fix(core): avoid reseting num_images when switching datasets

If the NUM_IMAGES_DEFAULT was smaller than current
num_images, then we would clamp num_images when
switching datasets.

src/nrtk_explorer/app/core.py

@@ -98,6 +98,7 @@ def __init__(self, server=None, **kwargs):
         self.ctrl.on_server_reload = self._build_ui
         self.ctrl.add("on_server_ready")(self.on_server_ready)
 
+        self.state.num_images = NUM_IMAGES_DEFAULT
         self.state.num_images_max = 0
         self.state.num_images_disabled = True
         self.state.random_sampling = False
@@ -126,7 +127,7 @@ def on_dataset_change(self, **kwargs):
         self.state.dataset_ids = []  # sampled images
         self.context.dataset = get_dataset(self.state.current_dataset)
         self.state.num_images_max = len(self.context.dataset.imgs)
-        self.state.num_images = min(self.state.num_images_max, NUM_IMAGES_DEFAULT)
+        self.state.num_images = min(self.state.num_images_max, self.state.num_images)
         self.state.dirty("num_images")  # Trigger resample_images()
         self.state.random_sampling_disabled = False
         self.state.num_images_disabled = False
@@ -150,18 +151,18 @@ def on_filter_apply(self, filter: FilterProtocol[Iterable[int]], **kwargs):
         self._embeddings_app.on_select(selected_ids)
 
     def resample_images(self, **kwargs):
-        images = list(self.context.dataset.imgs.values())
+        ids = [image["id"] for image in self.context.dataset.imgs.values()]
 
         selected_images = []
         if self.state.num_images:
             if self.state.random_sampling:
-                selected_images = random.sample(images, min(len(images), self.state.num_images))
+                selected_images = random.sample(ids, min(len(ids), self.state.num_images))
             else:
-                selected_images = images[: self.state.num_images]
+                selected_images = ids[: self.state.num_images]
         else:
-            selected_images = images
+            selected_images = ids
 
-        self.state.dataset_ids = [str(img["id"]) for img in selected_images]
+        self.state.dataset_ids = [str(id) for id in selected_images]
         self.state.user_selected_ids = self.state.dataset_ids
 
     def _build_ui(self):