Initial commit

.gitignore

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+.vs
+bin
+obj

WindowCapture.cs

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+using System;
+using System.Drawing;
+using System.Runtime.InteropServices;
+
+class Program {
+  [StructLayout(LayoutKind.Sequential)]
+  private struct RECT {
+    public int Left;
+    public int Top;
+    public int Right;
+    public int Bottom;
+  }
+
+  [DllImport("user32.dll")]
+  private static extern IntPtr GetDC(IntPtr hWnd);
+
+  [DllImport("user32.dll")]
+  private static extern int GetClientRect(IntPtr hWnd, out RECT rect);
+
+  [DllImport("user32.dll")]
+  private static extern int ReleaseDC(IntPtr hWnd, IntPtr hDC);
+
+  [DllImport("gdi32.dll")]
+  private static extern IntPtr CreateCompatibleDC(IntPtr hDC);
+
+  [DllImport("gdi32.dll")]
+  private static extern IntPtr CreateCompatibleBitmap(IntPtr hDC, int width,
+                                                      int height);
+
+  [DllImport("gdi32.dll")]
+  private static extern IntPtr SelectObject(IntPtr hDC, IntPtr hObject);
+
+  [DllImport("gdi32.dll")]
+  private static extern bool DeleteObject(IntPtr hObject);
+
+  [DllImport("gdi32.dll")]
+  private static extern bool DeleteDC(IntPtr hDC);
+
+  [DllImport("user32.dll")]
+  private static extern bool PrintWindow(IntPtr hwnd, IntPtr hdcBlt,
+                                         uint nFlags);
+
+  private const uint PW_RENDERFULLCONTENT = 0x00000002;
+
+  static bool CaptureWindow(IntPtr windowHandle, string outputPath) {
+    try {
+      // Get the window dimensions
+      GetClientRect(windowHandle, out RECT windowRect);
+      int width = windowRect.Right - windowRect.Left;
+      int height = windowRect.Bottom - windowRect.Top;
+
+      // Create compatible DC and bitmap
+      IntPtr sourceContext = GetDC(windowHandle);
+      IntPtr destContext = CreateCompatibleDC(sourceContext);
+      IntPtr bitmap = CreateCompatibleBitmap(sourceContext, width, height);
+
+      // Select the bitmap into the DC
+      IntPtr oldBitmap = SelectObject(destContext, bitmap);
+
+      // Use PrintWindow to capture the window content
+      PrintWindow(windowHandle, destContext, PW_RENDERFULLCONTENT);
+
+      // Create the final bitmap
+      using (Bitmap screenshot = Bitmap.FromHbitmap(bitmap)) {
+        screenshot.Save(outputPath, System.Drawing.Imaging.ImageFormat.Png);
+      }
+
+      // Clean up
+      SelectObject(destContext, oldBitmap);
+      DeleteObject(bitmap);
+      DeleteDC(destContext);
+      ReleaseDC(windowHandle, sourceContext);
+
+      return true;
+    } catch (Exception) {
+      return false;
+    }
+  }
+
+  static int Main(string[] args) {
+    if (args.Length != 2) {
+      Console.WriteLine(
+          "Usage: WindowCapture.exe <window_handle> <output_path>");
+      Console.WriteLine("Example: WindowCapture.exe 123456 screenshot.png");
+      return 1;
+    }
+
+    if (!IntPtr.TryParse(args[0], out IntPtr windowHandle)) {
+      Console.WriteLine(
+          "Invalid window handle. Please provide a valid number.");
+      return 1;
+    }
+
+    string outputPath = args[1];
+
+    if (CaptureWindow(windowHandle, outputPath)) {
+      Console.WriteLine($"Screenshot saved to: {outputPath}");
+      return 0;
+    } else {
+      Console.WriteLine("Failed to capture screenshot");
+      return 1;
+    }
+  }
+}

WindowCapture.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net8.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+  <ItemGroup>
+    <PackageReference Include="System.Drawing.Common" Version="9.0.6" />
+  </ItemGroup>
+</Project>