而不是使用locationimage 属性，为什么不使用附件ID？

这将允许您动态获取文件的URL，并使获取其他元数据（如alt文本）更加容易。以下是的重写版本hplocationsfn().

用法示例：[hpLocationSquare id=\'2299\' link=\'http://example.com\']

请注意link 属性是可选的。

function hplocationsfn( $atts ) {
    // Set up shortcode attributes.
    // User provided values are stored in $atts.
    // Default values are passed to shortcode_atts below.
    // Merged values are stored in the $a array.
    $a = shortcode_atts( [
                \'id\'   => false,
                \'size\' => \'thumbnail\',
                \'link\' => false,
    ], $atts );

    // Bail if we don\'t have an image.
    if ( ! $a[\'id\'] ) {
        return;
    }

    // Get the image and the image\'s alt value.
    $image     = wp_get_attachment_image_src( $a[\'id\'], $a[\'size\'] );
    $image_alt = get_post_meta( $a[\'id\'], \'_wp_attachment_image_alt\', true );

    // Bail if our image is invalid.
    if ( ! $image || empty ( $image ) ) {
        return;
    }

    // Generate the output.
    $output = \'<div class="locationSquare">\';
    if ( $a[\'link\'] ) {
        $output .= \'<a href="\' . esc_attr( $a[\'link\'] ) .\'">\';
    }

    $output .= \'<img src="\' . esc_attr( $image[0] ) . \'" alt="\' . esc_attr( $image_alt ) . \'"/>\';

    if ( $a[\'link\'] ) {
        $output .= \'</a>\';
    }
    $output .= \'</div><!-- locationSquare -->\';

    return $output;
}
add_shortcode( \'hpLocationSquare\', \'hplocationsfn\' );

对于用户来说，查找附件ID可能有点困难，因此，以下是一个将附件ID添加到媒体覆盖屏幕的功能：

/**
 * Add custom field to media
 */
add_filter( \'attachment_fields_to_edit\', \'wpse_attachment_fields_id\', 10, 2 );
function wpse_attachment_fields_id( $fields, $post ) {

    $fields[\'attachment_id\'] = [
            \'label\' =>  __( \'Attachment ID\', \'text-domain\' ),
            \'input\' => \'html\',
            \'value\' => $post->ID,
            \'html\'  => "<input type=\'text\' class=\'text attachment_idfield\' readonly=\'readonly\' name=\'attachments[{$post->ID}][attachment_id]\' value=\'" . esc_attr( $post->ID ) . "\' /><br />",
            \'show_in_edit\' => true,
    ];

    return $fields;         
}

编辑：从图像URL获取附件ID或者，我们可以使用attachment_url_to_postid().

Example usage:

[hpLocationSquare2 locationimage=\'http://domain.com/wp-content/uploads/2017/02/my-image.jpg\' link=\'http://example.com/2/\']

function hplocationsfn2( $atts ) {
    // Set up shortcode attrubutes.
    // User provided values are stored in $atts.
    // Default valued are passed to shortcode_atts below.
    // Merged valued are stored in the $a array.
    $a = shortcode_atts( [
                \'locationimage\' => false,
                \'link\'          => false,
    ], $atts );

    // Bail if we don\'t have an image.
    if ( ! $a[\'locationimage\'] ) {
        return;
    }

    $image_id = attachment_url_to_postid( $a[\'locationimage\'] );
    if ( ! $image_id ) {
        return;
    }

    // Get the image and the image\'s alt value.
    $image_alt = get_post_meta( $image_id, \'_wp_attachment_image_alt\', true );

    // Generate the output.
    $output = \'<div class="locationSquare">\';
    if ( $a[\'link\'] ) {
        $output .= \'<a href="\' . esc_attr( $a[\'link\'] ) .\'">\';
    }

    $output .= \'<img src="\' . esc_attr( $a[\'locationimage\'] ) . \'" alt="\' . esc_attr( $image_alt ) . \'"/>\';

    if ( $a[\'link\'] ) {
        $output .= \'</a>\';
    }
    $output .= \'</div><!-- locationSquare -->\';

    return $output;
}
add_shortcode( \'hpLocationSquare2\', \'hplocationsfn2\' );