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Create an Image which fades

Posted on 1998-10-28
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Last Modified: 2010-04-02
I am trying to create a bmp which will fade to black.  I am in 16-bit color mode - so I cannot use palette manipulation.  My attempt was to use a mask which goes from white to black and then SRCAND it with my image in memory and then finally Blt to the screen.  This works but it doesn't create a smooth fade.  I have also tried manipulating pixels - but it has very poor performance. Sure would be nice if I could use some alpha blending.  Any help would be great.  
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Question by:gpaige
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3 Comments
 
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Expert Comment

by:psdavis
ID: 1176422
Haven't you seen the new AlphaBlend function yet?  It's available for Win98 and WinNT?

Reject if you have... :)
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by:gpaige
ID: 1176423
Yes I did - but I am trying to keep compatibility with 95 and NT 4.0.
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bculver earned 200 total points
ID: 1176424
Simply subtracting fixed values from the rgb componets doesn't do very well for the reason that  the amount of rgb in a pixel cannot be decremented (faded) proportionally. Try this rgb to grayscale and back algorithm with your pixel manipulating routine.

gray = .30*red + .59*green + .11*blue;
gray=gray-x                // 0>x<255  try different fading step values to your liking
red=gray*.30;
green=gray*.59
blue=gray*.11


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