speed up iiif manifest generation

modules/islandora_iiif/src/Plugin/views/style/IIIFManifest.php

@@ -296,7 +296,7 @@ class IIIFManifest extends StylePluginBase {
           $canvas_id = $iiif_base_id . '/canvas/' . $entity->id();
           $annotation_id = $iiif_base_id . '/annotation/' . $entity->id();
 
-          [$width, $height] = $this->getCanvasDimensions($iiif_url, $image, $mime_type);
+          [$width, $height] = $this->getCanvasDimensions($iiif_url, $entity, $mime_type);
 
           $tmp_canvas = [
             // @see https://iiif.io/api/presentation/2.1/#canvas
@@ -365,11 +365,13 @@ class IIIFManifest extends StylePluginBase {
    * @return [string]
    *   The width and height of the image.
    */
-  protected function getCanvasDimensions(string $iiif_url, FieldItemInterface $image, string $mime_type) {
+  protected function getCanvasDimensions(string $iiif_url, $image, string $mime_type) {
 
-    if (isset($image->width) && is_numeric($image->width)
-    && isset($image->height) && is_numeric($image->height)) {
-      return [intval($image->width), intval($image->height)];
+     $height =  $image->get('field_height')->value;
+     $width = $image->get('field_width')->value;
+     if (isset($width) && is_numeric($width)
+       && isset($height) && is_numeric($height)) {
+       return [intval($width), intval($height)];
      }
 
     try {