图片裁切

    /// <summary>
    /// 图片转换
    /// </summary>
    public class ImageConvert
    {
        public ImageConvert()
        { }

        public bool ImageConvertToMiniPicture(string originalImagePath, string thumbnailPath, int width, int height, string mode)
        {
            try
            {
                System.Drawing.Image originalImage = System.Drawing.Image.FromFile(originalImagePath);

                int iImageWidth = originalImage.Width;
                int iImageHeight = originalImage.Height;

                originalImage.Dispose();

                if (iImageWidth > iImageHeight)
                {
                    this.MakeThumbnail(originalImagePath, thumbnailPath, width, height, "W");
                }
                else
                {
                    this.MakeThumbnail(originalImagePath, thumbnailPath, width, height, "H");
                }

                return true;
            }
            catch (Exception)
            {
                return false;
            }
        }

        public static System.Drawing.Image Crop(System.Drawing.Image originalImage)
        {
            int sideLength = 0;
            if (originalImage.Width > originalImage.Height)
                sideLength = originalImage.Height;
            else
                sideLength = originalImage.Width;

            return Crop(originalImage, -1, -1, sideLength, sideLength);
        }

        /// <summary>
        /// 切取给定图像中心位置指定宽度和高度的图像
        /// </summary>
        /// <param name="originalImage">原始图像</param>
        /// <param name="x">水平方向上从该位置开始截取，若未指定则截取水平方向中心位置的图像</param>
        /// <param name="y">垂直方向上从该位置开始截取，若未指定则截取垂直方向中心位置的图像</param>
        /// <param name="width">目标图像的宽度</param>
        /// <param name="height">目标图像的高度</param>
        /// <returns>目标图像</returns>
        public static System.Drawing.Image Crop(System.Drawing.Image originalImage, int x, int y, int width, int height)
        {
            if (originalImage == null)
            {
                throw new ArgumentNullException("originalImage");
            }
            if (width < 0 || height < 0)
            {
                throw new ArgumentOutOfRangeException();
            }


            if (width == 0 && height == 0)
            {
                return originalImage.Clone() as System.Drawing.Image;
            }

            // 如果宽按比例截取...
            if (width == 0)
            {
                width = (int)(height * originalImage.Width / originalImage.Height);
            }
            // 如果高按比例截取...
            if (height == 0)
            {
                height = (int)(width * originalImage.Height / originalImage.Width);
            }

            // 如果希望在水平方向上截取中心位置的图像...
            if (x < 0)
            {
                x = (int)(originalImage.Width - width) / 2;
            }
            // 如果希望在垂直方向上截取中心位置的图像...
            if (y < 0)
            {
                y = (int)(originalImage.Height - height) / 2;
            }

            //新建一个bmp图像
            System.Drawing.Image bitmap = new System.Drawing.Bitmap(width, height);

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

            //设置高质量插值法
            g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;

            //设置高质量,低速度呈现平滑程度
            g.SmoothingMode = System.Drawing.Drawing2D.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(originalImage,
                new Rectangle(0, 0, width, height),
                new Rectangle(x, y, width, height),
                GraphicsUnit.Pixel);

            g.Dispose();

            return bitmap;
        }

        /// <summary>
        /// 等比缩放图像，使其短边的最小长度或长边的最大长度等于指定的值。
        /// </summary>
        /// <param name="originalImage">原始图像</param>
        /// <param name="minmaxSideLength">缩放后图像的边长</param>
        /// <param name="kind">指定边长的类型（短边的最小长度或长边的最大长度）</param>
        /// <returns></returns>
        public static System.Drawing.Image Scale(System.Drawing.Image originalImage, int minmaxSideLength, string kind)
        {
            int width, height;

            if (kind.ToLower() == "min")
            {
                if (originalImage.Width > originalImage.Height)
                {
                    width = 0;
                    height = minmaxSideLength;
                }
                else
                {
                    width = minmaxSideLength;
                    height = 0;
                }
            }
            else
            {
                if (originalImage.Width > originalImage.Height)
                {
                    width = minmaxSideLength;
                    height = 0;
                }
                else
                {
                    width = 0;
                    height = minmaxSideLength;
                }
            }
            return Scale(originalImage, width, height);
        }

        /// <summary>
        /// 缩放图像，使其宽度和高度等于指定的值。若宽度或高度等于0，则图像将仅随不为0的边缩放（即等比缩放），若宽度和高度都等于0，则不进行缩放。
        /// </summary>
        /// <param name="originalImage">待缩放的图像</param>
        /// <param name="width">缩放后图像的宽度。若该参数为0，则图像在水平方向上按比例缩放。</param>
        /// <param name="height">缩放后图像的高度。若该参数为0，则图像在垂直方向上按比例缩放。</param>
        /// <returns>缩放后的图像。</returns>
        public static System.Drawing.Image Scale(System.Drawing.Image originalImage, int width, int height)
        {
            if (originalImage == null)
            {
                throw new ArgumentNullException("originalImage");
            }
            if (width < 0 || height < 0)
            {
                throw new ArgumentOutOfRangeException();
            }


            if (width == 0 && height == 0)
            {
                return originalImage.Clone() as System.Drawing.Image;
            }

            if (width == 0)
            {
                width = (int)(height * originalImage.Width / originalImage.Height);
            }
            else if (height == 0)
            {
                height = (int)(width * originalImage.Height / originalImage.Width);
            }


            //新建一个bmp图片
            System.Drawing.Image bitmap = new System.Drawing.Bitmap(width, height);

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

            //设置高质量插值法
            g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;

            //设置高质量,低速度呈现平滑程度
            g.SmoothingMode = System.Drawing.Drawing2D.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(originalImage,
                new Rectangle(0, 0, width, height),
                new Rectangle(0, 0, originalImage.Width, originalImage.Height),
                GraphicsUnit.Pixel);

            g.Dispose();

            return bitmap;
        }

        /// <summary>
        /// 保存图像到指定文件
        /// </summary>
        /// <param name="image"></param>
        /// <param name="fileName"></param>
        public static void Save(System.Drawing.Image image, string filePath, long quality)
        {
            //控制图片的质量等级
            ImageCodecInfo myImageCodecInfo;
            System.Drawing.Imaging.Encoder myEncoder;
            EncoderParameter myEncoderParameter;
            EncoderParameters myEncoderParameters;

            string mimeType = GetImageFormat(filePath);

            myImageCodecInfo = GetEncoderInfo(mimeType);
            myEncoder = System.Drawing.Imaging.Encoder.Quality;
            myEncoderParameters = new EncoderParameters(1);
            myEncoderParameter = new EncoderParameter(myEncoder, quality);
            myEncoderParameters.Param[0] = myEncoderParameter;

            try
            {
                System.IO.FileInfo tempFile = new System.IO.FileInfo(filePath);
                if (!tempFile.Directory.Exists)
                {
                    System.IO.Directory.CreateDirectory(tempFile.Directory.ToString());
                }
                image.Save(filePath, myImageCodecInfo, myEncoderParameters);
            }
            catch (System.Exception e)
            {
                image.Dispose();
                throw e;
            }
            finally
            {
                image.Dispose();
            }
        }

        /// <summary>
        /// 获取图片保存格式
        /// </summary>
        /// <param name="filePath"></param>
        /// <returns></returns>
        private static string GetImageFormat(string filePath)
        {
            string suffix = GetFileExtension(filePath).ToUpper();
            string mimeType = String.Empty;

            switch (suffix)
            {
                case "JPG":
                    mimeType = "image/jpeg";
                    break;
                case "PNG":
                    mimeType = "image/png";
                    break;
                default:
                    mimeType = "image/jpeg";
                    break;

            }

            return mimeType;
        }

        /// <summary>
        /// 获取ImageCodecInfo
        /// </summary>
        /// <param name="mimeType"></param>
        /// <returns></returns>
        private static ImageCodecInfo GetEncoderInfo(string mimeType)
        {
            ImageCodecInfo[] encoders;
            encoders = ImageCodecInfo.GetImageEncoders();

            for (int i = 0; i < encoders.Length; i++)
            {
                if (encoders[i].MimeType.Equals(mimeType))
                {
                    return encoders[i];
                }
            }

            return null;
        }


        /// <summary>
        /// 获取文件扩展名
        /// </summary>
        /// <param name="fileName"></param>
        /// <returns></returns>
        public static string GetFileExtension(string fileName)
        {
            int startIndex = fileName.LastIndexOf('.');
            return fileName.Substring(startIndex + 1, fileName.Length - 1 - startIndex);
        }

        /**/
        /// <summary>
        /// 生成缩略图
        /// </summary>
        /// <param name="originalImagePath">源图路径（物理路径）</param>
        /// <param name="thumbnailPath">缩略图路径（物理路径）</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>    
        private void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, string mode)
        {
            int towidth = width;
            int toheight = height;

            int x = 0;
            int y = 0;
            int ow = 0;
            int oh = 0;

            System.Drawing.Image originalImage = System.Drawing.Image.FromFile(originalImagePath);
            ow = originalImage.Width;
            oh = originalImage.Height;
            //originalImage.Dispose();

            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 = oh * width / ow;
                    break;
                case "H"://指定高，宽按比例
                    towidth = ow * height / oh;
                    break;
                default:
                    break;
            }

            //新建一个bmp图片
            System.Drawing.Image bitmap = new System.Drawing.Bitmap(towidth, toheight);

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

            //设置高质量插值法
            g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;

            //设置高质量,低速度呈现平滑程度
            g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;

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

            //获得要画图片的信息//*这里很重要*//
            ImageCodecInfo myImageCodecInfo;
            System.Drawing.Imaging.Encoder myEncoder;
            EncoderParameter myEncoderParameter;
            EncoderParameters myEncoderParameters;
            myImageCodecInfo = ImageCodecInfo.GetImageEncoders()[1];
            myEncoder = System.Drawing.Imaging.Encoder.Quality;
            myEncoderParameters = new EncoderParameters(1);
            myEncoderParameter = new EncoderParameter(myEncoder, 100L);
            myEncoderParameters.Param[0] = myEncoderParameter;
            //***********************************************//

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

            try
            {
                //以jpg格式保存缩略图
                //bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);
                bitmap.Save(thumbnailPath, myImageCodecInfo, myEncoderParameters);
                originalImage.Dispose();
                bitmap.Dispose();
                g.Dispose();
            }
            catch (System.Exception e)
            {
                originalImage.Dispose();
                bitmap.Dispose();
                g.Dispose();
                throw e;
            }
            finally
            {
                originalImage.Dispose();
                bitmap.Dispose();
                g.Dispose();
            }
        }
        /**/
        /// <summary>
        /// 生成缩略图
        /// </summary>
        /// <param name="originalImagePath">源图路径（物理路径）</param>
        /// <param name="thumbnailPath">缩略图路径（物理路径）</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> 
        private void MakeOperateImage(string originalImagePath, string thumbnailPath, int width, int height, string mode)
        {
            System.Drawing.Image originalImage = System.Drawing.Image.FromFile(originalImagePath);


            int towidth = width;
            int toheight = height;

            int x = 0;
            int y = 0;
            int ow = originalImage.Width;
            int oh = originalImage.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 = originalImage.Height * width / originalImage.Width;
                    break;
                case "H"://指定高，宽按比例
                    towidth = originalImage.Width * height / originalImage.Height;
                    break;
                case "Cut"://指定高宽裁减（不变形） 
                    if ((double)originalImage.Width / (double)originalImage.Height > (double)towidth / (double)toheight)
                    {
                        oh = originalImage.Height;
                        ow = originalImage.Height * towidth / toheight;
                        y = 0;
                        x = (originalImage.Width - ow) / 2;
                    }
                    else
                    {
                        ow = originalImage.Width;
                        oh = originalImage.Width * height / towidth;
                        x = 0;
                        y = (originalImage.Height - oh) / 2;
                    }
                    break;
                default:
                    break;
            }

            //新建一个bmp图片
            System.Drawing.Image bitmap = new System.Drawing.Bitmap(towidth, toheight);

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

            //设置高质量插值法
            g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;

            //设置高质量,低速度呈现平滑程度
            g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;

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

            //获得要画图片的信息//*这里很重要*//
            ImageCodecInfo myImageCodecInfo;
            System.Drawing.Imaging.Encoder myEncoder;
            EncoderParameter myEncoderParameter;
            EncoderParameters myEncoderParameters;
            myImageCodecInfo = ImageCodecInfo.GetImageEncoders()[1];
            myEncoder = System.Drawing.Imaging.Encoder.Quality;
            myEncoderParameters = new EncoderParameters(1);
            myEncoderParameter = new EncoderParameter(myEncoder, 100L);
            myEncoderParameters.Param[0] = myEncoderParameter;
            //***********************************************//

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

            try
            {
                //以jpg格式保存缩略图
                //bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);
                bitmap.Save(thumbnailPath, myImageCodecInfo, myEncoderParameters);
                originalImage.Dispose();
                bitmap.Dispose();
                g.Dispose();
            }
            catch (System.Exception e)
            {
                originalImage.Dispose();
                bitmap.Dispose();
                g.Dispose();
                throw e;
            }
            finally
            {
                originalImage.Dispose();
                bitmap.Dispose();
                g.Dispose();
            }
        }
    }