SquareTransformation.cs

    public class SquareTransformation : ITransformation
    {
        public string Key => "SquareTransformation";

        public IBitmap Transform(IBitmap source)
        {
            double sourceWidth = source.Width;
            double sourceHeight = source.Height;

            double desiredWidth = sourceWidth;
            double desiredHeight = sourceHeight;

            if (desiredWidth > desiredHeight)
            {
                desiredWidth = desiredHeight;
            }
            else if (desiredHeight > desiredWidth)
            {
                desiredHeight = desiredWidth;
            }
            else
            {
                return source;
            }

            double centerX = sourceWidth / 2;
            double centerY = sourceHeight / 2;

            double offsetX = centerX - (desiredWidth / 2);
            double offsetY = centerY - (desiredHeight / 2);

            var trans = new CropTransformation(1f, offsetX, offsetY);
            return trans.Transform(source);
        }
    }