在Silverlight中我们有时候需要手工绘制线条或者直线等，在这里我们认识一下InkPresenter控件，它将支持用户使用鼠标、手写板等工具来绘制图形或者笔迹，用途为涂鸦、笔迹确认等等。

        InkPresenter是继承于Canvas控件的支持所有的Canvas属性，并且其内部还可以嵌套显示其他控件。InkPresenter控件的显示分为三层：底层是InkPresenter的Background、中间层是InkPresenter的Children属性的控件、最后才是Strokes属性中的笔画层。

        对于Strokes属性中的笔画Stroke我们可以设置它的颜色、粗细、外边框颜色等等属性以获得满意的笔画类型。下面我们来看看如何使用InkPresenter控件，首先我们来看Xaml代码如下：

  然后我们来看看Xaml.cs代码如下：

public partial class MainPage : UserControl
    {
        public MainPage()
        {
            InitializeComponent();
            SetPresenterClip();
        }
        Stroke myStroke;

        private void iPresenter_MouseLeftButtonDown(object sender, MouseEventArgs e)
        {
            //让鼠标捕获数据
            iPresenter.CaptureMouse();
            //收集笔触数据点保存值StylusPointCollection集合中
            StylusPointCollection stylusPointCollection = new StylusPointCollection();
            stylusPointCollection.Add(e.StylusDevice.GetStylusPoints(iPresenter));
            //将数据点的结合保存为一个笔画
            myStroke = new Stroke(stylusPointCollection);
            //设置笔画的绘画效果，如颜色，大小等。
            myStroke.DrawingAttributes.Color = Colors.Gray;
            myStroke.DrawingAttributes.Width = 1;
            myStroke.DrawingAttributes.Height = 1;
            iPresenter.Strokes.Add(myStroke);
        }

        private void iPresenter_MouseMove(object sender, MouseEventArgs e)
        {
            //在鼠标移动的过程中将数据点加入到笔画中去。
            if (myStroke != null)
                myStroke.StylusPoints.Add(e.StylusDevice.GetStylusPoints(iPresenter));
        }

        private void iPresenter_LostMouseCapture(object sender, MouseEventArgs e)
        {
            //将笔画清空
            myStroke = null;
            iPresenter.ReleaseMouseCapture();//释放鼠标坐标
        }

        /// <summary>
        /// 设置绘画区域为InkPresenter的大小
        /// </summary>
        private void SetPresenterClip()
        {
            RectangleGeometry MyRectangleGeometry = new RectangleGeometry();
            MyRectangleGeometry.Rect = new Rect(0, 0, iPresenter.ActualWidth, iPresenter.ActualHeight);
            //设置获取绘画内容的有效区域
            iPresenter.Clip = MyRectangleGeometry;
        }

        private void button1_Click(object sender, RoutedEventArgs e)
        {
            //保存InkPresenter涂鸦板内绘画的图
            WriteableBitmap _bitmap = new WriteableBitmap(iPresenter, null);
            this.showIP.Source = _bitmap;
            SaveFileDialog sfd = new SaveFileDialog();
            sfd.Filter = "PNG Files (*.png)|*.png|All Files (*.*)|*.*";
            sfd.DefaultExt = ".png";
            sfd.FilterIndex = 1;

            if ((bool)sfd.ShowDialog())
            {
                using (Stream fs = sfd.OpenFile())
                {
                    int width = _bitmap.PixelWidth;
                    int height = _bitmap.PixelHeight;

                    EditableImage ei = new EditableImage(width, height);

                    for (int i = 0; i < height; i++)
                    {
                        for (int j = 0; j < width; j++)
                        {
                            int pixel = _bitmap.Pixels[(i * width) + j];
                            ei.SetPixel(j, i,
                                        (byte)((pixel >> 16) & 0xFF),
                                        (byte)((pixel >> 8) & 0xFF),
                                        (byte)(pixel & 0xFF),
                                        (byte)((pixel >> 24) & 0xFF)
                            );
                        }
                    }
                    //获取流
                    Stream png = ei.GetStream();
                    int len = (int)png.Length;
                    byte[] bytes = new byte[len];
                    png.Read(bytes, 0, len);
                    fs.Write(bytes, 0, len);
                    MessageBox.Show("图片保存成功！");
                }
            }

        }
    }

对于将InkPresenter中绘画出来的图片保存为Png图片得处理，我们在这里借鉴了园子中永恒的记忆兄弟的将元素转为Png图片的方法，在这里贴出两个辅助转Png格式的类。

/// <summary>
    /// 编辑图片
    /// </summary>
    public class EditableImage
    {
        private int _width = 0;
        private int _height = 0;
        private bool _init = false;
        private byte[] _buffer;
        private int _rowLength;

        /// <summary>
        /// 当图片错误时引发
        /// </summary>
        public event EventHandler<EditableImageErrorEventArgs> ImageError;

        /// <summary>
        /// 实例化
        /// </summary>
        /// <param name="width"></param>
        /// <param name="height"></param>
        public EditableImage(int width, int height)
        {
            this.Width = width;
            this.Height = height;
        }

        public int Width
        {
            get
            {
                return _width;
            }
            set
            {
                if (_init)
                {
                    OnImageError("错误: 图片初始化后不可以改变宽度");
                }
                else if ((value <= 0) || (value > 2047))
                {
                    OnImageError("错误: 宽度必须在 0 到 2047");
                }
                else
                {
                    _width = value;
                }
            }
        }

        public int Height
        {
            get
            {
                return _height;
            }
            set
            {
                if (_init)
                {
                    OnImageError("错误: 图片初始化后不可以改变高度");
                }
                else if ((value <= 0) || (value > 2047))
                {
                    OnImageError("错误: 高度必须在 0 到 2047");
                }
                else
                {
                    _height = value;
                }
            }
        }

        public void SetPixel(int col, int row, Color color)
        {
            SetPixel(col, row, color.R, color.G, color.B, color.A);
        }

        public void SetPixel(int col, int row, byte red, byte green, byte blue, byte alpha)
        {
            if (!_init)
            {
                _rowLength = _width * 4 + 1;
                _buffer = new byte[_rowLength * _height];

                // Initialize
                for (int idx = 0; idx < _height; idx++)
                {
                    _buffer[idx * _rowLength] = 0;      // Filter bit
                }

                _init = true;
            }

            if ((col > _width) || (col < 0))
            {
                OnImageError("Error: Column must be greater than 0 and less than the Width");
            }
            else if ((row > _height) || (row < 0))
            {
                OnImageError("Error: Row must be greater than 0 and less than the Height");
            }

            // Set the pixel
            int start = _rowLength * row + col * 4 + 1;
            _buffer[start] = red;
            _buffer[start + 1] = green;
            _buffer[start + 2] = blue;
            _buffer[start + 3] = alpha;
        }

        public Color GetPixel(int col, int row)
        {
            if ((col > _width) || (col < 0))
            {
                OnImageError("Error: Column must be greater than 0 and less than the Width");
            }
            else if ((row > _height) || (row < 0))
            {
                OnImageError("Error: Row must be greater than 0 and less than the Height");
            }

            Color color = new Color();
            int _base = _rowLength * row + col + 1;

            color.R = _buffer[_base];
            color.G = _buffer[_base + 1];
            color.B = _buffer[_base + 2];
            color.A = _buffer[_base + 3];

            return color;
        }

        public Stream GetStream()
        {
            Stream stream;

            if (!_init)
            {
                OnImageError("Error: Image has not been initialized");
                stream = null;
            }
            else
            {
                stream = PngEncoder.Encode(_buffer, _width, _height);
            }

            return stream;
        }

        private void OnImageError(string msg)
        {
            if (null != ImageError)
            {
                EditableImageErrorEventArgs args = new EditableImageErrorEventArgs();
                args.ErrorMessage = msg;
                ImageError(this, args);
            }
        }

        public class EditableImageErrorEventArgs : EventArgs
        {
            private string _errorMessage = string.Empty;

            public string ErrorMessage
            {
                get { return _errorMessage; }
                set { _errorMessage = value; }
            }
        }

    }

   这是Png操作类：

/// <summary>
    /// PNG格式操作类
    /// </summary>
    public class PngEncoder
    {
        private const int _ADLER32_BASE = 65521;
        private const int _MAXBLOCK = 0xFFFF;
        private static byte[] _HEADER = { 0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A };
        private static byte[] _IHDR = { (byte)'I', (byte)'H', (byte)'D', (byte)'R' };
        private static byte[] _GAMA = { (byte)'g', (byte)'A', (byte)'M', (byte)'A' };
        private static byte[] _IDAT = { (byte)'I', (byte)'D', (byte)'A', (byte)'T' };
        private static byte[] _IEND = { (byte)'I', (byte)'E', (byte)'N', (byte)'D' };
        private static byte[] _4BYTEDATA = { 0, 0, 0, 0 };
        private static byte[] _ARGB = { 0, 0, 0, 0, 0, 0, 0, 0, 8, 6, 0, 0, 0 };

        /// <summary>
        /// 编码
        /// </summary>
        /// <param name="data"></param>
        /// <param name="width"></param>
        /// <param name="height"></param>
        /// <returns></returns>
        public static Stream Encode(byte[] data, int width, int height)
        {
            MemoryStream ms = new MemoryStream();
            byte[] size;

            // Write PNG header
            ms.Write(_HEADER, 0, _HEADER.Length);

            // Write IHDR
            //  Width:              4 bytes
            //  Height:             4 bytes
            //  Bit depth:          1 byte
            //  Color type:         1 byte
            //  Compression method: 1 byte
            //  Filter method:      1 byte
            //  Interlace method:   1 byte

            size = BitConverter.GetBytes(width);
            _ARGB[0] = size[3]; _ARGB[1] = size[2]; _ARGB[2] = size[1]; _ARGB[3] = size[0];

            size = BitConverter.GetBytes(height);
            _ARGB[4] = size[3]; _ARGB[5] = size[2]; _ARGB[6] = size[1]; _ARGB[7] = size[0];

            // Write IHDR chunk
            WriteChunk(ms, _IHDR, _ARGB);

            // Set gamma = 1
            size = BitConverter.GetBytes(1 * 100000);
            _4BYTEDATA[0] = size[3]; _4BYTEDATA[1] = size[2]; _4BYTEDATA[2] = size[1]; _4BYTEDATA[3] = size[0];

            // Write gAMA chunk
            WriteChunk(ms, _GAMA, _4BYTEDATA);

            // Write IDAT chunk
            uint widthLength = (uint)(width * 4) + 1;
            uint dcSize = widthLength * (uint)height;

            // First part of ZLIB header is 78 1101 1010 (DA) 0000 00001 (01)
            // ZLIB info
            //
            // CMF Byte: 78
            //  CINFO = 7 (32K window size)
            //  CM = 8 = (deflate compression)
            // FLG Byte: DA
            //  FLEVEL = 3 (bits 6 and 7 - ignored but signifies max compression)
            //  FDICT = 0 (bit 5, 0 - no preset dictionary)
            //  FCHCK = 26 (bits 0-4 - ensure CMF*256+FLG / 31 has no remainder)
            // Compressed data
            //  FLAGS: 0 or 1
            //    00000 00 (no compression) X (X=1 for last block, 0=not the last block)
            //    LEN = length in bytes (equal to ((width*4)+1)*height
            //    NLEN = one's compliment of LEN
            //    Example: 1111 1011 1111 1111 (FB), 0000 0100 0000 0000 (40)
            //    Data for each line: 0 [RGBA] [RGBA] [RGBA] ...
            //    ADLER32

            uint adler = ComputeAdler32(data);
            MemoryStream comp = new MemoryStream();

            // 64K的块数计算
            uint rowsPerBlock = _MAXBLOCK / widthLength;
            uint blockSize = rowsPerBlock * widthLength;
            uint blockCount;
            ushort length;
            uint remainder = dcSize;

            if ((dcSize % blockSize) == 0)
            {
                blockCount = dcSize / blockSize;
            }
            else
            {
                blockCount = (dcSize / blockSize) + 1;
            }

            // 头部
            comp.WriteByte(0x78);
            comp.WriteByte(0xDA);

            for (uint blocks = 0; blocks < blockCount; blocks++)
            {
                // 长度
                length = (ushort)((remainder < blockSize) ? remainder : blockSize);

                if (length == remainder)
                {
                    comp.WriteByte(0x01);
                }
                else
                {
                    comp.WriteByte(0x00);
                }

                comp.Write(BitConverter.GetBytes(length), 0, 2);

                comp.Write(BitConverter.GetBytes((ushort)~length), 0, 2);

                // Write 块
                comp.Write(data, (int)(blocks * blockSize), length);

                //下一块
                remainder -= blockSize;
            }

            WriteReversedBuffer(comp, BitConverter.GetBytes(adler));
            comp.Seek(0, SeekOrigin.Begin);

            byte[] dat = new byte[comp.Length];
            comp.Read(dat, 0, (int)comp.Length);

            WriteChunk(ms, _IDAT, dat);

            // Write IEND chunk
            WriteChunk(ms, _IEND, new byte[0]);

            // Reset stream
            ms.Seek(0, SeekOrigin.Begin);

            return ms;
        }

        private static void WriteReversedBuffer(Stream stream, byte[] data)
        {
            int size = data.Length;
            byte[] reorder = new byte[size];

            for (int idx = 0; idx < size; idx++)
            {
                reorder[idx] = data[size - idx - 1];
            }
            stream.Write(reorder, 0, size);
        }

        private static void WriteChunk(Stream stream, byte[] type, byte[] data)
        {
            int idx;
            int size = type.Length;
            byte[] buffer = new byte[type.Length + data.Length];

            // 初始化缓冲
            for (idx = 0; idx < type.Length; idx++)
            {
                buffer[idx] = type[idx];
            }

            for (idx = 0; idx < data.Length; idx++)
            {
                buffer[idx + size] = data[idx];
            }

            WriteReversedBuffer(stream, BitConverter.GetBytes(data.Length));

            // Write 类型和数据
            stream.Write(buffer, 0, buffer.Length);   // Should always be 4 bytes

            // 计算和书写的CRC

            WriteReversedBuffer(stream, BitConverter.GetBytes(GetCRC(buffer)));
        }

        private static uint[] _crcTable = new uint[256];
        private static bool _crcTableComputed = false;

        private static void MakeCRCTable()
        {
            uint c;

            for (int n = 0; n < 256; n++)
            {
                c = (uint)n;
                for (int k = 0; k < 8; k++)
                {
                    if ((c & (0x00000001)) > 0)
                        c = 0xEDB88320 ^ (c >> 1);
                    else
                        c = c >> 1;
                }
                _crcTable[n] = c;
            }

            _crcTableComputed = true;
        }

        private static uint UpdateCRC(uint crc, byte[] buf, int len)
        {
            uint c = crc;

            if (!_crcTableComputed)
            {
                MakeCRCTable();
            }

            for (int n = 0; n < len; n++)
            {
                c = _crcTable[(c ^ buf[n]) & 0xFF] ^ (c >> 8);
            }

            return c;
        }

        //返回的字节的CRC缓冲区
        private static uint GetCRC(byte[] buf)
        {
            return UpdateCRC(0xFFFFFFFF, buf, buf.Length) ^ 0xFFFFFFFF;
        }

        private static uint ComputeAdler32(byte[] buf)
        {
            uint s1 = 1;
            uint s2 = 0;
            int length = buf.Length;

            for (int idx = 0; idx < length; idx++)
            {
                s1 = (s1 + (uint)buf[idx]) % _ADLER32_BASE;
                s2 = (s2 + s1) % _ADLER32_BASE;
            }

            return (s2 << 16) + s1;
        }
    }

   最后我们来看看运行的效果如下，如需源码请点击 SLInkPresenter.zip下载：