图片截剪

    public class ImageUtil
    {
        #region " 正方型裁剪 "
        /// <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> 
        /// <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(string fromFilePath, 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.FromFile(fromFilePath, 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);
            }
            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.FilenameExtension.Contains(fileSaveUrl.Substring(fileSaveUrl.LastIndexOf('.'), fileSaveUrl.Length - fileSaveUrl.LastIndexOf('.')).ToUpper()))
                    {
                        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>  
        /// <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(string fromFilePath, string fileSaveUrl, int maxWidth, int maxHeight, int quality)
        {
            string dir = Path.GetDirectoryName(fileSaveUrl);
            if (!Directory.Exists(dir))
                Directory.CreateDirectory(dir);
            //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.FromFile(fromFilePath, 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);
            }
            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.FilenameExtension.Contains(fileSaveUrl.Substring(fileSaveUrl.LastIndexOf('.'), fileSaveUrl.Length - fileSaveUrl.LastIndexOf('.')).ToUpper()))
                        {
                            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
    }