隐写术（将信息写入图片中）

 public partial class Form1 : Form
    {
        private Bitmap bitmapOriginal;
        private Bitmap bitmapModified;
        public Form1()
        {
            InitializeComponent();
            this.Paint += new System.Windows.Forms.PaintEventHandler(this.MyPaint);
            try
            {
                //load original bitmap from a file
                bitmapOriginal = (Bitmap)Bitmap.FromFile(
                    @"..\..\katie_plaintext.jpg");

                //center to screen
                this.CenterToScreen();
            }
            catch (Exception ex)
            {
                MessageBox.Show(
                    "Error loading image. " +
                    ex.Message);
            }
        }
        private void MyPaint(
            object sender,
            System.Windows.Forms.PaintEventArgs e)
        {
            try
            {
                //get Graphics object for painting original
                Graphics gPanelOriginal =
                    Graphics.FromHwnd(
                        panelOriginalImage.Handle);

                //draw original bitmap into panel
                gPanelOriginal.DrawImage(
                    bitmapOriginal, new Point(0, 0));

                //return if there is no modified image yet
                if (bitmapModified == null)
                    return;

                //get Graphics object for painting modified
                Graphics gPanelModified =
                    Graphics.FromHwnd(
                        panelModifiedImage.Handle);

                //draw modified bitmap into panel
                gPanelModified.DrawImage(
                    bitmapModified, new Point(0, 0));
            }
            catch (Exception ex)
            {
                MessageBox.Show(
                    "Error drawing image." +
                    ex.Message);
                this.Close();
            }
        }
        private void button1_Click(object sender, EventArgs e)//写入
        {
            try
            {
                //show wait cursor
                this.Cursor = Cursors.WaitCursor;

                //start off with copy of original image
                bitmapModified = new Bitmap(
                    bitmapOriginal,
                    bitmapOriginal.Width,
                    bitmapOriginal.Height);

                //get original message to be hidden
                int numberbytes =
                    (byte)textBoxOriginalMessage.Text.Length;
                byte[] bytesOriginal = new byte[numberbytes + 1];
                bytesOriginal[0] = (byte)numberbytes;
                Encoding.UTF8.GetBytes(
                    textBoxOriginalMessage.Text,
                    0,
                    textBoxOriginalMessage.Text.Length,
                    bytesOriginal,
                    1);

                //set bits 1, 2, 3 of byte into LSB red
                //set bits 4, 5, 6 of byte into LSB green
                //set bits 7 and 8 of byte into LSB blue
                int byteCount = 0;
                for (int i = 0; i < bitmapOriginal.Width; i++)
                {
                    for (int j = 0; j < bitmapOriginal.Height; j++)
                    {
                        if (bytesOriginal.Length == byteCount)
                            return;

                        Color clrPixelOriginal =
                            bitmapOriginal.GetPixel(i, j);
                        byte r =
                            (byte)((clrPixelOriginal.R & ~0x7) |
                            (bytesOriginal[byteCount] >> 0) & 0x7);
                        byte g =
                            (byte)((clrPixelOriginal.G & ~0x7) |
                            (bytesOriginal[byteCount] >> 3) & 0x7);
                        byte b =
                            (byte)((clrPixelOriginal.B & ~0x3) |
                            (bytesOriginal[byteCount] >> 6) & 0x3);
                        byteCount++;

                        //set pixel to modified color
                        bitmapModified.SetPixel(
                            i, j, Color.FromArgb(r, g, b));
                    }

                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(
                    "Error hiding message." +
                    ex.Message);
            }
            finally
            {
                //show normal cursor
                this.Cursor = Cursors.Arrow;

                //repaint
                Invalidate();
            }
        }

        private void button2_Click(object sender, EventArgs e)//读取
        {
            //get bytes of message from modified image
            byte[] bytesExtracted = new byte[256 + 1];
            try
            {
                //show wait cursor, can be time-consuming
                this.Cursor = Cursors.WaitCursor;

                //get bits 1, 2, 3 of byte from LSB red
                //get bits 4, 5, 6 of byte from LSB green
                //get bits 7 and 8 of byte from LSB blue
                int byteCount = 0;
                for (int i = 0; i < bitmapModified.Width; i++)
                {
                    for (int j = 0; j < bitmapModified.Height; j++)
                    {
                        if (bytesExtracted.Length == byteCount)
                            return;

                        Color clrPixelModified =
                            bitmapModified.GetPixel(i, j);
                        byte bits123 =
                            (byte)((clrPixelModified.R & 0x7) << 0);
                        byte bits456 = (
                            byte)((clrPixelModified.G & 0x7) << 3);
                        byte bits78 = (
                            byte)((clrPixelModified.B & 0x3) << 6);

                        bytesExtracted[byteCount] =
                            (byte)(bits78 | bits456 | bits123);
                        byteCount++;
                    }

                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(
                    "Error extracting message." +
                    ex.Message);
            }
            finally
            {
                //show normal cursor
                this.Cursor = Cursors.Arrow;

                //get number of bytes from start of array
                int numberbytes = bytesExtracted[0];

                //get remaining bytes in array into string
                textBoxExtractedlMessage.Text =
                    Encoding.UTF8.GetString(
                    bytesExtracted,
                    1,
                    numberbytes);
            }  
        }
    }


demo：https://files.cnblogs.com/hdjjun/windowsapplication1.rar