GCImagingAWSLambdaS3

GCImagingAWSLambdaS3.cs

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

    try
    {
        var rs = await this.S3Client.GetObjectMetadataAsync(
            s3Event.Bucket.Name,
            s3Event.Object.Key);
                
        if (rs.Headers.ContentType.StartsWith("image/"))
        {
            using (GetObjectResponse response = await S3Client.GetObjectAsync(
                s3Event.Bucket.Name,
                s3Event.Object.Key))
            {
                using (Stream responseStream = response.ResponseStream)
                {
                    using (StreamReader reader = new StreamReader(responseStream))
                    {
                        using (var memstream = new MemoryStream())
                        {
                            var buffer = new byte[512];
                            var bytesRead = default(int);
                            while ((bytesRead = reader.BaseStream.Read(buffer, 0, buffer.Length)) > 0)
                                memstream.Write(buffer, 0, bytesRead);
                        // Perform image manipulation
                        // We are choosing to grayscale
                            var transformedImage = GcImagingOperations.GetGrayScale(memstream);
                            PutObjectRequest putRequest = new PutObjectRequest()
                            {
                                BucketName = DestBucket,
                                Key = $"grayscale-{s3Event.Object.Key}",
                                ContentType = rs.Headers.ContentType,
                                ContentBody = transformedImage
                            };
                            await S3Client.PutObjectAsync(putRequest);
                        }
                    }
                }
            }
        }
        return rs.Headers.ContentType;
    }
    catch (Exception e)
    {
        throw;
    }
}