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Source code for mmocr.models.textdet.postprocess.pan_postprocessor
# Copyright (c) OpenMMLab. All rights reserved.
import cv2
import numpy as np
import torch
from mmcv.ops import pixel_group
from mmocr.core import points2boundary
from mmocr.models.builder import POSTPROCESSOR
from .base_postprocessor import BasePostprocessor
[docs]@POSTPROCESSOR.register_module()
class PANPostprocessor(BasePostprocessor):
"""Convert scores to quadrangles via post processing in PANet. This is
partially adapted from https://github.com/WenmuZhou/PAN.pytorch.
Args:
text_repr_type (str): The boundary encoding type 'poly' or 'quad'.
min_text_confidence (float): The minimal text confidence.
min_kernel_confidence (float): The minimal kernel confidence.
min_text_avg_confidence (float): The minimal text average confidence.
min_text_area (int): The minimal text instance region area.
"""
def __init__(self,
text_repr_type='poly',
min_text_confidence=0.5,
min_kernel_confidence=0.5,
min_text_avg_confidence=0.85,
min_text_area=16,
**kwargs):
super().__init__(text_repr_type)
self.min_text_confidence = min_text_confidence
self.min_kernel_confidence = min_kernel_confidence
self.min_text_avg_confidence = min_text_avg_confidence
self.min_text_area = min_text_area
def __call__(self, preds):
"""
Args:
preds (Tensor): Prediction map with shape :math:`(C, H, W)`.
Returns:
list[list[float]]: The instance boundary and its confidence.
"""
assert preds.dim() == 3
preds[:2, :, :] = torch.sigmoid(preds[:2, :, :])
preds = preds.detach().cpu().numpy()
text_score = preds[0].astype(np.float32)
text = preds[0] > self.min_text_confidence
kernel = (preds[1] > self.min_kernel_confidence) * text
embeddings = preds[2:].transpose((1, 2, 0)) # (h, w, 4)
region_num, labels = cv2.connectedComponents(
kernel.astype(np.uint8), connectivity=4)
contours, _ = cv2.findContours((kernel * 255).astype(np.uint8),
cv2.RETR_LIST, cv2.CHAIN_APPROX_NONE)
kernel_contours = np.zeros(text.shape, dtype='uint8')
cv2.drawContours(kernel_contours, contours, -1, 255)
text_points = pixel_group(text_score, text, embeddings, labels,
kernel_contours, region_num,
self.min_text_avg_confidence)
boundaries = []
for text_point in text_points:
text_confidence = text_point[0]
text_point = text_point[2:]
text_point = np.array(text_point, dtype=int).reshape(-1, 2)
area = text_point.shape[0]
if not self.is_valid_instance(area, text_confidence,
self.min_text_area,
self.min_text_avg_confidence):
continue
vertices_confidence = points2boundary(text_point,
self.text_repr_type,
text_confidence)
if vertices_confidence is not None:
boundaries.append(vertices_confidence)
return boundaries