public class LockBitmap
{
    Bitmap source = null;
    IntPtr Iptr = IntPtr.Zero;
    BitmapData bitmapData = null;
 
    public byte[] Pixels { get; set; }
    public int Depth { get; private set; }
    public int Width { get; private set; }
    public int Height { get; private set; }
 
    public LockBitmap(Bitmap source)
    {
        this.source = source;
    }
 
    /// <summary>
    /// Lock bitmap data
    /// </summary>
    public void LockBits()
    {
        try
        {
            // Get width and height of bitmap
            Width = source.Width;
            Height = source.Height;
 
            // get total locked pixels count
            int PixelCount = Width * Height;
 
            // Create rectangle to lock
            Rectangle rect = new Rectangle(0, 0, Width, Height);
 
            // get source bitmap pixel format size
            Depth = System.Drawing.Bitmap.GetPixelFormatSize(source.PixelFormat);
 
            // Check if bpp (Bits Per Pixel) is 8, 24, or 32
            if (Depth != 8 && Depth != 24 && Depth != 32)
            {
                throw new ArgumentException("Only 8, 24 and 32 bpp images are supported.");
            }
 
            // Lock bitmap and return bitmap data
            bitmapData = source.LockBits(rect, ImageLockMode.ReadWrite, 
                                         source.PixelFormat);
 
            // create byte array to copy pixel values
            int step = Depth / 8;
            Pixels = new byte[PixelCount * step];
            Iptr = bitmapData.Scan0;
 
            // Copy data from pointer to array
            Marshal.Copy(Iptr, Pixels, 0, Pixels.Length);
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }
 
    /// <summary>
    /// Unlock bitmap data
    /// </summary>
    public void UnlockBits()
    {
        try
        {
            // Copy data from byte array to pointer
            Marshal.Copy(Pixels, 0, Iptr, Pixels.Length);
 
            // Unlock bitmap data
            source.UnlockBits(bitmapData);
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }
 
    /// <summary>
    /// Get the color of the specified pixel
    /// </summary>
    /// <param name="x"></param>
    /// <param name="y"></param>
    /// <returns></returns>
    public Color GetPixel(int x, int y)
    {
        Color clr = Color.Empty;
 
        // Get color components count
        int cCount = Depth / 8;
 
        // Get start index of the specified pixel
        int i = ((y * Width) + x) * cCount;
 
        if (i > Pixels.Length - cCount)
            throw new IndexOutOfRangeException();
 
        if (Depth == 32) // For 32 bpp get Red, Green, Blue and Alpha
        {
            byte b = Pixels[i];
            byte g = Pixels[i + 1];
            byte r = Pixels[i + 2];
            byte a = Pixels[i + 3]; // a
            clr = Color.FromArgb(a, r, g, b);
        }
        if (Depth == 24) // For 24 bpp get Red, Green and Blue
        {
            byte b = Pixels[i];
            byte g = Pixels[i + 1];
            byte r = Pixels[i + 2];
            clr = Color.FromArgb(r, g, b);
        }
        if (Depth == 8)
        // For 8 bpp get color value (Red, Green and Blue values are the same)
        {
            byte c = Pixels[i];
            clr = Color.FromArgb(c, c, c);
        }
        return clr;
    }
 
    /// <summary>
    /// Set the color of the specified pixel
    /// </summary>
    /// <param name="x"></param>
    /// <param name="y"></param>
    /// <param name="color"></param>
    public void SetPixel(int x, int y, Color color)
    {
        // Get color components count
        int cCount = Depth / 8;
 
        // Get start index of the specified pixel
        int i = ((y * Width) + x) * cCount;
 
        if (Depth == 32) // For 32 bpp set Red, Green, Blue and Alpha
        {
            Pixels[i] = color.B;
            Pixels[i + 1] = color.G;
            Pixels[i + 2] = color.R;
            Pixels[i + 3] = color.A;
        }
        if (Depth == 24) // For 24 bpp set Red, Green and Blue
        {
            Pixels[i] = color.B;
            Pixels[i + 1] = color.G;
            Pixels[i + 2] = color.R;
        }
        if (Depth == 8)
        // For 8 bpp set color value (Red, Green and Blue values are the same)
        {
            Pixels[i] = color.B;
        }
    }
}