使用以下代碼打開一張帶有alpha通道的png圖片，但是無法繪制出透明效果，為什么呢？
HRESULT hr;
IWICBitmapDecoder *pDecoder = NULL;
IWICBitmapFrameDecode *pSource = NULL;
IWICStream *pStream = NULL;
IWICFormatConverter *pConverter = NULL;
IWICBitmapScaler *pScaler = NULL;
hr = pIWICFactory->CreateDecoderFromFilename(
uri,
NULL,
GENERIC_READ,
WICDecodeMetadataCacheOnLoad,
&pDecoder
);
if (SUCCEEDED(hr))
{
// Create the initial frame.
hr = pDecoder->GetFrame(0, &pSource);
}
if (SUCCEEDED(hr))
{
hr = pIWICFactory->CreateFormatConverter(&pConverter);
}
UINT originalWidth, originalHeight;
hr = pSource->GetSize(&originalWidth, &originalHeight);
if (SUCCEEDED(hr))
{
hr = pIWICFactory->CreateBitmapScaler(&pScaler);
if (SUCCEEDED(hr))
{
hr = pScaler->Initialize(
pSource,
originalWidth,
originalHeight,
WICBitmapInterpolationModeCubic
);
}
if (SUCCEEDED(hr))
{
hr = pConverter->Initialize(
pScaler,
GUID_WICPixelFormat32bppPRGBA,
WICBitmapDitherTypeNone,
NULL,
0.f,
WICBitmapPaletteTypeMedianCut
);
}
}
if (SUCCEEDED(hr))
{
// Create a Direct2D bitmap from the WIC bitmap.
hr = pRenderTarget->CreateBitmapFromWicBitmap(pConverter, NULL, ppBitmap);
}
D2D1::Matrix3x2F a = D2D1::Matrix3x2F::Scale(2, 2, D2D1::Point2F(250, 250));
g_pRenderTarget->SetTransform(a);
g_pRenderTarget->DrawBitmap(pBitmap,
D2D1::RectF(200.f, 200.f, 300.f, 300.f), 1.0f,
D2D1_BITMAP_INTERPOLATION_MODE_LINEAR,
D2D1::RectF(00, 00, 200.f, 200.f)
);
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