Capturing webcam image to bitmap in C#

can you tell me which bits to extract?

Hey, I've got a problem. This is the code I have:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Drawing.Imaging;
using System.Text;
using System.Windows.Forms;
using dshow;
using VideoSource;
using dshow.Core;

namespace IDAPT
{
    public partial class Form1 : Form
    {
        public Form1()
        {

            InitializeComponent();

            // Initialise the webcam
            InitialiseWebCam();
        }
       
        // The camera/video source object
        private IVideoSource m_cam;


        private void OnNewFrame(object sender, CameraEventArgs e)
        {
            this.pctTemp.Image = e.Bitmap;
        }

        private void InitialiseWebCam()
        {
            //only carry this out if a camera hasn't already been set up
            if (m_cam == null)
            {
                FilterCollection filters;
                try
                {
                    //get all of the devices attached
                    filters = new FilterCollection(FilterCategory.VideoInputDevice);
                    //get the first item in the collection of devices
                    Filter webCam = filters[0];
                    String deviceName = webCam.MonikerString;
                    //instantiate the web cam
                    m_cam = new CaptureDevice();
                    //bind to the device
                    m_cam.VideoSource = deviceName;

                    // Set the new frame event
                    m_cam.NewFrame += new CameraEventHandler(OnNewFrame); //where OnFirstFrame is my handler

                }
                catch
                {
                    MessageBox.Show("No webcams found");
                    Application.Exit();
                }
            }
        }

        private void pctTemp_Click(object sender, EventArgs e)
        {

            // Start the capture
            m_cam.Start();

        }

    }
}

When I click the picture (just a temp way of starting the capture) it runs for about 5 seconds, then closes the form and highlights the "                Application.Run(new Form1()); " in Program.cs.

The error is "Parameter is not valid."

BUT if I don't assign the image to the picturebox, then it never errors.

Hi,

do you know what the invalid parameter is? I dont have a web cam at the moment so can't really try your code.

So, for about 5 seconds the image is displayed in the picturebox?

Yes, the error is in system.drawing.

System.ArgumentException was unhandled
  Message="Parameter is not valid."
  Source="System.Drawing"
  StackTrace:
       at System.Drawing.Image.get_Width()
       at System.Drawing.Image.get_Size()
       at System.Windows.Forms.PictureBox.ImageRectangleFromSizeMode(PictureBoxSizeMode mode)
       at System.Windows.Forms.PictureBox.get_ImageRectangle()
       at System.Windows.Forms.PictureBox.OnPaint(PaintEventArgs pe)
       at System.Windows.Forms.Control.PaintWithErrorHandling(PaintEventArgs e, Int16 layer, Boolean disposeEventArgs)
       at System.Windows.Forms.Control.WmPaint(Message& m)
       at System.Windows.Forms.Control.WndProc(Message& m)
       at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
       at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
       at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
       at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
       at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(Int32 dwComponentID, Int32 reason, Int32 pvLoopData)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
       at System.Windows.Forms.Application.Run(Form mainForm)
       at IDAPT.Program.Main() in C:\Documents and Settings\Dan\My Documents\Visual Studio 2005\Projects\IDAPT\IDAPT\Program.cs:line 18
       at System.AppDomain.nExecuteAssembly(Assembly assembly, String[] args)
       at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
       at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
       at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
       at System.Threading.ThreadHelper.ThreadStart()

So it'll be the Image = e.Bitmap.

In my code i only really displayed the image for a preview, it was for an eye tracking system, to do this i just drew directly onto the form. I do remember having a similar problem, but because i didn't really need to display the frames for too long (only during calibration) i managed to avoid it. Soloutions i tried  that worked were ( i hope i remember correctly)

1) surrounding the     this.pctTemp.Image = e.Bitmap; with a try catch so it doesn't bail out
2) checking whether e.Bitmap is null  before assigning
3) cloning e.Bitmap before passing it to Image
4) using Monitors around the e.Bitmap to lock it before using it

It may be worth looking at the original code from the motion tracking project, look at the CameraWindow class, in particular the Paint method. In his code he is using a Camera instance instead of the IVideoSource, the Camera class exposes a last frame property, although i think i had the same problems with this as IVideoSource

The try catch statement worked, however I am using some unsafe {} areas now, and by putting the image = e.bitmap in the unsafe keyword, it fixes the error.

Thanks for all of your help.