How to Load a Bitmap from a File

Direct2D uses the Windows Imaging Component (WIC) to load bitmaps. To load a bitmap from a file, first use WIC objects to load the image and to convert it to a Direct2D-compatible format, then use the CreateBitmapFromWicBitmap method to create an ID2D1Bitmap.

  1. Create an IWICBitmapDecoder by using the IWICImagingFactory::CreateDecoderFromFileName method.

    
    HRESULT DemoApp::LoadBitmapFromFile(
        ID2D1RenderTarget *pRenderTarget,
        IWICImagingFactory *pIWICFactory,
        PCWSTR uri,
        UINT destinationWidth,
        UINT destinationHeight,
        ID2D1Bitmap **ppBitmap
        )
    {
        IWICBitmapDecoder *pDecoder = NULL;
        IWICBitmapFrameDecode *pSource = NULL;
        IWICStream *pStream = NULL;
        IWICFormatConverter *pConverter = NULL;
        IWICBitmapScaler *pScaler = NULL;
    
        HRESULT hr = pIWICFactory->CreateDecoderFromFilename(
            uri,
            NULL,
            GENERIC_READ,
            WICDecodeMetadataCacheOnLoad,
            &pDecoder
            );
            
    
    
    
  2. Retrieve a frame from the image and store the frame in an IWICBitmapFrameDecode object.

    
        if (SUCCEEDED(hr))
        {
            // Create the initial frame.
            hr = pDecoder->GetFrame(0, &pSource);
        }
    
    
    
  3. The bitmap must be converted to a format that Direct2D can use, so convert the image's pixel format to 32bppPBGRA. (For a list of supported formats, see Pixel Formats and Alpha Modes.). Call the IWICImagingFactory::CreateFormatConverter method to create an IWICFormatConverter object, then call the IWICFormatConverter object's Initialize method to perform the conversion.
    
        if (SUCCEEDED(hr))
        {
    
            // Convert the image format to 32bppPBGRA
            // (DXGI_FORMAT_B8G8R8A8_UNORM + D2D1_ALPHA_MODE_PREMULTIPLIED).
            hr = pIWICFactory->CreateFormatConverter(&pConverter);
    
        }
     
     
        if (SUCCEEDED(hr))
        {
    
    
    
    
            hr = pConverter->Initialize(
                pSource,
                GUID_WICPixelFormat32bppPBGRA,
                WICBitmapDitherTypeNone,
                NULL,
                0.f,
                WICBitmapPaletteTypeMedianCut
                );
    
    
    
    
        }
    
    
    
  4. Call the CreateBitmapFromWicBitmap method to create an ID2D1Bitmap object that can be drawn by a render target and used with other Direct2D objects.
    
        if (SUCCEEDED(hr))
        {
        
            // Create a Direct2D bitmap from the WIC bitmap.
            hr = pRenderTarget->CreateBitmapFromWicBitmap(
                pConverter,
                NULL,
                ppBitmap
                );
        }
    
        SafeRelease(&pDecoder);
        SafeRelease(&pSource);
        SafeRelease(&pStream);
        SafeRelease(&pConverter);
        SafeRelease(&pScaler);
    
        return hr;
    }
    
    
    

Some code has been omitted from this example. For the complete code, see the Simple Direct2D Application Sample.

Related topics

Simple Direct2D Application Sample
ID2D1Bitmap
CreateBitmapFromWicBitmap
How to Load a Bitmap from a Resource

 

 

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