Generating CAPTCHA images

Although this is not strictly data visualization in terms that we usually refer to, the ability to generate images using Python comes in handy in many cases, and this is one of them.

In this recipe, we will be covering the generation of random images to tell humans and computers apart—CAPTCHA image.

Getting ready

CAPTCHA stands for Completely Automated Public Turing test to tell Computers and Humans Apart, and is trademarked by Carnegie Mellon University. This test is used to challenge computer programs (usually referred to as bots) that automatically fill various web forms that are primarily targeted to humans and that should not be automated. Usual examples are sign-up forms, login forms, surveys, and similar.

CAPTCHA itself can take various forms, but the most common form consists of a challenge where humans should read an image with distorted characters and numbers and type in the result in the related response field.

In this recipe, we will learn how to harness...