How to Capture Screenshots of Windows Applications Using Win32 GDI?

Taking Screenshots in Windows Applications with Win32

Capturing the current screen display is a common need in application development. In Windows, this can be achieved efficiently using Win32's Graphics Device Interface (GDI) functions.

Solution

The following code snippet demonstrates how to take a screenshot using Win32:

HDC hScreenDC = GetDC(nullptr);
HDC hMemoryDC = CreateCompatibleDC(hScreenDC);
int width = GetDeviceCaps(hScreenDC,HORZRES);
int height = GetDeviceCaps(hScreenDC,VERTRES);
HBITMAP hBitmap = CreateCompatibleBitmap(hScreenDC,width,height);
HBITMAP hOldBitmap = static_cast<HBITMAP>(SelectObject(hMemoryDC,hBitmap));
BitBlt(hMemoryDC,0,0,width,height,hScreenDC,0,0,SRCCOPY);
hBitmap = static_cast<HBITMAP>(SelectObject(hMemoryDC,hOldBitmap));
DeleteDC(hMemoryDC);
DeleteDC(hScreenDC);

Explanation

• GetDC retrieves a device context for the screen.
• CreateCompatibleDC creates a memory device context compatible with the screen DC.
• GetDeviceCaps obtains the current screen resolution.
• CreateCompatibleBitmap creates a bitmap compatible with the screen DC and matching the resolution.
• SelectObject selects the bitmap into the memory DC.
• BitBlt copies the pixels from the screen DC to the bitmap in the memory DC.
• DeleteDC releases the memory and screen DCs.

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