WebMaestro.Fr

Upload the layers of your image, and create a parallax effect !
It works great on smart devices too !
The first step is to create with your favorite picture editing software (Photoshop, GIMP…) an independent image for each ground composing your image. All these layers shall be the same size, and should be in .png format as they are meant to include transparency areas. 
Then, on your post editing page in WordPress, click the Insert Media button, and (the same way you would create a gallery) upload your layers under the Create Parallax item. Reorganise the layers if needed, from the background to the front. 
You can finally configure the animation (calibrate, invert, limit, scalar, friction), and publish !
There is <a href="http://webmaestro.fr/image-parallax-plugin-wordpress/" rel="nofollow ugc">some examples</a> on the plugin page.
It uses <a href="http://wagerfield.github.io/parallax/" rel="nofollow ugc">parallax.js</a> by Matthew Wagerfield.

Image Parallax

Create images with a parallax effect. Upload some layers, configure the animation, and publish !

thehowarde

This is a simple parallax image plugin that uses the parallax.js script by pixelcog – http://pixelcog.github.io/parallax.js/
To insert your full width parallax image, simply use the [dd-parallax] shortcode. Include text to be overlaid on the parallax between the open and close [/dd-parallax] code. This plugin has been tested with WordPress 2014, 2015, 2016, and 2017 themes as well as a few themes that use Bootstrap. I can’t guarantee that it will work with all themes, but it’s worth a shot.
** Please note for WP 5.0 ** 
Currently this plugin works, but the TinyMCE button only works with the classic editor. A Gutenberg widget is in the works.
For example:
<pre><code>[dd-parallax img="imagename.jpg" height="600" speed="3" z-index="-100" mobile="mobile-image.jpg" offset="true"] 

Text to be overlaid on the paralllax window

[/dd-parallax]
</code></pre>
Available parameters for use:
<ul>
<li>img – use the filename from the media library for this, not the full path. Just use imagename.jpg or image.png. (You can also use a fully qualified URL)</li>
<li>height – This is the height of the parallax window. The unit is in pixels. Just enter a number</li>
<li>speed [optional] (default = 2) An integer between 0 and 10. The speed at which the parallax effect runs. 0 means the image will appear fixed in place, and 10 the image will flow at the same speed as the page content.</li>
<li>z-index [optional] (default = 0) – The z-index value of the fixed-position elements. By default these will be behind everything else on the page.</li>
<li>mobile [optional] – If you want a mobile fixed image for mobile display, choose a different image, otherwise it will select the full sized image from the parallax and make it a responsive image.</li>
<li>offset [default = false] (options: “true” or “false”) – This will pull the parallax content all the way to the left of your screen. You can put the contents into a “container” class if you’re using bootstrap or just center the contents for horizontal centering. On testing with the WordPress 2016 Theme, keep offset at False. With Bootstrap Themes, I recommend using the “offset=’true'” parameter.</li>
<li>position [optional] – (defaults to ‘Left’) This is analogous to the background-position-x css property. Specify coordinates as right, left, center, or pixel values (e.g. -10px 0px). The parallax image will be positioned as close to these values as possible while still covering the target element.</li>
<li>text-pos [optional] – Default is ‘top’ (to maintain compatibility with ver 1.6). Available options are “top”, “center”, “bottom”.</li>
</ul>
Admin-Settings page enables or disables the TinyMCE icon (if you don’t want it in your WP-Editor)
<h3>Demo</h3>
View a demo of this plugin <a href="https://www.duckdiverllc.com/parallax-image-plugin-demo/" rel="nofollow ugc">here</a>

Parallax Image

Great and easy to use

Insert a full width parallax image into your page with this simple shortcode. Parameters allow for setting several key functions like height

Image Parallax vs Parallax Image