AlphaBlend a bitmap   

Hello,

Can someone explain how to AlphaBlend a bitmap with a background color of a 
window!.  I would like to take a bitmap and make it light with the 
background color of a treeview and then paint that to the treeview.  I don't 
want to use GDI+ and I don't use the MS Visual C.  I tried using the windows 
API alphablend, but I couldn't get it to work.

Thanks,


James

date: Thu, 22 May 2008 23:51:38 -0500   author:   James L. Williams

Re: AlphaBlend a bitmap   

"James L. Williams"  wrote in message 
news:E73F8B04-BC35-4EFA-BCE6-5A3AA2B8FF9D@microsoft.com...
> Hello,
>
> Can someone explain how to AlphaBlend a bitmap with a background color of 
> a window!.  I would like to take a bitmap and make it light with the 
> background color of a treeview and then paint that to the treeview.  I 
> don't want to use GDI+ and I don't use the MS Visual C.  I tried using the 
> windows API alphablend, but I couldn't get it to work.
>
> Thanks,
>
>
> James

The AlphaBlend function displays bitmaps that have transparent or 
semitransparent pixels.
This means that your bitmap should contain an alpha chanel (32bit BMP)
It is not a simple task to create these and you would need a photo editing 
program that can save them.
I use Corel Photopaint, save them as PhotoShop files (PSD), load them into 
GifMovieGear and save them as 32bit BMPs.

hCurrentBmp=LoadBitmap((HINSTANCE)ghInstance,MAKEINTRESOURCE(IDB_BMP));
//should use LoadImage( ) and you can load from a file if not using a 
resource

HDC hDC=GetDC(m_hWnd);
HDC hCDC=CreateCompatibleDC(hDC);
GetTextMetrics(hDC,&tm);
if(hCurrentBmp){
   SetStretchBltMode(hDC,HALFTONE);
    SelectObject(hCDC,hCurrentBmp);
   BLENDFUNCTION bf;
   bf.BlendOp=AC_SRC_OVER;
   bf.BlendFlags=0;
   bf.SourceConstantAlpha=255;
   bf.AlphaFormat=AC_SRC_ALPHA;
   AlphaBlend(
      hDC,
      0,0,
      nWidthDest,nHeightDest,
      hCDC,
      0,0,
      nWidthSrc,nHeightSrc,
      bf);
}
DeleteDC(hCDC);
DeleteDC(hDC);

Hope that helps.

Regards,
Ron Francis
www.RonaldFrancis.com

date: Sat, 24 May 2008 11:14:11 +0930   author:   Ron Francis