namespace Insus.NET.Models
{
    public class Response
    {
        public bool Status { get; set; }
        public string Message { get; set; }
        public object Data { get; set; }

        public Response() { }

        public Response(bool status, string message, object data)
        {
            Status = status;
            Message = message;
            Data = data;
        }
    }
}

public async Task<IHttpActionResult> UploadImage()
{
    Response _Data;  //Model
    try
    {
        await ProcessPostImageFile();

        _Data = new Response()
        {
            Status = true,
            Message = "File uploaded successfully.",
            Data = null
        };
    }
    catch (Exception ex)
    {
        _Data = new Response()
        {
            Status = false,
            Message = ex.Message,
            Data = null
        };
    }
    return Ok(_Data);
}

 private async Task ProcessPostImageFile()
 {
     if (!Request.Content.IsMimeMultipartContent())
     {
         throw new HttpResponseException(HttpStatusCode.UnsupportedMediaType);
     }

     var provider = await Request.Content.ReadAsMultipartAsync<InsusNetMultipartFormDataStreamProvider>(
         new InsusNetMultipartFormDataStreamProvider()
     );

     NameValueCollection formData = provider.FormData;
     IList<HttpContent> files = provider.Files;


     foreach (var file in files)
     {
         var _ocr = new OcrFile();

         string ofn = file.Headers.ContentDisposition.FileName.Trim('"'); //去掉前后的引号
         _ocr.OriginalFileName = ofn; //上传的文件名
         _ocr.Extension = Path.GetExtension(ofn);  //扩展名
         _ocr.MimeType = file.Headers.ContentType.MediaType;  //图片文档的Media type。

         using (var ms = new MemoryStream())  //不管你是上传单文件，还是上传多文件，均需从内存流去读取数据。
         {
             var stream = await file.ReadAsStreamAsync();
             await stream.CopyToAsync(ms);

             _ocr.Size = ms.Length;
             ms.Position = 0; // 重置位置供后续使用
             using (var image = Image.FromStream(ms))
             {
                 System.Drawing.Imaging.ImageFormat format = ImageUtil.GetImageFormat(image);  //这里自定义方法，从图片获取其格式。
                 string extension = ImageUtil.GetExtensionByImageFormat(format);  //这里也是自定义方法，从图片格式获取其扩展名

                 string newFileName = $"{Guid.NewGuid()}{extension}"; //用GUID生成唯一文件名
                 _ocr.NewFileName = newFileName;

                 string newFileFullPath = Path.Combine(InsusIO.TempDirectory, newFileName);
                 image.Save(newFileFullPath, format); //存储入文件夹中。
             }
         }

         await Task.Run(() => xxx.Save2Db(_ocr)); //相关数据存入数据库中
     }
 }

namespace Insus.NET
{
    public static class ImageUtil
    {
        public static ImageFormat GetImageFormat(Image image)
        {
            if (image.RawFormat.Equals(ImageFormat.Jpeg))
                return ImageFormat.Jpeg;           
            else if (image.RawFormat.Equals(ImageFormat.Png))
                return ImageFormat.Png;
            else if (image.RawFormat.Equals(ImageFormat.Tiff))
                return ImageFormat.Tiff;
            else if (image.RawFormat.Equals(ImageFormat.Gif))
                return ImageFormat.Gif;
            else if (image.RawFormat.Equals(ImageFormat.Bmp))
                return ImageFormat.Bmp;
            else if (image.RawFormat.Equals(ImageFormat.Emf))
                return ImageFormat.Emf;
            else if (image.RawFormat.Equals(ImageFormat.Exif))
                return ImageFormat.Exif;
            else if (image.RawFormat.Equals(ImageFormat.Icon))
                return ImageFormat.Icon;
            else if (image.RawFormat.Equals(ImageFormat.Wmf))
                return ImageFormat.Wmf;
            else
                return ImageFormat.Jpeg; // 默认使用JPEG
        }

        public static string GetExtensionByImageFormat(ImageFormat format)
        {
            if (format.Equals(ImageFormat.Jpeg)) return ".jpg";
            if (format.Equals(ImageFormat.Png)) return ".png";
            if (format.Equals(ImageFormat.Tiff)) return ".tiff";
            if (format.Equals(ImageFormat.Gif)) return ".gif";
            if (format.Equals(ImageFormat.Bmp)) return ".bmp";
            if (format.Equals(ImageFormat.Icon)) return ".ico";
            // 其他格式...
            return ".jpg"; // 默认
        }
    }
}