ScreenRecorder/CaptureService.cs

using System.Drawing;
using System.Drawing.Imaging;
using System.Runtime.InteropServices;
using SharpAvi;
using SharpAvi.Output;
using SharpAvi.Codecs;

namespace ScreenRecorder;

public class CaptureService : IDisposable
{
    private AviWriter? _writer;
    private IAviVideoStream? _videoStream;
    private Thread? _captureThread;
    private volatile bool _isRecording;
    private readonly int _fps;
    private readonly int _quality;
    private readonly bool _hideCursor;
    private readonly Rectangle _captureArea;
    private string? _outputPath;

    public CaptureService(int fps = 30, int quality = 100, bool hideCursor = false)
    {
        _fps = fps;
        _quality = quality;
        _hideCursor = hideCursor;
        // 录制主屏幕
        var screen = System.Windows.Forms.Screen.PrimaryScreen!;
        _captureArea = screen.Bounds;
    }

    public void Start(string outputPath)
    {
        _outputPath = outputPath;
        _isRecording = true;

        _writer = new AviWriter(outputPath)
        {
            FramesPerSecond = _fps,
            EmitIndex1 = true
        };

        if (_quality == 101) // 无损模式：无压缩 RGB
        {
            var rawStream = _writer.AddVideoStream(
                _captureArea.Width,
                _captureArea.Height,
                BitsPerPixel.Bpp32
            );
            rawStream.Codec = KnownFourCCs.Codecs.Uncompressed;
            _videoStream = rawStream;
        }
        else // MJPEG 有损模式
        {
            _videoStream = _writer.AddMotionJpegVideoStream(
                _captureArea.Width,
                _captureArea.Height,
                quality: _quality
            );
        }

        _captureThread = new Thread(CaptureLoop) { IsBackground = true };
        _captureThread.Start();
    }

    public void Stop()
    {
        _isRecording = false;
        _captureThread?.Join(3000);
        _writer?.Close();
        _writer = null;
    }

    private void CaptureLoop()
    {
        var interval = TimeSpan.FromMilliseconds(1000.0 / _fps);
        int w = _captureArea.Width, h = _captureArea.Height;
        bool lossless = _quality == 101;

        using var bitmap = new Bitmap(w, h, PixelFormat.Format32bppRgb);
        using var graphics = Graphics.FromImage(bitmap);
        int stride = w * 4;
        var frameData = new byte[stride * h];

        while (_isRecording)
        {
            var start = DateTime.UtcNow;

            graphics.CopyFromScreen(_captureArea.Location, Point.Empty, _captureArea.Size);
            if (!_hideCursor) DrawCursor(graphics);

            var bits = bitmap.LockBits(
                new Rectangle(0, 0, w, h),
                ImageLockMode.ReadOnly,
                PixelFormat.Format32bppRgb
            );

            if (lossless)
            {
                // 无压缩 AVI 需要 BGR 从下到上（行翻转）
                for (int row = 0; row < h; row++)
                {
                    IntPtr src = bits.Scan0 + row * bits.Stride;
                    int dstOffset = (h - 1 - row) * stride;
                    Marshal.Copy(src, frameData, dstOffset, stride);
                }
            }
            else
            {
                Marshal.Copy(bits.Scan0, frameData, 0, frameData.Length);
            }

            bitmap.UnlockBits(bits);
            _videoStream!.WriteFrame(true, frameData, 0, frameData.Length);

            var elapsed = DateTime.UtcNow - start;
            var remaining = interval - elapsed;
            if (remaining > TimeSpan.Zero)
                Thread.Sleep(remaining);
        }
    }

    public void Dispose() => Stop();

    // Win32 API：获取鼠标位置和光标图标
    [StructLayout(LayoutKind.Sequential)]
    private struct CURSORINFO
    {
        public int cbSize;
        public int flags;
        public IntPtr hCursor;
        public POINT ptScreenPos;
    }

    [StructLayout(LayoutKind.Sequential)]
    private struct POINT { public int x, y; }

    [DllImport("user32.dll")] static extern bool GetCursorInfo(ref CURSORINFO ci);
    [DllImport("user32.dll")] static extern bool DrawIconEx(IntPtr hdc, int x, int y, IntPtr hIcon, int w, int h, int step, IntPtr brush, int flags);

    private const int CURSOR_SHOWING = 1;
    private const int DI_NORMAL = 3;

    private void DrawCursor(Graphics g)
    {
        var ci = new CURSORINFO { cbSize = Marshal.SizeOf<CURSORINFO>() };
        if (!GetCursorInfo(ref ci) || ci.flags != CURSOR_SHOWING) return;

        int x = ci.ptScreenPos.x - _captureArea.X;
        int y = ci.ptScreenPos.y - _captureArea.Y;
        var hdc = g.GetHdc();
        DrawIconEx(hdc, x, y, ci.hCursor, 0, 0, 0, IntPtr.Zero, DI_NORMAL);
        g.ReleaseHdc(hdc);
    }
}