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@@ -0,0 +1,213 @@
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+import cv2
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+import numpy as np
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+import typing as T
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+
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+from munch import munchify
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+from collections import namedtuple
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+from skimage import filters
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+
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+# the coordinates are relative!
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+BBoxInfo = namedtuple("BBoxInfo", "area ratio mean std selected", defaults=[-1, -1, -1, -1, False])
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+Detection = namedtuple("Detection", "bbox info")
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+
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+class BBox(namedtuple("BBox", "x0 y0 x1 y1")):
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+ __slots__ = ()
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+
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+ @property
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+ def w(self):
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+ return abs(self.x1 - self.x0)
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+
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+ @property
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+ def h(self):
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+ return abs(self.y1 - self.y0)
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+
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+
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+ @property
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+ def area(self):
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+ return self.h * self.w
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+
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+ @property
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+ def ratio(self):
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+ return min(self.h, self.w) / max(self.h, self.w)
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+
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+ def crop(self, im: np.ndarray, enlarge: bool = True):
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+
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+ x0, y0, x1, y1 = self
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+ H, W, *_ = im.shape
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+
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+ # translate from relative coordinates to pixel
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+ # coordinates for the given image
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+
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+ x0, x1 = int(x0 * W), int(x1 * W)
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+ y0, y1 = int(y0 * H), int(y1 * H)
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+
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+ # enlarge to a square extent
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+ if enlarge:
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+ h, w = int(self.h * H), int(self.h * W)
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+ size = max(h, w)
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+ dw, dh = (size - w) / 2, (size - h) / 2
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+ x0, x1 = max(int(x0 - dw), 0), int(x0 - dw + size)
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+ y0, y1 = max(int(y0 - dh), 0), int(y0 - dh + size)
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+
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+ if im.ndim == 2:
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+ return im[y0:y1, x0:x1]
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+
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+ elif im.ndim == 3:
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+ return im[y0:y1, x0:x1, :]
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+
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+ else:
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+ ValueError(f"Unsupported ndims: {im.ndims=}")
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+
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+
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+class Detector(object):
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+
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+
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+ def __init__(self, configuration: T.Dict[str, T.Dict]) -> None:
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+ super().__init__()
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+ config = munchify(configuration)
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+
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+ self.scale: float = config.preprocess.scale
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+ self.min_size: int = config.preprocess.min_size
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+ self.sigma: float = config.preprocess.sigma
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+
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+ self.block_size_scale: float = config.threshold.block_size_scale
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+
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+ self.dilate_iterations: int = config.postprocess.dilate_iterations
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+ self.kernel_size: int = config.postprocess.kernel_size
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+
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+
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+ def __call__(self, im: np.ndarray) -> T.List[Detection]:
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+
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+ _im = self.rescale(im)
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+
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+ im0 = self.preprocess(_im)
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+ im1 = self.threshold(im0)
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+ im2 = self.postprocess(im1)
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+
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+ bboxes = self.detect(im2)
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+
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+ return self.postprocess_boxes(_im, bboxes)
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+
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+
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+ def detect(self, im: np.ndarray) -> T.List[BBox]:
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+
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+ contours, hierarchy = cv2.findContours(im, cv2.RETR_TREE, cv2.CHAIN_APPROX_SIMPLE)
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+ contours = sorted(contours, key=cv2.contourArea, reverse=True)
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+
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+ return [_contour2bbox(c, im.shape) for c in contours]
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+
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+
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+ def rescale(self, im: np.ndarray) -> np.ndarray:
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+
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+ H, W = im.shape
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+ _scale = self.min_size / min(H, W)
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+ scale = max(self.scale, min(1, _scale))
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+ size = int(W * scale), int(H * scale)
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+
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+ return cv2.resize(im, dsize=size)
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+
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+
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+ def preprocess(self, im: np.ndarray) -> np.ndarray:
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+ res = filters.gaussian(im, sigma=self.sigma, preserve_range=True)
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+ return res.astype(im.dtype)
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+
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+
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+ def threshold(self, im: np.ndarray) -> np.ndarray:
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+ block_size_scale = self.block_size_scale
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+
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+ # make block size an odd number
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+ block_size = min(im.shape) * block_size_scale // 2 * 2 + 1
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+
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+ thresh = filters.threshold_local(im,
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+ block_size=block_size,
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+ mode="constant",
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+ )
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+
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+ max_value = 255
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+ bin_im = ((im > thresh) * max_value).astype(np.uint8)
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+ return max_value - bin_im
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+
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+
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+ def postprocess(self, im: np.ndarray) -> np.ndarray:
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+ kernel_size = self.kernel_size
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+ iterations = self.dilate_iterations
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+ kernel = np.ones((kernel_size, kernel_size), dtype=np.uint8)
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+
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+ im = cv2.morphologyEx(im, cv2.MORPH_OPEN, kernel)
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+ im = cv2.morphologyEx(im, cv2.MORPH_CLOSE, kernel)
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+
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+ if iterations >= 1:
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+ im = cv2.erode(im, kernel, iterations=iterations)
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+ im = cv2.dilate(im, kernel, iterations=iterations)
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+
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+ return im
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+
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+
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+ def postprocess_boxes(self, im: np.ndarray, bboxes: T.List[BBox]):
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+
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+ detections = [Detection(bbox, BBoxInfo()) for bbox in bboxes]
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+
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+ _im = im.astype(np.float64) / 255.
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+ integral, integral_sq = cv2.integral2(_im)
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+ # im_mean, im_std, im_n = _im_mean_std(integral, integral_sq)
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+
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+ inds = cv2.dnn.NMSBoxes([[x0, y0, x1-x0, y1-y0] for (x0, y0, x1, y1) in bboxes],
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+ np.ones(len(bboxes), dtype=np.float32),
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+ score_threshold=0.99,
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+ nms_threshold=0.1,
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+ )
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+
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+ # calculate the BBoxInfos only for the selected and update the detections
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+ for i in inds.squeeze():
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+ bbox, _ = detections[i]
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+ mean, std, n = _im_mean_std(integral, integral_sq, bbox)
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+ area, ratio = bbox.area, bbox.ratio
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+ selected = self.is_selected(mean, std, ratio, area)
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+ info = BBoxInfo(mean, std, area, ratio, selected)
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+ detections[i] = Detection(bbox, info)
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+
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+ return detections
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+
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+ def is_selected(self, mean: float, std: float, ratio: float, area: float) -> bool:
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+ # Caution, here are some magic numbers!
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+ return \
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+ std >= 5e-2 and \
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+ ratio >= 2.5e-1 and \
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+ 4e-4 <= area <= 1/9
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+
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+def _contour2bbox(contour: np.ndarray, shape: T.Tuple[int, int]) -> BBox:
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+ """ Gets the maximal extent of a contour and translates it to a bounding box. """
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+ x0, y0 = contour.min(axis=0)[0].astype(np.int32)
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+ x1, y1 = contour.max(axis=0)[0].astype(np.int32)
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+
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+ h, w = shape
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+ return BBox(x0/w, y0/h, x1/w, y1/h)
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+
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+
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+def _im_mean_std(integral: np.ndarray,
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+ integral_sq: np.ndarray,
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+ bbox: T.Optional[BBox] = None
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+ ) -> T.Tuple[float, float, int]:
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+
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+ h, w = integral.shape[0] - 1, integral.shape[1] - 1
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+
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+ if bbox is None:
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+ arr_sum = integral[-1, -1]
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+ arr_sum_sq = integral_sq[-1, -1]
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+ N = h * w
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+
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+ else:
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+ x0, y0, x1, y1 = bbox
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+ x0, x1 = int(x0 * w), int(x1 * w)
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+ y0, y1 = int(y0 * h), int(y1 * h)
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+
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+ A, B, C, D = (y0,x0), (y1,x0), (y0,x1), (y1,x1)
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+ arr_sum = integral[D] + integral[A] - integral[B] - integral[C]
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+ arr_sum_sq = integral_sq[D] + integral_sq[A] - integral_sq[B] - integral_sq[C]
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+
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+ N = (x1-x0) * (y1-y0)
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+
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+ arr_mean = arr_sum / N
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+ arr_std = np.sqrt((arr_sum_sq - (arr_sum**2) / N) / N)
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+
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+ return arr_mean, arr_std, N
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