From ce1e50970fc629a18bc0ad91956acbceaecb3234 Mon Sep 17 00:00:00 2001
From: Sasha Mitchell <sash.t.mitchell@gmail.com>
Date: Tue, 29 Sep 2026 03:24:08 +0700
Subject: [PATCH] Round pixels before storing them as bytes.

tensor2img_fast of 0.5 stored 127. The other converter rounds that value to 128.
---
 basicsr/utils/img_util.py |  2 +-
 tests/test_img_util.py    | 38 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 39 insertions(+), 1 deletion(-)
 create mode 100644 tests/test_img_util.py

diff --git a/basicsr/utils/img_util.py b/basicsr/utils/img_util.py
index 3a5f1da09..97d794d64 100644
--- a/basicsr/utils/img_util.py
+++ b/basicsr/utils/img_util.py
@@ -105,7 +105,7 @@ def tensor2img_fast(tensor, rgb2bgr=True, min_max=(0, 1)):
     """
     output = tensor.squeeze(0).detach().clamp_(*min_max).permute(1, 2, 0)
     output = (output - min_max[0]) / (min_max[1] - min_max[0]) * 255
-    output = output.type(torch.uint8).cpu().numpy()
+    output = output.round().type(torch.uint8).cpu().numpy()
     if rgb2bgr:
         output = cv2.cvtColor(output, cv2.COLOR_RGB2BGR)
     return output
diff --git a/tests/test_img_util.py b/tests/test_img_util.py
new file mode 100644
index 000000000..15d75af95
--- /dev/null
+++ b/tests/test_img_util.py
@@ -0,0 +1,38 @@
+import importlib.util
+import sys
+import types
+import unittest
+from pathlib import Path
+
+import torch
+
+
+def _load_img_util():
+    if "torchvision.utils" not in sys.modules:
+        torchvision = types.ModuleType("torchvision")
+        utils = types.ModuleType("torchvision.utils")
+        utils.make_grid = lambda *args, **kwargs: None
+        torchvision.utils = utils
+        sys.modules["torchvision"] = torchvision
+        sys.modules["torchvision.utils"] = utils
+    path = Path(__file__).resolve().parents[1] / "basicsr" / "utils" / "img_util.py"
+    spec = importlib.util.spec_from_file_location("basicsr_img_util", path)
+    module = importlib.util.module_from_spec(spec)
+    spec.loader.exec_module(module)
+    return module
+
+
+img_util = _load_img_util()
+
+
+class TestTensor2ImgFast(unittest.TestCase):
+    def test_a_half_step_is_rounded(self):
+        pixel = torch.tensor([0.5, 0.0, 1.0]).view(1, 3, 1, 1)
+        image = img_util.tensor2img_fast(pixel, rgb2bgr=False)
+        self.assertEqual(int(image[0, 0, 0]), 128)
+        self.assertEqual(int(image[0, 0, 1]), 0)
+        self.assertEqual(int(image[0, 0, 2]), 255)
+
+
+if __name__ == "__main__":
+    unittest.main()