.NET extension method for comparing System.Drawing.Images instances by value.

ImageExtensions.cs

namespace Extensions
{
    /// <summary>
    /// Contains <see cref="object"/> extension methods.
    /// </summary>
    public static class ImageExtensions
    {
        /// <summary>
        /// Determines if the two object are equavalent in a way that will not throw if the current obejct is null.
        /// </summary>
        /// <param name="param">The param.</param>
        /// <param name="obj">The obj.</param>
        /// <param name="format">The format.</param>
        /// <returns>
        ///   <c>true</c> if the two objects are equivalent; otherwise, <c>false</c>.
        /// </returns>
        public static bool NullSafeEquals(this Image param, Image obj, ImageFormat format)
        {
            return null != param ? CompareImages(param, obj, format) : (null == obj);
        }
 
        /// <summary>
        /// Compares the two images for value equality.
        /// </summary>
        /// <param name="image1">An image.</param>
        /// <param name="image2">Another image.</param>
        /// <param name="format">The format.</param>
        /// <returns>
        ///   <c>true</c> if the two images have value equality.
        /// </returns>
        private static bool CompareImages(Image image1, Image image2, ImageFormat format)
        {
            Debug.Assert(null != image1);
            Debug.Assert(null != image2);
 
            MemoryStream ms1 = new MemoryStream();
            MemoryStream ms2 = new MemoryStream();
 
            image1.Save(ms1, format);
            image2.Save(ms2, format);
 
            byte[] image1AsByteArray = ms1.ToArray();
            byte[] image2AsByteArray = ms2.ToArray();
 
            if (image1AsByteArray.Length != image2AsByteArray.Length)
            {
                return false;
            }
 
            return !image1AsByteArray.Where((t, i) => t != image2AsByteArray[i]).Any();
        }
    }
 }