无法调整上传到 Dot NET Lambda 函数项目中的 s3 存储桶的图像大小

Question

我正在使用 C# Dot NET Core 开发一个 AWS Lambda 函数项目。我现在正在做的是在将图像文件上传到 s3 时调整图像大小。这是我的项目结构。

我在单一解决方案中有三个项目。 AwsLambda.Domain 项目是 Dot NET Framework 项目，AwsLambda 是 Dot NET Core 项目。 Aws Lambda 项目依赖于 AwsLambda.Domain 项目。基本上，在 AwsLambda.Domain 项目中，我创建了一个名为 ImageHelper.cs 的新类，它负责使用 Dot NET Framework 中的功能调整图像大小。

这是我在 AwsLambda.Doamin 项目下的 ImageHelper.cs 类。

using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;

namespace AwsS3Lambda.Domain
{
   public class ImageHelper
   {
      public string CreateThumbImage(string sourcePath, string destPath, int width, int height)
      {
         Image imgOriginal = Image.FromFile(sourcePath);
         Image imgActual = Scale(imgOriginal, width, height);
         imgActual.Save(destPath);
         imgActual.Dispose();
         return destPath;
      }


      private Image Scale(Image imgPhoto, int width, int height)
      {
         float sourceWidth = imgPhoto.Width;
         float sourceHeight = imgPhoto.Height;
         float destHeight = 0;
         float destWidth = 0;
         int sourceX = 0;
         int sourceY = 0;
         int destX = 0;
         int destY = 0;

         // force resize, might distort image
         if(width != 0 && height != 0)
         {
            destWidth = width;
            destHeight = height;
         }
         // change size proportially depending on width or height
         else if(height != 0)
         {
            destWidth = (float)(height * sourceWidth) / sourceHeight;
            destHeight = height;
         }
         else
         {
            destWidth = width;
            destHeight = (float)(sourceHeight * width / sourceWidth);
         }

         Bitmap bmPhoto = new Bitmap((int)destWidth, (int)destHeight,
                                     PixelFormat.Format32bppPArgb);
         bmPhoto.SetResolution(imgPhoto.HorizontalResolution, imgPhoto.VerticalResolution);

         Graphics grPhoto = Graphics.FromImage(bmPhoto);
         grPhoto.InterpolationMode = InterpolationMode.HighQualityBicubic;

         grPhoto.DrawImage(imgPhoto,
             new Rectangle(destX, destY, (int)destWidth, (int)destHeight),
             new Rectangle(sourceX, sourceY, (int)sourceWidth, (int)sourceHeight),
             GraphicsUnit.Pixel);

         grPhoto.Dispose();

         return bmPhoto;
      }
   }
}

这是我的 lambda 函数类，它使用 ImageHelper.cs 类来调整上传图像的大小。

 public class Function
    {
      public static string IAM_KEY { get { return "xxx"; } }
      public static string IAM_SECRET { get { return "xxx"; } }
      public static string TEMP_IMG_FILE_PATH { get { return @"../../tmp/temp_img.jpeg"; } }
      public static string TEMP_RESIZED_IMG_PATH { get { return @"../../tmp/resized_img.jpeg"; } }

      private IAmazonS3 S3Client { get; set; }
      private ImageHelper imageHelper { get; set; }


      public Function()
      {
         S3Client = new AmazonS3Client();
         imageHelper = new ImageHelper();
      }


      public Function(IAmazonS3 s3Client)
      {
         this.S3Client = s3Client;
         this.imageHelper = new ImageHelper();
      }

      public async Task<string> FunctionHandler(S3Event evnt, ILambdaContext context)
      {
         var s3Event = evnt.Records?[0].S3;
         if(s3Event == null)
         {
            return null;
         }

         try
         {
            if(s3Event.Object.Key.ToLower().Contains("thumb"))
            {
               //Console.WriteLine("The image is already a thumb file");
               return "The file is aready a thumb image file";
            }

            string[] pathSegments = s3Event.Object.Key.Split('/');
            string eventCode = pathSegments[0];
            string userEmail = pathSegments[1];
            string filename = pathSegments[2];
            string extension = Path.GetExtension(filename); //.jpeg with "dot"
            string fileNameWithoutExtension = Path.GetFileNameWithoutExtension(filename);

            using(var objectResponse = await this.S3Client.GetObjectAsync(s3Event.Bucket.Name, s3Event.Object.Key))
            {
               using(Stream responseStream = objectResponse.ResponseStream)
               {
                  this.saveFile(responseStream, Function.TEMP_IMG_FILE_PATH);

                  imageHelper.CreateThumbImage(Function.TEMP_IMG_FILE_PATH, Function.TEMP_RESIZED_IMG_PATH, 200, 200);

                  ///This code is throwing error
                  await this.S3Client.PutObjectAsync(new Amazon.S3.Model.PutObjectRequest
                  {
                     BucketName = s3Event.Bucket.Name,
                     Key = fileNameWithoutExtension + ".thumb" + extension,
                     FilePath = Function.TEMP_RESIZED_IMG_PATH
                  });
               }
            }

            return "Thumbnail version of the image has been created";

         }
         catch(Exception e)
         {
            context.Logger.LogLine($"Error getting object {s3Event.Object.Key} from bucket {s3Event.Bucket.Name}. Make sure they exist and your bucket is in the same region as this function.");
            context.Logger.LogLine(e.Message);
            context.Logger.LogLine(e.StackTrace);
            throw;
         }
      }

      private void saveFile(Stream stream, string path)
      {
         using(var fileStream = File.Create(path))
         {
            //stream.Seek(0, SeekOrigin.Begin);
            stream.CopyTo(fileStream);
         }

      }
   }

当我在控制台中测试该函数时，它给了我这个关于在 AwsLambda.Domain 项目（Dot NET Framework）下实现的图像大小调整功能的错误。

{
  "errorType": "AggregateException",
  "errorMessage": "One or more errors occurred. (Could not load type 'System.Drawing.Image' from assembly 'System.Drawing, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'.)",
  "stackTrace": [
    "at System.Threading.Tasks.Task`1.GetResultCore(Boolean waitCompletionNotification)",
    "at lambda_method(Closure , Stream , Stream , LambdaContextInternal )"
  ],
  "cause": {
    "errorType": "TypeLoadException",
    "errorMessage": "Could not load type 'System.Drawing.Image' from assembly 'System.Drawing, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'.",
    "stackTrace": [
      "at AwsS3Lambda.Domain.ImageHelper.CreateThumbImage(String sourcePath, String destPath, Int32 width, Int32 height)",
      "at AwsS3Lambda.Function.<FunctionHandler>d__18.MoveNext() in C:\\Users\\Acer\\Documents\\Visual Studio 2017\\Projects\\AwsS3Lambda\\AwsS3Lambda\\Function.cs:line 106"
    ]
  },
  "causes": [
    {
      "errorType": "TypeLoadException",
      "errorMessage": "Could not load type 'System.Drawing.Image' from assembly 'System.Drawing, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'.",
      "stackTrace": [
        "at AwsS3Lambda.Domain.ImageHelper.CreateThumbImage(String sourcePath, String destPath, Int32 width, Int32 height)",
        "at AwsS3Lambda.Function.<FunctionHandler>d__18.MoveNext() in C:\\Users\\Acer\\Documents\\Visual Studio 2017\\Projects\\AwsS3Lambda\\AwsS3Lambda\\Function.cs:line 106"
      ]
    }
  ]
}

为什么会抛出那个错误。当我在 ASP.NET MVC 项目中使用图像大小调整类代码时，它正在工作。它只是不适用于这个 AWS Lambda 函数项目。我的项目中缺少什么？在基于 Dot NET Core 的 AWS Lambda 函数项目中调整上传图像大小的另一种方法是什么？

Answer 1

我的假设是您的 c# 代码将在 Linux 不支持 System.Drawing lib 的 Linux 机器下运行。那么你可能需要做一个桥来将绘图库导入到 linux 中。