python: opencv 4.5.3 ,cv2.error: OpenCV(4.5.3) C:\Users\runneradmin\AppData\Local\Temp\pip-req-build-q3d_8t8e\opencv\modules\dnn\src\model.cpp:1216: error: (-215:Assertion failed) length > FLT_EPSILON in function 'cv::dnn::TextDetectionModel_DB_Impl::unclip'

[syly666]

System information (version)

• OpenCV => 4.5.3
• Operating System / Platform => Windows 10 64 Bit
• Compiler => pycharm

Detailed description

when i use TextDetectionModel_DB in Multithreading， The exceptions are as follows

cv2.error: OpenCV(4.5.3) C:\Users\runneradmin\AppData\Local\Temp\pip-req-build-q3d_8t8e\opencv\modules\dnn\src\model.cpp:1216: error: (-215:Assertion failed) length > FLT_EPSILON in function 'cv::dnn::TextDetectionModel_DB_Impl::unclip'

when i set threadMaxNum = 1， it ok。

Is this a bug？
Please reply me. Thank you

my codes are as follows:

# !/usr/bin/python3

import threading
import os
import traceback
import cv2
import time

modelPath = "D:\\Dev_dan\\Dev_dan\\src\\main\\resources\\opencvDnnFiles\\DB_IC15_resnet18.onnx"
textModel = cv2.dnn_TextDetectionModel_DB(modelPath)
textModel.setBinaryThreshold(0.3)
textModel.setPolygonThreshold(0.5)
textModel.setMaxCandidates(200)
textModel.setUnclipRatio(2)
textModel.setInputParams(1.0/255.0, size=(736, 736), mean=(122.67891434, 116.66876762, 104.00698793))

path ="D:\\dataSet\\testfiles\\"
threadMaxNum = 2

class myThread(threading.Thread):
    def __init__(self, threadID,):
        threading.Thread.__init__(self)
        self.threadID = threadID

    def run(self):
        print("start：" + self.name)
        autoAdd(self.threadID)
        print("exit：" + self.name)

def autoAdd(threadID):
    num = 0
    files = os.listdir(path + threadID)
    while True:
        try:
            image_path = os.path.join(path+ threadID, files[num % len(files)])
            num+=1
            image = cv2.imread(image_path)
            if image is not None:
                start1 = time.time()
                result = textModel.detect(image)
                print("nums", len(result[0]))
                end1 = time.time()
                print((end1 - start1)*1000)
        except Exception as e:
            traceback.print_exc()
# create threads
threadingList = []
for i in range(0, threadMaxNum):
    thread = myThread(str(i))
    thread.start()
    threadingList.append(thread)
# start threads
for t in threadingList:
    t.join()

[alalek]

TextDetectionModel_DB in Multithreading

OpenCV algorithms are not thread-safe in general due to performance reasons.

Fork-based threading doesn't work properly for already multi-threaded libraries.

---

Usage questions should go to Users OpenCV Q/A forum: https://forum.opencv.org/

[syly666]

ok， thank you. SO if i want to use TextDetectionModel in Multithreading or for Microservices, i should try to use tensorflow or other deep learning frameworks instead of OpenCV？