Specify what faces to index with AWS Rekognition and Lambda - node.js

Question

My apologies in advance for the long post.
I am quite new to AWS Rekognition and Lambda, but I took on a project to build a facial recognition system using AWS S3, Rekognition and Lambda. I managed to get a working solution using a few of the Rekognition API's that are provided in the AWS JavaScript SDK Documentation, but it only works when there is one face in the input image. I started playing around with images that has multiple faces, but it doesn't give the response I'm looking for. After doing research I narrowed my problem down to the following:
I need to be able to specify what faces I want to index in an image with multiple faces using the indexFaces API.
NOTE: I'm using JavaScript.
My logic for a single face in an image is that I use the SearchFacesByImage API and I first see if I have indexed the face of Person 1 in the past to 'allFaces'. If I have, then I don't need to index Person 1's face again to 'allFaces', but if I have not, then I need to do that first.
Up until this point, everything works fine when I'm using an image with a single face as input. (See code example down below)
Here comes the problem, when I have an image with multiple faces, including the face of Person 1, it will index all the faces in that image, including Person 1's face again, and add it to the 'allFaces' collection, but what I want to achieve is where the system picks up that Person 1 has been indexed in the past, so it should not index Person 1 again, instead index all the other people in the image.
That's how I came to refine my problem to be able to specify what faces I want to index in an image that contains multiple faces, because if I can achieve that, then I can say that Person 1 has been indexed, so continue with Person 2.
In the indexFaces API, you can specify the "MaxFaces" and "QualityFilter" parameters. I have looked at that, but I don't believe that holds the answer to my solution so I'm steering away from that, unless it 100% holds the answer to my solution.
I'm also not sure if there might be an issue with my logic, or if my logic is okay but my lack in JavaScript knowledge is what's holding me back.
Here is what I've done thus far for a single face in an image:
const AWS = require('aws-sdk');
const s3 = new AWS.S3({apiVersion: "2006-03-01"});
const rekognition = new AWS.Rekognition();
//-----------------------------Exports Function-----------------------
exports.handler = function(event, context) {
bucket = event.Records[0].s3.bucket.name;
key = event.Records[0].s3.object.key;
console.log(bucket);
console.log(key);
searchingFacesByImage(bucket, key);
};
//--------------------------------------------------------------------
// Search for a face in an input image
function searchingFacesByImage(bucket, key) {
let params = {
CollectionId: "allFaces",
FaceMatchThreshold: 95,
Image: {
S3Object: {
Bucket: bucket,
Name: key
}
},
MaxFaces: 5
};
const searchingFace = rekognition.searchFacesByImage(params, function(err, searchdata) {
if (err) {
console.log(err, err.stack); // an error occurred
} else {
// console.log(JSON.stringify(searchdata, null, '\t'));
// if data.FaceMatches > 0 : There that face in the image exists in the collection
if (searchdata.FaceMatches.length > 0) {
console.log("Face is a match");
// Continue
} else {
console.log("Face is not a match");
console.log("Start indexing face to 'allFaces'");
indexToAllFaces(bucket, key);
}
}
});
return searchingFace;
}
//--------------------------------------------------------------------
// If face is not a match in 'allFaces', index face to 'allFaces' collection
function indexToAllFaces(bucket, key) {
let params = {
CollectionId: "allFaces",
DetectionAttributes: ['ALL'],
Image: {
S3Object: {
Bucket: bucket,
Name: key
}
}
};
const indexFace = rekognition.indexFaces(params, function(err, data) {
if (err) {
console.log(err, err.stack); // an error occurred
} else {
console.log("INDEXING TO 'allFaces'");
console.log(JSON.stringify(data, null, '\t'));
}
});
return indexFace;
}
//--------------------------------------------------------------------
Like I said, this works fine when using images with a single face, so that is why I'm hoping to add some logic to filter through the faces in an image with multiple faces and whoever's face has been indexed in the past, should not be indexed again.
Thanks in advance for any feedback.

Answer 1

You will need to use DetectFaces() to obtain a list of all faces detected in the image.
The, for each Face returned:
Use the BoundingBox to copy and crop the image, so it only shows the given face
Use SearchFacesByImage() to determine whether it is already in the Face Collection
If it is not in the Face Collection, use IndexImages() to add it to the Face Collection. It will add the single face to the collection.
From experience, it is also a good idea to associate an ExternalImageId with each image added. This can contain your own reference to the face and can be used in a database to store additional information about the Face (eg id, name, or which picture they came from). The ExternalImageId will be returned with cetain calls when the face is detected in images.