Detect AprilTags (https://april.eecs.umich.edu/software/apriltag) in an image. More...

Data Structures
struct	VPIAprilTagDecodeParams
	Decode parameters for vpiCreateAprilTagDetector. More...

struct	VPIAprilTagDetection
	Stores information about an AprilTag detection from AprilTag detector. More...

Enumerations
enum	VPIAprilTagFamily
	Specify the family of AprilTags to detect. More...

Functions
VPIStatus	vpiInitAprilTagDecodeParams (VPIAprilTagDecodeParams *params)
	Initializes VPIAprilTagDecodeParams with default values. More...

VPIStatus	vpiCreateAprilTagDetector (uint64_t backends, int32_t inputWidth, int32_t inputHeight, VPIAprilTagDecodeParams const params, VPIPayload payload)
	Creates a AprilTag detector payload. More...

VPIStatus	vpiSubmitAprilTagDetector (VPIStream stream, uint64_t backend, VPIPayload payload, uint32_t maxDetections, VPIImage input, VPIArray outDetections)
	Submits a AprilTag detector operation to the stream. More...

VPIStatus	vpiSubmitAprilTagPoseEstimation (VPIStream stream, uint64_t backend, VPIArray inDetections, const VPICameraIntrinsic intrinsics, float tagSize, VPIArray outPoses)
	Submits a AprilTag pose estimation operation to the stream. More...

Detailed Description

Detect AprilTags (https://april.eecs.umich.edu/software/apriltag) in an image.

Refer to AprilTag Detector and Pose Estimator for more details and usage examples.

Data Structure Documentation

◆ VPIAprilTagDecodeParams

struct VPIAprilTagDecodeParams

Decode parameters for vpiCreateAprilTagDetector.

Specifies family to decode and decode properties.

Definition at line 111 of file AprilTags.h.

Collaboration diagram for VPIAprilTagDecodeParams:

Data Fields
const uint16_t *	tagIdFilter	Optional array of tag ids from family which represent valid detections. Set to NULL to detect all tags from the family Data can be freed after call to vpiCreateAprilTagDetector.
int32_t	tagIdFilterSize	Size of tagIdFilter array if not NULL. Must be >=0. Must be less than the number of tags in the family.
int32_t	maxBitsCorrected	Maximum number of bits to correct during decoding. Must be in range [0,2]
VPIAprilTagFamily	family	Which family to detect.

◆ VPIAprilTagDetection

struct VPIAprilTagDetection

Stores information about an AprilTag detection from AprilTag detector.

Definition at line 772 of file Types.h.

Collaboration diagram for VPIAprilTagDetection:

Data Fields
uint16_t	id	The decoded ID of the tag.
int16_t	correctedBits	Number of bits corrected for this detection.
float	decisionMargin	A measure of the quality of the binary decoding process: the average difference between the intensity of a data bit versus the decision threshold. Higher numbers roughly indicate better decodes. This is a reasonable measure of detection accuracy only for very small tags.
VPIHomographyTransform2D	homography	The 3x3 homography matrix describing the projection from an "ideal" tag (with corners at (-1,1), (1,1), (1,-1), and (-1, -1)) to pixels in the image.
VPIKeypointF32	center	The center of the detection in image pixel coordinates.
VPIKeypointF32	corners[4]	The corners of the tag in image pixel coordinates, ordered counter-clockwise.

Enumeration Type Documentation

◆ VPIAprilTagFamily

enum VPIAprilTagFamily

#include <vpi/algo/AprilTags.h>

Specify the family of AprilTags to detect.

The family is defined by the layout, the number of bits in the tag and the minimum hamming distance between valid codewords.

Enumerator
VPI_APRILTAG_INVALID	Invalid value.
VPI_APRILTAG_16H5	16h5 family
VPI_APRILTAG_25H9	25h9 family
VPI_APRILTAG_36H10	36h10 family
VPI_APRILTAG_36H11	36h11 family
VPI_APRILTAG_CIRCLE21H7	Circle21h7 family.
VPI_APRILTAG_CIRCLE49H12	Circle49h12 family.
VPI_APRILTAG_CUSTOM48H12	Custom48h12 family.
VPI_APRILTAG_STANDARD41H12	Standard41h12 family.
VPI_APRILTAG_STANDARD52H13	Standard52h13 family.

Definition at line 83 of file AprilTags.h.

Function Documentation

◆ vpiInitAprilTagDecodeParams()

VPIStatus vpiInitAprilTagDecodeParams ( VPIAprilTagDecodeParams * params )

#include <vpi/algo/AprilTags.h>

Initializes VPIAprilTagDecodeParams with default values.

Defaults:

tagIdFilter: NULL
tagIdFilterSize: 0
maxBitsCorrected: 2
family: VPI_APRILTAG_36H11

Parameters

[out] params Structure to be filled with default values.

Return values

VPI_ERROR_INVALID_ARGUMENT	`params` is NULL
VPI_SUCCESS	Operation executed successfully.

◆ vpiCreateAprilTagDetector()

VPIStatus vpiCreateAprilTagDetector	(	uint64_t	backends,
		int32_t	inputWidth,
		int32_t	inputHeight,
		VPIAprilTagDecodeParams const *	params,
		VPIPayload *	payload
	)

#include <vpi/algo/AprilTags.h>

Creates a AprilTag detector payload.

This function allocates all temporary memory needed by the algorithm.

Parameters

[in]	backends	VPI backends that are eligible to execute the algorithm. Valid values: VPI_BACKEND_CPU VPI_BACKEND_PVA Backend must be enabled in current context. If VPI_BACKEND_PVA is used, the VPIStream and input/output buffers must support both VPI_BACKEND_PVA and VPI_BACKEND_CPU.
[in]	inputWidth,inputHeight	Dimensions of the input image that will be used with this payload. Must be > 0.
[in]	params	Decode parameters for the detector. Pass NULL to use the defaults given by vpiInitAprilTagDecodeParams.
[out]	payload	Pointer to the payload variable that receives the created handle.

Return values

VPI_ERROR_INVALID_ARGUMENT	`payload` is NULL.
VPI_ERROR_INVALID_ARGUMENT	`backends` refers to an invalid backend.
VPI_ERROR_INVALID_ARGUMENT	`inputWidth` or `inputHeight` outside valid range.
VPI_ERROR_INVALID_ARGUMENT	`params` is NULL or contains invalid configuration.
VPI_ERROR_INVALID_OPERATION	Backend hardware not available, or backend not available in current context.
VPI_ERROR_NOT_IMPLEMENTED	Algorithm does not support the given backend.
VPI_ERROR_INVALID_CONTEXT	Current context is destroyed.
VPI_ERROR_OUT_OF_MEMORY	Cannot allocate required resources.
VPI_SUCCESS	Operation executed successfully.

◆ vpiSubmitAprilTagDetector()

VPIStatus vpiSubmitAprilTagDetector	(	VPIStream	stream,
		uint64_t	backend,
		VPIPayload	payload,
		uint32_t	maxDetections,
		VPIImage	input,
		VPIArray	outDetections
	)

#include <vpi/algo/AprilTags.h>

Submits a AprilTag detector operation to the stream.

Parameters

[in]	stream	The stream where the operation will be queued in. Must not be NULL. Stream must have enabled the backends that will execute the algorithm.
[in]	backend	Backend that will execute the algorithm. Must be the backend specified during payload creation or 0 as a shorthand to use this backend.
[in]	payload	Payload to be submitted along the other parameters.
[in]	maxDetections	Maximum number of detections to be returned in outDetections.
[in]	input	Input image used for detection Must not be NULL. Must match dimensions used in vpiCreateAprilTagDetector. Image must have enabled the backends that will execute the algorithm. Must have format VPI_IMAGE_FORMAT_U8
[out]	outDetections	Array that will receive the detections. Array size is updated with the number of tags found. Must not be NULL. It must have type VPI_ARRAY_TYPE_APRILTAG_DETECTION. Array must have enabled the backends that will execute the algorithm. If more tags are detected than the array capacity, extra tag detections are discarded.

Return values

VPI_ERROR_INVALID_ARGUMENT	`stream` is NULL.
VPI_ERROR_INVALID_ARGUMENT	`input` is NULL.
VPI_ERROR_INVALID_ARGUMENT	`input` image dimensions do not match dimensions passed to vpiCreateAprilTagDetector.
VPI_ERROR_INVALID_ARGUMENT	`backend` does not match the backend used to create the payload.
VPI_ERROR_INVALID_IMAGE_FORMAT	`input` image format not supported.
VPI_ERROR_INVALID_PAYLOAD_TYPE	`payload` is invalid or NULL.
VPI_ERROR_NOT_IMPLEMENTED	Algorithm does not support the given backend.
VPI_ERROR_INVALID_OPERATION	Backend hardware not available.
VPI_ERROR_INVALID_OPERATION	The needed backends aren't enabled in `stream`, `input` or `outDetections`.
VPI_SUCCESS	Operation executed successfully.

◆ vpiSubmitAprilTagPoseEstimation()

VPIStatus vpiSubmitAprilTagPoseEstimation	(	VPIStream	stream,
		uint64_t	backend,
		VPIArray	inDetections,
		const VPICameraIntrinsic	intrinsics,
		float	tagSize,
		VPIArray	outPoses
	)

#include <vpi/algo/AprilTags.h>

Submits a AprilTag pose estimation operation to the stream.

Parameters

[in]	stream	The stream where the operation will be queued in. Must not be NULL. Stream must have enabled the backends that will execute the algorithm.
[in]	backend	Backend that will execute the algorithm. Valid values: VPI_BACKEND_CPU Backend must be enabled in current context.
[in]	inDetections	Array of AprilTag detections. Must not be NULL. It must have type VPI_ARRAY_TYPE_APRILTAG_DETECTION. Array must have enabled the backends that will execute the algorithm.
[in]	intrinsics	Camera intrinsics
[in]	tagSize	Tag edge length Must be > 0
[out]	outPoses	Array that will receive the pose estimations. Array size will be set to same as inDetections. Must not be NULL. It must have type VPI_ARRAY_TYPE_POSE. Array must have enabled the backends that will execute the algorithm. Capacity must be equal or greater than size of inDetections.

Return values

VPI_ERROR_INVALID_ARGUMENT	`stream` is NULL.
VPI_ERROR_INVALID_ARGUMENT	`inDetections` or `outPoses` is NULL.
VPI_ERROR_NOT_IMPLEMENTED	Algorithm does not support the given backend.
VPI_ERROR_INVALID_OPERATION	Backend hardware not available.
VPI_ERROR_INVALID_OPERATION	The needed backends aren't enabled in `stream`, `inDetections` or `outPoses`.
VPI_SUCCESS	Operation executed successfully.

VPI - Vision Programming Interface

3.2 Release

Data Structures

Enumerations

Functions

Detailed Description

Data Structure Documentation

◆ VPIAprilTagDecodeParams

◆ VPIAprilTagDetection

Enumeration Type Documentation

◆ VPIAprilTagFamily

Function Documentation

◆ vpiInitAprilTagDecodeParams()

◆ vpiCreateAprilTagDetector()

◆ vpiSubmitAprilTagDetector()

◆ vpiSubmitAprilTagPoseEstimation()