GDI +有标准的图像编码器CLSID吗？ [英] Does GDI+ have standard image encoder CLSIDs?

问题描述

GDI + Image ::保存 方法需要一个CLSID参数来指定要使用的编码器。文档指向一些示例代码，用于获取与编码器相关联的特定的MIME类型，例如image / jpeg或image / png。然而，我只是为了支持一个单行调试助手，我把中间结果保存到磁盘上，我想要复制一个半页函数。

The GDI+ Image::Save method requires a CLSID parameter to specify the encoder to use. The documentation points to some sample code for getting the encoder associated with a particular MIME type, such as image/jpeg or image/png. However I'm balking at the thought of copying a half-page function just to support a 1-line debugging aid where I save an intermediate result out to disk.

Shouldn有标准编码器的标准CLSID列表吗？我在哪里可以找到这样的列表？我无法通过搜索Microsoft的包含文件找到一个。

Shouldn't there be a list of standard CLSIDs for the standard encoders? Where would I find such a list? I haven't been able to find one by searching Microsoft's include files.

推荐答案

没有一个。我认为他们打算的编解码器列表是可扩展的，并支持插件，但从来没有得到它。鉴于他们在相当长的时间内没有对GDI +进行任何更改，他们很可能不会很快。您可以根据Gdiplus :: GetImageEncoders的枚举生成自己的硬编码列表。

There isn't one. I think they intended the codec list to be extensible and support plugins, but never got around to it. Given that they haven't made any changes to GDI+ in quite some time, they likely won't anytime soon. You could probably get away with generating your own hard coded list based on an enumeration of Gdiplus::GetImageEncoders.

这是：

image/bmp  : {557cf400-1a04-11d3-9a73-0000f81ef32e}
image/jpeg : {557cf401-1a04-11d3-9a73-0000f81ef32e} 
image/gif  : {557cf402-1a04-11d3-9a73-0000f81ef32e} 
image/tiff : {557cf405-1a04-11d3-9a73-0000f81ef32e}
image/png  : {557cf406-1a04-11d3-9a73-0000f81ef32e}

这里是我常规剪切和粘贴项目之间的函数以获取CLSID的函数编码器。您可以将其修改为表查找。

Here's the function I routinely cut&paste between projects for getting at the CLSID of the encoder. You could modify it to be a table lookup.

HRESULT GetGdiplusEncoderClsid(__in LPCWSTR pwszFormat, __out GUID *pGUID)
{
    HRESULT hr = E_FAIL;
    UINT  nEncoders = 0;          // number of image encoders
    UINT  nSize = 0;              // size of the image encoder array in bytes
    CAutoVectorPtr<BYTE> spData;
    Gdiplus::ImageCodecInfo* pImageCodecInfo = NULL;
    Gdiplus::Status status;
    bool fFound = false;

    // param check

    if ((pwszFormat == NULL) || (pwszFormat[0] == 0) || (pGUID == NULL))
    {
        return E_POINTER;
    }

    *pGUID = GUID_NULL;

    status = Gdiplus::GetImageEncodersSize(&nEncoders, &nSize);

    if ((status != Gdiplus::Ok) || (nSize == 0))
    {
        return E_FAIL;
    }


    spData.Allocate(nSize);

    if (spData == NULL)
    {
        return E_FAIL;
    }

    pImageCodecInfo = (Gdiplus::ImageCodecInfo*)(BYTE*)spData;

    status = Gdiplus::GetImageEncoders(nEncoders, nSize, pImageCodecInfo);

    if (status != Gdiplus::Ok)
    {
       return E_FAIL;
    }

    for(UINT j = 0; j < nEncoders; ++j)
    {
        if( wcscmp(pImageCodecInfo[j].MimeType, pwszFormat) == 0 )
        {
            *pGUID = pImageCodecInfo[j].Clsid;
            fFound = true;
            break;
        }    
    }

    hr = fFound ? S_OK : E_FAIL;

    return hr;
}

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