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Faces Comparison

On this page, find detailed information about faces comparison in Face SDK Web API.

Request

The SDK can compare faces on the same image as well as on two different images. This is defined by the type parameter.

The request contains the following parameters:

└── images
|   └── data
|   └── index
|   └── detectAll
|   └── type
└── thumbnails
Parameter Description
images The array of all images included in the comparison: data, index, detectAll, type for each image.
data Base64 image
index The index number of an image. Can be given, if not given, the index numbers are set automatically starting from 0. All index numbers must be whole and unique—not repeated.
detectAll

If set to true, the detection of all faces on the image is enabled.

If set to false, only one face on the image is detected: the most central one.

type

The type of the image, defines the way the comparison is performed. Should be set by a user.

"type": 1 (ift_DocumentPrinted = 1)—Image with a visual zone “document“.

"type": 2 (ift_DocumentRFID = 2)—Image from the RFID document.

"type": 3 (ift_Live = 3)—Live picture from a web camera.

"type": 4 (ift_LiveWithDoc = 4)—Compares all faces on one image with each other, for example, a photo of a person showing their passport (or any other document) photo.

"type": 5 (ift_External = 5)—Any other type or type is not defined.

thumbnails

If set to true, in Response, returns thumbnail—Base64 cropped image that contains the vertically aligned face.

If set to false, thumbnail is not returned.

Default: false.

Response

Before comparing faces, the Face SDK detects them. The detection result is displayed in the detections field.

Each face is identified by two parameters: faceIndex (the index number of the face) and imageIndex (the index number of the image on which the face is detected).

So, if there are two images each of which has two faces on them and all index numbers start from 0, the parameters will be the following:

First face on the first image:"faceIndex": 0, "imageIndex": 0

Second face in the first image: "faceIndex": 1, "imageIndex": 0

First face of the second image: "faceIndex": 0, "imageIndex": 1

Second face in the second image: "faceIndex": 1, "imageIndex": 1

The response contains the following parameters:

└── ErrorCode
└── code
└── detections
|   └── faces
|   |   └── faceIndex
|   |   └── landmarks
|   |   └── roi
|   |   └── rotationAngle
|   |   └── thumbnail
|   └── imageIndex
|   └── status
└── results
|   └── first
|   └── firstFaceIndex
|   └── firstIndex
|   └── score
|   └── second
|   └── secondFaceIndex
|   └── secondIndex
|   └── similarity
Parameter Description
ErrorCode Legacy parameter.
code

The result code the SDK returns.

If everything is OK, the result looks as follows:

"ErrorCode": 0,

"code": 0

See the list of error codes below.

detections The array of detected faces. Includes faces, imageIndex, status.
faces The array of detected faces. Includes faceIndex, landmarks, roi, rotationAngle, thumbnail for each of the detected faces.
faceIndex The index number of each of the detected face. Can be given, if not given, the index numbers are set automatically starting from 0. All index numbers must be whole and unique—not repeated.
landmarks Returns absolute coordinates (x,y) of five points of each detected face: left eye, right eye, nose, left point of lips, right point of lips.
rotationAngle Angle of rotation of the face from the vertical axis, degrees.
thumbnail Base64 cropped image that contains the vertically aligned face.
imageIndex The same as the index parameter from Request: The index number of the image on which the faces above are detected.
status

Returns the same value as code. If "code": 0 everything is OK. First status is detected, and if something is wrong, it is returned in code as well.

Possible errors:

"status": 1—image is empty, try again with another image

"status": 2—face is not detected

"status": 6—data can not be decoded as image

results The comparison results include first, firstFaceIndex, firstIndex, score, second, secondFaceIndex, secondIndex, similarity for each comparison of two faces.
first type (see the Request parameters) of the first compared face.
firstFaceIndex faceIndex of the first compared face.
firstIndex imageIndex of the image on which the first compared face is detected.
score A dimensionless number that shows how similar the compared faces are. 0—absolutely identical faces.
second type (see the Request parameters) of the second compared face.
secondFaceIndex faceIndex of the second compared face.
secondIndex imageIndex of the image on which the second compared face is detected.
similarity

The detected faces similarity, %.

100%—absolutely identical faces, 0%—absolutely not identical.

Errors

Here is a list of possible errors and their meanings:

Error Description
FR_FACE_NOT_DETECTED = 2 No faces are detected, most probably, the image does not contain faces.
FACER_NO_LICENSE = 200 There is no license.
FACER_IS_NOT_INITIALIZED = 201 The library is not initialized.
FACER_COMMAND_IS_NOT_SUPPORTED = 202 The command is not supported.
FACER_COMMAND_PARAMS_READ_ERROR = 203 The request is formed incorrectly.
FACER_LESS_THAN_TWO_IMAGES_IN_REQUEST = 224 There are fewer than two images selected.
FACER_OUTPUT_IS_NOT_DEFINED = 229 There is no memory allocated for the response.
FACER_IMAGES_COUNT_LIMIT_EXCEEDED = 238 The number of images of the same type for comparison is exceeded—you can’t compare more than two images of the same type.