图片保存时，按照不同比例裁切方法

ImageAuto

    public static class ImageHelper
    {
        /// <summary>
        /// 
        /// </summary>
        /// <param name="jpeg_image_upload"></param>
        /// <param name="target_height"></param>
        /// <param name="fixedType"></param>
        /// <param name="path"></param>
        /// <returns>返回是否保存成功</returns>
        public static bool SaveFileImageFixedByHight(HttpPostedFileBase jpeg_image_upload, int target_height, string path)
        {
            return SaveFileImage(jpeg_image_upload, 0, target_height, FixedRateType.FixedHeight, path);
        }
        /// <summary>
        /// 
        /// </summary>
        /// <param name="jpeg_image_upload"></param>
        /// <param name="target_width"></param>
        /// <param name="fixedType"></param>
        /// <param name="path"></param>
        /// <returns>返回是否保存成功</returns>
        public static bool SaveFileImageFixedByWidth(HttpPostedFileBase jpeg_image_upload, int target_width, string path)
        {
            return SaveFileImage(jpeg_image_upload, target_width, 0, FixedRateType.FixedWidth, path);
        }


        /// <summary>
        /// 
        /// </summary>
        /// <param name="jpeg_image_upload"></param>
        /// <param name="target_width"></param>
        /// <param name="target_height"></param>
        /// <param name="fixedType"></param>
        /// <param name="path">绝对路径</param>
        /// <returns>返回是否保存成功</returns>
        public static bool SaveFileImage(HttpPostedFileBase jpeg_image_upload, int target_width, int target_height, FixedRateType fixedType, string path)
        {
            bool isOkay = false;
            Image original_image = null;

            try
            {
                if (jpeg_image_upload != null && !string.IsNullOrEmpty(path))
                {
                    original_image = System.Drawing.Image.FromStream(jpeg_image_upload.InputStream);
                    string dirPath = path.Substring(0, path.LastIndexOfAny(new char[] { '\\', '/' }));
                    if (!Directory.Exists(dirPath))
                    {
                        Directory.CreateDirectory(dirPath);
                    }
                    isOkay = SaveImage(original_image, target_width, target_height, fixedType, path);
                }

            }
            catch (Exception ex)
            {
                LogUtil.Error("生成图片过程出错，详情：" + ex.Message);
            }
            finally
            {
                if (original_image != null) original_image.Dispose();
            }
            return isOkay;
        }
        /// <summary>
        /// 保存图片
        /// </summary>
        /// <param name="original_image">图片数据</param>
        /// <param name="target_width">画布宽度（图像宽度）</param>
        /// <param name="target_height">画布高度（图像高度）</param>
        /// <param name="fixedType">固定比率类型</param>
        /// <param name="path">保存路径</param>
        /// <returns>返回是否保存成功，失败可能原因：路径不正确  </returns>
        public static bool SaveImage(Image original_image, int target_width, int target_height, FixedRateType fixedType, string path)
        {
            bool isOkay = true;
            Image new_image = null;
            int width = original_image.Width;
            int height = original_image.Height;
            int new_width, new_height;
            #region 计算比例
            float target_ratio = (float)target_width / (float)target_height;
            float image_ratio = (float)width / (float)height;
            switch (fixedType)
            {
                case FixedRateType.Fixed:
                    new_height = target_ratio > image_ratio ? target_height : (int)Math.Floor((float)target_width / image_ratio);
                    new_width = target_ratio > image_ratio ? (int)Math.Floor(image_ratio * (float)target_height) : target_width;
                    break;
                case FixedRateType.FixedWidth:
                    new_height = (int)Math.Floor((float)target_width / image_ratio);
                    new_width = target_width;
                    target_height = new_height;
                    break;
                case FixedRateType.FixedHeight:
                    new_height = target_height;
                    new_width = (int)Math.Floor(image_ratio * (float)target_height);
                    target_width = new_width;
                    break;
                default:
                    new_width = target_width;
                    new_height = target_height;
                    break;
            }
            #endregion

            Graphics graphics = null;
            try
            {
                new_image = new Bitmap(target_width > new_width ? target_width : new_width,
                    target_height > new_height ? target_height : new_height);
                graphics = Graphics.FromImage(new_image);
                if (fixedType == FixedRateType.Fixed)
                {   //  判断是否填充
                    graphics.FillRectangle(new SolidBrush(Color.White), new Rectangle(0, 0, target_width, target_height));
                }

                graphics.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
                graphics.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;
                int paste_x = (target_width - new_width) / 2;
                int paste_y = (target_height - new_height) / 2;
                graphics.DrawImage(original_image, paste_x, paste_y, new_width, new_height);
                new_image.Save(path);
            }
            catch
            {
                isOkay = false;
            }
            finally
            {
                if (graphics != null) graphics.Dispose();
                if (new_image != null) new_image.Dispose();
            }
            return isOkay;
        }

    }
    public enum FixedRateType
    {
        /// <summary>
        /// 不固定比率
        /// </summary>
        None = 0,
        /// <summary>
        /// 固定比率,根据传进的画布大小，不足部分自动补白
        /// </summary>
        Fixed = 1,
        /// <summary>
        ///固定比率, 以宽度为主（不会出现填充），高度自适应
        /// </summary>
        FixedWidth = 2,
        /// <summary>
        /// 固定比率,以高度为主（不会出现填充），宽度自适应
        /// </summary>
        FixedHeight = 3
    }