IndexFacesRequest Class | AWS SDK for .NET V3

Container for the parameters to the IndexFaces operation. Detects faces in the input image and adds them to the specified collection.

Amazon Rekognition doesn't save the actual faces that are detected. Instead, the underlying detection algorithm first detects the faces in the input image. For each face, the algorithm extracts facial features into a feature vector, and stores it in the backend database. Amazon Rekognition uses feature vectors when it performs face match and search operations using the SearchFaces and SearchFacesByImage operations.

For more information, see Adding faces to a collection in the Amazon Rekognition Developer Guide.

To get the number of faces in a collection, call DescribeCollection.

If you're using version 1.0 of the face detection model, IndexFaces indexes the 15 largest faces in the input image. Later versions of the face detection model index the 100 largest faces in the input image.

If you're using version 4 or later of the face model, image orientation information is not returned in the OrientationCorrection field.

To determine which version of the model you're using, call DescribeCollection and supply the collection ID. You can also get the model version from the value of FaceModelVersion in the response from IndexFaces

For more information, see Model Versioning in the Amazon Rekognition Developer Guide.

If you provide the optional ExternalImageId for the input image you provided, Amazon Rekognition associates this ID with all faces that it detects. When you call the ListFaces operation, the response returns the external ID. You can use this external image ID to create a client-side index to associate the faces with each image. You can then use the index to find all faces in an image.

You can specify the maximum number of faces to index with the MaxFaces input parameter. This is useful when you want to index the largest faces in an image and don't want to index smaller faces, such as those belonging to people standing in the background.

The QualityFilter input parameter allows you to filter out detected faces that don’t meet a required quality bar. The quality bar is based on a variety of common use cases. By default, IndexFaces chooses the quality bar that's used to filter faces. You can also explicitly choose the quality bar. Use QualityFilter, to set the quality bar by specifying LOW, MEDIUM, or HIGH. If you do not want to filter detected faces, specify NONE.

To use quality filtering, you need a collection associated with version 3 of the face model or higher. To get the version of the face model associated with a collection, call DescribeCollection.

Information about faces detected in an image, but not indexed, is returned in an array of UnindexedFace objects, UnindexedFaces. Faces aren't indexed for reasons such as:

The number of faces detected exceeds the value of the MaxFaces request parameter.
The face is too small compared to the image dimensions.
The face is too blurry.
The image is too dark.
The face has an extreme pose.
The face doesn’t have enough detail to be suitable for face search.

In response, the IndexFaces operation returns an array of metadata for all detected faces, FaceRecords. This includes:

The bounding box, BoundingBox, of the detected face.
A confidence value, Confidence, which indicates the confidence that the bounding box contains a face.
A face ID, FaceId, assigned by the service for each face that's detected and stored.
An image ID, ImageId, assigned by the service for the input image.

If you request ALL or specific facial attributes (e.g., FACE_OCCLUDED) by using the detectionAttributes parameter, Amazon Rekognition returns detailed facial attributes, such as facial landmarks (for example, location of eye and mouth), facial occlusion, and other facial attributes.

If you provide the same image, specify the same collection, and use the same external ID in the IndexFaces operation, Amazon Rekognition doesn't save duplicate face metadata.

The input image is passed either as base64-encoded image bytes, or as a reference to an image in an Amazon S3 bucket. If you use the AWS CLI to call Amazon Rekognition operations, passing image bytes isn't supported. The image must be formatted as a PNG or JPEG file.

This operation requires permissions to perform the rekognition:IndexFaces action.

Inheritance Hierarchy

System.Object
  Amazon.Runtime.AmazonWebServiceRequest
    Amazon.Rekognition.AmazonRekognitionRequest
      Amazon.Rekognition.Model.IndexFacesRequest

Namespace: Amazon.Rekognition.Model
Assembly: AWSSDK.Rekognition.dll
Version: 3.x.y.z

Syntax

public class IndexFacesRequest : AmazonRekognitionRequest
         IAmazonWebServiceRequest

The IndexFacesRequest type exposes the following members

Constructors

	Name	Description
	IndexFacesRequest()

Properties

Name	Type	Description
CollectionId	System.String	Gets and sets the property CollectionId. The ID of an existing collection to which you want to add the faces that are detected in the input images.
DetectionAttributes	System.Collections.Generic.List<System.String>	Gets and sets the property DetectionAttributes. An array of facial attributes you want to be returned. A `DEFAULT` subset of facial attributes - `BoundingBox`, `Confidence`, `Pose`, `Quality`, and `Landmarks` - will always be returned. You can request for specific facial attributes (in addition to the default list) - by using `["DEFAULT", "FACE_OCCLUDED"]` or just `["FACE_OCCLUDED"]`. You can request for all facial attributes by using `["ALL"]`. Requesting more attributes may increase response time. If you provide both, `["ALL", "DEFAULT"]`, the service uses a logical AND operator to determine which attributes to return (in this case, all attributes).
ExternalImageId	System.String	Gets and sets the property ExternalImageId. The ID you want to assign to all the faces detected in the image.
Image	Amazon.Rekognition.Model.Image	Gets and sets the property Image. The input image as base64-encoded bytes or an S3 object. If you use the AWS CLI to call Amazon Rekognition operations, passing base64-encoded image bytes isn't supported. If you are using an AWS SDK to call Amazon Rekognition, you might not need to base64-encode image bytes passed using the `Bytes` field. For more information, see Images in the Amazon Rekognition developer guide.
MaxFaces	System.Int32	Gets and sets the property MaxFaces. The maximum number of faces to index. The value of `MaxFaces` must be greater than or equal to 1. `IndexFaces` returns no more than 100 detected faces in an image, even if you specify a larger value for `MaxFaces`. If `IndexFaces` detects more faces than the value of `MaxFaces`, the faces with the lowest quality are filtered out first. If there are still more faces than the value of `MaxFaces`, the faces with the smallest bounding boxes are filtered out (up to the number that's needed to satisfy the value of `MaxFaces`). Information about the unindexed faces is available in the `UnindexedFaces` array. The faces that are returned by `IndexFaces` are sorted by the largest face bounding box size to the smallest size, in descending order. `MaxFaces` can be used with a collection associated with any version of the face model.
QualityFilter	Amazon.Rekognition.QualityFilter	Gets and sets the property QualityFilter. A filter that specifies a quality bar for how much filtering is done to identify faces. Filtered faces aren't indexed. If you specify `AUTO`, Amazon Rekognition chooses the quality bar. If you specify `LOW`, `MEDIUM`, or `HIGH`, filtering removes all faces that don’t meet the chosen quality bar. The default value is `AUTO`. The quality bar is based on a variety of common use cases. Low-quality detections can occur for a number of reasons. Some examples are an object that's misidentified as a face, a face that's too blurry, or a face with a pose that's too extreme to use. If you specify `NONE`, no filtering is performed. To use quality filtering, the collection you are using must be associated with version 3 of the face model or higher.

Examples

This operation detects faces in an image and adds them to the specified Rekognition collection.

To add a face to a collection


var client = new AmazonRekognitionClient();
var response = client.IndexFaces(new IndexFacesRequest 
{
    CollectionId = "myphotos",
    DetectionAttributes = new List<string> {
                    
    },
    ExternalImageId = "myphotoid",
    Image = new Image { S3Object = new S3Object {
        Bucket = "mybucket",
        Name = "myphoto"
    } }
});

List<FaceRecord> faceRecords = response.FaceRecords;
string orientationCorrection = response.OrientationCorrection;

Version Information

.NET Core App:
Supported in: 3.1

.NET Standard:
Supported in: 2.0

.NET Framework:
Supported in: 4.5, 4.0, 3.5