C# 图片压缩

        /// <summary>  
        /// 按质量比和尺寸收缩呗数,生成缩略图，保存为另外路劲
        /// </summary>  
        /// <param name="sourceFile">原始图片文件</param>  
        /// <param name="quality">质量压缩比</param>  
        /// <param name="multiple">收缩倍数</param>  
        /// <param name="outputFile">输出文件名</param>  
        /// <returns>成功返回true,失败则返回false</returns>  
        public static bool getThumImage(String sourceFile, long quality, int multiple, String outputFile)
        {
            bool flag = false;
            try
            {
                flag = ThumImage(sourceFile, quality, multiple, outputFile);
            }
            catch
            {
                flag = false;
            }
            return flag;
        }

        /**/
        /// <summary>  
        /// 按质量比和尺寸收缩呗数,生成缩略图;保存在同一路径
        /// </summary>  
        /// <param name="sourceFile">原始图片文件</param>  
        /// <param name="quality">质量压缩比</param>  
        /// <param name="multiple">收缩倍数</param>  
        /// <param name="outputFile">输出文件名</param>  
        /// <returns>成功返回true,失败则返回false</returns>  
        public static bool getThumImage(String sourceFile, long quality, int multiple)
        {
            bool flag = false;
            try
            {
                flag = ThumImage(sourceFile, quality, multiple, sourceFile);
            }
            catch
            {
                flag = false;
            }
            return flag;
        }

        /// <summary>  
        /// 按图片尺寸大小压缩图片  ，保存在不同路径
        /// </summary>  
        /// <param name="sourceFile">原始图片文件</param>  
        /// <param name="multiple">收缩倍数</param>  
        /// <returns>成功返回true,失败则返回false</returns>  
        public static bool ImageByMultiple(String sourceFile, int multiple, String outputFile)
        {
            bool flag = false;
            try
            {
                flag = ThumImageByMultiple(sourceFile, multiple, outputFile);
            }
            catch
            {
                flag = false;
            }
            return flag;
        }


        /// <summary>  
        ///  按图片尺寸大小压缩图片  ，保存在同一路径
        /// </summary>  
        /// <param name="multiple">收缩倍数</param>  
        /// <returns>成功返回true,失败则返回false</returns>  
        public static bool ImageByMultiple(String sourceFile, int multiple)
        {
            bool flag = false;
            try
            {
                flag = ThumImageByMultiple(sourceFile, multiple, sourceFile);
            }
            catch
            {
                flag = false;
            }
            return flag;
        }


        /// <summary>  
        /// 质量压缩比，保存在不同一路径
        /// </summary>  
        /// <param name="sourceFile">原始图片文件</param>  
        /// <param name="quality">质量压缩比</param>  
        /// <returns>成功返回true,失败则返回false</returns>  
        public static bool ImageByQuality(String sourceFile, int quality, String outputFile)
        {
            bool flag = false;
            try
            {
                flag = ThumImageByQuality(sourceFile, quality, outputFile);
            }
            catch
            {
                flag = false;
            }
            return flag;
        }

        /// <summary>  
        /// 按质量压缩比压缩图片，保存在同一路径
        /// </summary>  
        /// <param name="sourceFile">原始图片文件</param>  
        /// <param name="quality">质量压缩比</param>  
        /// <returns>成功返回true,失败则返回false</returns>  
        public static bool ImageByQuality(String sourceFile, int quality)
        {
            bool flag = false;
            try
            {
                flag = ThumImageByQuality(sourceFile, quality, sourceFile);
            }
            catch
            {
                flag = false;
            }
            return flag;
        }
        #endregion

        #region 调用图片处理具体方法


        /// <summary>
        /// 按照图片质量生成图片,
        /// </summary>
        /// <param name="sourceFile">原始图片文件</param>  
        /// <param name="quality">质量压缩比</param>  
        /// <param name="outputFile">输出文件名</param>  
        /// <returns>成功返回true,失败则返回false</returns>  
        private static bool ThumImageByQuality(String sourceFile, long quality, String outputFile)
        {
            bool flag = false;
            try
            {
                long imageQuality = quality;
                Bitmap sourceImage = new Bitmap(sourceFile);
                ImageCodecInfo myImageCodecInfo = GetEncoderInfo("image/jpeg");
                System.Drawing.Imaging.Encoder myEncoder = System.Drawing.Imaging.Encoder.Quality;
                EncoderParameters myEncoderParameters = new EncoderParameters(1);
                EncoderParameter myEncoderParameter = new EncoderParameter(myEncoder, imageQuality);
                myEncoderParameters.Param[0] = myEncoderParameter;
                float xWidth = sourceImage.Width;
                float yWidth = sourceImage.Height;
                Bitmap newImage = new Bitmap((int)(xWidth), (int)(yWidth));
                Graphics g = Graphics.FromImage(newImage);
                g.DrawImage(sourceImage, 0, 0, xWidth, yWidth);
                sourceImage.Dispose();
                g.Dispose();
                newImage.Save(outputFile, myImageCodecInfo, myEncoderParameters);
                flag = true;
            }
            catch
            {
                flag = false;
            }
            return flag;

        }


        /// <summary>
        /// 生成缩略图
        /// </summary>
        /// <param name="sourceFile">原始图片文件</param>  
        /// <param name="quality">质量压缩比</param>  
        /// <param name="multiple">收缩倍数</param>  
        /// <param name="outputFile">输出文件名</param>  
        /// <returns>成功返回true,失败则返回false</returns>  
        private static bool ThumImage(String sourceFile, long quality, int multiple, String outputFile)
        {
            bool flag = false;
            try
            {
                long imageQuality = quality;
                Bitmap sourceImage = new Bitmap(sourceFile);
                ImageCodecInfo myImageCodecInfo = GetEncoderInfo("image/jpeg");
                System.Drawing.Imaging.Encoder myEncoder = System.Drawing.Imaging.Encoder.Quality;
                EncoderParameters myEncoderParameters = new EncoderParameters(1);
                EncoderParameter myEncoderParameter = new EncoderParameter(myEncoder, imageQuality);
                myEncoderParameters.Param[0] = myEncoderParameter;
                float xWidth = sourceImage.Width;
                float yWidth = sourceImage.Height;
                Bitmap newImage = new Bitmap((int)(xWidth / multiple), (int)(yWidth / multiple));
                Graphics g = Graphics.FromImage(newImage);
                g.DrawImage(sourceImage, 0, 0, xWidth / multiple, yWidth / multiple);
                sourceImage.Dispose();
                g.Dispose();
                newImage.Save(outputFile, myImageCodecInfo, myEncoderParameters);
                flag = true;
            }
            catch
            {
                flag = false;
            }
            return flag;

        }

        /// <summary>  
        /// 按图片尺寸大小压缩图片  
        /// </summary>  
        /// <param name="sourceFile">原始图片文件</param>  
        /// <param name="multiple">收缩倍数</param>  
        /// <param name="outputFile">输出文件名</param>  
        /// <returns>成功返回true,失败则返回false</returns>  
        public static bool ThumImageByMultiple(String sourceFile, int multiple, String outputFile)
        {
            try
            {
                Bitmap sourceImage = new Bitmap(sourceFile);
                ImageCodecInfo myImageCodecInfo = GetEncoderInfo("image/jpeg");
                float xWidth = sourceImage.Width;
                float yWidth = sourceImage.Height;
                Bitmap newImage = new Bitmap((int)(xWidth / multiple), (int)(yWidth / multiple));
                Graphics g = Graphics.FromImage(newImage);
                g.DrawImage(sourceImage, 0, 0, xWidth / multiple, yWidth / multiple);
                sourceImage.Dispose();
                g.Dispose();
                newImage.Save(outputFile);
                return true;
            }
            catch
            {
                return false;
            }
        }



        /// <summary>  
        /// 按图片尺寸大小压缩图片  
        /// </summary>  
        /// <param name="sourceFile">原始图片文件</param>  
        /// <param name="multiple">收缩倍数</param>  
        /// <param name="outputFile">输出文件名</param>  
        /// <returns>成功返回true,失败则返回false</returns>  
        public static bool FixSize(String sourceFile, int xWidth, int yWidth, String outputFile)
        {
            try
            {
                Bitmap sourceImage = new Bitmap(sourceFile);
                ImageCodecInfo myImageCodecInfo = GetEncoderInfo("image/jpeg");
                Bitmap newImage = new Bitmap((int)(xWidth), (int)(yWidth));
                Graphics g = Graphics.FromImage(newImage);
                g.DrawImage(sourceImage, 0, 0, xWidth, yWidth);
                sourceImage.Dispose();
                g.Dispose();
                newImage.Save(outputFile);
                return true;
            }
            catch
            {
                return false;
            }
        }
        #endregion getThumImage


        /// <summary>  
        /// 获取图片编码信息  
        /// </summary>  
        private static ImageCodecInfo GetEncoderInfo(String mimeType)
        {
            int j;
            ImageCodecInfo[] encoders;
            encoders = ImageCodecInfo.GetImageEncoders();
            for (j = 0; j < encoders.Length; ++j)
            {
                if (encoders[j].MimeType == mimeType)
                    return encoders[j];
            }
            return null;
        }