better-genshin-impact/Fischless.GameCapture/BitBlt/BitBltCapture.cs

using System.Diagnostics;
using Vanara.PInvoke;

namespace Fischless.GameCapture.BitBlt;

public class BitBltCapture : IGameCapture
{
    private nint _hWnd;

    public CaptureModes Mode => CaptureModes.BitBlt;

    public bool IsCapturing { get; private set; }

    public void Dispose() => Stop();

    public void Start(nint hWnd)
    {
        _hWnd = hWnd;
        IsCapturing = true;
    }

    public Bitmap? Capture()
    {
        if (_hWnd == IntPtr.Zero)
        {
            return null;
        }

        try
        {
            User32.GetClientRect(_hWnd, out var windowRect);
            int x = default, y = default;
            var width = windowRect.right - windowRect.left;
            var height = windowRect.bottom - windowRect.top;

            Bitmap bitmap = new(width, height);
            using System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap);
            var hdcDest = g.GetHdc();
            Gdi32.SafeHDC hdcSrc = User32.GetDC(_hWnd == IntPtr.Zero ? User32.GetDesktopWindow() : _hWnd);
            Gdi32.StretchBlt(hdcDest, 0, 0, width, height, hdcSrc, x, y, width, height, Gdi32.RasterOperationMode.SRCCOPY);
            g.ReleaseHdc();
            Gdi32.DeleteDC(hdcDest);
            Gdi32.DeleteDC(hdcSrc);
            return bitmap;
        }
        catch (Exception e)
        {
            Debug.WriteLine(e);
        }

        return null!;
    }

    public void Stop()
    {
        _hWnd = IntPtr.Zero;
        IsCapturing = false;
    }
}