直接2D 加载和绘制位图

Direct2D Loading and Drawing Bitmap

本文关键字:绘制 位图 加载 2D 直接      更新时间:2023-10-16

我正在尝试将位图绘制到屏幕上;调用以从文件加载位图的代码有效,但似乎实际的绘图部分导致一些程序崩溃。

我遵循了MSDN的教程,但我所做的唯一更改是使用ID2D1RenderTarget,而是使用ID2D1DCRenderTarget。

下面是有效的 Load 方法:

HRESULT LoadBitmapFromFile(
    ID2D1DCRenderTarget *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
        );

    if (SUCCEEDED(hr))
    {
        // Create the initial frame.
        hr = pDecoder->GetFrame(0, &pSource);
    }
    if (SUCCEEDED(hr))
    {
        // Convert the image format to 32bppPBGRA
        // (DXGI_FORMAT_B8G8R8A8_UNORM + D2D1_ALPHA_MODE_PREMULTIPLIED).
        hr = pIWICFactory->CreateFormatConverter(&pConverter);
    }

    if (SUCCEEDED(hr))
    {
        // If a new width or height was specified, create an
        // IWICBitmapScaler and use it to resize the image.
        if (destinationWidth != 0 || destinationHeight != 0)
        {
            UINT originalWidth, originalHeight;
            hr = pSource->GetSize(&originalWidth, &originalHeight);
            if (SUCCEEDED(hr))
            {
                if (destinationWidth == 0)
                {
                    FLOAT scalar = static_cast<FLOAT>(destinationHeight) / static_cast<FLOAT>(originalHeight);
                    destinationWidth = static_cast<UINT>(scalar * static_cast<FLOAT>(originalWidth));
                }
                else if (destinationHeight == 0)
                {
                    FLOAT scalar = static_cast<FLOAT>(destinationWidth) / static_cast<FLOAT>(originalWidth);
                    destinationHeight = static_cast<UINT>(scalar * static_cast<FLOAT>(originalHeight));
                }
                hr = pIWICFactory->CreateBitmapScaler(&pScaler);
                if (SUCCEEDED(hr))
                {
                    hr = pScaler->Initialize(
                        pSource,
                        destinationWidth,
                        destinationHeight,
                        WICBitmapInterpolationModeCubic
                        );
                }
                if (SUCCEEDED(hr))
                {
                    hr = pConverter->Initialize(
                        pScaler,
                        GUID_WICPixelFormat32bppPBGRA,
                        WICBitmapDitherTypeNone,
                        NULL,
                        0.f,
                        WICBitmapPaletteTypeMedianCut
                        );
                }
            }
        }
        else // Don't scale the image.
        {
            hr = pConverter->Initialize(
                pSource,
                GUID_WICPixelFormat32bppPBGRA,
                WICBitmapDitherTypeNone,
                NULL,
                0.f,
                WICBitmapPaletteTypeMedianCut
                );
        }
    }
    if (SUCCEEDED(hr))
    {
        // Create a Direct2D bitmap from the WIC bitmap.
        hr = pRenderTarget->CreateBitmapFromWicBitmap(
            pConverter,
            NULL,
            ppBitmap
            );
    }
    if (pDecoder) pDecoder->Release();
    if (pSource) pSource->Release();
    if (pStream) pStream->Release();
    if (pScaler) pScaler->Release();
    return hr;
}

在渲染目标的 BeginDraw() 和 EndDraw() 之间,我有以下代码来绘制位图。这是我尝试运行程序时使程序崩溃的部分:

d2dg->pRT->BeginDraw(); 
// Create a WIC Factory
HRESULT hr = CoCreateInstance(
CLSID_WICImagingFactory,
NULL,
CLSCTX_INPROC_SERVER,
IID_IWICImagingFactory,
(LPVOID*)&wicFactory);
hr = LoadBitmapFromFile(d2dg->pRT, wicFactory, L"image1.png", 400, 400, &pBitmap); 
D2D1_SIZE_F size = pBitmap->GetSize();
D2D1_POINT_2F upperLeftCorner = D2D1::Point2F(100.f, 10.f);
// Draw a bitmap.
d2dg->pRT->DrawBitmap(
    pBitmap,
    D2D1::RectF(
    upperLeftCorner.x,
    upperLeftCorner.y,
    upperLeftCorner.x + size.width,
    upperLeftCorner.y + size.height)
    );
d2dg->pRT->EndDraw();

发现问题:我想绘制的位图仍然是 NULL。

可以通过从LoadBitmapFromFile中删除 ID2D1Bitmap **ppBitmap 参数并仅使用指向&pBitmap的指针来修复对方法中位图的任何引用。

这样,pBitmap就会纵,并且不会保持 NULL。