Direct2D 加载和绘制位图答案

【问题标题】：Direct2D Loading and Drawing BitmapDirect2D 加载和绘制位图
【发布时间】：2016-06-11 00:25:10
【问题描述】：

我正在尝试在屏幕上绘制位图；调用从文件加载位图的代码有效，但实际绘图部分似乎导致某些程序崩溃。

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

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导致程序崩溃的部分：

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();

【问题讨论】：

标签： c++ bitmap render draw direct2d

【解决方案1】：

发现这个问题：我要绘制的位图仍然是 NULL。

这可以通过从LoadBitmapFromFile 中删除ID2D1Bitmap **ppBitmap 参数来解决，并且只需使用指向&pBitmap 的指针来获取对方法中位图的任何引用。

这样，pBitmap 被操纵并且不会保持为 NULL。

【讨论】：