Update add_image_size

Question

This has been asked before, but the answer is from three years ago and is not working for me, so I'm wondering if something fundamental has changed since then, or if I'm fundamentally misunderstanding something. I'm new at developing child themes.

I'm trying to do a child of a theme that is not supported by the creators (Duena). When I set the featured image for a page, add_image_size crops the image and I want to change that. Here's what's in the parent theme's functions.php:

function duena_setup() { 
// Various other things

if ( function_exists( 'add_theme_support' ) ) { // Added in 2.9
    add_theme_support( 'post-thumbnails' );
    set_post_thumbnail_size( 750, 290, true ); // Normal post thumbnails
    add_image_size( 'slider-post-thumbnail', 1140, 440, true ); // Slider Thumbnail
    add_image_size( 'image_post_format', 750, 440, true ); // Image Post Format output
    add_image_size( 'related-thumb', 160, 160, true ); // Realted Post Image output
    add_image_size( 'portfolio-large-th', 550, 210, true ); // 2 cols portfolio image
    add_image_size( 'portfolio-small-th', 265, 100, true ); // 4 cols portfolio image
}
}

For slider-post-thumbnail, I want the image height to be 600, or else set crop to false. I tried the solution in the other question by adding the following to my child theme's functions.php:

function hhc1_setup() {
    add_image_size( 'slider-post-thumbnail', 1140, 600, true ); // Slider Thumbnail
    }
add_action( 'after_setup_theme', 'hhc1_setup', 15 );

But, no dice, the featured images are still being cropped to 440 height. Am I missing something obvious?

Answer 1

@WisdmLabs is right. For old images you will have to use that plugin to regenerate thumbnails. For new images which you will upload it will respect the 600 height mentioned in child theme's functions.php file.