Ensure id attr can be set for IIIF tile output #2612

lib/output.js

@@ -727,6 +727,7 @@ function raw () {
  * @param {string} [options.layout='dz'] filesystem layout, possible values are `dz`, `iiif`, `zoomify` or `google`.
  * @param {boolean} [options.centre=false] centre image in tile.
  * @param {boolean} [options.center=false] alternative spelling of centre.
+ * @param {string} [options.id='https://example.com/iiif'] when `layout` is `iiif`, sets the `@id` attribute of `info.json`
  * @returns {Sharp}
  * @throws {Error} Invalid parameters
  */
@@ -800,6 +801,14 @@ function tile (options) {
     if (is.defined(centre)) {
       this._setBooleanOption('tileCentre', centre);
     }
+    // @id attribute for IIIF layout
+    if (is.defined(options.id)) {
+      if (is.string(options.id)) {
+        this.options.tileId = options.id;
+      } else {
+        throw is.invalidParameterError('id', 'string', options.id);
+      }
+    }
   }
   // Format
   if (is.inArray(this.options.formatOut, ['jpeg', 'png', 'webp'])) {