decoder: Use the original dimg ordering from iref

Instead of using the order from the constructed items, use the dimg
ordering from the iref box.

Fixes the libavif bug AOMediaCodec/libavif#2311

PiperOrigin-RevId: 655255206

src/decoder/mod.rs

@@ -688,6 +688,12 @@ impl Decoder {
                 "Expected number of tiles not found".into(),
             ));
         }
+        // ISO/IEC 23008-12: The input images are inserted in row-major order,
+        // top-row first, left to right, in the order of SingleItemTypeReferenceBox of type 'dimg'
+        // for this derived image item within the ItemReferenceBox.
+        // Sort the grid items by dimg_index. dimg_index is the order in which the items appear in
+        // the 'iref' box.
+        grid_item_ids.sort_by_key(|k| self.items.get(k).unwrap().dimg_index);
         let item = self.items.get_mut(&item_id).unwrap();
         item.properties
             .push(ItemProperty::CodecConfiguration(first_av1C.unwrap()));

tests/decoder_tests.rs

@@ -746,3 +746,26 @@ fn dimg_shared() {
     let mut decoder = get_decoder("color_grid_alpha_grid_tile_shared_in_dimg.avif");
     assert_eq!(decoder.parse(), Err(AvifError::NotImplemented));
 }
+
+#[test]
+fn dimg_ordering() {
+    if !HAS_DECODER {
+        return;
+    }
+    let mut decoder1 = get_decoder("sofa_grid1x5_420.avif");
+    let res = decoder1.parse();
+    assert!(res.is_ok());
+    let res = decoder1.next_image();
+    assert!(res.is_ok());
+    let mut decoder2 = get_decoder("sofa_grid1x5_420_random_dimg_order.avif");
+    let res = decoder2.parse();
+    assert!(res.is_ok());
+    let res = decoder2.next_image();
+    assert!(res.is_ok());
+    let image1 = decoder1.image().expect("image1 was none");
+    let image2 = decoder2.image().expect("image2 was none");
+    // Ensure that the pixels in image1 and image2 are not the same.
+    let row1 = image1.row(Plane::Y, 0).expect("row1 was none");
+    let row2 = image2.row(Plane::Y, 0).expect("row2 was none");
+    assert_ne!(row1, row2);
+}