# C API Documentation

# Structs

# DELPoint2d

Point2d class for landmarks

typedef struct DELPoint2d {
    float x;
    float y;
} DELPoint2d;

Members:

float x - x coordinate of the point
float y - y coordinate of the point

# DELPoint2dArray

Array of Point2d

typedef struct DELPoint2dArray {
    int count;
    DELPoint2d* points;
} DELPoint2dArray;

Members:

int count - number of points
DELPoint2d* points - pointer to the array of points

# DELBoundingBox

Bounding Box class for the faces

typedef struct DELBoundingBox {
    int x;
    int y;
    int width;
    int height;
} DELBoundingBox;

Members:

int x - x coordinate of the top-left corner
int y - y coordinate of the top-left corner
int width - width of the bounding box in pixels
int height - height of the bounding box in pixels

# DELImageHeader

Descriptor class for image data (non-owning)

typedef struct DELImageHeader {
    const uint8_t* data;
    int width;
    int height;
    int stride;
    DELImageFormat format;
} DELImageHeader;

Members:

const uint8_t* data - pointer to the byte array of the image
int width - width of the image in pixels
int height - height of the image in pixels
int stride - length of one row of pixels in bytes (e.g: 3*width + padding)
DELImageFormat format - image format

# DELOutput

Output struct for various estimated outputs

typedef struct DELOutput {
    DELOutputType type;
    union {
        DELGender gender;
        float float_value;
    };
    const char* name;
} DELOutput;

Members:

DELOutputType type - type of the output
DELGender gender - gender value (when type is DELOutputTypeGender)
float float_value - float value (when type is DELOutputTypeAge or DELOutputTypeAgeUncertainty)
const char* name - name of the output (valid only during callback)

# DELOutputArray

Array of Outputs

typedef struct DELOutputArray {
    int count;
    DELOutput* outputs;
} DELOutputArray;

Members:

int count - number of outputs
DELOutput* outputs - pointer to the array of outputs

# DELVersion

Semantic version number for the SDK

typedef struct DELVersion {
    int major;
    int minor;
    int patch;
} DELVersion;

# DELFaceArray

Array of Faces

typedef struct DELFaceArray {
    int count;
    DELFace** faces;
} DELFaceArray;

Members:

int count - number of faces
DELFace** faces - pointer to the array of face pointers

# Enums

# DELImageFormat

Image format enum

Values:

DELImageFormatGrayscale = 0 - 8-bit grayscale
DELImageFormatRGB = 1 - 24-bit RGB
DELImageFormatRGBA = 2 - 32-bit RGBA or 32-bit RGB_
DELImageFormatBGR = 3 - 24-bit BGR
DELImageFormatBGRA = 4 - 32-bit BGRA or 32-bit BGR_

# DELOutputType

Type of the output in Output struct

Values:

DELOutputTypeAge = 0 - Age estimation
DELOutputTypeGender = 1 - Gender classification
DELOutputTypeAgeUncertainty = 2 - Age uncertainty estimation

# DELGender

Gender enum

Values:

DELGenderFemale = 0 - Female
DELGenderMale = 1 - Male

# Callbacks

# DELDetectFacesCallback

typedef void (*DELDetectFacesCallback)(void* user_data, DELFaceArray* faces, const char* error_msg);

Callback for face detection

Parameters:

user_data - user data passed to the function
faces - array of detected faces. The array and its contents are owned by the library and are valid only during the callback.
error_msg - error message if any, otherwise NULL

# DELEstimateCallback

typedef void (*DELEstimateCallback)(void* user_data, DELOutputArray* outputs, const char* error_msg);

Callback for demographic estimation

Parameters:

user_data - user data passed to the function
outputs - array of estimation outputs. The array and its contents are owned by the library and are valid only during the callback.
error_msg - error message if any, otherwise NULL

# DemographicEstimator Functions

# del_demographic_estimator_new

DELDemographicEstimator* del_demographic_estimator_new(const char* model_file,
                                                       int max_concurrency,
                                                       char** errorMessage);

Constructor: loads model file, sets up the processing.

Parameters:

model_file - path for the used model
max_concurrency - maximum allowed concurrency, 0 means automatic (using all cores), default: 0
errorMessage - pointer to a char* that will be set to an error message string on failure, or NULL on success. The caller is responsible for freeing the string using free(). If errorMessage is a NULL pointer, no error message will be returned.

Returns: pointer to the new DemographicEstimator instance, or NULL on failure

# del_demographic_estimator_free

void del_demographic_estimator_free(DELDemographicEstimator* estimator);

Destructor

Parameters:

estimator - pointer to the DemographicEstimator instance to free

# del_demographic_estimator_detect_faces

void del_demographic_estimator_detect_faces(DELDemographicEstimator* estimator,
                                           const DELImageHeader* image_header,
                                           DELDetectFacesCallback callback,
                                           void* user_data);

Detects the faces on an image with a callback API.

Note: The given ImageHeader doesn't own the image data, and it is safe to delete the data after the call, a copy is happening internally. See DELImageHeader for details.

Note: Calling this function is non-blocking, so calling it again with the next frame without waiting for the result is possible. Also see del_demographic_estimator_get_concurrent_calculations().

Parameters:

estimator - pointer to the DemographicEstimator instance
image_header - image descriptor
callback - callback to call with the result
user_data - user data to pass to the callback

# del_demographic_estimator_estimate

void del_demographic_estimator_estimate(DELDemographicEstimator* estimator,
                                       const DELFace* face,
                                       DELEstimateCallback callback,
                                       void* user_data);

Returns the demographic estimation of the detected face.

Note: Calling this function is non-blocking, so calling it again with the next frame without waiting for the result is possible. Also see del_demographic_estimator_get_concurrent_calculations().

Parameters:

estimator - pointer to the DemographicEstimator instance
face - the previously detected face to estimate
callback - callback to call with the result
user_data - user data to pass to the callback

# del_demographic_estimator_get_concurrent_calculations

int del_demographic_estimator_get_concurrent_calculations(const DELDemographicEstimator* estimator);

Returns the value of the atomic counter for the number of calculations currently running concurrently. You can use this to limit the number of concurrent calculations.

Parameters:

estimator - pointer to the DemographicEstimator instance

Returns: The (approximate) number of calculations currently in-flight.

# del_demographic_estimator_get_model_name

char* del_demographic_estimator_get_model_name(const DELDemographicEstimator* estimator);

Returns the name (version etc) of the loaded model.

Parameters:

estimator - pointer to the DemographicEstimator instance

Returns: name of the model. The caller is responsible for freeing the returned string using free().

# del_demographic_estimator_get_sdk_version

DELVersion del_demographic_estimator_get_sdk_version();

Returns the version of the SDK (and not the model)

Returns: version of the SDK

# del_demographic_estimator_get_sdk_version_string

char* del_demographic_estimator_get_sdk_version_string();

Returns the version string of the SDK (and not the model)

Returns: version string of the SDK. The caller is responsible for freeing the returned string using free().

# Face Functions

# del_face_new

DELFace* del_face_new(const DELImageHeader* image_header,
                      const DELPoint2d* landmarks,
                      int num_landmarks,
                      const DELBoundingBox* bbox,
                      float confidence,
                      char** errorMessage);

Constructor for the Face object to support 3rd party face detectors

Parameters:

image_header - image descriptor
landmarks - face landmarks
num_landmarks - number of landmarks
bbox - face bounding box
confidence - face detection confidence
errorMessage - pointer to a char* that will be set to an error message string on failure, or NULL on success. The caller is responsible for freeing the string using free(). If errorMessage is a NULL pointer, no error message will be returned.

Returns: pointer to the new Face instance, or NULL on failure

# del_face_copy

DELFace* del_face_copy(const DELFace* other);

Copy constructor

Parameters:

other - pointer to the Face instance to copy

Returns: pointer to the new Face instance, or NULL on failure

# del_face_free

void del_face_free(DELFace* face);

Destructor

Parameters:

face - pointer to the Face instance to free

# del_face_bounding_box

DELBoundingBox del_face_bounding_box(const DELFace* face);

Returns the bounding box of the detected face

Parameters:

face - pointer to the Face instance

Returns: DELBoundingBox

# del_face_confidence

float del_face_confidence(const DELFace* face);

Returns the confidence value of the detected face

Parameters:

face - pointer to the Face instance

Returns: float

# del_face_landmarks

DELPoint2dArray* del_face_landmarks(const DELFace* face);

Returns the landmarks of the face

Parameters:

face - pointer to the Face instance

Returns: pointer to DELPoint2dArray. The caller is responsible for freeing the returned array using free().