Re: CImage outputting a black image

From:

"Mark Salsbery [MVP]" <MarkSalsbery[MVP]@newsgroup.nospam>

Newsgroups:

microsoft.public.vc.mfc

Date:

Thu, 30 Aug 2007 12:02:18 -0700

Message-ID:

<uGUfKhz6HHA.5316@TK2MSFTNGP04.phx.gbl>

Is the CImageDC necessary if you're just going to get a CDC freom its
handle?

If GetHeight() returns 200, why pass -200 to FillSolidRect()?

Mark

--
Mark Salsbery
Microsoft MVP - Visual C++

<stephen.yee1@gmail.com> wrote in message
news:1188423858.468460.27320@q5g2000prf.googlegroups.com...

This code outputs a black image, what am I doing wrong? I'm just
trying to make a white fill...
(If it helps, I want (0,0) to represent the top left corner of the
image..)
GetHeight() and GetWidth() return 200.

       CDC* mDC;
       ATL::CImage mImage;

           mImage.Create(GetWidth(), -GetHeight(), 32); // this call
is successful
           CImageDC imgDC(mImage);

           mDC = CDC::FromHandle(imgDC); // mDC looks like a valid
pointer
           mDC->SetWindowOrg( 0,0 );

           // have tried 0xFFFFFFFF too
            mDC->FillSolidRect( 0, 0, GetWidth(), -GetHeight(),
0x00FFFFFF);

           // this returns -1
           mDC->SetPixel(1,1);

           // temp is 0, and the array returned is all zeroes
           DWORD temp = mImage.GetPixel(1,1);
           return static_cast<const unsigned char*>(mImage.GetBits());