Listing Installed Decoders

Windows GDI+ provides the GetImageDecoders function so that you can determine which image decoders are available on your computer. GetImageDecoders returns an array of ImageCodecInfo objects. Before you call GetImageDecoders, you must allocate a buffer large enough to receive that array. You can call GetImageDecodersSize to determine the size of the required buffer.

The following console application lists the available image decoders:

#include <windows.h>
#include <gdiplus.h>
#include <stdio.h>
using namespace Gdiplus;

INT main()
{
   // Initialize GDI+.
   GdiplusStartupInput gdiplusStartupInput;
   ULONG_PTR gdiplusToken;
   GdiplusStartup(&gdiplusToken, &gdiplusStartupInput, NULL);

   UINT  num;        // number of image decoders
   UINT  size;       // size, in bytes, of the image decoder array

   ImageCodecInfo* pImageCodecInfo;

   // How many decoders are there?
   // How big (in bytes) is the array of all ImageCodecInfo objects?
   GetImageDecodersSize(&num, &size);

   // Create a buffer large enough to hold the array of ImageCodecInfo
   // objects that will be returned by GetImageDecoders.
   pImageCodecInfo = (ImageCodecInfo*)(malloc(size));

   // GetImageDecoders creates an array of ImageCodecInfo objects
   // and copies that array into a previously allocated buffer. 
   // The third argument, imageCodecInfo, is a pointer to that buffer. 
   GetImageDecoders(num, size, pImageCodecInfo);

   // Display the graphics file format (MimeType)
   // for each ImageCodecInfo object.
   for(UINT j = 0; j < num; ++j)
   { 
      wprintf(L"%s\n", pImageCodecInfo[j].MimeType);   
   }

   free(pImageCodecInfo);
   GdiplusShutdown(gdiplusToken);
   return 0;
}

When you run the preceding console application, the output will be similar to the following:

image/bmp
image/jpeg
image/gif
image/x-emf
image/x-wmf
image/tiff
image/png
image/x-icon