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Reference for ultralytics/trackers/utils/gmc.py

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This file is available at https://github.com/ultralytics/ultralytics/blob/main/ultralytics/trackers/utils/gmc.py. If you spot a problem please help fix it by contributing a Pull Request 🛠️. Thank you 🙏!


ultralytics.trackers.utils.gmc.GMC

GMC(method: str = 'sparseOptFlow', downscale: int = 2)

Generalized Motion Compensation (GMC) class for tracking and object detection in video frames.

This class provides methods for tracking and detecting objects based on several tracking algorithms including ORB, SIFT, ECC, and Sparse Optical Flow. It also supports downscaling of frames for computational efficiency.

Attributes:

Name Type Description
method str

The method used for tracking. Options include 'orb', 'sift', 'ecc', 'sparseOptFlow', 'none'.

downscale int

Factor by which to downscale the frames for processing.

prevFrame ndarray

Stores the previous frame for tracking.

prevKeyPoints List

Stores the keypoints from the previous frame.

prevDescriptors ndarray

Stores the descriptors from the previous frame.

initializedFirstFrame bool

Flag to indicate if the first frame has been processed.

Methods:

Name Description
apply

Applies the chosen method to a raw frame and optionally uses provided detections.

applyEcc

Applies the ECC algorithm to a raw frame.

applyFeatures

Applies feature-based methods like ORB or SIFT to a raw frame.

applySparseOptFlow

Applies the Sparse Optical Flow method to a raw frame.

reset_params

Resets the internal parameters of the GMC object.

Examples:

Create a GMC object and apply it to a frame

>>> gmc = GMC(method="sparseOptFlow", downscale=2)
>>> frame = np.array([[1, 2, 3], [4, 5, 6]])
>>> processed_frame = gmc.apply(frame)
>>> print(processed_frame)
array([[1, 2, 3],
       [4, 5, 6]])

Parameters:

Name Type Description Default
method str

The method used for tracking. Options include 'orb', 'sift', 'ecc', 'sparseOptFlow', 'none'.

'sparseOptFlow'
downscale int

Downscale factor for processing frames.

2

Examples:

Initialize a GMC object with the 'sparseOptFlow' method and a downscale factor of 2

>>> gmc = GMC(method="sparseOptFlow", downscale=2)
Source code in ultralytics/trackers/utils/gmc.py
def __init__(self, method: str = "sparseOptFlow", downscale: int = 2) -> None:
    """
    Initialize a Generalized Motion Compensation (GMC) object with tracking method and downscale factor.

    Args:
        method (str): The method used for tracking. Options include 'orb', 'sift', 'ecc', 'sparseOptFlow', 'none'.
        downscale (int): Downscale factor for processing frames.

    Examples:
        Initialize a GMC object with the 'sparseOptFlow' method and a downscale factor of 2
        >>> gmc = GMC(method="sparseOptFlow", downscale=2)
    """
    super().__init__()

    self.method = method
    self.downscale = max(1, downscale)

    if self.method == "orb":
        self.detector = cv2.FastFeatureDetector_create(20)
        self.extractor = cv2.ORB_create()
        self.matcher = cv2.BFMatcher(cv2.NORM_HAMMING)

    elif self.method == "sift":
        self.detector = cv2.SIFT_create(nOctaveLayers=3, contrastThreshold=0.02, edgeThreshold=20)
        self.extractor = cv2.SIFT_create(nOctaveLayers=3, contrastThreshold=0.02, edgeThreshold=20)
        self.matcher = cv2.BFMatcher(cv2.NORM_L2)

    elif self.method == "ecc":
        number_of_iterations = 5000
        termination_eps = 1e-6
        self.warp_mode = cv2.MOTION_EUCLIDEAN
        self.criteria = (cv2.TERM_CRITERIA_EPS | cv2.TERM_CRITERIA_COUNT, number_of_iterations, termination_eps)

    elif self.method == "sparseOptFlow":
        self.feature_params = dict(
            maxCorners=1000, qualityLevel=0.01, minDistance=1, blockSize=3, useHarrisDetector=False, k=0.04
        )

    elif self.method in {"none", "None", None}:
        self.method = None
    else:
        raise ValueError(f"Error: Unknown GMC method:{method}")

    self.prevFrame = None
    self.prevKeyPoints = None
    self.prevDescriptors = None
    self.initializedFirstFrame = False

apply

apply(raw_frame: np.array, detections: list = None) -> np.array

Apply object detection on a raw frame using the specified method.

Parameters:

Name Type Description Default
raw_frame ndarray

The raw frame to be processed, with shape (H, W, C).

required
detections List | None

List of detections to be used in the processing.

None

Returns:

Type Description
ndarray

Processed frame with applied object detection.

Examples:

>>> gmc = GMC(method="sparseOptFlow")
>>> raw_frame = np.random.rand(480, 640, 3)
>>> processed_frame = gmc.apply(raw_frame)
>>> print(processed_frame.shape)
(480, 640, 3)
Source code in ultralytics/trackers/utils/gmc.py
def apply(self, raw_frame: np.array, detections: list = None) -> np.array:
    """
    Apply object detection on a raw frame using the specified method.

    Args:
        raw_frame (np.ndarray): The raw frame to be processed, with shape (H, W, C).
        detections (List | None): List of detections to be used in the processing.

    Returns:
        (np.ndarray): Processed frame with applied object detection.

    Examples:
        >>> gmc = GMC(method="sparseOptFlow")
        >>> raw_frame = np.random.rand(480, 640, 3)
        >>> processed_frame = gmc.apply(raw_frame)
        >>> print(processed_frame.shape)
        (480, 640, 3)
    """
    if self.method in {"orb", "sift"}:
        return self.applyFeatures(raw_frame, detections)
    elif self.method == "ecc":
        return self.applyEcc(raw_frame)
    elif self.method == "sparseOptFlow":
        return self.applySparseOptFlow(raw_frame)
    else:
        return np.eye(2, 3)

applyEcc

applyEcc(raw_frame: np.array) -> np.array

Apply the ECC (Enhanced Correlation Coefficient) algorithm to a raw frame for motion compensation.

Parameters:

Name Type Description Default
raw_frame ndarray

The raw frame to be processed, with shape (H, W, C).

required

Returns:

Type Description
ndarray

The processed frame with the applied ECC transformation.

Examples:

>>> gmc = GMC(method="ecc")
>>> processed_frame = gmc.applyEcc(np.array([[[1, 2, 3], [4, 5, 6]], [[7, 8, 9], [10, 11, 12]]]))
>>> print(processed_frame)
[[1. 0. 0.]
 [0. 1. 0.]]
Source code in ultralytics/trackers/utils/gmc.py
def applyEcc(self, raw_frame: np.array) -> np.array:
    """
    Apply the ECC (Enhanced Correlation Coefficient) algorithm to a raw frame for motion compensation.

    Args:
        raw_frame (np.ndarray): The raw frame to be processed, with shape (H, W, C).

    Returns:
        (np.ndarray): The processed frame with the applied ECC transformation.

    Examples:
        >>> gmc = GMC(method="ecc")
        >>> processed_frame = gmc.applyEcc(np.array([[[1, 2, 3], [4, 5, 6]], [[7, 8, 9], [10, 11, 12]]]))
        >>> print(processed_frame)
        [[1. 0. 0.]
         [0. 1. 0.]]
    """
    height, width, _ = raw_frame.shape
    frame = cv2.cvtColor(raw_frame, cv2.COLOR_BGR2GRAY)
    H = np.eye(2, 3, dtype=np.float32)

    # Downscale image
    if self.downscale > 1.0:
        frame = cv2.GaussianBlur(frame, (3, 3), 1.5)
        frame = cv2.resize(frame, (width // self.downscale, height // self.downscale))

    # Handle first frame
    if not self.initializedFirstFrame:
        # Initialize data
        self.prevFrame = frame.copy()

        # Initialization done
        self.initializedFirstFrame = True

        return H

    # Run the ECC algorithm. The results are stored in warp_matrix.
    # (cc, H) = cv2.findTransformECC(self.prevFrame, frame, H, self.warp_mode, self.criteria)
    try:
        (_, H) = cv2.findTransformECC(self.prevFrame, frame, H, self.warp_mode, self.criteria, None, 1)
    except Exception as e:
        LOGGER.warning(f"WARNING: find transform failed. Set warp as identity {e}")

    return H

applyFeatures

applyFeatures(raw_frame: np.array, detections: list = None) -> np.array

Apply feature-based methods like ORB or SIFT to a raw frame.

Parameters:

Name Type Description Default
raw_frame ndarray

The raw frame to be processed, with shape (H, W, C).

required
detections List | None

List of detections to be used in the processing.

None

Returns:

Type Description
ndarray

Processed frame.

Examples:

>>> gmc = GMC(method="orb")
>>> raw_frame = np.random.randint(0, 255, (480, 640, 3), dtype=np.uint8)
>>> processed_frame = gmc.applyFeatures(raw_frame)
>>> print(processed_frame.shape)
(2, 3)
Source code in ultralytics/trackers/utils/gmc.py
def applyFeatures(self, raw_frame: np.array, detections: list = None) -> np.array:
    """
    Apply feature-based methods like ORB or SIFT to a raw frame.

    Args:
        raw_frame (np.ndarray): The raw frame to be processed, with shape (H, W, C).
        detections (List | None): List of detections to be used in the processing.

    Returns:
        (np.ndarray): Processed frame.

    Examples:
        >>> gmc = GMC(method="orb")
        >>> raw_frame = np.random.randint(0, 255, (480, 640, 3), dtype=np.uint8)
        >>> processed_frame = gmc.applyFeatures(raw_frame)
        >>> print(processed_frame.shape)
        (2, 3)
    """
    height, width, _ = raw_frame.shape
    frame = cv2.cvtColor(raw_frame, cv2.COLOR_BGR2GRAY)
    H = np.eye(2, 3)

    # Downscale image
    if self.downscale > 1.0:
        frame = cv2.resize(frame, (width // self.downscale, height // self.downscale))
        width = width // self.downscale
        height = height // self.downscale

    # Find the keypoints
    mask = np.zeros_like(frame)
    mask[int(0.02 * height) : int(0.98 * height), int(0.02 * width) : int(0.98 * width)] = 255
    if detections is not None:
        for det in detections:
            tlbr = (det[:4] / self.downscale).astype(np.int_)
            mask[tlbr[1] : tlbr[3], tlbr[0] : tlbr[2]] = 0

    keypoints = self.detector.detect(frame, mask)

    # Compute the descriptors
    keypoints, descriptors = self.extractor.compute(frame, keypoints)

    # Handle first frame
    if not self.initializedFirstFrame:
        # Initialize data
        self.prevFrame = frame.copy()
        self.prevKeyPoints = copy.copy(keypoints)
        self.prevDescriptors = copy.copy(descriptors)

        # Initialization done
        self.initializedFirstFrame = True

        return H

    # Match descriptors
    knnMatches = self.matcher.knnMatch(self.prevDescriptors, descriptors, 2)

    # Filter matches based on smallest spatial distance
    matches = []
    spatialDistances = []

    maxSpatialDistance = 0.25 * np.array([width, height])

    # Handle empty matches case
    if len(knnMatches) == 0:
        # Store to next iteration
        self.prevFrame = frame.copy()
        self.prevKeyPoints = copy.copy(keypoints)
        self.prevDescriptors = copy.copy(descriptors)

        return H

    for m, n in knnMatches:
        if m.distance < 0.9 * n.distance:
            prevKeyPointLocation = self.prevKeyPoints[m.queryIdx].pt
            currKeyPointLocation = keypoints[m.trainIdx].pt

            spatialDistance = (
                prevKeyPointLocation[0] - currKeyPointLocation[0],
                prevKeyPointLocation[1] - currKeyPointLocation[1],
            )

            if (np.abs(spatialDistance[0]) < maxSpatialDistance[0]) and (
                np.abs(spatialDistance[1]) < maxSpatialDistance[1]
            ):
                spatialDistances.append(spatialDistance)
                matches.append(m)

    meanSpatialDistances = np.mean(spatialDistances, 0)
    stdSpatialDistances = np.std(spatialDistances, 0)

    inliers = (spatialDistances - meanSpatialDistances) < 2.5 * stdSpatialDistances

    goodMatches = []
    prevPoints = []
    currPoints = []
    for i in range(len(matches)):
        if inliers[i, 0] and inliers[i, 1]:
            goodMatches.append(matches[i])
            prevPoints.append(self.prevKeyPoints[matches[i].queryIdx].pt)
            currPoints.append(keypoints[matches[i].trainIdx].pt)

    prevPoints = np.array(prevPoints)
    currPoints = np.array(currPoints)

    # Draw the keypoint matches on the output image
    # if False:
    #     import matplotlib.pyplot as plt
    #     matches_img = np.hstack((self.prevFrame, frame))
    #     matches_img = cv2.cvtColor(matches_img, cv2.COLOR_GRAY2BGR)
    #     W = self.prevFrame.shape[1]
    #     for m in goodMatches:
    #         prev_pt = np.array(self.prevKeyPoints[m.queryIdx].pt, dtype=np.int_)
    #         curr_pt = np.array(keypoints[m.trainIdx].pt, dtype=np.int_)
    #         curr_pt[0] += W
    #         color = np.random.randint(0, 255, 3)
    #         color = (int(color[0]), int(color[1]), int(color[2]))
    #
    #         matches_img = cv2.line(matches_img, prev_pt, curr_pt, tuple(color), 1, cv2.LINE_AA)
    #         matches_img = cv2.circle(matches_img, prev_pt, 2, tuple(color), -1)
    #         matches_img = cv2.circle(matches_img, curr_pt, 2, tuple(color), -1)
    #
    #     plt.figure()
    #     plt.imshow(matches_img)
    #     plt.show()

    # Find rigid matrix
    if prevPoints.shape[0] > 4:
        H, inliers = cv2.estimateAffinePartial2D(prevPoints, currPoints, cv2.RANSAC)

        # Handle downscale
        if self.downscale > 1.0:
            H[0, 2] *= self.downscale
            H[1, 2] *= self.downscale
    else:
        LOGGER.warning("WARNING: not enough matching points")

    # Store to next iteration
    self.prevFrame = frame.copy()
    self.prevKeyPoints = copy.copy(keypoints)
    self.prevDescriptors = copy.copy(descriptors)

    return H

applySparseOptFlow

applySparseOptFlow(raw_frame: np.array) -> np.array

Apply Sparse Optical Flow method to a raw frame.

Parameters:

Name Type Description Default
raw_frame ndarray

The raw frame to be processed, with shape (H, W, C).

required

Returns:

Type Description
ndarray

Processed frame with shape (2, 3).

Examples:

>>> gmc = GMC()
>>> result = gmc.applySparseOptFlow(np.array([[[1, 2, 3], [4, 5, 6]], [[7, 8, 9], [10, 11, 12]]]))
>>> print(result)
[[1. 0. 0.]
 [0. 1. 0.]]
Source code in ultralytics/trackers/utils/gmc.py
def applySparseOptFlow(self, raw_frame: np.array) -> np.array:
    """
    Apply Sparse Optical Flow method to a raw frame.

    Args:
        raw_frame (np.ndarray): The raw frame to be processed, with shape (H, W, C).

    Returns:
        (np.ndarray): Processed frame with shape (2, 3).

    Examples:
        >>> gmc = GMC()
        >>> result = gmc.applySparseOptFlow(np.array([[[1, 2, 3], [4, 5, 6]], [[7, 8, 9], [10, 11, 12]]]))
        >>> print(result)
        [[1. 0. 0.]
         [0. 1. 0.]]
    """
    height, width, _ = raw_frame.shape
    frame = cv2.cvtColor(raw_frame, cv2.COLOR_BGR2GRAY)
    H = np.eye(2, 3)

    # Downscale image
    if self.downscale > 1.0:
        frame = cv2.resize(frame, (width // self.downscale, height // self.downscale))

    # Find the keypoints
    keypoints = cv2.goodFeaturesToTrack(frame, mask=None, **self.feature_params)

    # Handle first frame
    if not self.initializedFirstFrame or self.prevKeyPoints is None:
        self.prevFrame = frame.copy()
        self.prevKeyPoints = copy.copy(keypoints)
        self.initializedFirstFrame = True
        return H

    # Find correspondences
    matchedKeypoints, status, _ = cv2.calcOpticalFlowPyrLK(self.prevFrame, frame, self.prevKeyPoints, None)

    # Leave good correspondences only
    prevPoints = []
    currPoints = []

    for i in range(len(status)):
        if status[i]:
            prevPoints.append(self.prevKeyPoints[i])
            currPoints.append(matchedKeypoints[i])

    prevPoints = np.array(prevPoints)
    currPoints = np.array(currPoints)

    # Find rigid matrix
    if (prevPoints.shape[0] > 4) and (prevPoints.shape[0] == prevPoints.shape[0]):
        H, _ = cv2.estimateAffinePartial2D(prevPoints, currPoints, cv2.RANSAC)

        if self.downscale > 1.0:
            H[0, 2] *= self.downscale
            H[1, 2] *= self.downscale
    else:
        LOGGER.warning("WARNING: not enough matching points")

    self.prevFrame = frame.copy()
    self.prevKeyPoints = copy.copy(keypoints)

    return H

reset_params

reset_params() -> None

Reset the internal parameters including previous frame, keypoints, and descriptors.

Source code in ultralytics/trackers/utils/gmc.py
def reset_params(self) -> None:
    """Reset the internal parameters including previous frame, keypoints, and descriptors."""
    self.prevFrame = None
    self.prevKeyPoints = None
    self.prevDescriptors = None
    self.initializedFirstFrame = False




📅 Created 11 months ago ✏️ Updated 1 month ago