转：C#图片处理类(裁剪,缩放,清晰度,水印)

using System;  

using System.Collections.Generic;  

using System.Text;  

using System.IO;  

using System.Drawing;  

using System.Drawing.Drawing2D;  

using System.Drawing.Imaging;  

   

namespace WuJian.Common  

{  

    /// <summary>  

    /// 图片处理类  

    /// 吴剑 2008-07-02 创建  

    /// 吴剑 2011-01-21 修改  

    /// </summary>  

    public class PTImage  

    {  

        #region 正方型裁剪并缩放  

        /// <summary>  

        /// 正方型裁剪  

        /// 以图片中心为轴心，截取正方型，然后等比缩放  

        /// 用于头像处理  

        /// </summary>  

        /// <remarks>吴剑 2010-11-23</remarks>  

        /// <param name="postedFile">原图HttpPostedFile对象</param>  

        /// <param name="fileSaveUrl">缩略图存放地址</param>  

        /// <param name="side">指定的边长（正方型）</param>  

        /// <param name="quality">质量（范围0-100）</param>  

        public static void CutForSquare(System.Web.HttpPostedFile postedFile, string fileSaveUrl, int side, int quality)  

        {  

            //创建目录  

            string dir = Path.GetDirectoryName(fileSaveUrl);  

            if (!Directory.Exists(dir))  

                Directory.CreateDirectory(dir);  

   

            //原始图片（获取原始图片创建对象，并使用流中嵌入的颜色管理信息）  

            System.Drawing.Image initImage = System.Drawing.Image.FromStream(postedFile.InputStream, true);  

   

            //原图宽高均小于模版，不作处理，直接保存  

            if (initImage.Width <= side && initImage.Height <= side)  

            {  

                initImage.Save(fileSaveUrl, System.Drawing.Imaging.ImageFormat.Jpeg);  

            }  

            else 

            {  

                //原始图片的宽、高  

                int initWidth = initImage.Width;  

                int initHeight = initImage.Height;  

   

                //非正方型先裁剪为正方型  

                if (initWidth != initHeight)  

                {  

                    //截图对象  

                    System.Drawing.Image pickedImage = null;  

                    System.Drawing.Graphics pickedG = null;  

   

                    //宽大于高的横图  

                    if (initWidth > initHeight)  

                    {  

                        //对象实例化  

                        pickedImage = new System.Drawing.Bitmap(initHeight, initHeight);  

                        pickedG = System.Drawing.Graphics.FromImage(pickedImage);  

                        //设置质量  

                        pickedG.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;  

                        pickedG.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;  

                        //定位  

                        Rectangle fromR = new Rectangle((initWidth - initHeight) / 2, 0, initHeight, initHeight);  

                        Rectangle toR = new Rectangle(0, 0, initHeight, initHeight);  

                        //画图  

                        pickedG.DrawImage(initImage, toR, fromR, System.Drawing.GraphicsUnit.Pixel);  

                        //重置宽  

                        initWidth = initHeight;  

                    }  

                    //高大于宽的竖图  

                    else 

                    {  

                        //对象实例化  

                        pickedImage = new System.Drawing.Bitmap(initWidth, initWidth);  

                        pickedG = System.Drawing.Graphics.FromImage(pickedImage);  

                        //设置质量  

                        pickedG.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;  

                        pickedG.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;  

                        //定位  

                        Rectangle fromR = new Rectangle(0, (initHeight - initWidth) / 2, initWidth, initWidth);  

                        Rectangle toR = new Rectangle(0, 0, initWidth, initWidth);  

                        //画图  

                        pickedG.DrawImage(initImage, toR, fromR, System.Drawing.GraphicsUnit.Pixel);  

                        //重置高  

                        initHeight = initWidth;  

                    }  

   

                    //将截图对象赋给原图  

                    initImage = (System.Drawing.Image)pickedImage.Clone();  

                    //释放截图资源  

                    pickedG.Dispose();  

                    pickedImage.Dispose();  

                }  

   

                //缩略图对象  

                System.Drawing.Image resultImage = new System.Drawing.Bitmap(side, side);  

                System.Drawing.Graphics resultG = System.Drawing.Graphics.FromImage(resultImage);  

                //设置质量  

                resultG.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;  

                resultG.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;  

                //用指定背景色清空画布  

                resultG.Clear(Color.White);  

                //绘制缩略图  

                resultG.DrawImage(initImage, new System.Drawing.Rectangle(0, 0, side, side), new System.Drawing.Rectangle(0, 0, initWidth, initHeight), System.Drawing.GraphicsUnit.Pixel);  

   

                //关键质量控制  

                //获取系统编码类型数组,包含了jpeg,bmp,png,gif,tiff  

                ImageCodecInfo[] icis = ImageCodecInfo.GetImageEncoders();  

                ImageCodecInfo ici = null;  

                foreach (ImageCodecInfo i in icis)  

                {  

                    if (i.MimeType == "image/jpeg" || i.MimeType == "image/bmp" || i.MimeType == "image/png" || i.MimeType == "image/gif")  

                    {  

                        ici = i;  

                    }  

                }  

                EncoderParameters ep = new EncoderParameters(1);  

                ep.Param[0] = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, (long)quality);  

   

                //保存缩略图  

                resultImage.Save(fileSaveUrl, ici, ep);  

   

                //释放关键质量控制所用资源  

                ep.Dispose();  

   

                //释放缩略图资源  

                resultG.Dispose();  

                resultImage.Dispose();  

   

                //释放原始图片资源  

                initImage.Dispose();  

            }  

        }  

   

        /// <summary>  

        /// 正方型裁剪  

        /// 以图片中心为轴心，截取正方型，然后等比缩放  

        /// 用于头像处理  

        /// </summary>  

        /// <remarks>吴剑 2010-11-23</remarks>  

        /// <param name="postedFile">原图HttpPostedFile对象</param>  

        /// <param name="fileSaveUrl">缩略图存放地址</param>  

        /// <param name="side">指定的边长（正方型）</param>  

        /// <param name="quality">质量（范围0-100）</param>  

        public static void CutForSquare(System.IO.Stream fromFile, string fileSaveUrl, int side, int quality)  

        {  

            //创建目录  

            string dir = Path.GetDirectoryName(fileSaveUrl);  

            if (!Directory.Exists(dir))  

                Directory.CreateDirectory(dir);  

   

            //原始图片（获取原始图片创建对象，并使用流中嵌入的颜色管理信息）  

            System.Drawing.Image initImage = System.Drawing.Image.FromStream(fromFile, true);  

   

            //原图宽高均小于模版，不作处理，直接保存  

            if (initImage.Width <= side && initImage.Height <= side)  

            {  

                initImage.Save(fileSaveUrl, System.Drawing.Imaging.ImageFormat.Jpeg);  

            }  

            else 

            {  

                //原始图片的宽、高  

                int initWidth = initImage.Width;  

                int initHeight = initImage.Height;  

   

                //非正方型先裁剪为正方型  

                if (initWidth != initHeight)  

                {  

                    //截图对象  

                    System.Drawing.Image pickedImage = null;  

                    System.Drawing.Graphics pickedG = null;  

   

                    //宽大于高的横图  

                    if (initWidth > initHeight)  

                    {  

                        //对象实例化  

                        pickedImage = new System.Drawing.Bitmap(initHeight, initHeight);  

                        pickedG = System.Drawing.Graphics.FromImage(pickedImage);  

                        //设置质量  

                        pickedG.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;  

                        pickedG.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;  

                        //定位  

                        Rectangle fromR = new Rectangle((initWidth - initHeight) / 2, 0, initHeight, initHeight);  

                        Rectangle toR = new Rectangle(0, 0, initHeight, initHeight);  

                        //画图  

                        pickedG.DrawImage(initImage, toR, fromR, System.Drawing.GraphicsUnit.Pixel);  

                        //重置宽  

                        initWidth = initHeight;  

                    }  

                    //高大于宽的竖图  

                    else 

                    {  

                        //对象实例化  

                        pickedImage = new System.Drawing.Bitmap(initWidth, initWidth);  

                        pickedG = System.Drawing.Graphics.FromImage(pickedImage);  

                        //设置质量  

                        pickedG.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;  

                        pickedG.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;  

                        //定位  

                        Rectangle fromR = new Rectangle(0, (initHeight - initWidth) / 2, initWidth, initWidth);  

                        Rectangle toR = new Rectangle(0, 0, initWidth, initWidth);  

                        //画图  

                        pickedG.DrawImage(initImage, toR, fromR, System.Drawing.GraphicsUnit.Pixel);  

                        //重置高  

                        initHeight = initWidth;  

                    }  

   

                    //将截图对象赋给原图  

                    initImage = (System.Drawing.Image)pickedImage.Clone();  

                    //释放截图资源  

                    pickedG.Dispose();  

                    pickedImage.Dispose();  

                }  

   

                //缩略图对象  

                System.Drawing.Image resultImage = new System.Drawing.Bitmap(side, side);  

                System.Drawing.Graphics resultG = System.Drawing.Graphics.FromImage(resultImage);  

                //设置质量  

                resultG.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;  

                resultG.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;  

                //用指定背景色清空画布  

                resultG.Clear(Color.White);  

                //绘制缩略图  

                resultG.DrawImage(initImage, new System.Drawing.Rectangle(0, 0, side, side), new System.Drawing.Rectangle(0, 0, initWidth, initHeight), System.Drawing.GraphicsUnit.Pixel);  

   

                //关键质量控制  

                //获取系统编码类型数组,包含了jpeg,bmp,png,gif,tiff  

                ImageCodecInfo[] icis = ImageCodecInfo.GetImageEncoders();  

                ImageCodecInfo ici = null;  

                foreach (ImageCodecInfo i in icis)  

                {  

                    if (i.MimeType == "image/jpeg" || i.MimeType == "image/bmp" || i.MimeType == "image/png" || i.MimeType == "image/gif")  

                    {  

                        ici = i;  

                    }  

                }  

                EncoderParameters ep = new EncoderParameters(1);  

                ep.Param[0] = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, (long)quality);  

   

                //保存缩略图  

                resultImage.Save(fileSaveUrl, ici, ep);  

   

                //释放关键质量控制所用资源  

                ep.Dispose();  

   

                //释放缩略图资源  

                resultG.Dispose();  

                resultImage.Dispose();  

   

                //释放原始图片资源  

                initImage.Dispose();  

            }  

        }  

        #endregion  

   

        #region 固定模版裁剪并缩放  

        /// <summary>  

        /// 指定长宽裁剪  

        /// 按模版比例最大范围的裁剪图片并缩放至模版尺寸  

        /// </summary>  

        /// <remarks>吴剑 2010-11-15</remarks>  

        /// <param name="postedFile">原图HttpPostedFile对象</param>  

        /// <param name="fileSaveUrl">保存路径</param>  

        /// <param name="maxWidth">最大宽(单位:px)</param>  

        /// <param name="maxHeight">最大高(单位:px)</param>  

        /// <param name="quality">质量（范围0-100）</param>  

        public static void CutForCustom(System.Web.HttpPostedFile postedFile, string fileSaveUrl, int maxWidth, int maxHeight, int quality)  

        {  

            //从文件获取原始图片，并使用流中嵌入的颜色管理信息  

            System.Drawing.Image initImage = System.Drawing.Image.FromStream(postedFile.InputStream, true);  

   

            //原图宽高均小于模版，不作处理，直接保存  

            if (initImage.Width <= maxWidth && initImage.Height <= maxHeight)  

            {  

                initImage.Save(fileSaveUrl, System.Drawing.Imaging.ImageFormat.Jpeg);  

            }  

            else 

            {  

                //模版的宽高比例  

                double templateRate = (double)maxWidth / maxHeight;  

                //原图片的宽高比例  

                double initRate = (double)initImage.Width / initImage.Height;  

   

                //原图与模版比例相等，直接缩放  

                if (templateRate == initRate)  

                {  

                    //按模版大小生成最终图片  

                    System.Drawing.Image templateImage = new System.Drawing.Bitmap(maxWidth, maxHeight);  

                    System.Drawing.Graphics templateG = System.Drawing.Graphics.FromImage(templateImage);  

                    templateG.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;  

                    templateG.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;  

                    templateG.Clear(Color.White);  

                    templateG.DrawImage(initImage, new System.Drawing.Rectangle(0, 0, maxWidth, maxHeight), new System.Drawing.Rectangle(0, 0, initImage.Width, initImage.Height), System.Drawing.GraphicsUnit.Pixel);  

                    templateImage.Save(fileSaveUrl, System.Drawing.Imaging.ImageFormat.Jpeg);  

                }  

                //原图与模版比例不等，裁剪后缩放  

                else 

                {  

                    //裁剪对象  

                    System.Drawing.Image pickedImage = null;  

                    System.Drawing.Graphics pickedG = null;  

   

                    //定位  

                    Rectangle fromR = new Rectangle(0, 0, 0, 0);//原图裁剪定位  

                    Rectangle toR = new Rectangle(0, 0, 0, 0);//目标定位  

   

                    //宽为标准进行裁剪  

                    if (templateRate > initRate)  

                    {  

                        //裁剪对象实例化  

                        pickedImage = new System.Drawing.Bitmap(initImage.Width, (int)Math.Floor(initImage.Width / templateRate));  

                        pickedG = System.Drawing.Graphics.FromImage(pickedImage);  

   

                        //裁剪源定位  

                        fromR.X = 0;  

                        fromR.Y = (int)Math.Floor((initImage.Height - initImage.Width / templateRate) / 2);  

                        fromR.Width = initImage.Width;  

                        fromR.Height = (int)Math.Floor(initImage.Width / templateRate);  

   

                        //裁剪目标定位  

                        toR.X = 0;  

                        toR.Y = 0;  

                        toR.Width = initImage.Width;  

                        toR.Height = (int)Math.Floor(initImage.Width / templateRate);  

                    }  

                    //高为标准进行裁剪  

                    else 

                    {  

                        pickedImage = new System.Drawing.Bitmap((int)Math.Floor(initImage.Height * templateRate), initImage.Height);  

                        pickedG = System.Drawing.Graphics.FromImage(pickedImage);  

   

                        fromR.X = (int)Math.Floor((initImage.Width - initImage.Height * templateRate) / 2);  

                        fromR.Y = 0;  

                        fromR.Width = (int)Math.Floor(initImage.Height * templateRate);  

                        fromR.Height = initImage.Height;  

   

                        toR.X = 0;  

                        toR.Y = 0;  

                        toR.Width = (int)Math.Floor(initImage.Height * templateRate);  

                        toR.Height = initImage.Height;  

                    }  

   

                    //设置质量  

                    pickedG.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;  

                    pickedG.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;  

   

                    //裁剪  

                    pickedG.DrawImage(initImage, toR, fromR, System.Drawing.GraphicsUnit.Pixel);  

   

                    //按模版大小生成最终图片  

                    System.Drawing.Image templateImage = new System.Drawing.Bitmap(maxWidth, maxHeight);  

                    System.Drawing.Graphics templateG = System.Drawing.Graphics.FromImage(templateImage);  

                    templateG.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;  

                    templateG.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;  

                    templateG.Clear(Color.White);  

                    templateG.DrawImage(pickedImage, new System.Drawing.Rectangle(0, 0, maxWidth, maxHeight), new System.Drawing.Rectangle(0, 0, pickedImage.Width, pickedImage.Height), System.Drawing.GraphicsUnit.Pixel);  

   

                    //关键质量控制  

                    //获取系统编码类型数组,包含了jpeg,bmp,png,gif,tiff  

                    ImageCodecInfo[] icis = ImageCodecInfo.GetImageEncoders();  

                    ImageCodecInfo ici = null;  

                    foreach (ImageCodecInfo i in icis)  

                    {  

                        if (i.MimeType == "image/jpeg" || i.MimeType == "image/bmp" || i.MimeType == "image/png" || i.MimeType == "image/gif")  

                        {  

                            ici = i;  

                        }  

                    }  

                    EncoderParameters ep = new EncoderParameters(1);  

                    ep.Param[0] = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, (long)quality);  

   

                    //保存缩略图  

                    templateImage.Save(fileSaveUrl, ici, ep);  

                    //templateImage.Save(fileSaveUrl, System.Drawing.Imaging.ImageFormat.Jpeg);  

   

                    //释放资源  

                    templateG.Dispose();  

                    templateImage.Dispose();  

   

                    pickedG.Dispose();  

                    pickedImage.Dispose();  

                }  

            }  

   

            //释放资源  

            initImage.Dispose();  

        }  

        #endregion  

   

        #region 等比缩放  

        /// <summary>  

        /// 图片等比缩放  

        /// </summary>  

        /// <remarks>吴剑 2011-01-21</remarks>  

        /// <param name="postedFile">原图HttpPostedFile对象</param>  

        /// <param name="savePath">缩略图存放地址</param>  

        /// <param name="targetWidth">指定的最大宽度</param>  

        /// <param name="targetHeight">指定的最大高度</param>  

        /// <param name="watermarkText">水印文字(为""表示不使用水印)</param>  

        /// <param name="watermarkImage">水印图片路径(为""表示不使用水印)</param>  

        public static void ZoomAuto(System.Web.HttpPostedFile postedFile, string savePath, System.Double targetWidth, System.Double targetHeight, string watermarkText, string watermarkImage)  

        {  

            //创建目录  

            string dir = Path.GetDirectoryName(savePath);  

            if (!Directory.Exists(dir))  

                Directory.CreateDirectory(dir);  

   

            //原始图片（获取原始图片创建对象，并使用流中嵌入的颜色管理信息）  

            System.Drawing.Image initImage = System.Drawing.Image.FromStream(postedFile.InputStream, true);  

   

            //原图宽高均小于模版，不作处理，直接保存  

            if (initImage.Width <= targetWidth && initImage.Height <= targetHeight)  

            {  

                //文字水印  

                if (watermarkText != "")  

                {  

                    using (System.Drawing.Graphics gWater = System.Drawing.Graphics.FromImage(initImage))  

                    {  

                        System.Drawing.Font fontWater = new Font("黑体", 10);  

                        System.Drawing.Brush brushWater = new SolidBrush(Color.White);  

                        gWater.DrawString(watermarkText, fontWater, brushWater, 10, 10);  

                        gWater.Dispose();  

                    }  

                }  

   

                //透明图片水印  

                if (watermarkImage != "")  

                {  

                    if (File.Exists(watermarkImage))  

                    {  

                        //获取水印图片  

                        using (System.Drawing.Image wrImage = System.Drawing.Image.FromFile(watermarkImage))  

                        {  

                            //水印绘制条件：原始图片宽高均大于或等于水印图片  

                            if (initImage.Width >= wrImage.Width && initImage.Height >= wrImage.Height)  

                            {  

                                Graphics gWater = Graphics.FromImage(initImage);  

   

                                //透明属性  

                                ImageAttributes imgAttributes = new ImageAttributes();  

                                ColorMap colorMap = new ColorMap();  

                                colorMap.OldColor = Color.FromArgb(255, 0, 255, 0);  

                                colorMap.NewColor = Color.FromArgb(0, 0, 0, 0);  

                                ColorMap[] remapTable = { colorMap };  

                                imgAttributes.SetRemapTable(remapTable, ColorAdjustType.Bitmap);  

   

                                float[][] colorMatrixElements = {   

                                   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,  0.5f, 0.0f},//透明度:0.5  

                                   new float[] {0.0f,  0.0f,  0.0f,  0.0f, 1.0f}  

                                };  

   

                                ColorMatrix wmColorMatrix = new ColorMatrix(colorMatrixElements);  

                                imgAttributes.SetColorMatrix(wmColorMatrix, ColorMatrixFlag.Default, ColorAdjustType.Bitmap);  

                                gWater.DrawImage(wrImage, new Rectangle(initImage.Width - wrImage.Width, initImage.Height - wrImage.Height, wrImage.Width, wrImage.Height), 0, 0, wrImage.Width, wrImage.Height, GraphicsUnit.Pixel, imgAttributes);  

   

                                gWater.Dispose();  

                            }  

                            wrImage.Dispose();  

                        }  

                    }  

                }  

   

                //保存  

                initImage.Save(savePath, System.Drawing.Imaging.ImageFormat.Jpeg);  

            }  

            else 

            {  

                //缩略图宽、高计算  

                double newWidth = initImage.Width;  

                double newHeight = initImage.Height;  

   

                //宽大于高或宽等于高（横图或正方）  

                if (initImage.Width > initImage.Height || initImage.Width == initImage.Height)  

                {  

                    //如果宽大于模版  

                    if (initImage.Width > targetWidth)  

                    {  

                        //宽按模版，高按比例缩放  

                        newWidth = targetWidth;  

                        newHeight = initImage.Height * (targetWidth / initImage.Width);  

                    }  

                }  

                //高大于宽（竖图）  

                else 

                {  

                    //如果高大于模版  

                    if (initImage.Height > targetHeight)  

                    {  

                        //高按模版，宽按比例缩放  

                        newHeight = targetHeight;  

                        newWidth = initImage.Width * (targetHeight / initImage.Height);  

                    }  

                }  

   

                //生成新图  

                //新建一个bmp图片  

                System.Drawing.Image newImage = new System.Drawing.Bitmap((int)newWidth, (int)newHeight);  

                //新建一个画板  

                System.Drawing.Graphics newG = System.Drawing.Graphics.FromImage(newImage);  

   

                //设置质量  

                newG.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;  

                newG.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;  

   

                //置背景色  

                newG.Clear(Color.White);  

                //画图  

                newG.DrawImage(initImage, new System.Drawing.Rectangle(0, 0, newImage.Width, newImage.Height), new System.Drawing.Rectangle(0, 0, initImage.Width, initImage.Height), System.Drawing.GraphicsUnit.Pixel);  

   

                //文字水印  

                if (watermarkText != "")  

                {  

                    using (System.Drawing.Graphics gWater = System.Drawing.Graphics.FromImage(newImage))  

                    {  

                        System.Drawing.Font fontWater = new Font("宋体", 10);  

                        System.Drawing.Brush brushWater = new SolidBrush(Color.White);  

                        gWater.DrawString(watermarkText, fontWater, brushWater, 10, 10);  

                        gWater.Dispose();  

                    }  

                }  

   

                //透明图片水印  

                if (watermarkImage != "")  

                {  

                    if (File.Exists(watermarkImage))  

                    {  

                        //获取水印图片  

                        using (System.Drawing.Image wrImage = System.Drawing.Image.FromFile(watermarkImage))  

                        {  

                            //水印绘制条件：原始图片宽高均大于或等于水印图片  

                            if (newImage.Width >= wrImage.Width && newImage.Height >= wrImage.Height)  

                            {  

                                Graphics gWater = Graphics.FromImage(newImage);  

   

                                //透明属性  

                                ImageAttributes imgAttributes = new ImageAttributes();  

                                ColorMap colorMap = new ColorMap();  

                                colorMap.OldColor = Color.FromArgb(255, 0, 255, 0);  

                                colorMap.NewColor = Color.FromArgb(0, 0, 0, 0);  

                                ColorMap[] remapTable = { colorMap };  

                                imgAttributes.SetRemapTable(remapTable, ColorAdjustType.Bitmap);  

   

                                float[][] colorMatrixElements = {   

                                   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,  0.5f, 0.0f},//透明度:0.5  

                                   new float[] {0.0f,  0.0f,  0.0f,  0.0f, 1.0f}  

                                };  

   

                                ColorMatrix wmColorMatrix = new ColorMatrix(colorMatrixElements);  

                                imgAttributes.SetColorMatrix(wmColorMatrix, ColorMatrixFlag.Default, ColorAdjustType.Bitmap);  

                                gWater.DrawImage(wrImage, new Rectangle(newImage.Width - wrImage.Width, newImage.Height - wrImage.Height, wrImage.Width, wrImage.Height), 0, 0, wrImage.Width, wrImage.Height, GraphicsUnit.Pixel, imgAttributes);  

                                gWater.Dispose();  

                            }  

                            wrImage.Dispose();  

                        }  

                    }  

                }  

   

                //保存缩略图  

                newImage.Save(savePath, System.Drawing.Imaging.ImageFormat.Jpeg);  

   

                //释放资源  

                newG.Dispose();  

                newImage.Dispose();  

                initImage.Dispose();  

            }  

        }  

           

        #endregion          

   

        #region 其它  

        /// <summary>  

        /// 判断文件类型是否为WEB格式图片  

        /// (注：JPG,GIF,BMP,PNG)  

        /// </summary>  

        /// <param name="contentType">HttpPostedFile.ContentType</param>  

        /// <returns></returns>  

        public static bool IsWebImage(string contentType)  

        {  

            if (contentType == "image/pjpeg" || contentType == "image/jpeg" || contentType == "image/gif" || contentType == "image/bmp" || contentType == "image/png")  

            {  

                return true;  

            }  

            else 

            {  

                return false;  

            }  

        }  

   

        #endregion  

    }//end class  

} 

感谢：吴剑

该代码来自：http://www.cnblogs.com/wu-jian/archive/2011/02/21/1959382.html