Cannot create IWICBitmap from ID2D1Bitmap

I am reading pixel data from a buffer which is loaded by a camera.  I am able to successfully create an ID2D1Bitmap from this pixel data.  However, I cannot seem to create an IWICBitmap from the ID2D1Bitmap.  Here is the code I am using.  This function "ImgFromPixelArray" is called when a camera frame has been loaded into the pixel buffer.  The pass parameters are:

W = Width of image
H = Height of image
Stride = Stride of image
PF = pixelformat
PixelArray = address of pixel buffer

Elsewhere in the app, I (successfully) create a D2D1Factory (called mpD2DFact) which in turn creates the HwndRenderTarget used below, called mpRTarg.  I also create IWICImagingFactory elsewhere in the class called mpWICFactory, which is also used below.

BOOL CViewerPlus::ImgFromPixelArray(DWORD W, DWORD H, int Stride, UINT PF, char* PixelArray)
{
    BYTE* Addr = (BYTE*)PixelArray;

    //Create a D2D1_SIZE_U struct using the size of the bitmap.
    D2D1_SIZE_U Size = D2D1::SizeU(W, H);

    //Release the pointer to the ID2D1Bitmap and NULL it out if it has already been defined.
    if (mpImgD2D != NULL)
      mpImgD2D->Release();
    mpImgD2D = NULL;

     //Use the render target to create the ID2D1Bitmap called mpImgD2D.
    HRESULT hr = mpRTarg->CreateBitmap(Size, (void*)PixelArray, Stride, mBmpProp, &mpImgD2D);
    //The above returns hr = S_OK

    //Now create a temporary IWICBitmap object.  At the moment, this temporary bitmap  
    //will be empty, but is created in the right size and format for us to use.
    IWICBitmap *WICBmp;
    D2D1_SIZE_U ImgSize = mpImgD2D->GetPixelSize();
    hr = mpWICFactory->CreateBitmap(ImgSize.width, ImgSize.height, GUID_WICPixelFormat32bppBGR, WICBitmapCacheOnLoad, &WICBmp);
    //The above returns hr = S_OK

    //Now we create a Direct2D render target based on our temporary WIC bitmap.
    ID2D1RenderTarget *WICRTarg;
    hr = mpD2DFact->CreateWicBitmapRenderTarget(WICBmp, D2D1::RenderTargetProperties(), &WICRTarg);
    //The above returns hr = S_OK

    //Now draw D2D1Bitmap image using the WIC render target, this should write the image
    //into the WICBitmap;
    WICRTarg->BeginDraw();
    WICRTarg->DrawBitmap(mpImgD2D);
    hr = WICRTarg->EndDraw();
    //The above returns hr = 0x88990015

    return 0;
}

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The very last step is the one that fails, and I believe that the returned error 0x88990015 indicates "The resource was realized on the wrong render target."  

If I change the code around so that the ID2D1Bitmap (mpImgD2D) is created by the WICRenderTarget (WICRTarg) rather than the HwndRenderTarget (mpRTarg), then the code works - I can draw the ID2D1Bitmap (mpImgD2D) on the IWICBitmap (WICBmp).  However, doing so prevents me from drawing mpImgD2D on the screen elsewhere in the app using the HwndRenderTarget.

So the problem is fundamentally this:  If you create an ID2D1Bitmap with a HwndRenderTarget, you can't draw that Bitmap on an IWICBitmap using a different render target (in this case, the WICBitmapRenderTarget).  And conversely, if you create an ID2D1Bitmap with a WICBitmapRenderTarget, then you can't draw it on the screen using a HwndRenderTarget.  SO, if you have an image, and need to go back and forth between an ID2D1Bitmap format (for screen display) and an IWICBitmap format (for reading and writing to disk), how do you do it?

Thank you very much.