add_action('plugins_loaded', 'initialize_custom_image_sizes');
plugins_loaded is fired off way before functions.php is included. Change that hook to init.
http://codex.wordpress.org/Plugin_API/Action_Reference#Actions_Run_During_a_Typical_Request
Related Posts:
- Disabling post images for not logged in users
- How can i change an image’s author?
- Set WordPress Featured Image For All Post Slugs Matching Image File Name in Specified Directory
- How to change ID of an attachment in wp_posts and its related tables correctly?
- bulk change of image setting “link to” to “link to: image url “
- Converting Attachment to Images?
- Get the url of the full sized attachment image using post ID?
- Inserting HTML tag with ACF into shortcode
- Redirect to another page using contact form 7? [closed]
- Image change on hover
- Search by Attachment ID
- JSON API Plugin not showing Attachments id reused
- Add_image_size not generating correct size
- Elementor Pro display featured image on section -> style -> image using shortcode
- Get all image in media Gallery with alt/title?
- How to wrap image tag into div for post only?
- How to force regenerate thumbnails in WordPress posts?
- How to show post attachment image
- Building custom pages with a video player
- How to disable hover zoom on woocommerce. None of the common methods work
- Change wordpress current_time function to different timezone
- How to upload images to WP Panel keeping correct folder in FTP
- Limit Number of Taxonomy Terms (Images) Displayed
- Images not showing after changing wp-content folder name
- Executing my function once on a specific time
- Preview featured image using frontend post plugin
- How to add an image from web-link?
- How to append to title via functions.php for auto-posting plugin [duplicate]
- How to stop or remove an action being called inside a function of an extended class
- Missing Argument
- load_plugin_textdomain error
- How to override a plugin function wrapped in a class?
- Bootstrap Drop Down menu is not working
- How to Display a Plugin function (content) on frontpage using index.php
- How can I implement an Add to Collection function on my Image Gallery to be downloaded later?
- How to Delete all Unused photos Function
- How to resize images due to container width automatically server side/without CSS
- wordpress plugin is not activating from widget
- Load post attached images on a single page site with fancybox
- Theme my Login plugin, how to update fields
- Image rotation fails to regenerate custom sized thumbnail
- Set featured image randomly from WordPress Database on post submission
- Edit Yoast SEO breadcrumbs output [closed]
- Adding Shortcode to Text Widget
- Date calculations from 2 custom fields
- Howto accurately position images with maximum flexibility?
- Media is not attached after import
- Snippets: is it better to add them in functions.php or make site-specific plugins?
- Does WordPress validate inputs to all functions? (such as get_user_meta and insert_user_meta)
- Show an image in my header.php
- Custom random quote widget breaks when used in multiple sidebars
- How to create a managed image repository in wordpress
- Using a function to change favorites listing
- Display post lists in 2nd paragraph
- How to debug error message: Cannot modify header information
- Using a post-signup hook to get user details
- How to change File URL in file uploaded to s3 compatible storage with self written plugin [closed]
- How to enable specific plugin only based around shop manager role?
- How to change constants in WordPress wp-config.php programmatically?
- Restrict media upload size by format
- How to use a class from another plugin
- Override Plugin Script Fucnction in WordPress
- Display images that are not in the content
- How to display custom sidebar in wordpress 5.5.2
- How can I restrict image upload dimensions for non-admin WordPress users?
- Calling plugin function inside custom plugin for onclick event
- Show function to super admin
- creating html reusable blocks via shortcodes
- get current date + 90 days and checking every day
- wp_generate_attachment_metadata is creating an empty array
- Adding a new field to the address field type in gravity forms
- Force media library editor to overwrite the original filename?
- Replacing a plugin function with a custom renamed function doesn’t work
- How to create an input field, and base the output on spreadsheet data? [closed]
- Facebook Messager Plugin
- Contact Form 7 Get Image Function [closed]
- How generate 200% image size and save with suffix @2x
- Load external images via proxy
- Nested shortcode functions accessing variable
- Calling an attribute from a plugin shortcode
- Fatal error: Call to undefined function cmsms_theme_page_layout_scheme()
- How to call WordPress function other files
- Bulk edit WP posts to update embeded images with new alt tags
- All sites themes functions.php have been changed
- How to upload WordPress Images to remote web server and display those images in WordPress gallery [closed]
- Customize permalink wordpress category id
- Conditional attributes and logic per product category
- Disqus deleted comments are syncing with wordpress but active comments do not
- Admin style for just one plugin in dashboard
- Add padding while generating thumbnail
- WP Query. Is there a maximum size?
- Can we have an ‘Update metadata’ button in Image Gallery for all image instances?
- How to remove custom post type and add category and post name
- Retrieving Meta from Image Attachment
- Grab WordPress Salt Data From URL
- Add ALT attribute to Pin It Button image to pass HTML5 validation
- Ajax : Call undefined function plugin_function() … can’t call any plugin function
- WordPress get_avatar function not correct working
- Make change in media library affect images in published articles
- Adding (image) caching to my Tumblr widget