结果是，image_get_intermediate_size() 很容易适应我的需要。而不是使用wp_get_attachment_metadata 要获取现有图像的可用大小，我使用自己的函数获取所有可用图像大小（基本上与建议的函数相同here). 然后，我只返回名称，而不是元数据数组。

它可以工作，但我需要做一些更彻底的测试，并且可能需要做一些更改（例如，我不确定我是否真的想返回小于“缩略图”大小的“缩略图”）。。。

下面是我的整个函数（它是实用程序类的静态方法）：

/**
 * Return the closest named size from an array of width and height values.
 *
 * Based off of WordPress\'s image_get_intermediate_size()
 * If the size matches an existing size then it will be used. If there is no
 * direct match, then the nearest image size larger than the specified size
 * will be used. If nothing is found, then the function will return false.
 * Uses get_image_sizes() to get all available sizes.
 *
 * @param  array|string $size   Image size. Accepts an array of width and height (in that order).
 * @return false|string $data   named image size e.g. \'thumbnail\'.
 */
public static function get_named_size( $size ) {

    $image_sizes = self::get_image_sizes();
    $data = array();

    // Find the best match when \'$size\' is an array.
    if ( is_array( $size ) ) {
        $candidates = array();

        foreach ( $image_sizes as $_size => $data ) {

            // If there\'s an exact match to an existing image size, short circuit.
            if ( $data[\'width\'] == $size[0] && $data[\'height\'] == $size[1] ) {
                $candidates[ $data[\'width\'] * $data[\'height\'] ] = array( $_size, $data );
                break;
            }

            // If it\'s not an exact match, consider larger sizes with the same aspect ratio.
            if ( $data[\'width\'] >= $size[0] && $data[\'height\'] >= $size[1] ) {
                if ( wp_image_matches_ratio( $data[\'width\'], $data[\'height\'], $size[0], $size[1] ) ) {
                    $candidates[ $data[\'width\'] * $data[\'height\'] ] = array( $_size, $data );
                }
            }
        }

        if ( ! empty( $candidates ) ) {
            // Sort the array by size if we have more than one candidate.
            if ( 1 < count( $candidates ) ) {
                ksort( $candidates );
            }

            $data = array_shift( $candidates );
            $data = $data[0];
        /*
         * When the size requested is smaller than the thumbnail dimensions, we
         * fall back to the thumbnail size to maintain backwards compatibility with
         * pre 4.6 versions of WordPress.
         */
        } elseif ( ! empty( $image_sizes[\'thumbnail\'] ) && $image_sizes[\'thumbnail\'][\'width\'] >= $size[0] && $image_sizes[\'thumbnail\'][\'width\'] >= $size[1] ) {
            $data = \'thumbnail\';
        } else {
            return false;
        }

    } elseif ( ! empty( $image_sizes[ $size ] ) ) {
        $data = $size;
    }

    // If we still don\'t have a match at this point, return false.
    if ( empty( $data ) ) {
        return false;
    }

    return $data;
}

$image_size = My_Utility_Class::get_named_size( array( 150, 150 ) ); // returns \'thumbnail\'