We'll create fresh WordPress site with Advanced Custom Fields: Image Size Select Field installed. You have 20 minutes to test the plugin after that site we'll be deleted.
Field to select registered image sizes within the WordPress dashboard.
This ACF field type is compatible with:
* ACF 5
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:
$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.