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

**joaquim** · 09-26-2015

i did these code for overloading << and >> operators on my image class:

Code:

int GetEncoderClsid(const WCHAR* format, CLSID* pClsid)
{
   UINT  num = 0;          // number of image encoders
   UINT  size = 0;         // size of the image encoder array in bytes

   ImageCodecInfo* pImageCodecInfo = NULL;

   GetImageEncodersSize(&num, &size);
   if(size == 0)
      return -1;  // Failure

   pImageCodecInfo = (ImageCodecInfo*)(malloc(size));
   if(pImageCodecInfo == NULL)
      return -1;  // Failure

   GetImageEncoders(num, size, pImageCodecInfo);

   for(UINT j = 0; j < num; ++j)
   {
      if( wcscmp(pImageCodecInfo[j].MimeType, format) == 0 )
      {
         *pClsid = pImageCodecInfo[j].Clsid;
         free(pImageCodecInfo);
         return j;  // Success
      }
   }

   free(pImageCodecInfo);
   return -1;  // Failure
}
////............
//for save it on file
friend std::ostream& operator << (std::ostream& lhs, const image& rhs)
    {
        /*if(IfFileExists(rhs.strfilename)==true)
            lhs<<rhs.strfilename;
        else
        {*/
            IStorage* pIStorage = NULL;
            IStream* pIStream1 = NULL;
            HRESULT hr;
            Status stat = Ok;
            hr = CoInitialize(NULL);

            hr = StgCreateDocfile( L"CompoundFile.cmp", STGM_READWRITE|STGM_CREATE|STGM_SHARE_EXCLUSIVE,0, &pIStorage);

            CLSID jpgClsid;
            GetEncoderClsid(L"image/gif", &jpgClsid);
            pIStorage->CreateStream(L"StreamImage1", STGM_READWRITE|STGM_SHARE_EXCLUSIVE, 0, 0,&pIStream1);
            rhs.img->Save(pIStream1, &jpgClsid, NULL);
        //}
        return lhs;
    }

or i miss something or i don't know.
i'm trying save the img data to file in stream way, instead file name.
i don't get anyerrors. the problem is that i don't get any image.

**Codeplug** · 09-26-2015

>> i'm trying save the img data to file in stream way, instead file name.
Why?
What is wrong with Image::Save(const WCHAR *filename, ...)?

gg

**joaquim** · 09-26-2015

Originally Posted by Codeplug

>> i'm trying save the img data to file in stream way, instead file name.
Why?
What is wrong with Image::Save(const WCHAR *filename, ...)?

gg

because i'm trying overloading the ostream << and istream >> operators. i need these

**Codeplug** · 09-26-2015

https://msdn.microsoft.com/en-us/lib...(v=vs.85).aspx

That will give you an IStream that writes to memory - then you can do a lhs.write() of that memory.

gg

**joaquim** · 09-26-2015

Originally Posted by Codeplug

https://msdn.microsoft.com/en-us/lib...(v=vs.85).aspx

That will give you an IStream that writes to memory - then you can do a lhs.write() of that memory.

gg

i continue with memory leak

Code:

friend std::ostream& operator << (std::ostream& lhs, const image& rhs)
    {
        /*if(IfFileExists(rhs.strfilename)==true)
            lhs<<rhs.strfilename;
        else
        {*/
            IStream* pIStream1 = NULL;
            CreateStreamOnHGlobal(NULL,FALSE,&pIStream1);
            CLSID pngClsid;
            GetEncoderClsid(L"image/gif", &pngClsid);
            rhs.img->Save(pIStream1,&pngClsid,NULL);
            lhs<< pIStream1;
        //}
        return lhs;
    }


    friend std::istream& operator >> (std::istream& lhs, image& rhs)
    {

        /*lhs>>rhs.strfilename;
        if(IfFileExists(rhs.strfilename)==true)
            rhs.readimagefile(rhs.strfilename);//FileName it's a property
        else
        {*/
            IStream* pIStream1 = NULL;

            lhs>> (char*)pIStream1;
            rhs.img->FromStream(pIStream1,FALSE);
        //}
        return lhs;
    }

what i'm doing wrong?

**Codeplug** · 09-26-2015

>> what i'm doing wrong?
To start, you are not checking any error codes.

>> lhs<< pIStream1;
>> [lhs>> (char*)pIStream1;
Explain what you think these lines are doing.

gg

**joaquim** · 09-27-2015

Originally Posted by Codeplug

>> what i'm doing wrong?
To start, you are not checking any error codes.

>> lhs<< pIStream1;
>> [lhs>> (char*)pIStream1;
Explain what you think these lines are doing.

gg

honestly i don't have the answer... sorry
what i know is that if i don't casting it, i will get a compiler error:

Code:

cannot bind 'std::istream {aka std::basic_istream<char>}' lvalue to 'std::basic_istream<char>&&'

now teel me why

**Elysia** · 09-27-2015

>>lhs>> (char*)pIStream1;
I've told you that this is always (almost) wrong. You can't just treat anything like some raw buffer. So stop doing that. You don't know what you're doing or how IStream works internally, so you cannot do any assumptions. You need to use its public interface to do operations on the object. That means calling Read/Write or whatever interface it exposes. The same goes for any other object, such as std::string. Stop using casts. The casts are just masking the actual error. The compiler is nice enough to tell you that you're doing something wrong. Casts should only be used when you are absolutely sure that you know better than the compiler.

**joaquim** · 09-27-2015

Originally Posted by Elysia

>>lhs>> (char*)pIStream1;
I've told you that this is always (almost) wrong. You can't just treat anything like some raw buffer. So stop doing that. You don't know what you're doing or how IStream works internally, so you cannot do any assumptions. You need to use its public interface to do operations on the object. That means calling Read/Write or whatever interface it exposes. The same goes for any other object, such as std::string. Stop using casts. The casts are just masking the actual error. The compiler is nice enough to tell you that you're doing something wrong. Casts should only be used when you are absolutely sure that you know better than the compiler.

i'm sorry, but how can i read the IStream?

**Codeplug** · 09-27-2015

what exactly to you want to put in the stream? Is it supposed to be the image data in some particular file format?

gg

**joaquim** · 09-27-2015

Originally Posted by Codeplug

what exactly to you want to put in the stream? Is it supposed to be the image data in some particular file format?

gg

i need put the Image stream on a file format, on actual file position. that's why i need overloading the operator

**Codeplug** · 09-27-2015

https://msdn.microsoft.com/en-us/lib...(v=vs.85).aspx
https://msdn.microsoft.com/en-us/lib...(v=vs.85).aspx
https://msdn.microsoft.com/en-us/lib...(v=vs.85).aspx
https://msdn.microsoft.com/en-us/lib...(v=vs.85).aspx

Those functions will give you a raw memory pointer to the IStream data and the size of that data - that was written by Image::Save(). Once you have that, you put that data in your ostream by calling ostream::write().

For the reverse process, there is example code in the first link on how to create an HGLOBAL, fill it's memory, and construct an IStream from it. You can then construct an Image from that IStream. If you are saving multiple binary elements to this ostream, then you will need to save the stream size as well.

Read each of those links carefully and completely. Understand them. Always check for error codes and report them.

Create a simple console application that has just the << and >> operators, with test code that tries to use it. Then you'll have a complete application that can you post so that others can compile it in order to help.

gg

**joaquim** · 10-02-2015

for write on file seems ok(i think, because i don't get errors):

Code:

friend std::ostream& operator << (std::ostream& lhs, const image& rhs)
    {
        STATSTG stats = {0};

        //Create an empty IStream:
        IStream* pIStream = nullptr;
        HGLOBAL hg=NULL;
        if(CreateStreamOnHGlobal(hg, FALSE, (LPSTREAM*)&pIStream)!=S_OK)
            DebugText("error on creating an empty IStream");

        //choose image format for save it on IStream:
        // Get encoder class id for jpg compression
        // for other compressions use
        //    image/bmp
        //    image/jpeg
        //    image/gif
        //    image/tiff
        //    image/png
        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
        Status SaveStatus = rhs.img->Save(pIStream, &pngClsid, &encoderParameters);
        if(SaveStatus != Ok)
        {
            pIStream->Release();
            DebugText("error on saving to IStream");
        }

        //getting the stream size:
        int buffsize=GlobalSize(&hg);

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

        //Read the stream to pBuff
        if(pIStream->Read(pBuff,buffsize, &ulBytesRead)!=S_OK)
            DebugText("error on saving IStream to buffer");

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

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

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

        return lhs;
    }

but for read it:

Code:

friend std::istream& operator >> (std::istream& lhs, image& rhs)
    {
        STATSTG stats = {0};
        IStream* pIStream = nullptr;

        // Create stream with 0 size
        if(CreateStreamOnHGlobal(nullptr, TRUE, (LPSTREAM*)&pIStream)!=S_OK)
            DebugText("error on creating an empty IStream");

        // Get encoder class id for jpg compression
        // for other compressions use
        //    image/bmp
        //    image/jpeg
        //    image/gif
        //    image/tiff
        //    image/png

        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;

        ULONG streamsize;
        lhs >> streamsize;
        char *pBuff = new char[streamsize];
        lhs >> pBuff;
        ULONG ulBytesRead;
        if(pIStream->Write(pBuff, streamsize, &ulBytesRead)!=S_OK)
            DebugText("error reading stream from a buffer");

        if(rhs.img->FromStream(pIStream,FALSE)!=S_OK)
            DebugText("error reading stream to Image");
        pIStream->Release();
        delete pBuff;
        return lhs;
    }

};

i get the error with FromStream(). what i'm doing wrong?

**Codeplug** · 10-02-2015

Here is my code review:

operator <<
Line 8 - The second parameter should be true. See documentation.
Line 20 - No error checking
Line 23 - Consider storing CLSID in the image class
Line 23 - Consider storing EncoderParameters in the image class
Line 42 - hg is still NULL at this point. You forgot to call GetHGlobalFromStream()
Line 44+ - Access the HGLOBAL directly instead of allocating more memory.
Line 52,55 - You should be using lhs.write(), not lhs<<

operator >>
Line 3 - Not used, remove.
Line 4 - NULL vs nullptr usage inconsistency (in other method)
Line 18 - Not used, remove.
Line 22 - Not used, remove.
Line 29 - Not used, remove.
Line 33,35 - You should be using lhs.read(), not lhs>>
Line 34 - You could read directly into an HGLOBAL and then call CreateStreamOnHGlobal() so the stream contents will already be in place.

I would get it working properly before making changes to read/write from/to HGLOBAL's.

gg

**joaquim** · 10-03-2015

i'm so sorry, but i continue with problems for reading the IStream

Code:

friend std::ostream& operator << (std::ostream& lhs, const image& rhs)
    {

        //Create an empty IStream:
        IStream* pIStream = nullptr;
        HGLOBAL hg=NULL;
        if(CreateStreamOnHGlobal(hg, TRUE, (LPSTREAM*)&pIStream)!=S_OK)
            DebugText("error on creating an empty IStream");

        //choose image format for save it on IStream:
        // Get encoder class id for jpg compression
        // for other compressions use
        //    image/bmp
        //    image/jpeg
        //    image/gif
        //    image/tiff
        //    image/png
        CLSID pngClsid;
        if(GetEncoderClsid(L"image/gif", &pngClsid)!=S_OK)
            DebugText("error on image format");

        // 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
        Status SaveStatus = rhs.img->Save(pIStream, &pngClsid, &encoderParameters);
        if(SaveStatus != Ok)
        {
            pIStream->Release();
            DebugText("error on saving to IStream");
        }

        //getting the stream size:
        if(GetHGlobalFromStream(pIStream,&hg)!=S_OK)
            DebugText("error on IStream information");

        int buffsize=GlobalSize(&hg);

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

        //Read the stream to pBuff
        if(pIStream->Read(pBuff,buffsize, &ulBytesRead)!=S_OK)
            DebugText("error on saving IStream to buffer");

        //write the stream size on file
        lhs.write(reinterpret_cast<char*>(&buffsize),sizeof(int));

        //write pBuff data on file
        lhs.write(pBuff,sizeof(pBuff));

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

        return lhs;
    }

    friend std::istream& operator >> (std::istream& lhs, image& rhs)
    {
        //getting IStream size:
        ULONG streamsize;
        lhs.read(reinterpret_cast<char*>(&streamsize), sizeof(ULONG));

        IStream* pIStream = nullptr;

        // Create stream with 0 size
        HGLOBAL hg=NULL;
        lhs.read(reinterpret_cast<char*>(&hg),sizeof(streamsize));
        if(CreateStreamOnHGlobal(&hg, TRUE, (LPSTREAM*)&pIStream)!=S_OK)
            DebugText("error on creating an empty IStream");

        //reading IStream on Image class:
        if(rhs.img->FromStream(pIStream,FALSE)!=S_OK)
            DebugText("error reading stream to Image");

        //realease resources:
        pIStream->Release();
        return lhs;
    }

theres 2 things that i didn't understand:
1 - 'Consider storing CLSID in the image class';
2 - 'Consider storing EncoderParameters in the image class'.
i'm sorry, but i'm totaly new with these code.. it's very complex, but i need it

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