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# Copyright (c) OpenMMLab. All rights reserved.
import cv2
import numpy as np
from mmdet.core import BitmapMasks
from mmdet.datasets.builder import PIPELINES
from numpy.linalg import norm
import mmocr.utils.check_argument as check_argument
from . import BaseTextDetTargets
@PIPELINES.register_module()
class TextSnakeTargets(BaseTextDetTargets):
"""Generate the ground truth targets of TextSnake: TextSnake: A Flexible
Representation for Detecting Text of Arbitrary Shapes.
[https://arxiv.org/abs/1807.01544]. This was partially adapted from
https://github.com/princewang1994/TextSnake.pytorch.
Args:
orientation_thr (float): The threshold for distinguishing between
head edge and tail edge among the horizontal and vertical edges
of a quadrangle.
"""
def __init__(self,
orientation_thr=2.0,
resample_step=4.0,
center_region_shrink_ratio=0.3):
super().__init__()
self.orientation_thr = orientation_thr
self.resample_step = resample_step
self.center_region_shrink_ratio = center_region_shrink_ratio
self.eps = 1e-8
def vector_angle(self, vec1, vec2):
if vec1.ndim > 1:
unit_vec1 = vec1 / (norm(vec1, axis=-1) + self.eps).reshape(
(-1, 1))
else:
unit_vec1 = vec1 / (norm(vec1, axis=-1) + self.eps)
if vec2.ndim > 1:
unit_vec2 = vec2 / (norm(vec2, axis=-1) + self.eps).reshape(
(-1, 1))
else:
unit_vec2 = vec2 / (norm(vec2, axis=-1) + self.eps)
return np.arccos(
np.clip(np.sum(unit_vec1 * unit_vec2, axis=-1), -1.0, 1.0))
def vector_slope(self, vec):
assert len(vec) == 2
return abs(vec[1] / (vec[0] + self.eps))
def vector_sin(self, vec):
assert len(vec) == 2
return vec[1] / (norm(vec) + self.eps)
def vector_cos(self, vec):
assert len(vec) == 2
return vec[0] / (norm(vec) + self.eps)
def find_head_tail(self, points, orientation_thr):
"""Find the head edge and tail edge of a text polygon.
Args:
points (ndarray): The points composing a text polygon.
orientation_thr (float): The threshold for distinguishing between
head edge and tail edge among the horizontal and vertical edges
of a quadrangle.
Returns:
head_inds (list): The indexes of two points composing head edge.
tail_inds (list): The indexes of two points composing tail edge.
"""
assert points.ndim == 2
assert points.shape[0] >= 4
assert points.shape[1] == 2
assert isinstance(orientation_thr, float)
if len(points) > 4:
pad_points = np.vstack([points, points[0]])
edge_vec = pad_points[1:] - pad_points[:-1]
theta_sum = []
adjacent_vec_theta = []
for i, edge_vec1 in enumerate(edge_vec):
adjacent_ind = [x % len(edge_vec) for x in [i - 1, i + 1]]
adjacent_edge_vec = edge_vec[adjacent_ind]
temp_theta_sum = np.sum(
self.vector_angle(edge_vec1, adjacent_edge_vec))
temp_adjacent_theta = self.vector_angle(
adjacent_edge_vec[0], adjacent_edge_vec[1])
theta_sum.append(temp_theta_sum)
adjacent_vec_theta.append(temp_adjacent_theta)
theta_sum_score = np.array(theta_sum) / np.pi
adjacent_theta_score = np.array(adjacent_vec_theta) / np.pi
poly_center = np.mean(points, axis=0)
edge_dist = np.maximum(
norm(pad_points[1:] - poly_center, axis=-1),
norm(pad_points[:-1] - poly_center, axis=-1))
dist_score = edge_dist / (np.max(edge_dist) + self.eps)
position_score = np.zeros(len(edge_vec))
score = 0.5 * theta_sum_score + 0.15 * adjacent_theta_score
score += 0.35 * dist_score
if len(points) % 2 == 0:
position_score[(len(score) // 2 - 1)] += 1
position_score[-1] += 1
score += 0.1 * position_score
pad_score = np.concatenate([score, score])
score_matrix = np.zeros((len(score), len(score) - 3))
x = np.arange(len(score) - 3) / float(len(score) - 4)
gaussian = 1. / (np.sqrt(2. * np.pi) * 0.5) * np.exp(-np.power(
(x - 0.5) / 0.5, 2.) / 2)
gaussian = gaussian / np.max(gaussian)
for i in range(len(score)):
score_matrix[i, :] = score[i] + pad_score[
(i + 2):(i + len(score) - 1)] * gaussian * 0.3
head_start, tail_increment = np.unravel_index(
score_matrix.argmax(), score_matrix.shape)
tail_start = (head_start + tail_increment + 2) % len(points)
head_end = (head_start + 1) % len(points)
tail_end = (tail_start + 1) % len(points)
if head_end > tail_end:
head_start, tail_start = tail_start, head_start
head_end, tail_end = tail_end, head_end
head_inds = [head_start, head_end]
tail_inds = [tail_start, tail_end]
else:
if self.vector_slope(points[1] - points[0]) + self.vector_slope(
points[3] - points[2]) < self.vector_slope(
points[2] - points[1]) + self.vector_slope(points[0] -
points[3]):
horizontal_edge_inds = [[0, 1], [2, 3]]
vertical_edge_inds = [[3, 0], [1, 2]]
else:
horizontal_edge_inds = [[3, 0], [1, 2]]
vertical_edge_inds = [[0, 1], [2, 3]]
vertical_len_sum = norm(points[vertical_edge_inds[0][0]] -
points[vertical_edge_inds[0][1]]) + norm(
points[vertical_edge_inds[1][0]] -
points[vertical_edge_inds[1][1]])
horizontal_len_sum = norm(
points[horizontal_edge_inds[0][0]] -
points[horizontal_edge_inds[0][1]]) + norm(
points[horizontal_edge_inds[1][0]] -
points[horizontal_edge_inds[1][1]])
if vertical_len_sum > horizontal_len_sum * orientation_thr:
head_inds = horizontal_edge_inds[0]
tail_inds = horizontal_edge_inds[1]
else:
head_inds = vertical_edge_inds[0]
tail_inds = vertical_edge_inds[1]
return head_inds, tail_inds
def reorder_poly_edge(self, points):
"""Get the respective points composing head edge, tail edge, top
sideline and bottom sideline.
Args:
points (ndarray): The points composing a text polygon.
Returns:
head_edge (ndarray): The two points composing the head edge of text
polygon.
tail_edge (ndarray): The two points composing the tail edge of text
polygon.
top_sideline (ndarray): The points composing top curved sideline of
text polygon.
bot_sideline (ndarray): The points composing bottom curved sideline
of text polygon.
"""
assert points.ndim == 2
assert points.shape[0] >= 4
assert points.shape[1] == 2
head_inds, tail_inds = self.find_head_tail(points,
self.orientation_thr)
head_edge, tail_edge = points[head_inds], points[tail_inds]
pad_points = np.vstack([points, points])
if tail_inds[1] < 1:
tail_inds[1] = len(points)
sideline1 = pad_points[head_inds[1]:tail_inds[1]]
sideline2 = pad_points[tail_inds[1]:(head_inds[1] + len(points))]
sideline_mean_shift = np.mean(
sideline1, axis=0) - np.mean(
sideline2, axis=0)
if sideline_mean_shift[1] > 0:
top_sideline, bot_sideline = sideline2, sideline1
else:
top_sideline, bot_sideline = sideline1, sideline2
return head_edge, tail_edge, top_sideline, bot_sideline
def cal_curve_length(self, line):
"""Calculate the length of each edge on the discrete curve and the sum.
Args:
line (ndarray): The points composing a discrete curve.
Returns:
tuple: Returns (edges_length, total_length).
- | edge_length (ndarray): The length of each edge on the
discrete curve.
- | total_length (float): The total length of the discrete
curve.
"""
assert line.ndim == 2
assert len(line) >= 2
edges_length = np.sqrt((line[1:, 0] - line[:-1, 0])**2 +
(line[1:, 1] - line[:-1, 1])**2)
total_length = np.sum(edges_length)
return edges_length, total_length
def resample_line(self, line, n):
"""Resample n points on a line.
Args:
line (ndarray): The points composing a line.
n (int): The resampled points number.
Returns:
resampled_line (ndarray): The points composing the resampled line.
"""
assert line.ndim == 2
assert line.shape[0] >= 2
assert line.shape[1] == 2
assert isinstance(n, int)
assert n > 2
edges_length, total_length = self.cal_curve_length(line)
t_org = np.insert(np.cumsum(edges_length), 0, 0)
unit_t = total_length / (n - 1)
t_equidistant = np.arange(1, n - 1, dtype=np.float32) * unit_t
edge_ind = 0
points = [line[0]]
for t in t_equidistant:
while edge_ind < len(edges_length) - 1 and t > t_org[edge_ind + 1]:
edge_ind += 1
t_l, t_r = t_org[edge_ind], t_org[edge_ind + 1]
weight = np.array([t_r - t, t - t_l], dtype=np.float32) / (
t_r - t_l + self.eps)
p_coords = np.dot(weight, line[[edge_ind, edge_ind + 1]])
points.append(p_coords)
points.append(line[-1])
resampled_line = np.vstack(points)
return resampled_line
def resample_sidelines(self, sideline1, sideline2, resample_step):
"""Resample two sidelines to be of the same points number according to
step size.
Args:
sideline1 (ndarray): The points composing a sideline of a text
polygon.
sideline2 (ndarray): The points composing another sideline of a
text polygon.
resample_step (float): The resampled step size.
Returns:
resampled_line1 (ndarray): The resampled line 1.
resampled_line2 (ndarray): The resampled line 2.
"""
assert sideline1.ndim == sideline2.ndim == 2
assert sideline1.shape[1] == sideline2.shape[1] == 2
assert sideline1.shape[0] >= 2
assert sideline2.shape[0] >= 2
assert isinstance(resample_step, float)
_, length1 = self.cal_curve_length(sideline1)
_, length2 = self.cal_curve_length(sideline2)
avg_length = (length1 + length2) / 2
resample_point_num = max(int(float(avg_length) / resample_step) + 1, 3)
resampled_line1 = self.resample_line(sideline1, resample_point_num)
resampled_line2 = self.resample_line(sideline2, resample_point_num)
return resampled_line1, resampled_line2
def draw_center_region_maps(self, top_line, bot_line, center_line,
center_region_mask, radius_map, sin_map,
cos_map, region_shrink_ratio):
"""Draw attributes on text center region.
Args:
top_line (ndarray): The points composing top curved sideline of
text polygon.
bot_line (ndarray): The points composing bottom curved sideline
of text polygon.
center_line (ndarray): The points composing the center line of text
instance.
center_region_mask (ndarray): The text center region mask.
radius_map (ndarray): The map where the distance from point to
sidelines will be drawn on for each pixel in text center
region.
sin_map (ndarray): The map where vector_sin(theta) will be drawn
on text center regions. Theta is the angle between tangent
line and vector (1, 0).
cos_map (ndarray): The map where vector_cos(theta) will be drawn on
text center regions. Theta is the angle between tangent line
and vector (1, 0).
region_shrink_ratio (float): The shrink ratio of text center.
"""
assert top_line.shape == bot_line.shape == center_line.shape
assert (center_region_mask.shape == radius_map.shape == sin_map.shape
== cos_map.shape)
assert isinstance(region_shrink_ratio, float)
for i in range(0, len(center_line) - 1):
top_mid_point = (top_line[i] + top_line[i + 1]) / 2
bot_mid_point = (bot_line[i] + bot_line[i + 1]) / 2
radius = norm(top_mid_point - bot_mid_point) / 2
text_direction = center_line[i + 1] - center_line[i]
sin_theta = self.vector_sin(text_direction)
cos_theta = self.vector_cos(text_direction)
tl = center_line[i] + (top_line[i] -
center_line[i]) * region_shrink_ratio
tr = center_line[i + 1] + (
top_line[i + 1] - center_line[i + 1]) * region_shrink_ratio
br = center_line[i + 1] + (
bot_line[i + 1] - center_line[i + 1]) * region_shrink_ratio
bl = center_line[i] + (bot_line[i] -
center_line[i]) * region_shrink_ratio
current_center_box = np.vstack([tl, tr, br, bl]).astype(np.int32)
cv2.fillPoly(center_region_mask, [current_center_box], color=1)
cv2.fillPoly(sin_map, [current_center_box], color=sin_theta)
cv2.fillPoly(cos_map, [current_center_box], color=cos_theta)
cv2.fillPoly(radius_map, [current_center_box], color=radius)
def generate_center_mask_attrib_maps(self, img_size, text_polys):
"""Generate text center region mask and geometric attribute maps.
Args:
img_size (tuple): The image size of (height, width).
text_polys (list[list[ndarray]]): The list of text polygons.
Returns:
center_region_mask (ndarray): The text center region mask.
radius_map (ndarray): The distance map from each pixel in text
center region to top sideline.
sin_map (ndarray): The sin(theta) map where theta is the angle
between vector (top point - bottom point) and vector (1, 0).
cos_map (ndarray): The cos(theta) map where theta is the angle
between vector (top point - bottom point) and vector (1, 0).
"""
assert isinstance(img_size, tuple)
assert check_argument.is_2dlist(text_polys)
h, w = img_size
center_region_mask = np.zeros((h, w), np.uint8)
radius_map = np.zeros((h, w), dtype=np.float32)
sin_map = np.zeros((h, w), dtype=np.float32)
cos_map = np.zeros((h, w), dtype=np.float32)
for poly in text_polys:
assert len(poly) == 1
text_instance = [[poly[0][i], poly[0][i + 1]]
for i in range(0, len(poly[0]), 2)]
polygon_points = np.array(text_instance).reshape(-1, 2)
n = len(polygon_points)
keep_inds = []
for i in range(n):
if norm(polygon_points[i] -
polygon_points[(i + 1) % n]) > 1e-5:
keep_inds.append(i)
polygon_points = polygon_points[keep_inds]
_, _, top_line, bot_line = self.reorder_poly_edge(polygon_points)
resampled_top_line, resampled_bot_line = self.resample_sidelines(
top_line, bot_line, self.resample_step)
resampled_bot_line = resampled_bot_line[::-1]
center_line = (resampled_top_line + resampled_bot_line) / 2
if self.vector_slope(center_line[-1] - center_line[0]) > 0.9:
if (center_line[-1] - center_line[0])[1] < 0:
center_line = center_line[::-1]
resampled_top_line = resampled_top_line[::-1]
resampled_bot_line = resampled_bot_line[::-1]
else:
if (center_line[-1] - center_line[0])[0] < 0:
center_line = center_line[::-1]
resampled_top_line = resampled_top_line[::-1]
resampled_bot_line = resampled_bot_line[::-1]
line_head_shrink_len = norm(resampled_top_line[0] -
resampled_bot_line[0]) / 4.0
line_tail_shrink_len = norm(resampled_top_line[-1] -
resampled_bot_line[-1]) / 4.0
head_shrink_num = int(line_head_shrink_len // self.resample_step)
tail_shrink_num = int(line_tail_shrink_len // self.resample_step)
if len(center_line) > head_shrink_num + tail_shrink_num + 2:
center_line = center_line[head_shrink_num:len(center_line) -
tail_shrink_num]
resampled_top_line = resampled_top_line[
head_shrink_num:len(resampled_top_line) - tail_shrink_num]
resampled_bot_line = resampled_bot_line[
head_shrink_num:len(resampled_bot_line) - tail_shrink_num]
self.draw_center_region_maps(resampled_top_line,
resampled_bot_line, center_line,
center_region_mask, radius_map,
sin_map, cos_map,
self.center_region_shrink_ratio)
return center_region_mask, radius_map, sin_map, cos_map
def generate_text_region_mask(self, img_size, text_polys):
"""Generate text center region mask and geometry attribute maps.
Args:
img_size (tuple): The image size (height, width).
text_polys (list[list[ndarray]]): The list of text polygons.
Returns:
text_region_mask (ndarray): The text region mask.
"""
assert isinstance(img_size, tuple)
assert check_argument.is_2dlist(text_polys)
h, w = img_size
text_region_mask = np.zeros((h, w), dtype=np.uint8)
for poly in text_polys:
assert len(poly) == 1
text_instance = [[poly[0][i], poly[0][i + 1]]
for i in range(0, len(poly[0]), 2)]
polygon = np.array(
text_instance, dtype=np.int32).reshape((1, -1, 2))
cv2.fillPoly(text_region_mask, polygon, 1)
return text_region_mask
def generate_targets(self, results):
"""Generate the gt targets for TextSnake.
Args:
results (dict): The input result dictionary.
Returns:
results (dict): The output result dictionary.
"""
assert isinstance(results, dict)
polygon_masks = results['gt_masks'].masks
polygon_masks_ignore = results['gt_masks_ignore'].masks
h, w, _ = results['img_shape']
gt_text_mask = self.generate_text_region_mask((h, w), polygon_masks)
gt_mask = self.generate_effective_mask((h, w), polygon_masks_ignore)
(gt_center_region_mask, gt_radius_map, gt_sin_map,
gt_cos_map) = self.generate_center_mask_attrib_maps((h, w),
polygon_masks)
results['mask_fields'].clear() # rm gt_masks encoded by polygons
mapping = {
'gt_text_mask': gt_text_mask,
'gt_center_region_mask': gt_center_region_mask,
'gt_mask': gt_mask,
'gt_radius_map': gt_radius_map,
'gt_sin_map': gt_sin_map,
'gt_cos_map': gt_cos_map
}
for key, value in mapping.items():
value = value if isinstance(value, list) else [value]
results[key] = BitmapMasks(value, h, w)
results['mask_fields'].append(key)
return results
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