From dfe62a30c89d1a3f34da4584ab1492fb0d25d70c Mon Sep 17 00:00:00 2001
From: Thomas MALLET <t.mallet@codra.fr>
Date: Thu, 4 Jun 2026 16:45:32 +0200
Subject: [PATCH 1/4] fix sign after regression

---
 sigima/tools/coordinates.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/sigima/tools/coordinates.py b/sigima/tools/coordinates.py
index 1e1d160d..17886e17 100644
--- a/sigima/tools/coordinates.py
+++ b/sigima/tools/coordinates.py
@@ -98,7 +98,7 @@ def ellipse_to_diameters(
         Ellipse X/Y diameters (major/minor axes) coordinates
     """
     dxa, dya = a * np.cos(theta), a * np.sin(theta)
-    dxb, dyb = -b * np.sin(theta), b * np.cos(theta)
+    dxb, dyb = b * np.sin(theta), b * np.cos(theta)
     x0, y0, x1, y1 = xc - dxa, yc - dya, xc + dxa, yc + dya
     x2, y2, x3, y3 = xc - dxb, yc - dyb, xc + dxb, yc + dyb
     return x0, y0, x1, y1, x2, y2, x3, y3
@@ -117,7 +117,7 @@ def array_ellipse_to_diameters(data: np.ndarray) -> np.ndarray:
     """
     xc, yc, a, b, theta = data[:, 0], data[:, 1], data[:, 2], data[:, 3], data[:, 4]
     dxa, dya = a * np.cos(theta), a * np.sin(theta)
-    dxb, dyb = -b * np.sin(theta), b * np.cos(theta)
+    dxb, dyb = b * np.sin(theta), b * np.cos(theta)
     x0, y0, x1, y1 = xc - dxa, yc - dya, xc + dxa, yc + dya
     x2, y2, x3, y3 = xc - dxb, yc - dyb, xc + dxb, yc + dyb
     result = np.column_stack((x0, y0, x1, y1, x2, y2, x3, y3)).astype(float)

From 8e04e39cd876caaa5af4a29f2af52bd67e80cdf4 Mon Sep 17 00:00:00 2001
From: Thomas MALLET <t.mallet@codra.fr>
Date: Thu, 4 Jun 2026 17:27:39 +0200
Subject: [PATCH 2/4] fadd dedicated test with computed ground truth for circle
 and ellipse contour detection

---
 .../image/preprocessing_tools_unit_test.py    | 43 +++++++++++++++++++
 1 file changed, 43 insertions(+)

diff --git a/sigima/tests/image/preprocessing_tools_unit_test.py b/sigima/tests/image/preprocessing_tools_unit_test.py
index 220adf00..c1c19fe5 100644
--- a/sigima/tests/image/preprocessing_tools_unit_test.py
+++ b/sigima/tests/image/preprocessing_tools_unit_test.py
@@ -84,6 +84,49 @@ def test_fit_ellipse_model_failure() -> None:
     assert result is None or isinstance(result, tuple)
 
 
+def test_fit_circle_model_ground_truth() -> None:
+    """Verify that ``fit_circle_model`` recovers **all** circle parameters
+    (xc, yc, radius) from a noise-free contour.
+
+    Note: the functions swap x/y because scikit-image models interpret the
+    contour columns as (row, col), so the returned ``xc`` corresponds to the
+    contour's second column and ``yc`` to the first.
+    """
+    xc_in, yc_in, r_in = 7.0, -5.0, 12.0
+    contour = _circle_contour(xc_in, yc_in, r_in, n=256)
+    result = fit_circle_model(contour)
+    assert result is not None
+    # xc/yc are swapped by the row/col → x/y conversion
+    yc, xc, r = result
+    assert xc == pytest.approx(xc_in, abs=1e-6)
+    assert yc == pytest.approx(yc_in, abs=1e-6)
+    assert r == pytest.approx(r_in, abs=1e-6)
+
+
+def test_fit_ellipse_model_ground_truth() -> None:
+    """Verify that ``fit_ellipse_model`` recovers **all** ellipse parameters
+    (xc, yc, a, b, theta) from a noise-free contour.
+
+    Note: the functions swap x/y and a/b because scikit-image models interpret
+    the contour columns as (row, col), so centre and semi-axes are transposed.
+    """
+    xc_in, yc_in = -3.0, 5.0
+    a_in, b_in = 4.0, 8.0
+    theta_in = np.pi / 6
+    contour = _ellipse_contour(xc_in, yc_in, a_in, b_in, theta0=theta_in, n=256)
+    result = fit_ellipse_model(contour)
+    assert result is not None
+    # xc/yc are swapped by the row/col → x/y conversion
+    yc, xc, a, b, theta = result
+    assert xc == pytest.approx(xc_in, abs=1e-4)
+    assert yc == pytest.approx(yc_in, abs=1e-4)
+    assert a == pytest.approx(a_in, abs=1e-4)
+    assert b == pytest.approx(b_in, abs=1e-4)
+    # The fitted angle is expected to differ by π/2,
+    # theta along y axis instead of x axis
+    assert theta == pytest.approx(theta_in + np.pi / 2, abs=1e-4)
+
+
 # ===========================================================================
 # get_absolute_level
 # ===========================================================================

From 4caf11ccd82fb416d9989bfd6245009306654451 Mon Sep 17 00:00:00 2001
From: Thomas MALLET <t.mallet@codra.fr>
Date: Thu, 4 Jun 2026 17:56:48 +0200
Subject: [PATCH 3/4] prevent test to run with scikit-image < v0.26

---
 sigima/tests/image/preprocessing_tools_unit_test.py | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/sigima/tests/image/preprocessing_tools_unit_test.py b/sigima/tests/image/preprocessing_tools_unit_test.py
index c1c19fe5..c3d43d66 100644
--- a/sigima/tests/image/preprocessing_tools_unit_test.py
+++ b/sigima/tests/image/preprocessing_tools_unit_test.py
@@ -11,6 +11,7 @@
 
 from sigima.enums import BinningOperation
 from sigima.tools.image.preprocessing import (
+    _USE_NEW_SHAPE_API,
     binning,
     distance_matrix,
     fit_circle_model,
@@ -92,6 +93,8 @@ def test_fit_circle_model_ground_truth() -> None:
     contour columns as (row, col), so the returned ``xc`` corresponds to the
     contour's second column and ``yc`` to the first.
     """
+    if not _USE_NEW_SHAPE_API:
+        pytest.skip()
     xc_in, yc_in, r_in = 7.0, -5.0, 12.0
     contour = _circle_contour(xc_in, yc_in, r_in, n=256)
     result = fit_circle_model(contour)
@@ -110,6 +113,8 @@ def test_fit_ellipse_model_ground_truth() -> None:
     Note: the functions swap x/y and a/b because scikit-image models interpret
     the contour columns as (row, col), so centre and semi-axes are transposed.
     """
+    if not _USE_NEW_SHAPE_API:
+        pytest.skip()
     xc_in, yc_in = -3.0, 5.0
     a_in, b_in = 4.0, 8.0
     theta_in = np.pi / 6

From fb7fdc0f443c30cd2ac081e097b41ca289f26dda Mon Sep 17 00:00:00 2001
From: Thomas MALLET <t.mallet@codra.fr>
Date: Thu, 4 Jun 2026 17:59:09 +0200
Subject: [PATCH 4/4] bump to v1.1.4 and update changelog

---
 doc/release_notes/release_1.01.md | 8 ++++++++
 sigima/__init__.py                | 2 +-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/doc/release_notes/release_1.01.md b/doc/release_notes/release_1.01.md
index 6cda14e5..7187dc8e 100644
--- a/doc/release_notes/release_1.01.md
+++ b/doc/release_notes/release_1.01.md
@@ -1,5 +1,13 @@
 # Version 1.1 #
 
+## Sigima Version 1.1.4 ##
+
+### 🛠️ Bug Fixes since version 1.1.3 ###
+
+* **Ellipse/circle contour detection**: Fixed regression in axis orientation after the v1.1.3 coordinate swap fix. This closes [Issue #27](https://github.com/DataLab-Platform/Sigima/issues/27).
+  * The sign correction applied in v1.1.3 for the `(row, col)` → `(x, y)` conversion introduced a regression in ellipse axis orientation, causing the semi-major and semi-minor axes to be transposed
+  * Added ground-truth unit tests for `fit_circle_model` and `fit_ellipse_model` verifying all output parameters (center coordinates, radius/semi-axes, and rotation angle)
+
 ## Sigima Version 1.1.3 ##
 
 ### 🛠️ Bug Fixes since version 1.1.2 ###
diff --git a/sigima/__init__.py b/sigima/__init__.py
index 0c466b49..7f2bbff9 100644
--- a/sigima/__init__.py
+++ b/sigima/__init__.py
@@ -144,7 +144,7 @@
 # Set validation mode to ENABLED by default (issue warnings for invalid inputs)
 set_validation_mode(ValidationMode.ENABLED)
 
-__version__ = "1.1.3"
+__version__ = "1.1.4"
 __docurl__ = "https://sigima.readthedocs.io/"
 __homeurl__ = "https://github.com/DataLab-Platform/Sigima"
 __supporturl__ = "https://github.com/DataLab-Platform/sigima/issues/new/choose"