I don’t want to use the many available plugins or a custom field.
Even a code only solution would use a custom field for this.
It’s metadata about the post, so you use a custom field for it. That’s what custom fields are.
Also, the code for your custom solution would live in a plugin, because that’s where you put custom solutions.
So, as it stands, there is no answer to your question, because you placed restrictions on it that prevent any viable answer from being correct.
Related Posts:
- How to get image title/alt attribute?
- How to set featured image to custom post from outside programmatically
- Generate Thumbnails only for Featured Images
- How to add post featured image to RSS item tag?
- Get featured image URL by page id
- wp_get_attachment_image_src() and custom sizes
- What’s the difference between post thumbnails and featured images (if any)?
- What is your take: TimThumb vs. WordPress Thumbnails? The great debate [closed]
- How to change the naming of the resized image files
- How to get featured post title & image using JSON API?
- Display thumbnail only on the very first post in the loop?
- Allow user to manually set crop area of default/custom image sizes on upload [closed]
- Display child pages on a parent and child page using Featured Thumbnails
- How to display a post’s Featured Image with this code?
- Conditional to grab parent page thumbnail URL
- Show featured image in sidebar
- Featured Image VS Post_thumbnail — has_post_thumbnail lies?
- Use get/the_post_thumbnail with Custom Size & Crop
- The Thumbnail aspect Ratio Issue
- Cropped thumbnail still displaying as full image
- Use Video as Featured Image
- Media thumbnail for custom post inside post content
- Why am I getting errors in product.thumbnails.php? [closed]
- Featured image always rendered with 198px of height?
- How to retrieve the post featured image (thumbnail) ID in Gutenberg blocks?
- MultiPostThumbnail and the_post_thumbnail
- Featured image is not uploading
- how to use the new image size
- Image still attached to post even after removing it as featured image
- Create custom thumbnail size on existing posts
- thumbnails are getting clipped down, want to resize instead
- Multiple Post thumbnails (at least three)
- How check that there is post thumbnail feature image or not on wordpress?
- Force WordPress to strip/remove EXIF/IPTC metadata when resizing thumbnails
- How to offset thumbnails to the center?
- Secondary Featured Image Function (post_thumbnail)
- Sidebar Thumbs Squished?
- Adding Videos as post-thumbnails (no stills, just the player in a smaller size)
- Getting thubnails for previous posts
- Setting fallback (default) image to featured image block
- Featured Images Not Loading In Blog Archives
- how i can add title to my featured image?
- 2 image size for post
- Needs to add anchor tag in featured image to open in new tab
- Different Featured Images depending on context: loop or single view
- How to both crop (with tool) and resize thumbnails having only a max width constrain?
- Featured image not working, because of custom user role?
- “Medium” size image displayed instead of “thumbnail” in only one post, other posts are fine
- Function to scan for image, attach it to post, set it as featured [duplicate]
- Static news page has for thumbnail the featured image of the first posts
- How to set post thumbnail size?
- Check if parent post is sticky on attachment page?
- get_the_post_thumbnail not working inside wp_get_nav_menu_items hook
- Adding in support thumbnail removes editor
- the_post_thumbnail(‘my_image_size’) always outputs full image
- the post thumbnail, scale
- Why use foreach to get attachment_id if numberposts is equal to 1?
- Retrieving featured image on static blog posts page
- How to allow the user to add an arbitrary amount of post thumbnails
- default post thumbnail and category if there is no thumbnail and category
- Conditional post thumbnail based on logged status and post tag
- How do I add thumbnail to current Prev and next buttons in posts?
- custom class and size for the_post_thumbail
- Check category before displaying featured image
- Pull through featured image in a custom menu
- How do I get posts where image is larger than…?
- Category page with thumb is ok but can’t do the same with tags
- Programmatically set thumbnail via URL using DOM and XPATH – Where to add ELSEIF
- Retrieve a post’s featured image with PHP outside of WordPress
- Better way to show Description and image Captions
- Different size thumbnails on home and single pages
- Next Prev Post link rendering current post thumbnail
- How to add thumbnail images? (Set Featured Image doesn’t work)
- custom image size not being fetched
- Resizing images failing
- How to add a new thumbnail size only to a certain custom post type?
- Tag,php – how to get it to display featured post image? [closed]
- Featured images have disappeared in the Trending section only of my website
- Blog replace single post page featured image
- How to use tag in featured image
- How to automatically add first image of post as thumbnail?
- Change wording of default thumbnail metabox
- featured image metabox not moving custom post type
- How to convert feature image as background image
- about featured image
- Moving Featured Images
- Add Play Icon on thumbnail overlay for video post types
- How do I Get WordPress Featured image from Frontend
- Featured Image, and Image in post
- Get Post thumbnail without width/height attribute
- if statement for featured images
- Thumbnail size according to width and height
- Featured Image URL is Showing but not thumbnail
- Custom image sizes are not used
- Import Dummy Content and Post Thumbnails
- Source problem for children page image
- Fetch first image URL from post and set as featured image URL
- How to set featured image from a variable
- How to stop WordPress from creating native thumbnails?
- Why not attaching images after impoting using wp cli