WgcSharp 1.1.1

WgcSharp

Capture any window by HWND — including occluded, minimized, and DirectX/OpenGL game windows.

Uses Windows.Graphics.Capture (WGC) as primary capture method with DXGI Desktop Duplication fallback. Handles all the COM/WinRT interop complexity so you don't have to.

Why?

• PrintWindow returns black for DirectX/OpenGL game windows
• BitBlt/CopyFromScreen can't capture hardware-accelerated content
• DXGI Desktop Duplication only captures visible (non-occluded) windows
• Using Windows.Graphics.Capture directly from C# requires painful COM interop with CsWinRT, HSTRING marshaling, and ComWrappers registration — and CsWinRT's ComWrappers conflicts with WPF/.NET 9+ apps

WgcSharp wraps all of this into a single method call. The WGC backend uses raw COM vtable calls internally — no CsWinRT dependency, no ComWrappers conflicts.

Install

dotnet add package WgcSharp

Usage

using WgcSharp;

// Capture any window by its handle
var bitmap = WindowCapture.CaptureWindow(hwnd);
bitmap?.Save("screenshot.png");

Choose a strategy

// WGC only — works for occluded/minimized/DirectX windows (Win10 1803+)
var bitmap = WindowCapture.CaptureWindow(hwnd, CaptureStrategy.WgcOnly);

// DXGI only — captures visible windows via Desktop Duplication
var bitmap = WindowCapture.CaptureWindow(hwnd, CaptureStrategy.DxgiOnly);

// Auto (default) — tries WGC first, falls back to DXGI
var bitmap = WindowCapture.CaptureWindow(hwnd, CaptureStrategy.Auto);

Logging

Pass an optional ILogger to get detailed capture diagnostics:

using Microsoft.Extensions.Logging;

var loggerFactory = LoggerFactory.Create(b => b.AddConsole());
var logger = loggerFactory.CreateLogger("WgcSharp");

var bitmap = WindowCapture.CaptureWindow(hwnd, CaptureStrategy.Auto, timeoutMs: 2000, logger: logger);

Full example

using System.Diagnostics;
using System.Drawing.Imaging;
using WgcSharp;

var process = Process.GetProcessesByName("notepad").First();
var bitmap = WindowCapture.CaptureWindow(process.MainWindowHandle);
bitmap?.Save("notepad.png", ImageFormat.Png);

How it works

WGC Backend (primary)

1. Creates a D3D11 device and wraps it as a WinRT IDirect3DDevice
2. Creates a GraphicsCaptureItem for the target HWND via IGraphicsCaptureItemInterop
3. Sets up a free-threaded Direct3D11CaptureFramePool and capture session
4. Skips the first frame (often blank) and captures the second frame
5. Extracts the D3D11 texture via IDirect3DDxgiInterfaceAccess
6. Copies to a staging texture and reads pixels into a System.Drawing.Bitmap

All WinRT interaction uses raw COM vtable calls — no CsWinRT, no ComWrappers registration, no conflicts with WPF or other frameworks.

DXGI Backend (fallback)

1. Creates a D3D11 device and finds the DXGI output for the target window's monitor
2. Uses IDXGIOutput1.DuplicateOutput to capture the full desktop frame
3. Crops to the target window's screen coordinates (via DwmGetWindowAttribute)

API

// Simple — uses Auto strategy, 2s timeout
Bitmap? CaptureWindow(IntPtr hwnd, int timeoutMs = 2000)

// Full control
Bitmap? CaptureWindow(IntPtr hwnd, CaptureStrategy strategy, int timeoutMs = 2000, ILogger? logger = null)

Requirements

• Windows 10 version 1803+ (build 17134) for WGC
• .NET 9.0+ or .NET 10.0+ (Windows TFM)
• Hardware GPU (D3D11)

License

MIT