AWS SDK Version 3 for .NET
API Reference

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For a given input image, first detects the largest face in the image, and then searches the specified collection for matching faces. The operation compares the features of the input face with faces in the specified collection.

To search for all faces in an input image, you might first call the operation, and then use the face IDs returned in subsequent calls to the operation.

You can also call the DetectFaces operation and use the bounding boxes in the response to make face crops, which then you can pass in to the SearchFacesByImage operation.

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

The response returns an array of faces that match, ordered by similarity score with the highest similarity first. More specifically, it is an array of metadata for each face match found. Along with the metadata, the response also includes a similarity indicating how similar the face is to the input face. In the response, the operation also returns the bounding box (and a confidence level that the bounding box contains a face) of the face that Amazon Rekognition used for the input image.

For an example, Searching for a Face Using an Image in the Amazon Rekognition Developer Guide.

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


For .NET Core and PCL this operation is only available in asynchronous form. Please refer to SearchFacesByImageAsync.

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


public virtual SearchFacesByImageResponse SearchFacesByImage(
         SearchFacesByImageRequest request
Type: Amazon.Rekognition.Model.SearchFacesByImageRequest

Container for the necessary parameters to execute the SearchFacesByImage service method.

Return Value
The response from the SearchFacesByImage service method, as returned by Rekognition.


AccessDeniedException You are not authorized to perform the action.
ImageTooLargeException The input image size exceeds the allowed limit. For more information, see Limits in Amazon Rekognition in the Amazon Rekognition Developer Guide.
InternalServerErrorException Amazon Rekognition experienced a service issue. Try your call again.
InvalidImageFormatException The provided image format is not supported.
InvalidParameterException Input parameter violated a constraint. Validate your parameter before calling the API operation again.
InvalidS3ObjectException Amazon Rekognition is unable to access the S3 object specified in the request.
ProvisionedThroughputExceededException The number of requests exceeded your throughput limit. If you want to increase this limit, contact Amazon Rekognition.
ResourceNotFoundException The collection specified in the request cannot be found.
ThrottlingException Amazon Rekognition is temporarily unable to process the request. Try your call again.


This operation searches for faces in a Rekognition collection that match the largest face in an S3 bucket stored image.

To search for faces matching a supplied image

var response = client.SearchFacesByImage(new SearchFacesByImageRequest 
    CollectionId = "myphotos",
    FaceMatchThreshold = 95,
    Image = new Image { S3Object = new S3Object {
        Bucket = "mybucket",
        Name = "myphoto"
    } },
    MaxFaces = 5

List faceMatches = response.FaceMatches;
BoundingBox searchedFaceBoundingBox = response.SearchedFaceBoundingBox;
float searchedFaceConfidence = response.SearchedFaceConfidence;


Version Information

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

Portable Class Library:
Supported in: Windows Store Apps
Supported in: Windows Phone 8.1
Supported in: Xamarin Android
Supported in: Xamarin iOS (Unified)
Supported in: Xamarin.Forms

See Also