Kyle Charlton

Adds a honeypot and an image captcha to your Gravity Forms by adding the Image Captcha from the Advanced Fields in the Gravity Forms editor where you want the captcha to appear. This CAPTCHA is GDPR compliant and becuase the images are inline SVG’s, this plugin will not slow down your site with additional header requests like Google’s ReCAPTCHA.
Like the plugin? 
Please consider leaving a review.
<h3>Go Pro!</h3>
Get even better spam protection with the All-in-one Image CAPTCHA Pro version of this plugin which includes additional options to improve spam protection, options to control the look and style of the CAPTCHA, additional forms support including login screens, gravity forms, WooCommerce, WPForms and more.
PRO Demo 
See the Pro version in action on my <a href="https://kccomputing.net/contact-me/" rel="nofollow ugc">Contact page</a>. You can also check out my <a href="https://www.youtube.com/channel/UCZznQBUawR-YqPBW8JjXzcw" rel="nofollow ugc">YouTube channel</a> for instructional videos and demos.
Check out our <a href="https://kccomputing.net/downloads/contact-form-7-image-captcha-pro/" rel="nofollow ugc">pro version</a> for more details.
PRO Features:
<ul>
<li>GDPR compliant</li>
<li>ADA/a11y/WCAG compliant</li>
<li>Gravity Forms support</li>
<li>WPForms support</li>
<li>WooCommerce support for login, registration and checkout forms (optional)</li>
<li>WordPress login/registration form support (optional)</li>
<li>Default WordPress comment support</li>
<li>Customize the look of the WordPress login/registration screen and form</li>
<li>CAPTCHA refreshes on submit to make it harder for automated spammers</li>
<li>Reverse honeypot which checks if you are human through form engagement</li>
<li>Stronger security with hashed answers to make it harder for automated spammers to read the answers</li>
<li>Add additional icons to increase the chances of a random guess getting through. You can increase it from a 1 and 3 chance all the way up to a 1 in 10 chance! </li>
<li>Select which icons you wish to use</li>
<li>Add additional icons from Font Awesome 4.7</li>
<li>Add your own custom SVG icons</li>
<li>Customize the icon titles</li>
<li>Change the captcha message</li>
<li>Change the captcha errors</li>
<li>Change the box color and border</li>
<li>Change font and icon color and size independently</li>
<li>Change the selected icon appearance</li>
<li>Change where the icons appear</li>
<li>Change the box from full width to content width</li>
<li>jQuery free on the front end</li>
</ul>
<a href="http://kccomputing.net/downloads/contact-form-7-image-captcha-pro/" rel="nofollow ugc">Go Pro!</a>

Image Captcha For Gravity Forms

Adds a Honeypot and a clean image captcha to Gravity Forms. Images are made using Font Awesome's font icon.

Takayuki Miyoshi

Really Simple CAPTCHA does not work alone and is intended to work with other plugins. It is originally created for <a href="https://contactform7.com/" rel="nofollow ugc">Contact Form 7</a>, however, you can use it with your own plugin.
Note: This product is “really simple” as its name suggests, i.e., it is not strongly secure. If you need perfect security, you should try other solutions.
<h4>How does it work?</h4>
Really Simple CAPTCHA does not use PHP “Sessions” for storing states, unlike many other PHP CAPTCHA solutions, but stores them as temporary files. This allows you to embed it into WordPress without worrying about conflicts.
When you generate a CAPTCHA, Really Simple CAPTCHA creates two files for it; one is an image file of CAPTCHA, and the other is a text file which stores the correct answer to the CAPTCHA.
The two files have the same (random) prefix in their file names, for example, “a7hk3ux8p.png” and “a7hk3ux8p.txt.” In this case, for example, when the respondent answers “K5GF” as an answer to the “a7hk3ux8p.png” image, then Really Simple CAPTCHA calculates hash of “K5GF” and tests it against the hash stored in the “a7hk3ux8p.txt” file. If the two match, the answer is confirmed as correct.
<h4>How to use with your plugin</h4>
Note: Below are instructions for plugin developers.
First, create an instance of ReallySimpleCaptcha class:
<pre><code>$captcha_instance = new ReallySimpleCaptcha();
</code></pre>
You can change the instance variables as you wish.
<pre><code>// Change the background color of CAPTCHA image to black
$captcha_instance->bg = array( 0, 0, 0 );
</code></pre>
See really-simple-captcha.php if you are interested in other variables.
Generate a random word for CAPTCHA.
<pre><code>$word = $captcha_instance->generate_random_word();
</code></pre>
Generate an image file and a corresponding text file in the temporary directory.
<pre><code>$prefix = wp_rand();
$captcha_instance->generate_image( $prefix, $word );
</code></pre>
Then, show the image and get an answer from respondent.
Check the correctness of the answer.
<pre><code>$correct = $captcha_instance->check( $prefix, $the_answer_from_respondent );
</code></pre>
If the $correct is true, go ahead. Otherwise, block the respondent — as it would appear not to be human.
And last, remove the temporary image and text files, as they are no longer in use.
<pre><code>$captcha_instance->remove( $prefix );
</code></pre>
That’s all.
If you wish to see a live sample of this, you can try <a href="https://contactform7.com/captcha/" rel="nofollow ugc">Contact Form 7</a>.

Really Simple CAPTCHA

Needed this for an installation with custom forms. I used the plugin developers instructions and was able to make a fully custom implementation based on server side validation within 30 minutes. No more spam bots misusing the forms. Thank you!

Great work - easy to implement

Really Simple CAPTCHA is a CAPTCHA module intended to be called from other plugins. It is originally created for my Contact Form 7 plugin.

Image Captcha For Gravity Forms vs Really Simple CAPTCHA