Taking a screenshot of the Windows desktop with a C program. - c

Question

Is it possible to take a screenshot of the desktop and save it as .jpg,jpeg,...at any location in the computer by C programming? I am curious to know if there is any method and way to achieve this task. I'm using Windows XP.

Answer 1

Assuming Visual Studio:
This is copy & paste from working code (some lines ommited):
HDC hdcScreen = NULL;
HDC hdcMemDC = NULL;
HBITMAP hbmScreen = NULL;
CImage myimage;
IStream* pIStream = NULL;
STATSTG stg;
HGLOBAL hGlobal = NULL;
HRESULT hResult = 0;
UINT nDataSize = 0;
do
{
//
// Get the screen capture in an HBITMAP.
// -------------------------------------
// Retrieve the handle to a display device context for the client
// area of the window.
hdcScreen = ::GetDC(NULL);
if ( hdcScreen == NULL )
{
SET_CHECKPOINT();
break;
}
// Create a compatible DC which is used in a BitBlt from the window DC
hdcMemDC = CreateCompatibleDC(hdcScreen);
if ( hdcMemDC == NULL )
{
SET_CHECKPOINT();
break;
}
// Get the client area for size calculation
int cx = GetSystemMetrics(SM_CXSCREEN);
int cy = GetSystemMetrics(SM_CYSCREEN);
// Create a compatible bitmap from the Window DC
hbmScreen = CreateCompatibleBitmap(hdcScreen, cx, cy);
if ( hbmScreen == NULL )
{
SET_CHECKPOINT();
break;
}
// Select the compatible bitmap into the compatible memory DC.
SelectObject(hdcMemDC,hbmScreen);
// Bit block transfer into our compatible memory DC.
BitBlt(hdcMemDC, 0,0, cx, cy, hdcScreen, 0,0, SRCCOPY);
// Create a stream to have CImage write data to.
hResult = CreateStreamOnHGlobal(NULL, TRUE, &pIStream);
if ( hResult != S_OK )
{
SET_CHECKPOINT();
break;
}
// Attach an ATL CImage to the hbitmap.
myimage.Attach(hbmScreen);
// Write data to stream.
hResult = myimage.Save(pIStream, Gdiplus::ImageFormatJPEG);
if ( hResult != S_OK )
{
SET_CHECKPOINT();
break;
}
myimage.Detach();
// Get the stream's HGLOBAL.
hResult = GetHGlobalFromStream(pIStream, &hGlobal);
if ( hResult != S_OK )
{
SET_CHECKPOINT();
break;
}
// Get a pointer to the data in the HGLOBAL.
char* pJPGData = (char*)GlobalLock(hGlobal);
pIStream->Stat(&stg, STATFLAG_NONAME);
nDataSize = (UINT)stg.cbSize.QuadPart;
// TODO: Open a file instead of a pipe...
//pJPGData points to the data, nDataSize is, well...
if ( WriteFile(hFile, pJPGData, nDataSize, &dwBytesWritten, NULL) == FALSE )
{
SET_CHECKPOINT();
break;
}
// TODO: Close the file.
}
while (0,0);
//
// Free resources.
// ---------------
if ( pIStream != NULL ) pIStream->Release();
//Clean up
if ( hbmScreen ) DeleteObject(hbmScreen);
if ( hdcMemDC ) DeleteObject(hdcMemDC);
if ( hdcScreen ) ::ReleaseDC(NULL,hdcScreen);