change frame size of video Capture

Summary of your issue

I have 5MP camera, and I can use opencvsharp to capture(or liveview ) at 2 resolution 2592x1944 and 1280x1024, but I want to make liveview at 1280 and capture single image at 2592, it return black image at size 2592, how to do that, I stop camera and re-init it but it does not work.

Environment

window 7, opencv sharp 4.1.0 Write your environment.

What did you do when you faced the problem?

//write here

Example code:

bool InitCamCapture()
        {
            _capture = new VideoCapture();

            _nCamIndex = CheckCamID();

            if (_nCamIndex <= -1) return false;

            if (_capture.IsOpened())
                _capture.Release();

            _capture.Open(_nCamIndex);

            _capture.FrameWidth = 1280;
            _capture.FrameHeight = 1044;

            _capture.Read(_framePreview);

            if (_framePreview.Height > 0)
            {
                timerWebCam.Enabled = true;

                _bmpCam = _framePreview.ToBitmap();

                //_bmpCam.RotateFlip(RotateFlipType.Rotate90FlipNone);

                picCamera.Image = _bmpCam;
                return true;
            }

            return false;
        }

private void btCapture_Click(object sender, EventArgs e)

        {
            _nCamIndex = 1;
            timerWebCam.Enabled = false;
            Thread.Sleep(100);

            if (_capture.IsOpened())
            {
                _capture.Release();
            }

            _capture = new VideoCapture();
            _capture.FrameWidth = 2592;
            _capture.FrameHeight = 1944;

            _frameCapture = new Mat();

            _capture.Open(_nCamIndex);

            _capture.Read(_frameCapture);

            _frameCapture.SaveImage("cap.bmp");

            InitCamCapture();
        }

Output:

paste your output

What did you intend to be?

[ydeydier]

After lots of searching, I discovered that there’s a way to reduce the resolution but you have to structure your code in a specific way.

• First of all, Define the VideoCapture

// 0 is the device index, you can change it as per your needs
deviceIndex = 0;
capture = new VideoCapture(deviceIndex);

• Then Open the Device

capture.Open(deviceIndex);

• Then define the frame height and frame width

capture.FrameHeight = 64;
capture.FrameWidth = 36;

• Finally, write it into a file

outputVideo = new VideoWriter("video.mp4", FourCC.AVC, 29, new OpenCvSharp.Size(capture.FrameWidth, capture.FrameHeight));

“Open” BEFORE “FrameHeight” and “FrameWidth” did the job for me. Thanks a lot.

[ticTechtoee]

After lots of searching, I discovered that there’s a way to reduce the resolution but you have to structure your code in a specific way.

• First of all, Define the VideoCapture

// 0 is the device index, you can change it as per your needs
deviceIndex = 0;
capture = new VideoCapture(deviceIndex);

• Then Open the Device

capture.Open(deviceIndex);

• Then define the frame height and frame width

capture.FrameHeight = 64;
capture.FrameWidth = 36;

• Finally, write it into a file

outputVideo = new VideoWriter("video.mp4", FourCC.AVC, 29, new OpenCvSharp.Size(capture.FrameWidth, capture.FrameHeight));