如何将 ID2D1Bitmap 保存为 PNG 文件 [英] How to save ID2D1Bitmap to PNG file

问题描述

我在尝试将 ID2D1Bitmap(从 ID2D1HwndRenderTarget 创建的)保存到 PNG 文件时遇到问题.输出图像只是空白的白色.从函数调用 EndDraw() 返回的 HRESULT 为 -2003238894.

I faced a problem when trying to save ID2D1Bitmap (that created from ID2D1HwndRenderTarget) to PNG File. The output image is just empty with white color. HRESULT returned from function call EndDraw() is -2003238894.

感谢您的帮助.

这是我的代码:

HRESULT CImageUtil::SaveBitmapToFile(PCWSTR uri,ID2D1Bitmap* pBitmap,ID2D1RenderTarget* pRenderTarget)
{

HRESULT hr = S_OK;

ID2D1Factory *pD2DFactory = NULL;
IWICBitmap *pWICBitmap = NULL;
ID2D1RenderTarget *pRT = NULL;
IWICBitmapEncoder *pEncoder = NULL;
IWICBitmapFrameEncode *pFrameEncode = NULL;
IWICStream *pStream = NULL;

if (SUCCEEDED(hr))
{
    hr = D2D1CreateFactory(D2D1_FACTORY_TYPE_SINGLE_THREADED, &pD2DFactory);
}

//
// Create IWICBitmap and RT
//

UINT sc_bitmapWidth = pBitmap->GetSize().width;
UINT sc_bitmapHeight = pBitmap->GetSize().height;

if (SUCCEEDED(hr))
{
    hr = m_pWICFactory->CreateBitmap(
        sc_bitmapWidth,
        sc_bitmapHeight,
    GUID_WICPixelFormat32bppPBGRA,
        WICBitmapCacheOnLoad,
        &pWICBitmap
        );
}

if (SUCCEEDED(hr))
{
    D2D1_RENDER_TARGET_PROPERTIES rtProps = D2D1::RenderTargetProperties();
    rtProps.pixelFormat = D2D1::PixelFormat(DXGI_FORMAT_B8G8R8A8_UNORM, D2D1_ALPHA_MODE_PREMULTIPLIED);
    rtProps.type = D2D1_RENDER_TARGET_TYPE_DEFAULT;
    rtProps.usage = D2D1_RENDER_TARGET_USAGE_NONE;

    hr = pD2DFactory->CreateWicBitmapRenderTarget(
        pWICBitmap,
    rtProps,
        &pRT
        );
}

if (SUCCEEDED(hr))
{
    //
    // Render into the bitmap
    //
    pRT->BeginDraw();

pRT->Clear(D2D1::ColorF(D2D1::ColorF::White));


pRT->DrawBitmap(pBitmap);

    pRT->EndDraw();
}
if (SUCCEEDED(hr))
{

    //
    // Save image to file
    //
    hr = m_pWICFactory->CreateStream(&pStream);
}

WICPixelFormatGUID format = GUID_WICPixelFormat32bppPBGRA;
if (SUCCEEDED(hr))
{

    hr = pStream->InitializeFromFilename(uri, GENERIC_WRITE);
}
if (SUCCEEDED(hr))
{
    hr = m_pWICFactory->CreateEncoder(GUID_ContainerFormatPng, NULL, &pEncoder);
}
if (SUCCEEDED(hr))
{
    hr = pEncoder->Initialize(pStream, WICBitmapEncoderNoCache);
}
if (SUCCEEDED(hr))
{
    hr = pEncoder->CreateNewFrame(&pFrameEncode, NULL);
}
if (SUCCEEDED(hr))
{
    hr = pFrameEncode->Initialize(NULL);
}

if (SUCCEEDED(hr))
{
    hr = pFrameEncode->SetSize(sc_bitmapWidth, sc_bitmapHeight);
}
if (SUCCEEDED(hr))
{
    hr = pFrameEncode->SetPixelFormat(&format);
}
if (SUCCEEDED(hr))
{
    hr = pFrameEncode->WriteSource(pWICBitmap, NULL);
}
if (SUCCEEDED(hr))
{
    hr = pFrameEncode->Commit();
}
if (SUCCEEDED(hr))
{
    hr = pEncoder->Commit();
}

SafeRelease(&pD2DFactory);
SafeRelease(&pWICBitmap);
SafeRelease(&pRT);
SafeRelease(&pEncoder);
SafeRelease(&pFrameEncode);
SafeRelease(&pStream);

return hr;
}

推荐答案

你怎么知道你是否有错误，因为你只是吞下错误并继续而不是记录它们的来源?你得到一个非零的 hresult，所以首先通过在每个函数调用之后添加 printf 或 fprintf 来确定它来自哪个函数.而且你在这个街区有一个明显的遗漏:

How would you even know if you had an error, since you just swallow errors and continue instead of logging where they came from? You get a non-zero hresult, so first figure out which function it comes from by adding a printf or fprintf after every single function call. And you have a glaring omission in the block:

if (SUCCEEDED(hr))
{
    //
    // Render into the bitmap
    //
    pRT->BeginDraw();

pRT->Clear(D2D1::ColorF(D2D1::ColorF::White));


pRT->DrawBitmap(pBitmap);

    pRT->EndDraw();
}
if (SUCCEEDED(hr))

您不必费心将 hr 分配到那里的任何地方，因此您甚至不知道其中是否有任何错误.显然，Clear() 和最终的 png 写入工作正常，因为你得到了一个好的文件，所以它是 DrawBitmap 或失败的位图创建调用之一.

You don't bother to assign hr anywhere in there, so you wouldn't even know if any of them are erroring out. Obviously, Clear() and the final png writing work fine, since you get a good file, so it's DrawBitmap or one of the bitmap creation calls that are failing.

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