I have a camera which has a library developed in C# and a client application written in C++ 6. I have created a C# COM wrapper to link the two systems together and it is working quite well.
In the C# COM wrapper I have a System.Drawing.Bitmap object that contains the current frame from the camera.
In the C# COM wrapper I have a function public void GetFrameHandle(ref IntPtr hBitmap, [MarshalAs(UnmanagedType.SysInt)] ref int width, [MarshalAs(UnmanagedType.SysInt)] ref int height) which basically gets the HBITMAP from the frame bitmap into C++
This seems to work somewhat, and I can see the image in C++ but it is all garbled due to the pixelformat not being correct.
How can I determine the pixelformat from the HBITMAP in C++ and then display the correct image in the picture control?
I have performed a lot of investigation and it seems as if I need to create a new BITMAP from the transferred HBITMAP and then create a new HBITMAP from that which will be the correct pixel format and then use that to populate the picture control.
I'm not very sure how to begin this process
C# COM server:
/// <summary>
/// Called when an image has been grabbed and is ready to process
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
public void StreamGrabber_ImageGrabbed(object sender, ImageGrabbedEventArgs e)
{
// process the image
try
{
// Acquire the image from the camera. Only show the latest image. The camera may acquire images faster than the images can be displayed.
// Get the grab result.
IGrabResult grabResult = e.GrabResult;
// Check if the image can be displayed.
if (grabResult.GrabSucceeded)
{
if (grabResult.IsValid)
{
// create a new bitmap object for holding the image data from the camera
// the bits and things need to be able to be set according to the c++ program's requirements.
System.Drawing.Bitmap bitmap = new System.Drawing.Bitmap(grabResult.Width, grabResult.Height, System.Drawing.Imaging.PixelFormat.Format32bppRgb);
// Lock the bits of the bitmap.
System.Drawing.Imaging.BitmapData bmpData = bitmap.LockBits(new System.Drawing.Rectangle(0, 0, bitmap.Width, bitmap.Height), System.Drawing.Imaging.ImageLockMode.ReadWrite, bitmap.PixelFormat);
// Place the pointer to the buffer of the bitmap.
converter.OutputPixelFormat = PixelType.BGR8packed;
IntPtr ptrBmp = bmpData.Scan0;
converter.Convert(ptrBmp, bmpData.Stride * bitmap.Height, grabResult); //Exception handling TODO
bitmap.UnlockBits(bmpData);
// Assign a temporary variable to dispose the bitmap after assigning the new bitmap to the display control.
System.Drawing.Bitmap bitmapOld = this.currentFrame;
// Provide the display control with the new bitmap. This action automatically updates the display.
// this may require some mutex to ensure that only entire frames are retrieved
this.currentFrame = bitmap;
// if the client window is set, output bitmap to it.
if (m_clientWindow != null)
m_clientWindow.DrawImage(currentFrame, new System.Drawing.Point(0, 0));
if (bitmapOld != null)
{
// Dispose the bitmap.
bitmapOld.Dispose();
}
// notify that a frame is ready to obtain
BroadcastFrameEvent();
}
}
else
{
BroadcastErrorEvent("StreamGrabber_ImageGrabbed", String.Format("Error: {0} {1}", grabResult.ErrorCode, grabResult.ErrorDescription));
}
}
catch (Exception exception)
{
BroadcastErrorEvent("StreamGrabber_ImageGrabbed", exception.ToString());
}
finally
{
// Dispose the grab result if needed for returning it to the grab loop.
e.DisposeGrabResultIfClone();
}
}
public void GetFrameHandle(ref IntPtr hBitmap, [MarshalAs(UnmanagedType.SysInt)] ref int width, [MarshalAs(UnmanagedType.SysInt)] ref int height)
{
if (this.currentFrame != null)
{
// System.Drawing.Imaging.BitmapData bmpData = null;
try
{
hBitmap = this.currentFrame.GetHbitmap();
width = currentFrame.Width;
height = currentFrame.Height;
}
catch (Exception ex)
{
BroadcastErrorEvent("GetFrame", ex.ToString());
}
}
}
public void SaveFrame(string filename)
{
try
{
if (m_debugMode == 1)
MessageBox.Show("Filename = " + filename, "GigE COM Wrapper Debug");
if (this.currentFrame != null)
this.currentFrame.Save(filename, System.Drawing.Imaging.ImageFormat.Bmp);
}
catch (Exception ex)
{
BroadcastErrorEvent("SaveFrame", ex.ToString());
}
}
C++ client:
// When a frame is ready to process
HRESULT CameraEventHandler::OnFrameReady()
{
HRESULT hr = S_OK;
// if (m_debug == 1)
// MessageBox(NULL, "Frame is ready", "COM event received", MB_OK);
// grab the frame from the COM wrapper and display it
long pOutHb;
if (pCamera != NULL)
{
BSTR bsFilename = SysAllocString(L"frame.bmp");
hr = pCamera->SaveFrame(bsFilename);
if (!SUCCEEDED(hr))
{
MessageBox(NULL, "COM Error", "Fail", MB_OK);
return hr;
}
hr = pCamera->GetFrameHandle(&pOutHb, &width, &height);
if (SUCCEEDED(hr))
{
BITMAP bm;
HBITMAP hbFrameFromCOM;
hbFrameFromCOM = (HBITMAP)pOutHb;
// get the bitmap from the HBITMAP
GetObject(hbFrameFromCOM, sizeof(BITMAP), &bm);
LONG size = bm.bmWidthBytes * bm.bmHeight;
//create the bitmap?
// copy data across?
// create a new HBITMAP (hb)
if (pDialog != NULL)
{
// post the message
// this signals the dialog to update the picture control with the HBITMAP
pDialog->SendMessage(WM_REFRESH_BITMAP);
}
}
else
if (m_debug == 1)
MessageBox(NULL, "Get bitmap handle failed", "Fail", MB_OK);
}
return hr;
}
Unsure how to proceed with this.
Interestingly, the frame.bmp that I'm saving from the C# code is also garbled. I think the two issues are related but I can't join the dots here.
Thanks for any help with it.
Thanks for the help I was able to get it working.
The code above was pretty much correct, except the pixelFormats needed to match in the C# COM wrapper between the camera and the bitmap that is used as the internal frame buffer.
The grayscale image output after the frame became stable was caused because I was setting the camera mode to grayscale in the c++ client. I changed it to YUV and it was all good.
There are a lot of places where modes can be set!
I didn't need to worry about changing anything in the C++ client. All that is required is to throw the HBITMAP sent by the COM wrapper at the dialog's picture control to display it.
Cheers.