Simple Digit Recognition OCR in OpenCV-Python

Michael Zippo

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I am trying to implement a "Digit Recognition OCR" in OpenCV-Python (cv2). It is just for learning purposes. I would like to learn both KNearest and SVM features in OpenCV.

I have 100 samples (i.e. images) of each digit. I would like to train with them.

There is a sample letter_recog.py that comes with OpenCV sample. But I still couldn"t figure out on how to use it. I don"t understand what are the samples, responses etc. Also, it loads a txt file at first, which I didn"t understand first.

Later on searching a little bit, I could find a letter_recognition.data in cpp samples. I used it and made a code for cv2.KNearest in the model of letter_recog.py (just for testing):

import numpy as np
import cv2

fn = "letter-recognition.data"
a = np.loadtxt(fn, np.float32, delimiter=",", converters={ 0 : lambda ch : ord(ch)-ord("A") })
samples, responses = a[:,1:], a[:,0]

model = cv2.KNearest()
retval = model.train(samples,responses)
retval, results, neigh_resp, dists = model.find_nearest(samples, k = 10)
print results.ravel()

It gave me an array of size 20000, I don"t understand what it is.

Questions:

1) What is letter_recognition.data file? How to build that file from my own data set?

2) What does results.reval() denote?

3) How we can write a simple digit recognition tool using letter_recognition.data file (either KNearest or SVM)?

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Simple Digit Recognition OCR in OpenCV-Python del: Questions

__del__

How can I make a time delay in Python?

5 answers

I would like to know how to put a time delay in a Python script.

2973

Answer #1

import time
time.sleep(5)   # Delays for 5 seconds. You can also use a float value.

Here is another example where something is run approximately once a minute:

import time
while True:
    print("This prints once a minute.")
    time.sleep(60) # Delay for 1 minute (60 seconds).

2973

Answer #2

You can use the sleep() function in the time module. It can take a float argument for sub-second resolution.

from time import sleep
sleep(0.1) # Time in seconds

Simple Digit Recognition OCR in OpenCV-Python del: Questions

__del__

How to delete a file or folder in Python?

5 answers

How do I delete a file or folder in Python?

2639

Answer #1

os.remove() removes a file.
os.rmdir() removes an empty directory.
shutil.rmtree() deletes a directory and all its contents.

Path objects from the Python 3.4+ pathlib module also expose these instance methods:

pathlib.Path.unlink() removes a file or symbolic link.
pathlib.Path.rmdir() removes an empty directory.

We hope this article has helped you to resolve the problem. Apart from Simple Digit Recognition OCR in OpenCV-Python, check other __del__-related topics.

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Marie Wu

Paris | 2023-02-06

I was preparing for my coding interview, thanks for clarifying this - Simple Digit Recognition OCR in OpenCV-Python in Python is not the simplest one. Checked yesterday, it works!

Olivia Danburry

Boston | 2023-02-06

Python functions is always a bit confusing 😭 Simple Digit Recognition OCR in OpenCV-Python is not the only problem I encountered. I just hope that will not emerge anymore

Anna OConnell

California | 2023-02-06

imp Python module is always a bit confusing 😭 Simple Digit Recognition OCR in OpenCV-Python is not the only problem I encountered. I am just not quite sure it is the best method