Dynamically generating images in ISAPI extension using GDI+ with live demo

#include "StdAfx.h"
#include "gdipisapi.h"

int CGDIpISAPI::GetEncoderClsid(const WCHAR* format, CLSID* pClsid)
{
	using namespace Gdiplus;
	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
}

void CGDIpISAPI::WriteContext(LPCTSTR pszFormat,...)
{
	static TCHAR szBuffer[1024];
	
	if (!m_pCtxt)
		return;

	va_list arg_ptr;
	va_start(arg_ptr, pszFormat);
	vsprintf(szBuffer,pszFormat, arg_ptr);
	va_end(arg_ptr);

	*m_pCtxt<<szBuffer;
}

void CGDIpISAPI::DumpError(LPCTSTR pszFormat, ...)
{
	static TCHAR szBuffer[2048];

	if (!m_pCtxt)
		return;

	va_list arg_ptr;
	va_start(arg_ptr, pszFormat);
	vsprintf(szBuffer,pszFormat, arg_ptr);
	va_end(arg_ptr);

	CString str("<p>A error message has occured:</p>\r\n<p><b>");
	str+=szBuffer;
	str+="</b></p>\r\n";

	DWORD dwSize=(DWORD)str.GetLength();

	m_pServer->StartContent(m_pCtxt);
	*m_pCtxt<<str;
	m_pServer->EndContent(m_pCtxt);
}

void CGDIpISAPI::WriteImage()
{
	using namespace Gdiplus;
	USES_CONVERSION;

	IStream* pIStream = NULL;
	HGLOBAL hGlobal;
	HRESULT hResult;
	CString str;
	CString strHeader;
	SIZE_T size;
	EncoderParameters encoderParameters;
 
	if (!m_pCtxt)
		return;
	if (!m_pServer)
		return;
	if (!m_pImage)
		return;

	hGlobal = ::GlobalAlloc( GHND , 0);
	if (hGlobal == NULL)
	{
		DumpError("Could not allocate global handle\r\n");
		goto Exit;
	}

	hResult=::CreateStreamOnHGlobal(
		hGlobal,         //Memory handle for the stream object
		true,   //Whether to free memory when the 
                           // object is released
		&pIStream          //Address of output variable that 
                           // receives the IStream interface pointer
	);
	if (FAILED(hResult))
	{
		ISAPIASSERT(FALSE);
		goto Exit;
	}

	CLSID imgClsid;
	if (GetEncoderClsid(A2BSTR(GetImageTypeString()), &imgClsid) == -1)
	{
		ISAPIASSERT(FALSE);
		goto Exit;
	}

	if (m_eImageType == ImagePNG || m_eImageType == ImageJPEG)
	{
		encoderParameters.Count = 1;
		encoderParameters.Parameter[0].Guid = EncoderQuality;
		encoderParameters.Parameter[0].Type = EncoderParameterValueTypeLong;
		encoderParameters.Parameter[0].NumberOfValues = 1;
		encoderParameters.Parameter[0].Value = &m_ulQuality;

		// Save to IStream...
		m_pImage->Save(pIStream, &imgClsid, &encoderParameters);
	}
	else
		m_pImage->Save(pIStream, &imgClsid);

	if (m_pImage->GetLastStatus() != Gdiplus::Ok)
	{
		ISAPIASSERT(FALSE);
		goto Exit;
	}

	// getting size of hGlobal
	size = ::GlobalSize(hGlobal);
	// formulate a proper header
	m_pCtxt->m_bSendHeaders=FALSE;
	strHeader.Format(_T("HTTP/1.0 200 OK\r\n%s\r\nContent-length: %d\r\n\r\n"), GetImageTypeString(),size);
	m_pServer->AddHeader(m_pCtxt, strHeader);
	ISAPIVERIFY( m_pCtxt->m_pECB->WriteClient(
		m_pCtxt->m_pECB->ConnID, ::GlobalLock(hGlobal), &size, 0) );
	::GlobalUnlock(hGlobal);

Exit:
	// Cleaning..	
	if (pIStream)
		pIStream->Release();
	if (hGlobal)
		::GlobalFree(hGlobal);
}

LPCTSTR CGDIpISAPI::GetImageTypeString() const
{
	switch(m_eImageType)
	{
	case ImagePNG:
		return "image/png";
	case ImageJPEG:
		return "image/jpeg";
	case ImageBMP:
		return "image/bmp";
	default:
		return "text/plain";
	}
}

void CGDIpISAPI::WriteInfo()
{
	using namespace Gdiplus;
	USES_CONVERSION;

	IStream* pIStream = NULL;
	HGLOBAL hGlobal;
	HRESULT hResult;
	CString str;
	CString strHeader;
	SIZE_T size;
	EncoderParameters encoderParameters;

	if (!m_pCtxt)
		return;
	if (!m_pServer)
		return;
	if (!m_pImage)
		return;

	hGlobal = ::GlobalAlloc( GHND , 0);
	if (hGlobal == NULL)
	{
		DumpError("Could not allocate global handle\r\n");
		goto Exit;
	}

	hResult=::CreateStreamOnHGlobal(
		hGlobal,         //Memory handle for the stream object
		true,   //Whether to free memory when the 
                           // object is released
		&pIStream          //Address of output variable that 
                           // receives the IStream interface pointer
	);
	if (FAILED(hResult))
	{
		ISAPIASSERT(FALSE);
		goto Exit;
	}

	CLSID imgClsid;

	if (GetEncoderClsid(A2BSTR(GetImageTypeString()), &imgClsid) == -1)
	{
		ISAPIASSERT(FALSE);
		goto Exit;
	}


	if (m_eImageType == ImagePNG || m_eImageType == ImageJPEG)
	{
		encoderParameters.Count = 1;
		encoderParameters.Parameter[0].Guid = EncoderQuality;
		encoderParameters.Parameter[0].Type = EncoderParameterValueTypeLong;
		encoderParameters.Parameter[0].NumberOfValues = 1;
		encoderParameters.Parameter[0].Value = &m_ulQuality;

		// Save to IStream...
		m_pImage->Save(pIStream, &imgClsid, &encoderParameters);
	}
	else
		m_pImage->Save(pIStream, &imgClsid);

	if (m_pImage->GetLastStatus() != Gdiplus::Ok)
	{
		ISAPIASSERT(FALSE);
		goto Exit;
	}

	// getting size of hGlobal
	size = ::GlobalSize(hGlobal);
		
	m_pServer->StartContent(m_pCtxt);
	WriteContext("<table>\r\n");
	WriteContext("<tr><td>Image Type</td><td>%s</td></tr>\r\n",GetImageTypeString());
	WriteContext("<tr><td>Size</td><td>%dx%d</td></tr>\r\n", m_pImage->GetWidth(), m_pImage->GetHeight());
	WriteContext("<tr><td>Size (Bytes)</td><td>%d</td></tr>\r\n", size);
	WriteContext("</table>\r\n");
	m_pServer->EndContent(m_pCtxt);

Exit:
	// Cleaning..	
	if (pIStream)
		pIStream->Release();
	if (hGlobal)
		::GlobalFree(hGlobal);
}