How to extract Text from Images? APIs, Programming Libraries and Online Tools

With the surge in the creation and consumption of digital content, the need for automated tools that can interpret and analyze images has skyrocketed. One critical aspect of this is the extraction of text from images. For those unfamiliar, this refers to the process of converting the text present in an image into editable and searchable data.

This post is dedicated to walking you through some of the most effective methods for extracting text from images, including optical character recognition (OCR), and various tools and programming techniques you can use to get this job done.

1. Optical Character Recognition (OCR)

OCR is the most commonly used technique for extracting text from images. It’s a technology that recognizes text within digital images (like scanned documents, photos of documents, or even text superimposed on an image).

How OCR Works

OCR software works by analyzing the shapes and patterns of the pixels in the image, and then comparing them to stored sets of character patterns. More advanced OCR systems also include language modeling, such as dictionary lookups, to make educated guesses about ambiguous characters based on the context.

OCR Software and Tools

Here are a few of the best OCR tools available today:

1. Adobe Acrobat Pro DC: Adobe’s Acrobat software includes OCR capabilities. You can open a PDF or image file, and the software will recognize the text and allow you to save it as an editable document.
2. ABBYY FineReader: This is a highly robust OCR tool, and it’s capable of recognizing a large number of languages. It can handle complex formatting and even recognizes handwriting to some degree.
3. Readiris: This is another powerful OCR software that’s known for its speed. It can handle documents in multiple languages and formats.
4. Google Docs: Google’s free word processor has built-in OCR. You can upload an image or PDF, and Google will convert it into a text document that you can edit.

2. Using APIs for Text Extraction

You can leverage APIs offered by tech giants like Google, Microsoft, and IBM for OCR tasks. These OCR APIs usually employ machine learning techniques, which often yield better results than traditional OCR.

1. Google Cloud Vision API: This API allows developers to extract text from images of documents, signs, etc. It supports a broad set of languages and has robust support for complex layouts and handwriting.
2. Microsoft Azure Computer Vision API: Microsoft’s OCR API is known for its high accuracy and the ability to recognize text in more than 25 languages.
3. IBM Watson Visual Recognition: IBM’s Watson Visual Recognition API has OCR capabilities that are used to identify and analyze text in images.

3. Programming Libraries

If you have some programming skills, there are numerous libraries you can use to extract text from images.

1. Tesseract: Tesseract is an open-source OCR engine sponsored by Google. It supports many languages and can be trained to recognize other languages.
2. Pytesseract: This is a Python library that uses Tesseract’s OCR capabilities. It’s straightforward to use and works well for simple OCR tasks.
3. OpenCV: This is a library of programming functions mainly aimed at real-time computer vision. It’s very powerful and versatile but also quite complex.

Here’s a simple code snippet using Pytesseract:

import pytesseract
from PIL import Image

# Open image file
img = Image.open('image.png')
# Use Tesseract to do OCR on the image
text = pytesseract.image_to_string(img)

print(text)

4. Machine Learning for OCR

With the advent of deep learning and neural networks, OCR has significantly improved in recent years. Convolutional neural networks (CNNs)

and recurrent neural networks (RNNs) have proved to be very effective in tasks like OCR.

1. Convolutional Neural Networks (CNNs): CNNs have been very effective in image classification tasks and can also be used for OCR. They work by automatically and adaptively learning spatial hierarchies of features from the provided training data.
2. Recurrent Neural Networks (RNNs): RNNs are used when we have sequences of data, and one piece of data in the sequence depends on the previous one. This property of RNNs makes them suitable for OCR.

A popular architecture for OCR tasks is the combination of CNN and RNN layers, along with a Connectionist Temporal Classification (CTC) layer, for the task of text recognition.

CRNNs (Convolutional Recurrent Neural Networks): These have been very successful in dealing with OCR problems, especially when it comes to recognizing sequences of characters in images, like a line of text.

Conclusion

The landscape of OCR and text extraction from images is quite rich, ranging from commercial software and free online tools to APIs and programming libraries. The choice among these depends on your specific needs, the volume of images you need to process, the complexity and variability of the text in the images, and whether you have programming resources available.

Remember that OCR is a hard problem, and no solution will be perfect. However, with the continual advancements in machine learning and AI, OCR tools are becoming more powerful and accurate.

Whether you need to digitize a library of old books, recognize license plates in a parking lot, or just convert a few pages of text, there’s likely an OCR solution that fits your needs. Happy text extracting!