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from __future__ import absolute_import, division, print_function, unicode_literals
import cv2
import numpy as np
np.seterr(divide="ignore", invalid="ignore")
import warnings
import pyclipper
from shapely.geometry import Polygon
warnings.simplefilter("ignore")
__all__ = ["MakeBorderMap"]
class MakeBorderMap(object):
def __init__(self, shrink_ratio=0.4, thresh_min=0.3, thresh_max=0.7, **kwargs):
self.shrink_ratio = shrink_ratio
self.thresh_min = thresh_min
self.thresh_max = thresh_max
def __call__(self, data):
img = data["image"]
text_polys = data["polys"]
ignore_tags = data["ignore_tags"]
canvas = np.zeros(img.shape[:2], dtype=np.float32)
mask = np.zeros(img.shape[:2], dtype=np.float32)
for i in range(len(text_polys)):
if ignore_tags[i]:
continue
self.draw_border_map(text_polys[i], canvas, mask=mask)
canvas = canvas * (self.thresh_max - self.thresh_min) + self.thresh_min
data["threshold_map"] = canvas
data["threshold_mask"] = mask
return data
def draw_border_map(self, polygon, canvas, mask):
polygon = np.array(polygon)
assert polygon.ndim == 2
assert polygon.shape[1] == 2
polygon_shape = Polygon(polygon)
if polygon_shape.area <= 0:
return
distance = (
polygon_shape.area
* (1 - np.power(self.shrink_ratio, 2))
/ polygon_shape.length
)
subject = [tuple(l) for l in polygon]
padding = pyclipper.PyclipperOffset()
padding.AddPath(subject, pyclipper.JT_ROUND, pyclipper.ET_CLOSEDPOLYGON)
padded_polygon = np.array(padding.Execute(distance)[0])
cv2.fillPoly(mask, [padded_polygon.astype(np.int32)], 1.0)
xmin = padded_polygon[:, 0].min()
xmax = padded_polygon[:, 0].max()
ymin = padded_polygon[:, 1].min()
ymax = padded_polygon[:, 1].max()
width = xmax - xmin + 1
height = ymax - ymin + 1
polygon[:, 0] = polygon[:, 0] - xmin
polygon[:, 1] = polygon[:, 1] - ymin
xs = np.broadcast_to(
np.linspace(0, width - 1, num=width).reshape(1, width), (height, width)
)
ys = np.broadcast_to(
np.linspace(0, height - 1, num=height).reshape(height, 1), (height, width)
)
distance_map = np.zeros((polygon.shape[0], height, width), dtype=np.float32)
for i in range(polygon.shape[0]):
j = (i + 1) % polygon.shape[0]
absolute_distance = self._distance(xs, ys, polygon[i], polygon[j])
distance_map[i] = np.clip(absolute_distance / distance, 0, 1)
distance_map = distance_map.min(axis=0)
xmin_valid = min(max(0, xmin), canvas.shape[1] - 1)
xmax_valid = min(max(0, xmax), canvas.shape[1] - 1)
ymin_valid = min(max(0, ymin), canvas.shape[0] - 1)
ymax_valid = min(max(0, ymax), canvas.shape[0] - 1)
canvas[ymin_valid : ymax_valid + 1, xmin_valid : xmax_valid + 1] = np.fmax(
1
- distance_map[
ymin_valid - ymin : ymax_valid - ymax + height,
xmin_valid - xmin : xmax_valid - xmax + width,
],
canvas[ymin_valid : ymax_valid + 1, xmin_valid : xmax_valid + 1],
)
def _distance(self, xs, ys, point_1, point_2):
"""
compute the distance from point to a line
ys: coordinates in the first axis
xs: coordinates in the second axis
point_1, point_2: (x, y), the end of the line
"""
height, width = xs.shape[:2]
square_distance_1 = np.square(xs - point_1[0]) + np.square(ys - point_1[1])
square_distance_2 = np.square(xs - point_2[0]) + np.square(ys - point_2[1])
square_distance = np.square(point_1[0] - point_2[0]) + np.square(
point_1[1] - point_2[1]
)
cosin = (square_distance - square_distance_1 - square_distance_2) / (
2 * np.sqrt(square_distance_1 * square_distance_2)
)
square_sin = 1 - np.square(cosin)
square_sin = np.nan_to_num(square_sin)
result = np.sqrt(
square_distance_1 * square_distance_2 * square_sin / square_distance
)
result[cosin < 0] = np.sqrt(np.fmin(square_distance_1, square_distance_2))[
cosin < 0
]
# self.extend_line(point_1, point_2, result)
return result
def extend_line(self, point_1, point_2, result, shrink_ratio):
ex_point_1 = (
int(round(point_1[0] + (point_1[0] - point_2[0]) * (1 + shrink_ratio))),
int(round(point_1[1] + (point_1[1] - point_2[1]) * (1 + shrink_ratio))),
)
cv2.line(
result,
tuple(ex_point_1),
tuple(point_1),
4096.0,
1,
lineType=cv2.LINE_AA,
shift=0,
)
ex_point_2 = (
int(round(point_2[0] + (point_2[0] - point_1[0]) * (1 + shrink_ratio))),
int(round(point_2[1] + (point_2[1] - point_1[1]) * (1 + shrink_ratio))),
)
cv2.line(
result,
tuple(ex_point_2),
tuple(point_2),
4096.0,
1,
lineType=cv2.LINE_AA,
shift=0,
)
return ex_point_1, ex_point_2
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