C#

using System;
using System.Collections;
using System.Drawing;
using System.Drawing.Imaging;
using System.Reflection;

public class Test
{
  static void Main(string[] args)
  {
    string fe = "gif";
    if (args.Length > 0) fe = args[0];

    ImageCodecInfo[] codecs = ImageCodecInfo.GetImageEncoders();
    ImageCodecInfo codec = null;
    foreach (ImageCodecInfo ci in codecs)
    {
      if (ci.FilenameExtension.ToLower().IndexOf(fe.ToLower()) >= 0)
      {
        codec = ci;
        break;
      }
    }

    if (codec == null)
    {
      Console.Error.WriteLine("No image codec found for extension " + fe);
      return;
    }

    Image img = new Bitmap(1, 1);
    EncoderParameters encparams = null;
    try
    {
      encparams = img.GetEncoderParameterList(codec.Clsid);
    }
    catch (NotImplementedException)
    {
      Console.Error.WriteLine("No encoder parameters supported for extension " + fe);
      return;
    }

    foreach (EncoderParameter encparam in encparams.Param)
    {
      string encname = GetEncoderName(encparam.Encoder.Guid);
      Console.WriteLine("{0}: {1}", encname, encparam.Type);
    }
  }

  static Hashtable encnames;
  static string GetEncoderName(Guid g)
  {
    if (encnames == null)
    {
      encnames = new Hashtable();

      Type t = typeof(Encoder);
      FieldInfo[] fields = t.GetFields(BindingFlags.Public | BindingFlags.Static);
      foreach (FieldInfo field in fields)
      {
        Encoder enc = (Encoder)field.GetValue(null);
        encnames[enc.Guid] = field.Name;
      }
    }

    return encnames[g] as string;
  }
}