How to use GDI+ to save image in WMF, EXIF or EMF format

Introduction

When I use the Image::Save() function in GDI+ to save an image as BMP, GIF, TIFF, PNG or JPEG, the program works very well. But it fails to do so if I want to save an image as WMF, EXIF or EMF.

The reason of such a case has been well explained in MSDN.

However, I also found that in C#, we could use Image::Save() function to save an image as WMF, EXIF or EMF format, with no pains.

Finally, Feng Yuan helped me out of this problem. Thanks a lot for him.

The solution

Actually, the solution code is quite simple. First, construct a Metafile object and then draw graphics on it. For example, we can have:

Bitmap* m_pBitmap;
...
// do some paintings on m_pBitmap
...
CString sFileName = "c:\\1.emf";
// you can use "c:\\1.exi" or "c:\\1.wmf" here,
// and you can also build it as IStream
CDC *cdc = GetDC();
Metafile *metafile = 
         new Metafile(ToWChar(sFileName.GetBuffer(sFileName.GetLength())), 
         cdc->m_hDC);
Graphics graphics(metafile);
graphics.DrawImage(m_pBitmap, 0, 0, m_pBitmap->GetWidth(), 
                                  m_pBitmap->GetHeight());

Then, we can find the resulting image on driver C:. Simple, isn't it? Here, ToWChar() is a simple function to transform a CString object to WCHAR*. It can be written as:

static WCHAR* ToWChar(char * str) 
{
  // in GDI+, all the parameters about the symbol are WCHAR type
  // this funciton is a tranformation function

  static WCHAR buffer[1024];
  wcsset(buffer,0);
  MultiByteToWideChar(CP_ACP,0,str,strlen(str),buffer,1024);
  return buffer;
}

History

• Initial release 2004-04-27.