Thread: GDIPLUS::Image: how save it on a file in stream way?

Originally Posted by Codeplug

>> but these continues confused
What are you confused about?

gg

you(both) told me for i do in these way:
(for save it on file)
1 - create an empty IStream:

Code:

IStream* pIStream = nullptr;
        HGLOBAL hg=NULL;
        if(CreateStreamOnHGlobal(hg, FALSE, (LPSTREAM*)&pIStream)!=S_OK)

2 - save the Image to IStream:

Code:

CLSID pngClsid;
        GetEncoderClsid(L"image/gif", &pngClsid);

        // Setup encoder parameters
        EncoderParameters encoderParameters;
        encoderParameters.Count = 1;
        encoderParameters.Parameter[0].Guid = EncoderQuality;
        encoderParameters.Parameter[0].Type = EncoderParameterValueTypeLong;
        encoderParameters.Parameter[0].NumberOfValues = 1;

        // setup compression level
        ULONG quality = 50;
        encoderParameters.Parameter[0].Value = &quality;

        //  Save the image to the stream

        if(rhs.img->Save(pIStream, &pngClsid, &encoderParameters) != Ok)

3 - getting IStream size:

Code:

int buffsize=GlobalSize(&hg);

4 - i must save the IStream on a buffer:

Code:

char *pBuff = new char[buffsize];
        ULONG ulBytesRead;

        //Read the stream to pBuff
        if(pIStream->Read(pBuff,buffsize, &ulBytesRead)!=S_OK)

5 -now save the buffer size on file and the buffer:

Code:

//write the stream size on file
        lhs << buffsize;

        //write pBuff data on file
        lhs << pBuff;

6 - we must delete the resources:

Code:

//clean resources
        delete[] pBuff;
        pIStream->Release();

PS: i know the file it's created, what i don't have sure if the data it's right on file.

now for read it from a file:

1 - create an empty IStream:

Code:

IStream* pIStream = nullptr;
        HGLOBAL hg=NULL;
        if(CreateStreamOnHGlobal(hg, FALSE, (LPSTREAM*)&pIStream)!=S_OK)

2 - read the buffer(inclued the buffer size) from the file to a new IStream:

Code:

/getting IStream size:
        int streamsize;
        lhs.read(reinterpret_cast<char*>(&streamsize), sizeof(streamsize));

        IStream* pIStream = nullptr;

        // Create stream with 0 size
        HGLOBAL hg= ::GlobalAlloc(GMEM_MOVEABLE,streamsize);
        GlobalLock(hg);
        lhs.read(reinterpret_cast<char*>(&hg),sizeof(streamsize));
        GlobalUnlock(hg);

        if(CreateStreamOnHGlobal(&hg, TRUE, (LPSTREAM*)&pIStream)!=S_OK)
            DebugText("error on creating an empty IStream");

(i don't get any error)
3 - reading IStream to Image class:

Code:

if(rhs.img->FromStream(pIStream,TRUE)!=S_OK)
            DebugText("error reading stream to Image");

4 - clean resources:

Code:

//realease resources:
        pIStream->Release();
        GlobalFree(hg);

i see what i must do(unless i miss something). but if the FromStream() give me an error, means the IStream isn't right. i don't understand why.. i'm totaly confused.
sorry to all, but i'm trying to understand and see what isn't right