Resize image in cirlce

Yes. Please.

Twenty Thirteen has a rule to resize images to that size (604×270):

/*
	 * This theme uses a custom image size for featured images, displayed on
	 * "standard" posts and pages.
	 */
	add_theme_support( 'post-thumbnails' );
	set_post_thumbnail_size( 604, 270, true );

So, only until you re-uploaded the image did this “set_post_thumbnail_size” function kick-in.

Spun has the same kind of rule:

/**
	 * Enable support for Post Thumbnails
	 */
	add_theme_support( 'post-thumbnails' );
	add_image_size( 'home-post', 360, 360, true );

And what you did in your Child Theme functions.php file (recommended above) was do the same thing as the add_image_size function, but instead of passing “true” you passed “false”. You can explore why by looking at the $crop parameter explanation in the Codex guidelines, but that’s not important – I don’t think.

Again, only until you re-uploaded an image in Spun did this add_image_size rule kick in.

Okay I think that’s enough testing on Twenty Thirteen, you can switch back to Spun.

It’s difficult to draw a conclusion as to what’s going on.

An issue I’ve seen people experience when using the add_image_size function is that they have to re-upload the image(s), re-upload it to the media library.
You might then think it’s safe to conclude that this is what’s going on: the Spun theme changed the way it resized its circle images, and the way it did meant you had to re-upload the images – HOWEVER – the Twenty Thirteen theme that you just switched to used the same function as the old Spun theme

set_post_thumbnail_size( 604, 270, true );

And yet you still experienced an issue with the first image (until you re-uploaded it).

After some very brief research it seems both the set_post_thumbnail_size and add_image_size could may well do the same stuff, as in, produce the same issue: http://wordpress.stackexchange.com/questions/108572/set-post-thumbnail-size-vs-add-image-size

So, set_post_thumbnail_size($width, $height, $crop) is a sort of shortcut for add_image_size(‘post-thumbnail’, $width, $height, $crop)

When an image size change, for every reason, the change has effect on the images uploaded after that change, images uploaded before don’t change dimension and are not rescaled and resaved. If someone want rely on specific image sizes, after a lot of images are already uploaded (e.g . after changing theme) then the plugin Regenerate image thumbnail will be life saver.

Backtracking, maybe it is to do with the add_image_size function in the Spun theme. Maybe when you switch from one function to the other WordPress hiccups, or maybe that’s standard behaviour of WordPress.
E.g. When we switched between Spun, to Twenty Thirteen, WordPress switched between using the ‘add_image_size‘ function to the ‘set_post_thumbnail_size' and it was the act of switching between these functions that caused the issue(?).

I’ve done some initial testing and it seems to confirm our little hypothesis

We said:

it was the act of switching between these functions that caused the issue(?).

To test whether whether this is true I switched between these functions to try to provoke the same result.

We already knew that:
– The Twenty Thirteen theme used the ‘set_post_thumbnail_size‘ function to resize images in the library,
– And the Spun (v.2+) used the ‘add_image_size‘ function to resize images in the library

Methodology

1. Switch to the Twenty Thirteen theme
2. Upload an image to the library
3. Attach that image to a featured post/ insert it in the content of the post
4. Switch to the Spun theme
5. View the home page
6. Inspect the element using your browser’s developer tools
7. Look at the actual size of that image (still on the Webpage using your browser’s developer tools) that you had just uploaded from the Twenty Thirteen theme

Results
The image that was uploaded in the Twenty Thirteen theme does not resize in the Spun theme home page. It should have resized to 360×360 (but didn’t).