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# This file is part of OpenCV Zoo project.
# It is subject to the license terms in the LICENSE file found in the same directory.
#
# Copyright (C) 2021, Shenzhen Institute of Artificial Intelligence and Robotics for Society, all rights reserved.
# Third party copyrights are property of their respective owners.
import numpy as np
import cv2 as cv
class CRNN:
def __init__(self, modelPath):
self._model = cv.dnn.readNet(modelPath)
self._inputSize = [100, 32] # Fixed
self._targetVertices = np.array([
[0, self._inputSize[1] - 1],
[0, 0],
[self._inputSize[0] - 1, 0],
[self._inputSize[0] - 1, self._inputSize[1] - 1]
], dtype=np.float32)
@property
def name(self):
return self.__class__.__name__
def setBackend(self, backend_id):
self._model.setPreferableBackend(backend_id)
def setTarget(self, target_id):
self._model.setPreferableTarget(target_id)
def _preprocess(self, image, rbbox):
# Remove conf, reshape and ensure all is np.float32
vertices = rbbox.reshape((4, 2)).astype(np.float32)
rotationMatrix = cv.getPerspectiveTransform(vertices, self._targetVertices)
cropped = cv.warpPerspective(image, rotationMatrix, self._inputSize)
cropped = cv.cvtColor(cropped, cv.COLOR_BGR2GRAY)
return cv.dnn.blobFromImage(cropped, size=self._inputSize, mean=127.5, scalefactor=1 / 127.5)
def infer(self, image, rbbox):
# Preprocess
inputBlob = self._preprocess(image, rbbox)
# Forward
self._model.setInput(inputBlob)
outputBlob = self._model.forward()
# Postprocess
results = self._postprocess(outputBlob)
return results
def _postprocess(self, outputBlob):
'''Decode charaters from outputBlob
'''
text = ""
alphabet = "0123456789abcdefghijklmnopqrstuvwxyz"
for i in range(outputBlob.shape[0]):
c = np.argmax(outputBlob[i][0])
if c != 0:
text += alphabet[c - 1]
else:
text += '-'
# adjacent same letters as well as background text must be removed to get the final output
char_list = []
for i in range(len(text)):
if text[i] != '-' and (not (i > 0 and text[i] == text[i - 1])):
char_list.append(text[i])
return ''.join(char_list) |