How to get the URL of a each custom image size of a featured image

Question

I would like to get the URL's of my custom image sizes for a featured image - so I can inject them conditionally.

(this in functions.php)
To start off, I'm removing the default crop sizes because I never use them.

// remove all the default image sizes
function sgr_filter_image_sizes( $sizes) {
    unset( $sizes['thumbnail']);
    unset( $sizes['medium']);
    unset( $sizes['large']);
    return $sizes;
}
add_filter('intermediate_image_sizes_advanced', 'sgr_filter_image_sizes');

Then defining the new sizes that I'll use.

// add custom image sizes
function add_custom_image_sizes() {
    add_image_size ( 'small-screen', 700, 350, true );
    add_image_size ( 'medium-screen', 1200, 600, true );
    add_image_size ( 'large-screen', 2000, 1000, true );
    add_image_size ( 'extra-large-screen', 3200, 1600, true );
}
add_action('init', 'add_custom_image_sizes');

Then in my HTML/PHP, I'm doing something like this

    <?php if ( has_post_thumbnail() ) { ?>

        <?php $thisPostId = get_post_thumbnail_id(); ?>
        <img src="some-blank-image-of-the-correct-ratio.png"
            data-url-small="<?php echo wp_get_attachment_image_src( $thisPostId, 'small-screen' ); ?>"
            data-url-medium="<?php echo wp_get_attachment_image_src( $thisPostId, 'medium-screen' ); ?>"
            data-url-large="<?php echo wp_get_attachment_image_src( $thisPostId, 'large-screen' ); ?>"
            data-url-extra-large="<?php echo wp_get_attachment_image_src( $thisPostId, 'extra-large-screen' ); ?>"
            alt=''>

    <?php } else { ?>

        <img src='http://placehold.it/1600x800/333/&text=No featured image yet' alt=''>

    <?php } ?>

Then in my JavaScript - I can choose white URL to use based on a set of circumstances.

I'm getting a soft failure that returns the full image for each.

This is on a single-customPostType page, and is not in a loop.

Answer 1

So, I finally noticed that what I was doing, was returning an array, and that I needed the [0] of that array. The code is on the ugly side, but it works.

<?php
    $thumb_id = get_post_thumbnail_id();
    $small_screen = wp_get_attachment_image_src($thumb_id,'small-screen', true);
    $medium_screen = wp_get_attachment_image_src($thumb_id,'medium-screen', true);
    $large_screen = wp_get_attachment_image_src($thumb_id,'large-screen', true);
    $extra_large_screen = wp_get_attachment_image_src($thumb_id,'extra-large-screen', true);
?>

-

<div class='container hero-w'
    data-background-large='<?php echo $large_screen[0]; ?>'
    data-background-extra-large='<?php echo $extra_large_screen[0]; ?>'>

    <div class='inner-w'>

        <div class='image-w hero'>

            <?php if ( has_post_thumbnail() ) { ?>

                <img src="<?php echo get_template_directory_uri(); ?>/images/2x1.png"
                    data-image-small="<?php echo $small_screen[0]; ?>"
                    data-image-medium="<?php echo $medium_screen[0]; ?>"
                    data-image-large="<?php echo $large_screen[0]; ?>"
                    alt=''>

            <?php } else { ?>

                <img src='http://placehold.it/1600x800/333/&text=No featured image yet' alt=''>

            <?php } ?>


        </div>

    </div>
</div>