Jeremy Ross

Field to select registered image sizes within the WordPress dashboard.
<h3>Compatibility</h3>
This ACF field type is compatible with: 
* ACF 5
<h3>How to Use</h3>
Once activated, this plugin will create a Image Size field type in ACF. This field type will list all registered field types as a drop down within the field group.
To use this field within your custom templates you will use the following code:
<pre><code>$my_image_id = get_field('my_image_id'); // ACF Image return type set to ID for this demo
$my_image_size = get_field('my_image_size'); // The selected image size (eg. large)

echo wp_get_attachment_image( $my_image_id, $my_image_size ); // Output the image based on the ID, and the Image Size selected.
</code></pre>

Advanced Custom Fields: Image Size Select Field

Field to select registered image sizes within the WordPress dashboard.

Yudiz Solutions Ltd.

This fabulous plugin has been developed by <a href="http://www.yudiz.com/" rel="nofollow ugc">Yudiz Solutions Ltd.</a> WP Recreate Thumbnails plugin helps you to recreate thumbnails for the uploaded images.
How to use this plugin? 
Follow the below steps: 
1) Install and activate the plugin. 
2) After successful activation of the plugin, you will find one menu item in Left Hand Side in WP Admin named “Recreate Thumbnails”. 
3) Click on that link and then you will find one button named “Recreate Thumbnails”. Click on the button to initialize the process of regenerating thumbnails. 
4) In case you just want to regenerate thumbnail for a single image, then you can do so by going media and that particular image and there you will find “Recreate Thumbnail” button. You just need to click on it and you are good to go.
In case you might have deleted any thumbnail(s) from the uploads folder then this plugin will help you to rescue from such a critical situation and even if you have replaced the image from the uploads folder then it will create related thumbnails.
Hope you find this plugin useful. <a href="http://www.yudiz.com/get-in-touch/" rel="nofollow ugc">Contact us</a> if you want to develop such a custom WordPress plugin.

WP Recreate Thumbnails

This Plugin helps to create thumbnails of uploaded images

Advanced Custom Fields: Image Size Select Field vs WP Recreate Thumbnails