Media: Make the `is_gd_image()` function available on front end.

This avoids a fatal error if a plugin calls image creation or editing functions like `wp_imagecreatetruecolor()` outside of the admin.

Follow-up to [48798]

Props BackuPs.
Fixes #51174. See #50833.
Built from https://develop.svn.wordpress.org/trunk@48905


git-svn-id: http://core.svn.wordpress.org/trunk@48667 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/includes/image.php

@@ -912,29 +912,6 @@ function file_is_displayable_image( $path ) {
 	return apply_filters( 'file_is_displayable_image', $result, $path );
 }
 
-/**
- * Determines whether the value is an acceptable type for GD image functions.
- *
- * In PHP 8.0, the GD extension uses GdImage objects for its data structures.
- * This function checks if the passed value is either a resource of type `gd`
- * or a GdImage object instance. Any other type will return false.
- *
- * @since 5.6.0
- *
- * @param resource|GdImage|false $image A value to check the type for.
- * @return bool True if $image is either a GD image resource or GdImage instance,
- *              false otherwise.
- */
-function is_gd_image( $image ) {
-	if ( is_resource( $image ) && 'gd' === get_resource_type( $image )
-		|| is_object( $image ) && $image instanceof GdImage
-	) {
-		return true;
-	}
-
-	return false;
-}
-
 /**
  * Load an image resource for editing.
  *

wp-includes/media.php

@@ -3458,6 +3458,29 @@ function get_taxonomies_for_attachments( $output = 'names' ) {
 	return $taxonomies;
 }
 
+/**
+ * Determines whether the value is an acceptable type for GD image functions.
+ *
+ * In PHP 8.0, the GD extension uses GdImage objects for its data structures.
+ * This function checks if the passed value is either a resource of type `gd`
+ * or a GdImage object instance. Any other type will return false.
+ *
+ * @since 5.6.0
+ *
+ * @param resource|GdImage|false $image A value to check the type for.
+ * @return bool True if $image is either a GD image resource or GdImage instance,
+ *              false otherwise.
+ */
+function is_gd_image( $image ) {
+	if ( is_resource( $image ) && 'gd' === get_resource_type( $image )
+		|| is_object( $image ) && $image instanceof GdImage
+	) {
+		return true;
+	}
+
+	return false;
+}
+
 /**
  * Create new GD image resource with transparency support
  *

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.6-alpha-48904';
+$wp_version = '5.6-alpha-48905';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.