silverlight导出图片文件

新建一个Silverlight应用程序，添加下面两个控件：

image控件：image1；

Button控件：Click="Button1_Click";

code-Behind代码如下：

        private void Button1_Click(object sender, RoutedEventArgs e)
        {
            ElementToPNG eTP = new ElementToPNG();
            eTP.ShowSaveDialog(image1);
        }

并添加下面三个类：

//* -------------------------------------------------------------------------------------------------
//* 下面的三个类是处理图片导出的
//* -------------------------------------------------------------------------------------------------
# region Class ElementToPNG
    public class ElementToPNG
    {
        public void ShowSaveDialog(UIElement elementToExport)
        {
            SaveFileDialog sfd = new SaveFileDialog()
            {
                DefaultExt = "png",
                Filter = "Png files (*.png)|*.png|All files (*.*)|*.*",
                FilterIndex = 1
            };

            if (sfd.ShowDialog() == true)
            {
                SaveAsPNG(sfd, elementToExport);
            }
        }
        private void SaveAsPNG(SaveFileDialog sfd, UIElement elementToExport)
        {
            WriteableBitmap bitmap = new WriteableBitmap(elementToExport, new TranslateTransform());
            EditableImage imageData = new EditableImage(bitmap.PixelWidth, bitmap.PixelHeight);
            try
            {
                for (int y = 0; y < bitmap.PixelHeight; ++y)
                {
                    for (int x = 0; x < bitmap.PixelWidth; ++x)
                    {
                        int pixel = bitmap.Pixels[bitmap.PixelWidth * y + x];
                        imageData.SetPixel(x, y,
                        (byte)((pixel >> 16) & 0xFF),
                        (byte)((pixel >> 8) & 0xFF),
                        (byte)(pixel & 0xFF), (byte)((pixel >> 24) & 0xFF)
                        );
                    }
                }
            }
            catch (System.Security.SecurityException)
            {
                throw new Exception("Cannot print images from other domains");
            }
            Stream pngStream = imageData.GetStream();
            byte[] binaryData = new Byte[pngStream.Length];
            long bytesRead = pngStream.Read(binaryData, 0, (int)pngStream.Length);
            Stream stream = sfd.OpenFile();
            stream.Write(binaryData, 0, binaryData.Length);
            stream.Close();
        }
    }
# endregion

# region Class EditableImage
    public class EditableImage
    {
        private int _width = 0;
        private int _height = 0;
        private bool _init = false;
        private byte[] _buffer;
        private int _rowLength;

        public event EventHandler<EditableImageErrorEventArgs> ImageError;

        public EditableImage(int width, int height)
        {
            this.Width = width;
            this.Height = height;
        }

        public int Width
        {
            get
            {
                return _width;
            }
            set
            {
                if (_init)
                {
                    OnImageError("Error: Cannot change Width after the EditableImage has been initialized");
                }
                else if ((value <= 0) || (value > 2047))
                {
                    OnImageError("Error: Width must be between 0 and 2047");
                }
                else
                {
                    _width = value;
                }
            }
        }

        public int Height
        {
            get
            {
                return _height;
            }
            set
            {
                if (_init)
                {
                    OnImageError("Error: Cannot change Height after the EditableImage has been initialized");
                }
                else if ((value <= 0) || (value > 2047))
                {
                    OnImageError("Error: Height must be between 0 and 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; }
            }
        }

    }
# endregion

# region Class PngEncoder
    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 };


        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);

            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;

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

            // Calculate number of 64K blocks
            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;
            }

            // Write headers
            comp.WriteByte(0x78);
            comp.WriteByte(0xDA);

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

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

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

                // Write one's compliment of LEN
                comp.Write(BitConverter.GetBytes((ushort)~length), 0, 2);

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

                // Next block
                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];

            // Initialize buffer
            for (idx = 0; idx < type.Length; idx++)
            {
                buffer[idx] = type[idx];
            }

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

            // Write length
            WriteReversedBuffer(stream, BitConverter.GetBytes(data.Length));

            // Write type and data
            stream.Write(buffer, 0, buffer.Length);   // Should always be 4 bytes

            // Compute and write the 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;
        }
        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;
        }
    }
# endregion
//* -------------------------------------------------------------------------------------------------
//* -------------------------------------------------------------------------------------------------