Visual C++ MFC - Problem drawing bitmaps with alphachannel

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Problem drawing bitmaps with alphachannel

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Forum Name: Visual C++ MFC
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URL: http://forum.codejock.com/forum_posts.asp?TID=15736
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Topic: Problem drawing bitmaps with alphachannel

Posted By: andolo
Subject: Problem drawing bitmaps with alphachannel
Date Posted: 27 November 2009 at 10:11am

Hi,

the following problem:

Drawing an image with semi-transparency (using alpha32 bitmaps / png) f.E. from the Styles works fine.
Now i am changing some pixels to RGB values bigger than 0x80.

(f.E. COLOUR1 0x14001E is ok, COLOUR2 RGB 0xFFCC00 shows wrong colour and no alpha, both with 30% alpha )
The stripe behind the text: purple colour is ok on the left

right side colour should be a light pink an transparent

I can't properly draw an image containing pixels of COLOUR2 independent of the alpha channel.

remark: using the same image with CImageList::Draw works fine! Problem: I am unable to change the output size.

Am i using the wrong functions? i use the following code:

// xtptoolkit 13.x
// class inherited from CXTPRibbonTheme -> calling CXTPOffice2007Theme::LoadImage

CXTPOffice2007Image* pImage = CXTPRibbonTheme::LoadImage(_T("RIBBONTABBACKGROUNDDWM"));
pImage->DrawImage(pDC, rcDest, pImage->GetSource());