使用 WIC 阅读剪贴板

Question

我正在尝试编写一个函数来读取使用 Windows 映像组件复制到剪贴板的图像。目前，我的代码基于我加载资源的方式，但经过修改以使用剪贴板。初始化流的一切工作正常，但是一旦我尝试使用CreateDecoderFromeStream，它就会失败。我试过从很多地方复制图像，但无济于事。 WIC无法读取的复制图像格式有什么不同吗？

下面是我的代码...

创建一个内存对象以从剪贴板中读取

COMStreamSPtr WIC::createStreamFromClipboard() {
    IStream* ipStream = NULL;
    COMStreamSPtr stream = nullptr;
    CoInitialize(nullptr);
    if (!IsClipboardFormatAvailable(CF_BITMAP) && !IsClipboardFormatAvailable(CF_DIB) && !IsClipboardFormatAvailable(CF_DIBV5))
        goto Return;

    if (!OpenClipboard(NULL))
        goto Return;

    // Load the clipboard
    HGLOBAL hMem = GetClipboardData(CF_BITMAP);
    if (hMem == NULL || hMem == INVALID_HANDLE_VALUE)
        hMem = GetClipboardData(CF_DIB);
    if (hMem == NULL || hMem == INVALID_HANDLE_VALUE)
        hMem = GetClipboardData(CF_DIBV5);
    if (hMem == NULL || hMem == INVALID_HANDLE_VALUE)
        goto CloseClipboard;

    // Lock the clipboard, getting a pointer to its data
    LPVOID pvSourceClipboardData = GlobalLock(hMem);
    if (pvSourceClipboardData == NULL)
        goto CloseClipboard;

    // Read the clipboard data size
    DWORD dwClipboardSize = GlobalSize(hMem);
    if (dwClipboardSize == 0)
        goto GlobalUnlock;

    // Allocate memory to hold the clipboard data
    HGLOBAL hgblClipboardData = GlobalAlloc(GMEM_MOVEABLE, dwClipboardSize);
    if (hgblClipboardData == NULL)
        goto GlobalUnlock;

    // Get a pointer to the allocated memory
    LPVOID pvClipboardData = GlobalLock(hgblClipboardData);
    if (pvClipboardData == NULL)
        goto FreeData;

    // Copy the data from the clipboard to the new memory block
    CopyMemory(pvClipboardData, pvSourceClipboardData, dwClipboardSize);
    GlobalUnlock(hgblClipboardData);

    // Create a stream on the HGLOBAL containing the data
    if (SUCCEEDED(CreateStreamOnHGlobal(hgblClipboardData, TRUE, &ipStream))) {
        stream = std::make_shared<COMStream>(ipStream);
        goto CloseClipboard;
    }

FreeData:
    // Couldn't create stream; free the memory
    GlobalFree(hgblClipboardData);
GlobalUnlock:
    // Unlock the clipboard data
    GlobalUnlock(hMem);
CloseClipboard:
    // Close the clipboard
    CloseClipboard();
Return:
    // No need to unlock or free the resource
    CoUninitialize(); // CoInialize is called by my COMObjects in the constructor so this is just decrementing the count.
    return stream;
}

在代码的其他地方使用返回的流。

WICBitmapDecoderSPtr WIC::createDecoderFromStream(COMStreamSPtr stream) {
    if (isCOMObjectNull(stream))
        return nullptr;

    IWICImagingFactory* ipFactory = NULL;
    IWICBitmapDecoder* ipDecoder = NULL;
    WICBitmapDecoderSPtr decoder = nullptr;

    // Create the factory
    if (FAILED(CoCreateInstance(CLSID_WICImagingFactory, NULL, CLSCTX_INPROC_SERVER, IID_PPV_ARGS(&ipFactory))))
        goto Return;

    // Create the decoder
    if (FAILED(ipFactory->CreateDecoderFromStream(stream->ipObject, NULL, WICDecodeMetadataCacheOnDemand, &ipDecoder)))
        goto ReleaseFactory; // FAILS HERE

    decoder = std::make_shared<WICBitmapDecoder>(ipDecoder);
ReleaseFactory:
    ipFactory->Release();
Return:
    return decoder;
}

Answer 1

我终于想出了如何做到这一点。我所做的是我使用了IWICImagingFactory 的CreateBitmapFromHBITMAP 函数。由于从剪贴板读取HBITMAP 工作很简单，因此解决方案变得非常简单。

IWICBitmapSource* WIC::readSourceFromClipboard() {
    IWICBitmapSource* ipSource = NULL;
    if (Clipboard::containsFormat(CF_BITMAP)) {
        if (OpenClipboard(NULL)) {
            HBITMAP hBitmap = (HBITMAP)GetClipboardData(CF_BITMAP);
            ipSource = createSourceFromHBitmap(hBitmap);
            CloseClipboard();
        }
    }
    return ipSource;
}

IWICBitmapSource* WIC::createSourceFromHBitmap(HBITMAP hBitmap) {
    if (hBitmap == NULL)
        return NULL;

    IWICImagingFactory* ipFactory = NULL;
    IWICBitmap* ipBitmap = NULL;

    CoInitialize(NULL);

    // Create the factory
    if (FAILED(CoCreateInstance(CLSID_WICImagingFactory, NULL, CLSCTX_INPROC_SERVER, IID_PPV_ARGS(&ipFactory))))
        goto Return;

    // Create the bitmap
    if (FAILED(ipFactory->CreateBitmapFromHBITMAP(hBitmap, NULL, WICBitmapIgnoreAlpha, &ipBitmap)))
        goto ReleaseFactory;

ReleaseFactory:
    ipFactory->Release();
Return:
    CoUninitialize();
    return ipBitmap;
}