[ui] factorize exif orientation transform in utility functions

meshroom/ui/qml/Utils/ExifOrientation.qml

@@ -0,0 +1,49 @@
+pragma Singleton
+import QtQuick 2.11
+
+/**
+ * Singleton that defines utility functions for supporting exif orientation tags.
+ *
+ * If you are looking for a way to create a Loader that supports exif orientation tags,
+ * you can directly use ExifOrientedViewer instead.
+ *
+ * However if you want to apply an exif orientation tag to another type of QML component,
+ * you will need to redefine its transform property using the utility methods given below.
+ */
+QtObject {
+
+    function rotation(orientationTag) {
+        switch(orientationTag) {
+            case "3":
+                return 180;
+            case "4":
+                return 180;
+            case "5":
+                return 90;
+            case "6":
+                return 90;
+            case "7":
+                return -90;
+            case "8":
+                return -90;
+            default:
+                return 0;
+        }
+    }
+
+    function xscale(orientationTag) {
+        switch(orientationTag) {
+            case "2":
+                return -1;
+            case "4":
+                return -1;
+            case "5":
+                return -1;
+            case "7":
+                return -1;
+            default:
+                return 1;
+        }
+    }
+
+}