Image preview size always displaying as 'standard featured image' size?

• weddje

• December 19, 2019 at 7:06 am

I’m trying to create a post image gallery with different thumbnail sizes.

I’ve created image meta-boxes with with different preview sizes (horizontal, square and vertical etc). Instead of the featured image, I want to choose one of the images from the meta-box to populate as the post-thumbnail.

I do get the image from the meta-box but the size is the same as the standard wordpress featured image. How do I get the post-thumbnail to be displayed in the size chosen in the meta-box?