/// <summary>
/// Default constructor used by AWS Lambda to construct the function. Credentials and Region information will
/// be set by the running Lambda environment.
///
/// This constuctor will also search for the environment variable overriding the default minimum confidence level
/// for label detection.
/// </summary>
public Function()
{
this.S3Client = new AmazonS3Client();
this.RekognitionClient = new AmazonRekognitionClient();
this._dynamoService = new DynamoService();
var environmentMinConfidence = System.Environment.GetEnvironmentVariable(MIN_CONFIDENCE_ENVIRONMENT_VARIABLE_NAME);
if (!string.IsNullOrWhiteSpace(environmentMinConfidence))
{
float value;
if (float.TryParse(environmentMinConfidence, out value))
{
this.MinConfidence = value;
Console.WriteLine($"Setting minimum confidence to {this.MinConfidence}");
}
else
{
Console.WriteLine($"Failed to parse value {environmentMinConfidence} for minimum confidence. Reverting back to default of {this.MinConfidence}");
}
}
else
{
Console.WriteLine($"Using default minimum confidence of {this.MinConfidence}");
}
}
/// <summary>
/// Constructor used for testing which will pass in the already configured service clients.
/// </summary>
/// <param name="s3Client"></param>
/// <param name="rekognitionClient"></param>
/// <param name="minConfidence"></param>
public Function(IAmazonS3 s3Client, IAmazonRekognition rekognitionClient, float minConfidence, DynamoService dynamoService)
{
this.S3Client = s3Client;
this.RekognitionClient = rekognitionClient;
this.MinConfidence = minConfidence;
this._dynamoService = dynamoService;
}
/// <summary>
/// A function for responding to S3 create events. It will determine if the object is an image and use Amazon Rekognition
/// to detect labels and add the labels as tags on the S3 object.
/// </summary>
/// <param name="input"></param>
/// <param name="context"></param>
/// <returns></returns>
public async Task FunctionHandler(S3Event input, ILambdaContext context)
{
DynamoService dynamoService = new DynamoService();
foreach (var record in input.Records)
{
if (!SupportedImageTypes.Contains(Path.GetExtension(record.S3.Object.Key)))
{
Console.WriteLine($"Object {record.S3.Bucket.Name}:{record.S3.Object.Key} is not a supported image type");
continue;
}
Console.WriteLine($"Looking for labels in image {record.S3.Bucket.Name}:{record.S3.Object.Key}");
var detectResponses = await this.RekognitionClient.DetectLabelsAsync(new DetectLabelsRequest
{
MinConfidence = MinConfidence,
Image = new Image
{
S3Object = new Amazon.Rekognition.Model.S3Object
{
Bucket = record.S3.Bucket.Name,
Name = record.S3.Object.Key
}
}
});
var tags = new List <Tag>();
var tagFiltered = new List <Tag>();
foreach (var label in detectResponses.Labels)
{
if (tags.Count < 10)
{
Console.WriteLine($"\tFound Label {label.Name} with confidence {label.Confidence}");
tags.Add(new Tag {
Key = label.Name, Value = label.Confidence.ToString()
});
if (label.Confidence > 90)
{
tagFiltered.Add(new Tag {
Key = label.Name, Value = label.Confidence.ToString()
});
Console.WriteLine($"\tAdding Labek {label.Name} with confidence {label.Confidence} to dynamo Db");
}
}
else
{
Console.WriteLine($"\tSkipped label {label.Name} with confidence {label.Confidence} because the maximum number of tags has been reached");
}
}
ImageMetadata imageMetadata = new ImageMetadata();
{
imageMetadata.ImageKey = record.S3.Object.Key;
imageMetadata.TagsList = tagFiltered;
}
await dynamoService.Store(imageMetadata);
Console.WriteLine("Stored in dynamo Db");
await this.S3Client.PutObjectTaggingAsync(new PutObjectTaggingRequest
{
BucketName = record.S3.Bucket.Name,
Key = record.S3.Object.Key,
Tagging = new Tagging
{
TagSet = tags
}
});
}
return;
}