From 1ee3a39e303e91b9cd8d9b1aa6717c403229285c Mon Sep 17 00:00:00 2001
From: Grzegorz Bokota <bokota+github@gmail.com>
Date: Mon, 22 Jan 2024 23:26:01 +0100
Subject: [PATCH] Fix wrong working interpolation of labels in 3d (#6596)

# References and relevant issues

closes #6595

# Description

Set interpolation for rendering of 3D data for labels.
---
 napari/_qt/_tests/test_qt_viewer.py | 16 ++++++++++++++++
 napari/_qt/qt_viewer.py             |  3 ++-
 napari/_vispy/layers/labels.py      |  1 +
 3 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/napari/_qt/_tests/test_qt_viewer.py b/napari/_qt/_tests/test_qt_viewer.py
index a9530ae1d0d..196df5014f8 100644
--- a/napari/_qt/_tests/test_qt_viewer.py
+++ b/napari/_qt/_tests/test_qt_viewer.py
@@ -911,6 +911,22 @@ def test_background_color(qtbot, qt_viewer: QtViewer, dtype):
         )
 
 
+def test_rendering_interpolation(qtbot, qt_viewer):
+    data = np.zeros((20, 20, 20), dtype=np.uint8)
+    data[1:-1, 1:-1, 1:-1] = 5
+    layer = qt_viewer.viewer.add_labels(
+        data, opacity=1, rendering="translucent"
+    )
+    layer.selected_label = 5
+    qt_viewer.viewer.dims.ndisplay = 3
+    QApplication.processEvents()
+    canvas_screenshot = qt_viewer.screenshot(flash=False)
+    shape = np.array(canvas_screenshot.shape[:2])
+    pixel = canvas_screenshot[tuple((shape * 0.5).astype(int))]
+    color = layer.colormap.map(5)[0] * 255
+    npt.assert_array_equal(pixel, color)
+
+
 def test_shortcut_passing(make_napari_viewer):
     viewer = make_napari_viewer(ndisplay=3)
     layer = viewer.add_labels(
diff --git a/napari/_qt/qt_viewer.py b/napari/_qt/qt_viewer.py
index f540036cd66..3b89e43bd80 100644
--- a/napari/_qt/qt_viewer.py
+++ b/napari/_qt/qt_viewer.py
@@ -21,6 +21,7 @@
 )
 from weakref import WeakSet, ref
 
+import numpy as np
 from qtpy.QtCore import QCoreApplication, QObject, Qt, QUrl
 from qtpy.QtGui import QGuiApplication
 from qtpy.QtWidgets import QFileDialog, QSplitter, QVBoxLayout, QWidget
@@ -784,7 +785,7 @@ def _screenshot(self, flash=True):
             add_flash_animation(self._welcome_widget)
         return img
 
-    def screenshot(self, path=None, flash=True):
+    def screenshot(self, path=None, flash=True) -> np.ndarray:
         """Take currently displayed screen and convert to an image array.
 
         Parameters
diff --git a/napari/_vispy/layers/labels.py b/napari/_vispy/layers/labels.py
index 726770e3a32..f04bf480f69 100644
--- a/napari/_vispy/layers/labels.py
+++ b/napari/_vispy/layers/labels.py
@@ -337,6 +337,7 @@ def _setup_nodes(self, texture_format):
             ),
             clim=[0, 2**23 - 1],
             texture_format=texture_format,
+            interpolation='nearest',
         )
 
     def get_node(self, ndisplay: int, dtype=None) -> Node: