How to save ID2D1Bitmap to PNG file - image

Question

I faced a problem when trying to save ID2D1Bitmap (that created from ID2D1HwndRenderTarget) to PNG File. The output image is just empty with white color. HRESULT returned from function call EndDraw() is -2003238894.
Thanks for any help.
Here is my code:
HRESULT CImageUtil::SaveBitmapToFile(PCWSTR uri,ID2D1Bitmap* pBitmap,ID2D1RenderTarget* pRenderTarget)
{
HRESULT hr = S_OK;
ID2D1Factory *pD2DFactory = NULL;
IWICBitmap *pWICBitmap = NULL;
ID2D1RenderTarget *pRT = NULL;
IWICBitmapEncoder *pEncoder = NULL;
IWICBitmapFrameEncode *pFrameEncode = NULL;
IWICStream *pStream = NULL;
if (SUCCEEDED(hr))
{
hr = D2D1CreateFactory(D2D1_FACTORY_TYPE_SINGLE_THREADED, &pD2DFactory);
}
//
// Create IWICBitmap and RT
//
UINT sc_bitmapWidth = pBitmap->GetSize().width;
UINT sc_bitmapHeight = pBitmap->GetSize().height;
if (SUCCEEDED(hr))
{
hr = m_pWICFactory->CreateBitmap(
sc_bitmapWidth,
sc_bitmapHeight,
GUID_WICPixelFormat32bppPBGRA,
WICBitmapCacheOnLoad,
&pWICBitmap
);
}
if (SUCCEEDED(hr))
{
D2D1_RENDER_TARGET_PROPERTIES rtProps = D2D1::RenderTargetProperties();
rtProps.pixelFormat = D2D1::PixelFormat(DXGI_FORMAT_B8G8R8A8_UNORM, D2D1_ALPHA_MODE_PREMULTIPLIED);
rtProps.type = D2D1_RENDER_TARGET_TYPE_DEFAULT;
rtProps.usage = D2D1_RENDER_TARGET_USAGE_NONE;
hr = pD2DFactory->CreateWicBitmapRenderTarget(
pWICBitmap,
rtProps,
&pRT
);
}
if (SUCCEEDED(hr))
{
//
// Render into the bitmap
//
pRT->BeginDraw();
pRT->Clear(D2D1::ColorF(D2D1::ColorF::White));
pRT->DrawBitmap(pBitmap);
pRT->EndDraw();
}
if (SUCCEEDED(hr))
{
//
// Save image to file
//
hr = m_pWICFactory->CreateStream(&pStream);
}
WICPixelFormatGUID format = GUID_WICPixelFormat32bppPBGRA;
if (SUCCEEDED(hr))
{
hr = pStream->InitializeFromFilename(uri, GENERIC_WRITE);
}
if (SUCCEEDED(hr))
{
hr = m_pWICFactory->CreateEncoder(GUID_ContainerFormatPng, NULL, &pEncoder);
}
if (SUCCEEDED(hr))
{
hr = pEncoder->Initialize(pStream, WICBitmapEncoderNoCache);
}
if (SUCCEEDED(hr))
{
hr = pEncoder->CreateNewFrame(&pFrameEncode, NULL);
}
if (SUCCEEDED(hr))
{
hr = pFrameEncode->Initialize(NULL);
}
if (SUCCEEDED(hr))
{
hr = pFrameEncode->SetSize(sc_bitmapWidth, sc_bitmapHeight);
}
if (SUCCEEDED(hr))
{
hr = pFrameEncode->SetPixelFormat(&format);
}
if (SUCCEEDED(hr))
{
hr = pFrameEncode->WriteSource(pWICBitmap, NULL);
}
if (SUCCEEDED(hr))
{
hr = pFrameEncode->Commit();
}
if (SUCCEEDED(hr))
{
hr = pEncoder->Commit();
}
SafeRelease(&pD2DFactory);
SafeRelease(&pWICBitmap);
SafeRelease(&pRT);
SafeRelease(&pEncoder);
SafeRelease(&pFrameEncode);
SafeRelease(&pStream);
return hr;
}

Answer 1

How would you even know if you had an error, since you just swallow errors and continue instead of logging where they came from? You get a non-zero hresult, so first figure out which function it comes from by adding a printf or fprintf after every single function call. And you have a glaring omission in the block:
if (SUCCEEDED(hr))
{
//
// Render into the bitmap
//
pRT->BeginDraw();
pRT->Clear(D2D1::ColorF(D2D1::ColorF::White));
pRT->DrawBitmap(pBitmap);
pRT->EndDraw();
}
if (SUCCEEDED(hr))
You don't bother to assign hr anywhere in there, so you wouldn't even know if any of them are erroring out. Obviously, Clear() and the final png writing work fine, since you get a good file, so it's DrawBitmap or one of the bitmap creation calls that are failing.