Does the documentation clearly state which commands only work on bitonal images? I've searched the documentation for "bitonal command" and found a couple of hits, but I want a definitive list (or a way to detect a specific filter's requirements, like InPlaceProcessing) so I can code and document accordingly.

Does this make sense as a workaround?

public static AtalaImage ToSupportedFormat( AtalaImage image, Atalasoft.Imaging.ImageProcessing.ImageCommand cmd )
{
    if( cmd.IsPixelFormatSupported( image.PixelFormat ) )
        return image;
    else
        return image.GetChangedPixelFormat( cmd.SupportedPixelFormats[0] );
}

This is probably not an ideal solution as the first supported pixel format might not be the best one to translate to - be aware that you might be either throwing away information or adding in way too much.  You probably want to write a method like this:
public static PixelFormat SelectBestAlternatePixelFormat(PixelFormat whatIHave, PixelFormat[] whatICanChooseFrom)
{
}

Here's a code snippet I just put together which will list all commands in dotImage that support bitonal images:

using System;
using System.Reflection;
using System.Runtime;
using Atalasoft.Imaging;
using Atalasoft.Imaging.ImageProcessing;

namespace FindBitonalCommands
{
    /// <summary>
    /// Summary description for Class1.
    /// </summary>
    class Class1
    {
        /// <summary>
        /// The main entry point for the application.
        /// </summary>
        [STAThread]
        static void Main(string[] args)
        {
            Assembly dotImage = Assembly.GetAssembly(typeof(AtalaImage));

            Type[] allTypes = dotImage.GetExportedTypes();
            Type[] emptyList = new Type[0];
            foreach (Type t in allTypes)
            {
                if (!t.IsSubclassOf(typeof(Atalasoft.Imaging.ImageProcessing.ImageCommand)))
                    continue;
                ConstructorInfo ctor = t.GetConstructor(emptyList);
                if (ctor != null)
                {
                    object obj = ctor.Invoke(null);
                    ImageCommand command = (ImageCommand)obj;
                    if (command.IsPixelFormatSupported(PixelFormat.Pixel1bppIndexed))
                    {
                        System.Console.WriteLine(command.GetType().Name);
                    }
                }
            }
            System.Console.ReadLine();
        }
    }
}

---

Steve Hawley
Architect & Exception Handler
Atalasoft, Inc.