Does GDI+ have standard image encoder CLSIDs?

Question

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'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.

selbie · Accepted Answer · 2019-10-25T20:45:04.450

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.

That is:

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}

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.

#include <windows.h>
#include <gdiplus.h>
#include <string>
#include <vector>

HRESULT GetGdiplusEncoderClsid(const std::wstring& format, GUID* pGuid)
{
    HRESULT hr = S_OK;
    UINT  nEncoders = 0;          // number of image encoders
    UINT  nSize = 0;              // size of the image encoder array in bytes
    std::vector<BYTE> spData;
    Gdiplus::ImageCodecInfo* pImageCodecInfo = NULL;
    Gdiplus::Status status;
    bool found = false;

    if (format.empty() || !pGuid)
    {
        hr = E_INVALIDARG;
    }

    if (SUCCEEDED(hr))
    {
        *pGuid = GUID_NULL;
        status = Gdiplus::GetImageEncodersSize(&nEncoders, &nSize);

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

    if (SUCCEEDED(hr))
    {

        spData.resize(nSize);
        pImageCodecInfo = (Gdiplus::ImageCodecInfo*)&spData.front();
        status = Gdiplus::GetImageEncoders(nEncoders, nSize, pImageCodecInfo);

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

    if (SUCCEEDED(hr))
    {
        for (UINT j = 0; j < nEncoders && !found; j++)
        {
            if (pImageCodecInfo[j].MimeType == format)
            {
                *pGuid = pImageCodecInfo[j].Clsid;
                found = true;
            }
        }

        hr = found ? S_OK : E_FAIL;
    }

    return hr;
}


int main()
{
    Gdiplus::GdiplusStartupInput gdiplusStartupInput;
    ULONG_PTR gdiplusToken;
    GdiplusStartup(&gdiplusToken, &gdiplusStartupInput, NULL);

    GUID guidBmp = {};
    GUID guidJpeg = {};
    GUID guidGif = {};
    GUID guidTiff = {};
    GUID guidPng = {};

    GetGdiplusEncoderClsid(L"image/bmp", &guidBmp);
    GetGdiplusEncoderClsid(L"image/jpeg", &guidJpeg);
    GetGdiplusEncoderClsid(L"image/gif", &guidGif);
    GetGdiplusEncoderClsid(L"image/tiff", &guidTiff);
    GetGdiplusEncoderClsid(L"image/png", &guidPng);

    return 0;
}

These CLSIDs do not exist in registry. The only codec CLSIDs I could find that actually exist in the Registry turned out to be for Windows Imaging Component (WIC) codecs, rather than GDI+ codecs. Does GDI+'s Image::Save() map the encoder CLSID it receives to an actual encoder using an hard-coded list? — Medinoc, Oct 25 '19 at 19:31
If they were in the registry's CLSID key, it would mean they can be used from outside of GDI+ like ordinary COM classes (that's what a CLSID means, after all). But more importantly I'd have expected a key referencing all codecs, where codecs can be added for extensibility. Unfortunately it seems GDI+ can't be extended with new codecs, only WIC can. — Medinoc, Oct 26 '19 at 14:25

score 5 · Answer 2 · edited May 23 '17 at 12:34

5

If you just want to write a PNG, this appears to work:

// image/png  : {557cf406-1a04-11d3-9a73-0000f81ef32e}
const CLSID pngEncoderClsId = { 0x557cf406, 0x1a04, 0x11d3,{ 0x9a,0x73,0x00,0x00,0xf8,0x1e,0xf3,0x2e } }; 
stat = image->Save(L"test.png", &pngEncoderClsId, NULL);

Note the reformatting of the hex values.

From: How to initialize a constant CLSID

edited May 23 '17 at 12:34

Community

1
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answered Oct 17 '15 at 00:25

James Newton

698
9
19

GetEncoderClsid(L"image/png", ...) didn't work for some reason, but the this worked just fine. – Lucky Luke Apr 10 '20 at 16:23

AJG85 · Answer 3 · 2011-03-17T22:30:53.110

3

You will probably want to use ImageCodecInfo with GetImageEncodersSize() and GetImageEncoders() I'm not aware of any easier way.

EDIT: If you know specifically what you want and damn all the rest you can get away with doing something like this ...

CLSID pngClsid;
GetEncoderClsid("image/png", &pngClsid);
image.Save("imagename.png", &pngClsid, NULL);

edited Mar 17 '11 at 22:30

answered Mar 17 '11 at 22:10

AJG85

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13
42
50

2

That's exactly what I tried to do, but `GetEncoderClsid` isn't part of GDI+ - you have to copy it from the documentation. – Mark Ransom Mar 17 '11 at 22:39

Does GDI+ have standard image encoder CLSIDs?

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