ImageUploadAssist--ImageHelper

public static class ImageHelper
    {

        /// <summary>
        /// 读图片
        /// </summary>
        /// <param name="filepath"></param>
        /// <returns></returns>
        public static string ImgToBase64String(string filepath)
        {
            try
            {
                Bitmap bmp = new Bitmap(filepath);
                MemoryStream ms = new MemoryStream();
                bmp.Save(ms, ImageFormat.Jpeg);
                byte[] arr = new byte[ms.Length];
                ms.Position = 0;
                ms.Read(arr, 0, (int)ms.Length);
                ms.Close();
                return Convert.ToBase64String(arr);
            }
            catch (Exception ex)
            {
                return string.Empty;
            }

        }


        /// <summary>
        /// 无损压缩图片
        /// </summary>
        /// <param name="sFile">原图片</param>
        /// <param name="dFile">压缩后保存位置</param>
        /// <param name="fileName"></param>
        /// <param name="dHeight">高度</param>
        /// <param name="dWidth"></param>
        /// <param name="flag">压缩质量 1-100</param>
        /// <returns></returns>
        public static bool GetPicThumbnail(string sFile, string dFile, string fileName, int dHeight, int dWidth, int flag)
        {
            Image iSource = Image.FromFile(sFile);
            ImageFormat tFormat = iSource.RawFormat;
            int sW = 0, sH = 0;

            //按比例缩放
            Size tem_size = new Size(iSource.Width, iSource.Height);
            if (dWidth == 0)
                dWidth = dHeight * tem_size.Width / tem_size.Height;
            if (dHeight == 0)
                dHeight = dWidth * tem_size.Height / tem_size.Width;

            if (tem_size.Width > dHeight || tem_size.Width > dWidth) //将**改成c#中的或者操作符号
            {
                if ((tem_size.Width * dHeight) > (tem_size.Height * dWidth))
                {
                    sW = dWidth;
                    sH = (dWidth * tem_size.Height) / tem_size.Width;
                }
                else
                {
                    sH = dHeight;
                    sW = (tem_size.Width * dHeight) / tem_size.Height;
                }
            }
            else
            {
                sW = tem_size.Width;
                sH = tem_size.Height;
            }

            Bitmap ob = new Bitmap(dWidth, dHeight);
            Graphics g = Graphics.FromImage(ob);
            g.Clear(Color.WhiteSmoke);
            g.CompositingQuality = CompositingQuality.HighQuality;
            g.SmoothingMode = SmoothingMode.HighQuality;
            g.InterpolationMode = InterpolationMode.HighQualityBicubic;
            g.DrawImage(iSource, new Rectangle((dWidth - sW) / 2, (dHeight - sH) / 2, sW, sH), 0, 0, iSource.Width, iSource.Height, GraphicsUnit.Pixel);
            g.Dispose();

            //以下代码为保存图片时，设置压缩质量
            EncoderParameters ep = new EncoderParameters();
            long[] qy = new long[1];
            qy[0] = flag;//设置压缩的比例1-100
            EncoderParameter eParam = new EncoderParameter(Encoder.Quality, qy);
            ep.Param[0] = eParam;

            try
            {
                ImageCodecInfo[] arrayICI = ImageCodecInfo.GetImageEncoders();
                ImageCodecInfo jpegICIinfo = null;
                for (int x = 0; x < arrayICI.Length; x++)
                {
                    if (arrayICI[x].FormatDescription.Equals("JPEG"))
                    {
                        jpegICIinfo = arrayICI[x];
                        break;
                    }
                }

                //创建文件夹
                if (!Directory.Exists(dFile))
                {
                    var directoryInfo = new DirectoryInfo(dFile);
                    directoryInfo.Create();
                }

                if (jpegICIinfo != null)
                {
                    ob.Save(dFile + fileName, jpegICIinfo, ep);//dFile是压缩后的新路径
                }
                else
                {
                    ob.Save(dFile, tFormat);
                }
                return true;

            }
            catch
            {
                return false;
            }

            finally
            {
                iSource.Dispose();
                ob.Dispose();
            }
        }


        /// <summary>
        /// 判断文件扩展名
        /// </summary>
        /// <param name="fileName"></param>
        /// <returns></returns>
        public static FileExtension CheckImageFile(string fileName)
        {
            FileStream fs = new FileStream(fileName, FileMode.Open, FileAccess.Read);
            var br = new BinaryReader(fs);
            string fileType = string.Empty; ;
            try
            {
                byte data = br.ReadByte();
                fileType += data.ToString();
                data = br.ReadByte();
                fileType += data.ToString();
                FileExtension extension;
                try
                {
                    extension = (FileExtension)Enum.Parse(typeof(FileExtension), fileType);
                }
                catch
                {

                    extension = FileExtension.VALIDFILE;
                }
                return extension;
            }
            catch (Exception ex)
            {
                throw ex;
            }
            finally
            {
                fs.Close();
                br.Close();
            }
        }

        public enum FileExtension
        {
            JPG = 255216,
            GIF = 7173,
            PNG = 13780,
            SWF = 6787,
            RAR = 8297,
            ZIP = 8075,
            _7Z = 55122,
            VALIDFILE = 9999999
        }
    }