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Draw Transparency To Memory

Posted on 2001-08-05
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Last Modified: 2013-12-26
I use Draw to Bitmap in the RAM,
for printing or saving a bmp file.

The code is the same code as used for rendering to the viewport.

But although I have no problems with transparency in the
viewport, The transparent triangles look opaque in the printer's output or in the BMP file created.

- Is it because the blending is not handled corectly for
memory rendering ?
- How can I solve this problem ?
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Question by:Yossi
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5 Comments
 
LVL 1

Expert Comment

by:jacobkristensen
ID: 6353824
bmp's don't support transparency and I quess a printer doesn't either.
You could of cource copy the pixels from your screen, although it is not a very elegant solution...
0
 

Author Comment

by:Yossi
ID: 6403585
Copy screen pixels does not feet my code requirments, since it will copy unwanted graphics such as dialogs or highlited lines with the picture.
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LVL 4

Accepted Solution

by:
ct.smith earned 100 total points
ID: 6634451
I'd try a draw to an offscreen buffer and do a pixel copy from there.  The pixel copy should be reading off the buffer without using any alpha channels.  How you would do this is entirely dependant on the API you use.
0
 

Author Comment

by:Yossi
ID: 6640367
I figured out that it is a driver dependent problem whether alpha is used correctly for memory draw.
Some graphic cards supply driver which does it right, while other have a bug.

0
 

Author Comment

by:Yossi
ID: 6640371
It seems like a good bypass to the driver problem.
I won't test it since I found that some graphic cards have drivers which do it right.

Many Thanks.
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