IO帮助类是什么？IO帮助类的实例介绍（附代码）

using System;
using System.IO;
using System.Web;
using System.Drawing;
using System.Drawing.Imaging;
using System.Drawing.Drawing2D;
using System.Xml.Serialization;

namespace ZMM.Core
{
    /// <summary>
    /// IO帮助类
    /// </summary>
    public class IOHelper
    {
        //是否已经加载了JPEG编码解码器
        private static bool _isloadjpegcodec = false;
        //当前系统安装的JPEG编码解码器
        private static ImageCodecInfo _jpegcodec = null;

        /// <summary>
        /// 获得文件物理路径
        /// </summary>
        /// <returns></returns>
        public static string GetMapPath(string path)
        {
            if (HttpContext.Current != null)
            {
                return HttpContext.Current.Server.MapPath(path);
            }
            else
            {
                return System.Web.Hosting.HostingEnvironment.MapPath(path);
            }
        }

        #region  序列化

        /// <summary>
        /// XML序列化
        /// </summary>
        /// <param name="obj">序列对象</param>
        /// <param name="filePath">XML文件路径</param>
        /// <returns>是否成功</returns>
        public static bool SerializeToXml(object obj, string filePath)
        {
            bool result = false;

            FileStream fs = null;
            try
            {
                fs = new FileStream(filePath, FileMode.Create, FileAccess.Write, FileShare.ReadWrite);
                XmlSerializer serializer = new XmlSerializer(obj.GetType());
                serializer.Serialize(fs, obj);
                result = true;
            }
            catch (Exception ex)
            {
                throw ex;
            }
            finally
            {
                if (fs != null)
                    fs.Close();
            }
            return result;

        }

        /// <summary>
        /// XML反序列化
        /// </summary>
        /// <param name="type">目标类型(Type类型)</param>
        /// <param name="filePath">XML文件路径</param>
        /// <returns>序列对象</returns>
        public static object DeserializeFromXML(Type type, string filePath)
        {
            FileStream fs = null;
            try
            {
                fs = new FileStream(filePath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
                XmlSerializer serializer = new XmlSerializer(type);
                return serializer.Deserialize(fs);
            }
            catch (Exception ex)
            {
                throw ex;
            }
            finally
            {
                if (fs != null)
                    fs.Close();
            }
        }

        #endregion

        #region  水印,缩略图

        /// <summary>
        /// 获得当前系统安装的JPEG编码解码器
        /// </summary>
        /// <returns></returns>
        public static ImageCodecInfo GetJPEGCodec()
        {
            if (_isloadjpegcodec == true)
                return _jpegcodec;

            ImageCodecInfo[] codecsList = ImageCodecInfo.GetImageEncoders();
            foreach (ImageCodecInfo codec in codecsList)
            {
                if (codec.MimeType.IndexOf("jpeg") > -1)
                {
                    _jpegcodec = codec;
                    break;
                }

            }
            _isloadjpegcodec = true;
            return _jpegcodec;
        }

        /// <summary>
        /// 生成缩略图
        /// </summary>
        /// <param name="imagePath">图片路径</param>
        /// <param name="thumbPath">缩略图路径</param>
        /// <param name="width">缩略图宽度</param>
        /// <param name="height">缩略图高度</param>
        /// <param name="mode">生成缩略图的方式</param>   
        public static void GenerateThumb(string imagePath, string thumbPath, int width, int height, string mode)
        {
            Image image = Image.FromFile(imagePath);

            string extension = imagePath.Substring(imagePath.LastIndexOf(".")).ToLower();
            ImageFormat imageFormat = null;
            switch (extension)
            {
                case ".jpg":
                case ".jpeg":
                    imageFormat = ImageFormat.Jpeg;
                    break;
                case ".bmp":
                    imageFormat = ImageFormat.Bmp;
                    break;
                case ".png":
                    imageFormat = ImageFormat.Png;
                    break;
                case ".gif":
                    imageFormat = ImageFormat.Gif;
                    break;
                default:
                    imageFormat = ImageFormat.Jpeg;
                    break;
            }

            int toWidth = width > 0 ? width : image.Width;
            int toHeight = height > 0 ? height : image.Height;

            int x = 0;
            int y = 0;
            int ow = image.Width;
            int oh = image.Height;

            switch (mode)
            {
                case "HW"://指定高宽缩放（可能变形）           
                    break;
                case "W"://指定宽，高按比例             
                    toHeight = image.Height * width / image.Width;
                    break;
                case "H"://指定高，宽按比例
                    toWidth = image.Width * height / image.Height;
                    break;
                case "Cut"://指定高宽裁减（不变形）           
                    if ((double)image.Width / (double)image.Height > (double)toWidth / (double)toHeight)
                    {
                        oh = image.Height;
                        ow = image.Height * toWidth / toHeight;
                        y = 0;
                        x = (image.Width - ow) / 2;
                    }
                    else
                    {
                        ow = image.Width;
                        oh = image.Width * height / toWidth;
                        x = 0;
                        y = (image.Height - oh) / 2;
                    }
                    break;
                default:
                    break;
            }

            //新建一个bmp
            Image bitmap = new Bitmap(toWidth, toHeight);

            //新建一个画板
            Graphics g = Graphics.FromImage(bitmap);

            //设置高质量插值法
            g.InterpolationMode = InterpolationMode.High;

            //设置高质量,低速度呈现平滑程度
            g.SmoothingMode = SmoothingMode.HighQuality;

            //清空画布并以透明背景色填充
            g.Clear(Color.Transparent);

            //在指定位置并且按指定大小绘制原图片的指定部分
            g.DrawImage(image,
                        new Rectangle(0, 0, toWidth, toHeight),
                        new Rectangle(x, y, ow, oh),
                        GraphicsUnit.Pixel);

            try
            {
                bitmap.Save(thumbPath, imageFormat);
            }
            catch (Exception ex)
            {
                throw ex;
            }
            finally
            {
                if (g != null)
                    g.Dispose();
                if (bitmap != null)
                    bitmap.Dispose();
                if (image != null)
                    image.Dispose();
            }
        }

        /// <summary>
        /// 生成图片水印
        /// </summary>
        /// <param name="originalPath">源图路径</param>
        /// <param name="watermarkPath">水印图片路径</param>
        /// <param name="targetPath">保存路径</param>
        /// <param name="position">位置</param>
        /// <param name="opacity">透明度</param>
        /// <param name="quality">质量</param>
        public static void GenerateImageWatermark(string originalPath, string watermarkPath, string targetPath, int position, int opacity, int quality)
        {
            Image originalImage = null;
            Image watermarkImage = null;
            //图片属性
            ImageAttributes attributes = null;
            //画板
            Graphics g = null;
            try
            {

                originalImage = Image.FromFile(originalPath);
                watermarkImage = new Bitmap(watermarkPath);

                if (watermarkImage.Height >= originalImage.Height || watermarkImage.Width >= originalImage.Width)
                {
                    originalImage.Save(targetPath);
                    return;
                }

                if (quality < 0 || quality > 100)
                    quality = 80;

                //水印透明度
                float iii;
                if (opacity > 0 && opacity <= 10)
                    iii = (float)(opacity / 10.0F);
                else
                    iii = 0.5F;

                //水印位置
                int x = 0;
                int y = 0;
                switch (position)
                {
                    case 1:
                        x = (int)(originalImage.Width * (float).01);
                        y = (int)(originalImage.Height * (float).01);
                        break;
                    case 2:
                        x = (int)((originalImage.Width * (float).50) - (watermarkImage.Width / 2));
                        y = (int)(originalImage.Height * (float).01);
                        break;
                    case 3:
                        x = (int)((originalImage.Width * (float).99) - (watermarkImage.Width));
                        y = (int)(originalImage.Height * (float).01);
                        break;
                    case 4:
                        x = (int)(originalImage.Width * (float).01);
                        y = (int)((originalImage.Height * (float).50) - (watermarkImage.Height / 2));
                        break;
                    case 5:
                        x = (int)((originalImage.Width * (float).50) - (watermarkImage.Width / 2));
                        y = (int)((originalImage.Height * (float).50) - (watermarkImage.Height / 2));
                        break;
                    case 6:
                        x = (int)((originalImage.Width * (float).99) - (watermarkImage.Width));
                        y = (int)((originalImage.Height * (float).50) - (watermarkImage.Height / 2));
                        break;
                    case 7:
                        x = (int)(originalImage.Width * (float).01);
                        y = (int)((originalImage.Height * (float).99) - watermarkImage.Height);
                        break;
                    case 8:
                        x = (int)((originalImage.Width * (float).50) - (watermarkImage.Width / 2));
                        y = (int)((originalImage.Height * (float).99) - watermarkImage.Height);
                        break;
                    case 9:
                        x = (int)((originalImage.Width * (float).99) - (watermarkImage.Width));
                        y = (int)((originalImage.Height * (float).99) - watermarkImage.Height);
                        break;
                }

                //颜色映射表
                ColorMap colorMap = new ColorMap();
                colorMap.OldColor = Color.FromArgb(255, 0, 255, 0);
                colorMap.NewColor = Color.FromArgb(0, 0, 0, 0);
                ColorMap[] newColorMap = { colorMap };

                //颜色变换矩阵,iii是设置透明度的范围0到1中的单精度类型
                float[][] newColorMatrix ={ 
                                            new float[] {1.0f,  0.0f,  0.0f,  0.0f, 0.0f},
                                            new float[] {0.0f,  1.0f,  0.0f,  0.0f, 0.0f},
                                            new float[] {0.0f,  0.0f,  1.0f,  0.0f, 0.0f},
                                            new float[] {0.0f,  0.0f,  0.0f,  iii, 0.0f},
                                            new float[] {0.0f,  0.0f,  0.0f,  0.0f, 1.0f}
                                           };
                //定义一个 5 x 5 矩阵
                ColorMatrix matrix = new ColorMatrix(newColorMatrix);

                //图片属性
                attributes = new ImageAttributes();
                attributes.SetRemapTable(newColorMap, ColorAdjustType.Bitmap);
                attributes.SetColorMatrix(matrix, ColorMatrixFlag.Default, ColorAdjustType.Bitmap);

                //画板
                g = Graphics.FromImage(originalImage);
                //绘制水印
                g.DrawImage(watermarkImage, new Rectangle(x, y, watermarkImage.Width, watermarkImage.Height), 0, 0, watermarkImage.Width, watermarkImage.Height, GraphicsUnit.Pixel, attributes);
                //保存图片
                EncoderParameters encoderParams = new EncoderParameters();
                encoderParams.Param[0] = new EncoderParameter(Encoder.Quality, new long[] { quality });
                if (GetJPEGCodec() != null)
                    originalImage.Save(targetPath, _jpegcodec, encoderParams);
                else
                    originalImage.Save(targetPath);
            }
            catch (Exception ex)
            {
                throw ex;
            }
            finally
            {
                if (g != null)
                    g.Dispose();
                if (attributes != null)
                    attributes.Dispose();
                if (watermarkImage != null)
                    watermarkImage.Dispose();
                if (originalImage != null)
                    originalImage.Dispose();
            }
        }

        /// <summary>
        /// 生成文字水印
        /// </summary>
        /// <param name="originalPath">源图路径</param>
        /// <param name="targetPath">保存路径</param>
        /// <param name="text">水印文字</param>
        /// <param name="textSize">文字大小</param>
        /// <param name="textFont">文字字体</param>
        /// <param name="position">位置</param>
        /// <param name="quality">质量</param>
        public static void GenerateTextWatermark(string originalPath, string targetPath, string text, int textSize, string textFont, int position, int quality)
        {
            Image originalImage = null;
            //画板
            Graphics g = null;
            try
            {
                originalImage = Image.FromFile(originalPath);
                //画板
                g = Graphics.FromImage(originalImage);
                if (quality < 0 || quality > 100)
                    quality = 80;

                Font font = new Font(textFont, textSize, FontStyle.Regular, GraphicsUnit.Pixel);
                SizeF sizePair = g.MeasureString(text, font);

                float x = 0;
                float y = 0;

                switch (position)
                {
                    case 1:
                        x = (float)originalImage.Width * (float).01;
                        y = (float)originalImage.Height * (float).01;
                        break;
                    case 2:
                        x = ((float)originalImage.Width * (float).50) - (sizePair.Width / 2);
                        y = (float)originalImage.Height * (float).01;
                        break;
                    case 3:
                        x = ((float)originalImage.Width * (float).99) - sizePair.Width;
                        y = (float)originalImage.Height * (float).01;
                        break;
                    case 4:
                        x = (float)originalImage.Width * (float).01;
                        y = ((float)originalImage.Height * (float).50) - (sizePair.Height / 2);
                        break;
                    case 5:
                        x = ((float)originalImage.Width * (float).50) - (sizePair.Width / 2);
                        y = ((float)originalImage.Height * (float).50) - (sizePair.Height / 2);
                        break;
                    case 6:
                        x = ((float)originalImage.Width * (float).99) - sizePair.Width;
                        y = ((float)originalImage.Height * (float).50) - (sizePair.Height / 2);
                        break;
                    case 7:
                        x = (float)originalImage.Width * (float).01;
                        y = ((float)originalImage.Height * (float).99) - sizePair.Height;
                        break;
                    case 8:
                        x = ((float)originalImage.Width * (float).50) - (sizePair.Width / 2);
                        y = ((float)originalImage.Height * (float).99) - sizePair.Height;
                        break;
                    case 9:
                        x = ((float)originalImage.Width * (float).99) - sizePair.Width;
                        y = ((float)originalImage.Height * (float).99) - sizePair.Height;
                        break;
                }

                g.DrawString(text, font, new SolidBrush(Color.White), x + 1, y + 1);
                g.DrawString(text, font, new SolidBrush(Color.Black), x, y);

                //保存图片
                EncoderParameters encoderParams = new EncoderParameters();
                encoderParams.Param[0] = new EncoderParameter(Encoder.Quality, new long[] { quality });
                if (GetJPEGCodec() != null)
                    originalImage.Save(targetPath, _jpegcodec, encoderParams);
                else
                    originalImage.Save(targetPath);
            }
            catch (Exception ex)
            {
                throw ex;
            }
            finally
            {
                if (g != null)
                    g.Dispose();
                if (originalImage != null)
                    originalImage.Dispose();
            }
        }

        #endregion
    }
}