How to copy image without using the clipboard?

Question

Question: I have the below code to capture an image from a webcam.

My problem is this part:

SendMessage(hCaptureWnd, WM_CAP_COPY, 0, 0);                    // copy it to the clipboard

What it does is copy the image from the window to the clipboard, and then create a byte array out of it.

It works - as long as you don't use the clipboard while the program is running.
The problem is, this doesn't even work for myself, as I sometimes copy something while Visual Studio takes ages to start debug the web application, and then it crashes.

So here my question:
How can I get the image without using the clipboard ? Or more specifically, how to transform hCaptureWnd to System.Drawing.Image ?

---

-- Edit:
I missed to say "without creating a file, i want a byte array".
It's a web application, so the user the application runs under shouldn't have write access to the file system (writing to a file only for temporary testing) ...
-- End Edit:

---

/// <summary>
/// Captures a frame from the webcam and returns the byte array associated
/// with the captured image
/// </summary>
/// <param name="connectDelay">number of milliseconds to wait between connect 
/// and capture - necessary for some cameras that take a while to 'warm up'</param>
/// <returns>byte array representing a bitmp or null (if error or no webcam)</returns>
private static byte[] InternalCaptureToByteArray(int connectDelay = 500)
{
    Clipboard.Clear();                                              // clear the clipboard
    int hCaptureWnd = capCreateCaptureWindowA("ccWebCam", 0, 0, 0,  // create the hidden capture window
        350, 350, 0, 0);
    SendMessage(hCaptureWnd, WM_CAP_CONNECT, 0, 0);                 // send the connect message to it
    Thread.Sleep(connectDelay);                                     // sleep the specified time
    SendMessage(hCaptureWnd, WM_CAP_GET_FRAME, 0, 0);               // capture the frame
    SendMessage(hCaptureWnd, WM_CAP_COPY, 0, 0);                    // copy it to the clipboard
    SendMessage(hCaptureWnd, WM_CAP_DISCONNECT, 0, 0);              // disconnect from the camera
    Bitmap bitmap = (Bitmap)Clipboard.GetDataObject().GetData(DataFormats.Bitmap);  // copy into bitmap

    if (bitmap == null)
        return null;

    using (MemoryStream stream = new MemoryStream())
    {
        bitmap.Save(stream, ImageFormat.Bmp);    // get bitmap bytes
        return stream.ToArray();
    } // End Using stream

} // End Function InternalCaptureToByteArray

Note (http://msdn.microsoft.com/en-us/library/windows/desktop/dd756879(v=vs.85).aspx):

HWND VFWAPI capCreateCaptureWindow(
  LPCTSTR lpszWindowName,
  DWORD dwStyle,
  int x,
  int y,
  int nWidth,
  int nHeight,
  HWND hWnd,
  int nID
);


#define VFWAPI  WINAPI 

typedef HANDLE HWND;
typedef PVOID HANDLE;
typedef void *PVOID;

Full code for reference

using System;
using System.IO;
using System.Drawing;
using System.Threading;
using System.Windows.Forms;
using System.Drawing.Imaging;
using System.Collections.Generic;
using System.Runtime.InteropServices;


// http://www.creativecodedesign.com/node/66
// http://www.barebonescoder.com/2012/01/finding-your-web-cam-with-c-directshow-net/
// http://www.codeproject.com/Articles/15219/WebCam-Fast-Image-Capture-Service-using-WIA
// http://www.c-sharpcorner.com/uploadfile/yougerthen/integrate-the-web-webcam-functionality-using-C-Sharp-net-and-com-part-viii/
// http://forums.asp.net/t/1410057.aspx


namespace cc.Utility
{


    // bool isCaptured = ccWebCam.CaptureSTA("capture.jpg"); // Access to path C:\Program Files (x86)\Common Files\Microsoft Shared\DevServer\10.0\capture.jpg" denied.
    // byte[] captureBytes = ccWebCam.CaptureSTA();

    /// <summary>
    /// Timur Kovalev (http://www.creativecodedesign.com):
    /// This class provides a method of capturing a webcam image via avicap32.dll api.
    /// </summary>    
    public static class ccWebCam
    {
        #region *** PInvoke Stuff - methods to interact with capture window ***

        [DllImport("user32", EntryPoint = "SendMessage")]
        private static extern int SendMessage(int hWnd, uint Msg, int wParam, int lParam);

        [DllImport("avicap32.dll", EntryPoint = "capCreateCaptureWindowA")]
        private static extern int capCreateCaptureWindowA(string lpszWindowName, int dwStyle, 
            int X, int Y, int nWidth, int nHeight, int hwndParent, int nID);  


        private const int WM_CAP_CONNECT = 1034;
        private const int WM_CAP_DISCONNECT = 1035;
        private const int WM_CAP_COPY = 1054;
        private const int WM_CAP_GET_FRAME = 1084;


        #endregion


        private static object objWebCamThreadLock = new object();


        //CaptureToFile(@"D:\Stefan.Steiger\Documents\Visual Studio 2010\Projects\Post_Ipag\image3.jpg"):
        public static bool Capture(string filePath, int connectDelay = 500)
        {
            lock (objWebCamThreadLock)
            {
                return cc.Utility.ccWebCam.InternalCaptureAsFileInThread(filePath, connectDelay);
            }
        } // End Treadsafe Function Capture


        public static byte[] Capture(int connectDelay = 500)
        {
            lock (objWebCamThreadLock)
            {
                return InternalCaptureToByteArrayInThread(connectDelay);
            }
        } // End Treadsafe Function Capture


        /// <summary>
        /// Captures a frame from the webcam and returns the byte array associated
        /// with the captured image. The image is also stored in a file
        /// </summary>
        /// <param name="filePath">path the file wher ethe image will be saved</param>
        /// <param name="connectDelay">number of milliseconds to wait between connect 
        /// and capture - necessary for some cameras that take a while to 'warm up'</param>
        /// <returns>true on success, false on failure</returns>
        private static bool InternalCaptureAsFileInThread(string filePath, int connectDelay = 500)
        {
            bool success = false;
            Thread catureThread = new Thread(() =>
            {
                success = InternalCaptureAsFile(filePath, connectDelay);
            });
            catureThread.SetApartmentState(ApartmentState.STA);
            catureThread.Start();
            catureThread.Join();
            return success;
        } // End Function InternalCaptureAsFileInThread


        /// <summary>
        /// Captures a frame from the webcam and returns the byte array associated
        /// with the captured image. The image is also stored in a file
        /// </summary>
        /// <param name="filePath">path the file wher ethe image will be saved</param>
        /// <param name="connectDelay">number of milliseconds to wait between connect 
        /// and capture - necessary for some cameras that take a while to 'warm up'</param>
        /// <returns>true on success, false on failure</returns>
        private static bool InternalCaptureAsFile(string filePath, int connectDelay = 500)
        {
            byte[] capture = ccWebCam.InternalCaptureToByteArray(connectDelay);
            if (capture != null)
            {
                // Access to path C:\Program Files (x86)\Common Files\Microsoft Shared\DevServer\10.0\image1.jpg" denied.
                File.WriteAllBytes(filePath, capture);
                return true;
            }
            return false;
        } // End Function InternalCaptureAsFile


        /// <summary>
        /// Captures a frame from the webcam and returns the byte array associated
        /// with the captured image. Runs in a newly-created STA thread which is 
        /// required for this method of capture
        /// </summary>
        /// <param name="connectDelay">number of milliseconds to wait between connect 
        /// and capture - necessary for some cameras that take a while to 'warm up'</param>
        /// <returns>byte array representing a bitmp or null (if error or no webcam)</returns>
        private static byte[] InternalCaptureToByteArrayInThread(int connectDelay = 500)
        {
            byte[] bytes = null;
            Thread catureThread = new Thread(() =>
            {
                bytes = InternalCaptureToByteArray(connectDelay);
            });
            catureThread.SetApartmentState(ApartmentState.STA);
            catureThread.Start();
            catureThread.Join();
            return bytes;
        } // End Function InternalCaptureToByteArrayInThread


        /// <summary>
        /// Captures a frame from the webcam and returns the byte array associated
        /// with the captured image
        /// </summary>
        /// <param name="connectDelay">number of milliseconds to wait between connect 
        /// and capture - necessary for some cameras that take a while to 'warm up'</param>
        /// <returns>byte array representing a bitmp or null (if error or no webcam)</returns>
        private static byte[] InternalCaptureToByteArray(int connectDelay = 500)
        {
            Clipboard.Clear();                                              // clear the clipboard
            int hCaptureWnd = capCreateCaptureWindowA("ccWebCam", 0, 0, 0,  // create the hidden capture window
                350, 350, 0, 0);
            SendMessage(hCaptureWnd, WM_CAP_CONNECT, 0, 0);                 // send the connect message to it
            Thread.Sleep(connectDelay);                                     // sleep the specified time
            SendMessage(hCaptureWnd, WM_CAP_GET_FRAME, 0, 0);               // capture the frame
            SendMessage(hCaptureWnd, WM_CAP_COPY, 0, 0);                    // copy it to the clipboard
            SendMessage(hCaptureWnd, WM_CAP_DISCONNECT, 0, 0);              // disconnect from the camera
            Bitmap bitmap = (Bitmap)Clipboard.GetDataObject().GetData(DataFormats.Bitmap);  // copy into bitmap

            if (bitmap == null)
                return null;

            using (MemoryStream stream = new MemoryStream())
            {
                bitmap.Save(stream, ImageFormat.Bmp);    // get bitmap bytes
                return stream.ToArray();
            } // End Using stream

        } // End Function InternalCaptureToByteArray


    }


}

---

I tried like this, but it only gets a black image...

    [DllImport("user32.dll")]
    static extern IntPtr GetWindowDC(IntPtr hWnd);

    [DllImport("gdi32.dll", SetLastError = true)]
    static extern IntPtr CreateCompatibleDC(IntPtr hdc);

    enum TernaryRasterOperations : uint
    {
        /// <summary>dest = source</summary>
        SRCCOPY = 0x00CC0020,
        /// <summary>dest = source OR dest</summary>
        SRCPAINT = 0x00EE0086,
        /// <summary>dest = source AND dest</summary>
        SRCAND = 0x008800C6,
        /// <summary>dest = source XOR dest</summary>
        SRCINVERT = 0x00660046,
        /// <summary>dest = source AND (NOT dest)</summary>
        SRCERASE = 0x00440328,
        /// <summary>dest = (NOT source)</summary>
        NOTSRCCOPY = 0x00330008,
        /// <summary>dest = (NOT src) AND (NOT dest)</summary>
        NOTSRCERASE = 0x001100A6,
        /// <summary>dest = (source AND pattern)</summary>
        MERGECOPY = 0x00C000CA,
        /// <summary>dest = (NOT source) OR dest</summary>
        MERGEPAINT = 0x00BB0226,
        /// <summary>dest = pattern</summary>
        PATCOPY = 0x00F00021,
        /// <summary>dest = DPSnoo</summary>
        PATPAINT = 0x00FB0A09,
        /// <summary>dest = pattern XOR dest</summary>
        PATINVERT = 0x005A0049,
        /// <summary>dest = (NOT dest)</summary>
        DSTINVERT = 0x00550009,
        /// <summary>dest = BLACK</summary>
        BLACKNESS = 0x00000042,
        /// <summary>dest = WHITE</summary>
        WHITENESS = 0x00FF0062,
        /// <summary>
        /// Capture window as seen on screen.  This includes layered windows 
        /// such as WPF windows with AllowsTransparency="true"
        /// </summary>
        CAPTUREBLT = 0x40000000
    }

    [DllImport("gdi32.dll")]
    [return: MarshalAs(UnmanagedType.Bool)]
    static extern bool BitBlt(IntPtr hdc, int nXDest, int nYDest, int nWidth, int nHeight, IntPtr hdcSrc, int nXSrc, int nYSrc, TernaryRasterOperations dwRop);

    [DllImport("gdi32.dll")]
    static extern IntPtr CreateCompatibleBitmap(IntPtr hdc, int nWidth, int nHeight);

    [DllImport("gdi32.dll", ExactSpelling = true, PreserveSig = true, SetLastError = true)]
    static extern IntPtr SelectObject(IntPtr hdc, IntPtr hgdiobj);

    [DllImport("gdi32.dll")]
    static extern bool DeleteDC(IntPtr hdc);

    [DllImport("user32.dll")]
    static extern bool ReleaseDC(IntPtr hWnd, IntPtr hDC);

    [DllImport("gdi32.dll")]
    static extern bool DeleteObject(IntPtr hObject);


    public static void ScreenshotWindow(IntPtr windowHandle)
    {
        Rect Rect = new Rect();

        GetWindowRect(windowHandle, ref Rect);
        int width = Rect.Right - Rect.Left;
        int height = Rect.Bottom - Rect.Top;

        IntPtr windowDeviceContext = GetWindowDC(windowHandle);
        IntPtr destDeviceContext = CreateCompatibleDC(windowDeviceContext);
        IntPtr bitmapHandle = CreateCompatibleBitmap(windowDeviceContext, width, height);
        IntPtr oldObject = SelectObject(destDeviceContext, bitmapHandle);

        BitBlt(destDeviceContext, 0, 0, width, height, windowDeviceContext, 0, 0, TernaryRasterOperations.CAPTUREBLT | TernaryRasterOperations.SRCCOPY);
        SelectObject(destDeviceContext, oldObject);

        DeleteDC(destDeviceContext);
        ReleaseDC(windowHandle, destDeviceContext);


        Image screenshot = Image.FromHbitmap(bitmapHandle);
        DeleteObject(bitmapHandle);

        screenshot.Save("d:\\temp\\mywebcamimage.png", System.Drawing.Imaging.ImageFormat.Png);

        /*
        // TODO - Remove above save when it works
        using (MemoryStream stream = new MemoryStream())
        {
            screenshot.Save(stream, System.Drawing.Imaging.ImageFormat.Png);
            return stream.ToArray();
        }
        */
    }

And then this after SendMessage(hCaptureWnd, WM_CAP_GET_FRAME, 0, 0);

ScreenshotWindow(new IntPtr(hCaptureWnd));

Answer 1

There is no such thing as WM_CAP_GET_FRAME. The correct name of the message is WM_CAP_GRAB_FRAME and it's described on MSDN.

What it does is:

The WM_CAP_GRAB_FRAME message retrieves and displays a single frame from the capture driver. After capture, overlay and preview are disabled. You can send this message explicitly or by using the capGrabFrame macro.

To obtain the actual data you need to use frame callback as described further on MSDN. The callback gets you the picture bytes, which you can write to file or use for whatever processing without need to transfer through clipboard.

...is the callback function used with streaming capture to optionally process a frame of captured video. The name capVideoStreamCallback is a placeholder for the application-supplied function name.

[And you have there a] ... Pointer to a VIDEOHDR structure containing information about the captured frame.

Again, this API is unlucky choice for video capture. Too old, too limited.

Answer 2

You have to send a different message, specifically WM_CAP_FILE_SAVEDIB, to save data in a file on disk. You then'll be able to load it in a Bitmap object for further processing (I'm not aware of any builtin cam-to-byte[] functionality).

[DllImport("user32", EntryPoint = "SendMessage")]
private static extern int SendMessage(
    int hWnd, uint Msg, int wParam, string strFileName);

private const int WM_USER = 0x0400;
private const int WM_CAP_START = WM_USER;
private const int WM_CAP_FILE_SAVEDIB = WM_CAP_START + 25;

---

//before
SendMessage(hCaptureWnd, WM_CAP_COPY, 0, 0);

//after
string tempFile = Server.MapPath("~/App_Data/tempCap.bmp");
SendMessage(hCaptureWnd, WM_CAP_FILE_SAVEDIB, 0, tempFile); //create tempfile
Bitmap bitmap = new Bitmap(tempFile); //read tempfile
using (MemoryStream stream = new MemoryStream())
{
    bitmap.Save(stream, ImageFormat.Bmp);
    return stream.ToArray();
}