From fff671cdd28c85a555ee9fc0b7dd6f4bad4eccc9 Mon Sep 17 00:00:00 2001
From: Peter Corke <peter.i.corke@gmail.com>
Date: Sun, 16 Aug 2026 09:01:23 +1000
Subject: [PATCH] fix: PointCloud.Read() double-joins a caller-supplied "data/"
 prefix

Read() hardcodes "data" as the mvtbdata subfolder via
mvtb_path_to_datafile("data", filename) -- the documented convention is
that callers pass a bare filename (PointCloud.Read('bunny.ply')). But
both of the book's own figure-generation scripts
(figures/code/chapter14/fig14_43.py, fig14_44.py) call
PointCloud.Read('data/bunny.ply') with a redundant "data/" prefix, a
convention that predates mvtb_path_to_datafile's current auto-prefixing
design. That redundant prefix made the lookup search for
mvtbdata/data/data/bunny.ply, which doesn't exist, even though
mvtbdata/data/bunny.ply is genuinely present in the package.

Strip a leading "data" path component before joining, so both
PointCloud.Read('bunny.ply') and PointCloud.Read('data/bunny.ply')
resolve to the same file.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
---
 src/machinevisiontoolbox/PointCloud.py | 13 +++++++++++++
 tests/test_pointcloud.py               | 12 ++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/src/machinevisiontoolbox/PointCloud.py b/src/machinevisiontoolbox/PointCloud.py
index 8611e5df..14305878 100644
--- a/src/machinevisiontoolbox/PointCloud.py
+++ b/src/machinevisiontoolbox/PointCloud.py
@@ -2,6 +2,7 @@
 Thin wrapper around Open3D point-cloud objects with MVTB look and feel.
 """
 
+from pathlib import Path
 from warnings import warn
 from typing import Any, Callable
 
@@ -244,10 +245,22 @@ def Read(cls, filename: str, *args: Any, **kwargs: Any) -> "PointCloud":
         the ``data`` folder of the
         `mvtb_data package <https://github.com/petercorke/machinevision-toolbox-python/tree/master/packages/mvtb-data>`_.
 
+        .. note:: ``filename`` may be given as a bare name (``'bunny.ply'``)
+            or with a redundant leading ``data/`` (``'data/bunny.ply'``, the
+            older convention some book examples still use) -- both resolve
+            to the same file.
+
         """
 
         from machinevisiontoolbox import mvtb_path_to_datafile
 
+        # accept a caller-supplied redundant "data/" prefix (older
+        # convention) without double-joining it against the "data" this
+        # method already prepends
+        parts = Path(filename).parts
+        if parts and parts[0] == "data":
+            filename = str(Path(*parts[1:])) if len(parts) > 1 else ""
+
         filename = mvtb_path_to_datafile("data", filename, string=True)
         pcd = o3d.io.read_point_cloud(filename, *args, **kwargs)
         return cls(pcd)
diff --git a/tests/test_pointcloud.py b/tests/test_pointcloud.py
index 84bae3f1..410acc65 100644
--- a/tests/test_pointcloud.py
+++ b/tests/test_pointcloud.py
@@ -39,6 +39,18 @@ def test_constructor(self):
         rgbd = Image.Pstack((d, rgb.astype("uint16")), colororder="DRGB")
         pc = PointCloud.DepthImage(rgbd, camera)
 
+    def test_read(self):
+        # bare filename -- the documented convention
+        pc = PointCloud.Read("bunny.ply")
+        self.assertIsInstance(pc, PointCloud)
+        self.assertEqual(len(pc), 35947)
+
+        # a caller-supplied redundant "data/" prefix (the older convention
+        # some book examples still use) must resolve to the same file,
+        # not double-join to data/data/bunny.ply
+        pc2 = PointCloud.Read("data/bunny.ply")
+        self.assertEqual(len(pc2), len(pc))
+
 
 # ----------------------------------------------------------------------- #
 if __name__ == "__main__":