920517 - how to get pixels of an Image?

using System.Drawing;
using System.Text;
using System;

namespace ParseTest
{
    internal class Program
    {
        private const int Black = unchecked((int)0xFF000000);
        private const int White = unchecked((int)0xFFFFFFFF);

        private static bool IsValid(Color pixel)
        {
            var argb = pixel.ToArgb();
            return argb == Black || argb == White;
        }

        private static int GetBlackBit(Color pixel) {
            var argb = pixel.ToArgb();
            return argb == Black ? 1 : 0;
        }

        static void Main()
        {
            var image = (Bitmap)Image.FromFile(@"C:\Temp\Input.png");
            var result = new StringBuilder();

            for (var y = 0; y < image.Size.Height; ++y)
            {

                for (var x = 0; x < image.Size.Width; x += 8)
                {
                    var value = 0;
                    for (var i = 0; i < 8; ++i)
                    {
                        var pixel = image.GetPixel(x + i, y);
                        if (!IsValid(pixel))
                            throw new Exception("Image is not monochrome!!!");

                        value |= GetBlackBit(pixel) << (7 - i);
                    }
                    result.AppendFormat("0x{0:X2} ", value);
                }
                result.AppendLine();
            }
            Console.WriteLine(result);
        }
    }
}