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GeneralRe: Problem in windows7 Pin
David Crow16-Dec-10 5:16
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GeneralRe: Problem in windows7 Pin
«_Superman_»16-Dec-10 8:05
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QuestionHow to pass text file data from MFC line Graph? Pin
mathivanaan16-Dec-10 1:38
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Rajesh R Subramanian16-Dec-10 1:42
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Cedric Moonen16-Dec-10 2:00
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QuestionHow to save TransParent IMage after drawing on another image? Pin
002comp15-Dec-10 20:55
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AnswerRe: How to save TransParent IMage after drawing on another image? Pin
Rozis16-Dec-10 12:59
MemberRozis16-Dec-10 12:59 
I hope i understand your questions clearly. Im not using GDIplus (but GDI) and Im not using your program language, but maybe this helps a little:

- to get transparency on the pixellevel every pixel in your bitmap must be 4 bytes (RGBA) and not 3 bytes (RGB). See MSDN for exact info. In the A byte (called alpha channel) you may set the transparency level between 0 and 255. You should use the winapi function Alphablend() (or the gdiplus equevalent) to copy the bitmap to the screen.

- One of the problems with transparent bitmaps is that when you put them on screen the transparency is visible but this information is lost (on the screen). Let me explain this: Suppose you want to fade in a bitmap. Then for every step you must first repaint the background (that what wad on the screen before the bitmap was painted on it) and then copy the transparent bitmap on it, decreasing transparency in every step. If you don't repaint the background first you will not get the desired result (but a transparent bitmap on a tranparent bitmap).

The screen has no transparency set (it is a RGB-surface) so saving it will result in a bitmap that only shows 'what was on screen'. Transparency is a property of a bitmap not of the screen that displays it (the screen shows the result only).

Hope this helps a bit...

Good luck,

Rozis
GeneralRe: How to save TransParent IMage after drawing on another image? Pin
002comp16-Dec-10 19:15
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QuestionSingleton Class Pin
pix_programmer15-Dec-10 19:00
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QuestionCSV Pin
MsmVc15-Dec-10 18:33
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QuestionSubclassing CHeaderCtrl in CListCtrl Pin
mesajflaviu15-Dec-10 9:54
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