Silverlight &Windows phone7 中使用Isolated Storage存储与读取图片

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1.将ImageSource转化成WriteableBitmap

var bitmap= new System.Windows.Media.Imaging.WriteableBitmap((System.Windows.Media.Imaging.BitmapSource)this.imgCreatedTag.Source);

2.代码：
 

 /// <summary>
      /// 载入指定名称的图片
      /// </summary>
      /// <param name="fileName"></param>
      /// <returns>返回指定文件的byte[]流</returns>
        private static byte[] _LoadIfExists(string fileName)
        {
            byte[] retVal;

            using (IsolatedStorageFile iso = IsolatedStorageFile.GetUserStoreForApplication())
            {
                if (iso.FileExists(fileName))
                {
                    using (IsolatedStorageFileStream stream =
                    iso.OpenFile(fileName, FileMode.Open))
                    {
                        retVal = new byte[stream.Length];
                        stream.Read(retVal, 0, retVal.Length);
                    }
                }
                else
                {
                    retVal = new byte[0];
                }
            }
            return retVal;
        }
        /// <summary>
        /// 保存byte[]流到Storage
        /// </summary>
        /// <param name="buffer"></param>
        /// <param name="fileName"></param>
        private static void _SaveToDisk(byte[] buffer, string fileName)
        {
            using (IsolatedStorageFile iso =
                IsolatedStorageFile.GetUserStoreForApplication())
            {
                using (
                    IsolatedStorageFileStream stream =
                new IsolatedStorageFileStream(fileName, FileMode.CreateNew,
                                iso))
                {
                    stream.Write(buffer, 0, buffer.Length);
                }
            }
        }
        /// <summary>
        /// 从Storage获取图片
        /// </summary>
        /// <param name="buffer">图片的byte[]流</param>
        /// <returns></returns>
        private static WriteableBitmap _GetImage(byte[] buffer)
        {
            int width = buffer[0] * 256 + buffer[1];
            int height = buffer[2] * 256 + buffer[3];

            long matrixSize = width * height;

            WriteableBitmap retVal = new WriteableBitmap(width, height);

            int bufferPos = 4;

            for (int matrixPos = 0; matrixPos < matrixSize; matrixPos++)
            {
                int pixel = buffer[bufferPos++];
                pixel = pixel << 8 | buffer[bufferPos++];
                pixel = pixel << 8 | buffer[bufferPos++];
                pixel = pixel << 8 | buffer[bufferPos++];
                retVal.Pixels[matrixPos] = pixel;
            }

            return retVal;
        }

        /// <summary>
        /// 将图片转换成byte[]流
        /// </summary>
        /// <param name="bitmap"></param>
        /// <returns></returns>
        private static byte[] _GetSaveBuffer(WriteableBitmap bitmap)
        {
            long matrixSize = bitmap.PixelWidth * bitmap.PixelHeight;

            long byteSize = matrixSize * 4 + 4;

            byte[] retVal = new byte[byteSize];

            long bufferPos = 0;

            retVal[bufferPos++] = (byte)((bitmap.PixelWidth / 256) & 0xff);
            retVal[bufferPos++] = (byte)((bitmap.PixelWidth % 256) & 0xff);
            retVal[bufferPos++] = (byte)((bitmap.PixelHeight / 256) & 0xff);
            retVal[bufferPos++] = (byte)((bitmap.PixelHeight % 256) & 0xff);

            for (int matrixPos = 0; matrixPos < matrixSize; matrixPos++)
            {
                retVal[bufferPos++] = (byte)((bitmap.Pixels[matrixPos] >> 24) & 0xff);
                retVal[bufferPos++] = (byte)((bitmap.Pixels[matrixPos] >> 16) & 0xff);
                retVal[bufferPos++] = (byte)((bitmap.Pixels[matrixPos] >> 8) & 0xff);
                retVal[bufferPos++] = (byte)((bitmap.Pixels[matrixPos]) & 0xff);
            }

            return retVal;
        }