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Web Scraping with Python by Ryan Mitchell

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Chapter 11. Image Processing and Text Recognition

From Google’s self-driving cars to vending machines that recognize counterfeit currency, machine vision is a huge field with far-reaching goals and implications. In this chapter, we will focus on one very small aspect of the field: text recognition, specifically how to recognize and use text-based images found online by using a variety of Python libraries. 

Using an image in lieu of text is a common technique when you don’t want text to be found and read by bots. This is often seen on contact forms when an email address is partially or completely rendered as an image. Depending on how skillfully it is done, it might not even be noticeable to human viewers but bots have a very difficult time reading these images and the technique is enough to stop most spammers from acquiring your email address. 

CAPTCHAs, of course, take advantage of the fact that users can read security images but most bots can’t. Some CAPTCHAs are more difficult than others, an issue we’ll tackle later in this book.

But CAPTCHAs aren’t the only place on the Web where scrapers need image-to-text translation assistance. Even in this day and age, many documents are simply scanned from hard copies and put on the Web, making these documents inaccessible as far as much of the Internet is concerned, although they are “hiding in plain sight.” Without image-to-text capabilities, the only way to make these documents accessible is for a human to type them up by hand—and ...

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