Screen shots with OPenGL

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I am trying to get a screenshot of a window with usage glReadPixels API's
exposed from OPenGLafter getting the current context. But if I move another
application window above my application window, the screen shot which i get
gets blurred and I get a screen shot which gets overlapped. My code is as
below
RECT r;
GetClientRect(g_windowRef,&r);
CRect rect(r);

CSize size(rect.Width(),rect.Height());
const int bytesPerPixel = 3;
int bytesPerRow = (bytesPerPixel * rect.Width() + 3) & ~3;
int NbBytes = bytesPerRow * rect.Height();

BITMAPINFO bmi;
BITMAPINFOHEADER header;
bmi.bmiHeader.biWidth = size.cx;
bmi.bmiHeader.biHeight = size.cy;
bmi.bmiHeader.biSizeImage = NbBytes;
bmi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
bmi.bmiHeader.biPlanes = 1;
bmi.bmiHeader.biBitCount = bytesPerPixel * 8; // RGB
bmi.bmiHeader.biCompression =0;
bmi.bmiHeader.biXPelsPerMeter = 0;
bmi.bmiHeader.biYPelsPerMeter = 0;

bmi.bmiHeader.biClrUsed = 0;
bmi.bmiHeader.biClrImportant = 0;
HANDLE handle = (HANDLE)::GlobalAlloc (GHND,sizeof(BITMAPINFOHEADER) +
NbBytes);
char *pData = NULL;
if(handle != NULL)
{
// Lock handle
pData = (char *) ::GlobalLock((HGLOBAL)handle);
// Copy header and data
memcpy(pData, &bmi.bmiHeader, sizeof(BITMAPINFOHEADER));

// Copy from OpenGL
glReadPixels(0, size.cx,size.cy,0,

GL_BGR_EXT,GL_UNSIGNED_BYTE,
pData + sizeof(BITMAPINFOHEADER));
// Unlock::GlobalUnlock((HGLOBAL)handle);
// Push DIB in
clipboard
OpenClipboard(g_windowRef);

EmptyClipboard();

SetClipboardData(CF_DIB,handle);
CloseClipboard();
}



.

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