Export (0) Print
Expand All

IWICStream::InitializeFromFilename method

Initializes a stream from a particular file.

Syntax


HRESULT InitializeFromFilename(
  [in]  LPCWSTR wzFileName,
  [in]  DWORD dwDesiredAccess
);

Parameters

wzFileName [in]

Type: LPCWSTR

The file used to initialize the stream.

dwDesiredAccess [in]

Type: DWORD

The desired file access mode.

ValueMeaning
GENERIC_READ

Read access.

GENERIC_WRITE

Write access.

 

Return value

Type: HRESULT

If this method succeeds, it returns S_OK. Otherwise, it returns an HRESULT error code.

Remarks

The IWICStream interface methods do not enable you to provide a file sharing option. To create a shared file stream for an image, use the SHCreateStreamOnFileEx function. This stream can then be used to create an IWICBitmapDecoder using the CreateDecoderFromStream method.

Examples

This example demonstrates the use of the InitializeFromFilename to create an image decoder.


    IWICImagingFactory *pFactory = NULL;
    IWICStream *pStream = NULL;
    IWICBitmapDecoder *pDecoder = NULL;

    HRESULT hr = CoCreateInstance(
                    CLSID_WICImagingFactory,
                    NULL,
                    CLSCTX_INPROC_SERVER,
                    IID_PPV_ARGS(&pFactory));

    // Create the stream.
    if (SUCCEEDED(hr))
    {
        hr = pFactory->CreateStream(&pStream);
    }

    // Initialize the stream from a specific file.
    if (SUCCEEDED(hr))
    {
        hr = pStream->InitializeFromFilename(L"test.jpg", GENERIC_READ);
    }    

    // Create a JPEG decoder.
    // Since the stream is created from the JPEG file, an explicit JPEG decoder
    // can be created using the generic IWICImagingFactory::CreateDecoder method.
    // However, use IWICImagingFactory::CreateDecoderFromStream method to auto
    // detect the stream and instantiate the appropriate codec.  
    if (SUCCEEDED(hr))
    {        
        hr = pFactory->CreateDecoder(
                GUID_ContainerFormatJpeg,   // Explicitly create a JPEG decoder.
                NULL,                       // No preferred vendor.
                &pDecoder);                 // Pointer to the decoder.
    } 

    // Initialize the decoder
    if (SUCCEEDED(hr))
    {
        hr = pDecoder->Initialize(
                pStream,                            // The stream to use.
                WICDecodeMetadataCacheOnDemand);    // Decode metadata when needed.
    } 

    // Process image frame.
    if (SUCCEEDED(hr))
    {
        UINT cFrames = 0;

        hr = pDecoder->GetFrameCount(&cFrames);

        if (SUCCEEDED(hr) && (cFrames > 0))
        {
            UINT width = 0, height = 0;        
            IWICBitmapFrameDecode *pBitmapFrame = NULL;

            hr = pDecoder->GetFrame(0, &pBitmapFrame);

            if (SUCCEEDED(hr))
            {
                // Do something with the frame here.
            }

            if (pBitmapFrame)
            {
                pBitmapFrame->Release();
            }
        }
    } 

    if (pStream)
    {
        pStream->Release();
    }

    if (pFactory)
    {
        pFactory->Release();
    }

    if (pDecoder)
    {
        pDecoder->Release();
    }

Requirements

Minimum supported client

Windows XP with SP2, Windows Vista [desktop apps | Windows Store apps]

Minimum supported server

Windows Server 2008 [desktop apps | Windows Store apps]

Header

Wincodec.h

IDL

Wincodec.idl

Library

Windowscodecs.lib

DLL

Windowscodecs.dll

 

 

Community Additions

ADD
Show:
© 2014 Microsoft