一、前言

    因项目需要需关闭相机自身的自动白平衡和自动曝光时间，统统设定为恒定值，开始实验了opencvCvSharp，但是不起作用，故实验了更底层的 DirectShowLib ，可成功关闭相机自带的自动白平衡和自动曝光时间，再使用 opencvCvSharp 读取摄像头

二、 代码

（1）安装 DirectShowLib 包， 直接在nuget

        简单整2按钮2文本框，用于输入需要定义的白平衡温度值和曝光时间值，曝光值-3表示是10的-3次方的意思，值越大则曝光时间越长，图像越亮；白平衡温度值是有范围，可以通过接口 int hr = videoProcAmp.GetRange(prop, out minValue, out maxValue, out steppingDelta, out defaultValue, out flags);   查询获得，温度值越大则偏暖色

（2）重点代码

using DirectShowLib;
using System.Runtime.InteropServices;
using OpenCvSharp;


    public class CameraManager
    {
        private IBaseFilter cameraFilter;
        private DsDevice cameraDevice; // DirectShow 设备

        public void InitializeCamera()
        {
            try
            {
                // 枚举视频输入设备
                var devices = DsDevice.GetDevicesOfCat(DirectShowLib.FilterCategory.VideoInputDevice);
                if (devices.Length == 0)
                {
                    Console.WriteLine("No video input devices found.");
                    return;
                }

                // 选择第一个设备（通常是默认相机）
                cameraDevice = devices[0];

                // 使用 Moniker 来创建相机的 BaseFilter 对象
                object cameraObject = null;
                Guid iid = typeof(IBaseFilter).GUID;
                cameraDevice.Mon.BindToObject(null, null, ref iid, out cameraObject);
                cameraFilter = cameraObject as IBaseFilter;

                if (cameraFilter == null)
                {
                    Console.WriteLine("Failed to create camera filter.");
                    return;
                }

                Console.WriteLine("Camera initialized successfully.");
            }
            catch (Exception ex)
            {
                Console.WriteLine($"Error initializing camera: {ex.Message}");
            }
        }

        // Getter 方法获取相机的 BaseFilter 对象
        public IBaseFilter GetCameraFilter()
        {
            return cameraFilter;
        }

        // 释放相机资源
        public void CloseCamera()
        {
            if (cameraFilter != null)
            {
                Marshal.ReleaseComObject(cameraFilter);
                cameraFilter = null;
            }
            cameraDevice = null;
            Console.WriteLine("Camera resources released.");
        }
    }

        private void button3_Click(object sender, EventArgs e) {

            int expos_v = int.Parse(textBox2.Text);
            int wb_v = int.Parse(textBox3.Text);

            int hr;

            CameraManager cameraManager = new CameraManager();
            cameraManager.InitializeCamera();
            IBaseFilter cameraFilter = cameraManager.GetCameraFilter();
            if (cameraFilter != null)
            {
                // 在这里可以继续操作相机，比如设置属性、连接到视频源等
                // 例如关闭相机的自动白平衡：
                //  

                IAMCameraControl cameraControl = cameraFilter as IAMCameraControl;
                if (cameraControl != null)
                {
                    hr = cameraControl.Set(DirectShowLib.CameraControlProperty.Exposure, expos_v, DirectShowLib.CameraControlFlags.Manual/* 设置关闭白平衡的值 */);
                    DsError.ThrowExceptionForHR(hr);


                }

                IAMVideoProcAmp videoProcAmp = cameraFilter as IAMVideoProcAmp;
                if (videoProcAmp != null)
                {
                    // 获取 WhiteBalance 属性  

                    VideoProcAmpProperty prop = VideoProcAmpProperty.WhiteBalance;

                    // 获取当前值
                    int minValue, maxValue, steppingDelta, defaultValue;
                    VideoProcAmpFlags flags;

                    // 这一句获取白平衡参数，范围2800-6500 ,默认是4600
                    //int hr = videoProcAmp.GetRange(prop, out minValue, out maxValue, out steppingDelta, out defaultValue, out flags);  

                    hr = videoProcAmp.Set(prop, wb_v, VideoProcAmpFlags.Manual);
                    if (hr >= 0)
                    {
                        textBox1.Text = "白平衡设置成功";
                    }
                    else
                    {
                        textBox1.Text = "白平衡设置失败";
                    }

                }
                else
                {


                }
            }
       
        }

        private void button4_Click(object sender, EventArgs e)
        {
            // 打开摄像头
            using (VideoCapture capture = new VideoCapture(0 , VideoCaptureAPIs.DSHOW ))
            {

                // 设置分辨率和帧率
                 

                // 检查摄像头是否成功打开
                if (!capture.IsOpened())
                {
                    Console.WriteLine("无法打开摄像头.");
                    return;
                }

                capture.Set(VideoCaptureProperties.FrameWidth,3840  ); // 设置宽度
                capture.Set(VideoCaptureProperties.FrameHeight,  2880); // 设置高度
                capture.Set(VideoCaptureProperties.FourCC, VideoWriter.FourCC('M', 'J', 'P', 'G'));

                //capture.Set(VideoCaptureProperties.Fps, 20); // 设置帧率

                // 获取摄像头的宽度和高度
                int width = (int)capture.Get(VideoCaptureProperties.FrameWidth);
                int height = (int)capture.Get(VideoCaptureProperties.FrameHeight);
                 
                // 创建窗口以显示图像
                string windowName = $"sp{width}*{height}";
                Cv2.NamedWindow(windowName);
                Cv2.NamedWindow("cap");
                // 循环获取并显示图像
                int count = 0;
                while (true)
                {
                    count++;
                    Stopwatch stopwatch = new Stopwatch();
                    stopwatch.Start();
                    // 从摄像头捕获一帧图像
                    Mat frame = new Mat();
                    capture.Read(frame);

                    stopwatch.Stop();
                    //textBox1.Text = $"Milliseconds elapsed: {count}";
                    // 检查是否成功捕获图像
                    if (frame.Empty())
                    {
                        Console.WriteLine("无法从摄像头捕获图像.");
                        break;
                    }

                    // 在窗口中显示图像
                    Cv2.ImShow(windowName , frame);

                    // 等待并检测按键，按下 ESC 键退出循环
                    int key = Cv2.WaitKey(1);
                    if (key == 27) // ASCII码 27 表示 ESC 键
                        break;
                    else if (key == 32) // ASCII码 27 表示 ESC 键
                    {
                        Cv2.ImShow("cap", frame);
                        Cv2.ImWrite("cap.png", frame);
                    }
                }
                // 释放资源
                capture.Release();
                Cv2.DestroyAllWindows();

            }
        }

三、效果

白平衡温度值3000

白平衡温度值6200