get_wordpress_image_sizes.php

/**
 * Get information about available image sizes
 */
function get_image_sizes($size = '')
{

    global $_wp_additional_image_sizes;

    $sizes = array();
    $get_intermediate_image_sizes = get_intermediate_image_sizes();

    // Create the full array with sizes and crop info
    foreach ($get_intermediate_image_sizes as $_size) {
        if (in_array($_size, array('thumbnail', 'medium', 'large'))) {
            $sizes[$_size]['width'] = get_option($_size . '_size_w');
            $sizes[$_size]['height'] = get_option($_size . '_size_h');
            $sizes[$_size]['crop'] = (bool) get_option($_size . '_crop');
        }
        elseif (isset($_wp_additional_image_sizes[$_size])) {
            $sizes[$_size] = array(
                'width' => $_wp_additional_image_sizes[$_size]['width'],
                'height' => $_wp_additional_image_sizes[$_size]['height'],
                'crop' => $_wp_additional_image_sizes[$_size]['crop']
            );
        }
    }

    // Get only 1 size if found
    if ($size) {
        if (isset($sizes[$size])) {
            return $sizes[$size];
        }
        else {
            return false;
        }
    }
    return $sizes;
}