How Can I Capture a Screenshot of a Specific Application in C#?

Taking Screenshots of Individual Applications in C#

While capturing a full-screen screenshot with Graphics.CopyFromScreen() is simple, capturing a specific application requires a more sophisticated technique. The optimal solution leverages the PrintWindow Win32 API function. This function allows you to capture a window's image, irrespective of its visibility or whether it's hidden behind other windows.

Here's a breakdown of the process:

1. Identify the Target Window: Use GetWindowRect to obtain the handle (HWND) of the application window you want to capture.
2. Use PrintWindow: Call the PrintWindow function, providing the window handle and a handle to a Windows device context (HDC). This function will capture the window's bitmap.
3. Retrieve the Bitmap: Create a Bitmap object and get its Graphics context using Graphics.FromImage(). Use GetHdc() to retrieve the bitmap's HDC and pass it to PrintWindow.
4. Clean Up: Release the HDC and dispose of the Graphics object to avoid resource leaks.

This method ensures you can capture a precise screenshot of a target application, even if it's partially or completely obscured.

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