How To Change Default Image Thumbnail Sizes in Wordpress

Question

Hey.. quite embarrassed to ask this actually - I should be able to find this on Google, but because of all the new WP functionality as well as the older methods of doing this in older versions are riddled all over Google Results that I have resorted to leverage the knowledge of a good samaritan out there somewhere.

I already know how to set up custom thumbnail sizes (I'm developing a Magazine style theme), and at the moment I'm working on getting my gallery working. When I choose to "insert to post" an image, it gives me 4 options - small, medium and large thumbnails plus the original size.

I need to know, for embedding purposes (not the featured post thumbnails), how to set the default sizes of these thumbnails so that they appear in the Media section of the Post editing screen.

Any ideas?

Answer 1

Look in your wordpress root folder as such:

wordpress_root\wp-includes

In this folder there is a file called: media.php

Starting on Line 34 there is a function:

function image_constrain_size_for_editor($width, $height, $size = 'medium')

in this function, starting on Line 41, there is the following code. Just edit this for your needs:

elseif ( $size == 'thumb' || $size == 'thumbnail' ) {
        $max_width = intval(get_option('thumbnail_size_w'));
        $max_height = intval(get_option('thumbnail_size_h'));
        // last chance thumbnail size defaults
        if ( !$max_width && !$max_height ) {
            $max_width = 128;
            $max_height = 96;
        }
    }

Answer 2

I answered my own question folks, and I feel quite dumb.. haha.

It was in the Admin screen. Left bar.. Settings -> Media, and there they are. Thumbnail, medium, and large sizes. No file hacks, no custom size settings in the functions.php file necessary.

Oops!