this image on a form, as a transparent image, but also having the form either transparent as well, or, displaying the image independantly (without a form).  Does that help???  I will have to think a bit harder to try and explain it any better.

Stu
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Accepted Solution

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altena earned 100 total points
ID: 1354149
Ok I'll also try again:

If you want to draw a transparent picture you basically do this:
  Define a color in the bitmap that is means transparent
  Use bitblt a few times to create a bitmap in memory that
  blends the "key" bitmap with the background. (See the animation book by Nigel Thomson for details). Then bitblt
that bitmap onto the screen: voila results.

To display this "key" independantly (without form): Just grab the screen-hdc and perfornm the same trick i described above.
and do the same trick.
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