Add hilbert_pixels_from_pixel_scale to model_util

autogalaxy/analysis/model_util.py

@@ -204,6 +204,39 @@ def mge_point_model_from(
     return af.Model(Basis, profile_list=gaussian_list)
 
 
+def hilbert_pixels_from_pixel_scale(pixel_scale: float) -> int:
+    """
+    Return the number of Hilbert-curve pixels appropriate for a given image pixel scale.
+
+    The Hilbert pixel count controls the resolution of the Hilbert-curve ordering used
+    in adaptive source-plane pixelizations. Finer pixel scales resolve smaller angular
+    features and therefore benefit from a higher Hilbert resolution.
+
+    Parameters
+    ----------
+    pixel_scale
+        The pixel scale of the image in arcseconds per pixel.
+
+    Returns
+    -------
+    int
+        The recommended number of Hilbert pixels.
+    """
+    if not np.isfinite(pixel_scale) or pixel_scale <= 0:
+        raise ValueError(
+            f"hilbert_pixels_from_pixel_scale requires pixel_scale to be finite and > 0, got {pixel_scale}."
+        )
+
+    if pixel_scale > 0.06:
+        return 1000
+    elif pixel_scale > 0.04:
+        return 1250
+    elif pixel_scale >= 0.03:
+        return 1500
+    else:
+        return 1750
+
+
 def simulator_start_here_model_from():
 
     from autogalaxy.profiles.light.snr import Sersic

test_autogalaxy/analysis/test_model_util.py

@@ -58,6 +58,48 @@ def test__mge_point_model_from__shared_centre_and_ell_comps():
     assert model.prior_count == 4
 
 
+def test__hilbert_pixels_from_pixel_scale__above_006():
+    assert ag.model_util.hilbert_pixels_from_pixel_scale(0.07) == 1000
+    assert ag.model_util.hilbert_pixels_from_pixel_scale(0.1) == 1000
+
+
+def test__hilbert_pixels_from_pixel_scale__between_004_and_006():
+    assert ag.model_util.hilbert_pixels_from_pixel_scale(0.05) == 1250
+    assert ag.model_util.hilbert_pixels_from_pixel_scale(0.061) == 1000
+    assert ag.model_util.hilbert_pixels_from_pixel_scale(0.041) == 1250
+
+
+def test__hilbert_pixels_from_pixel_scale__between_003_and_004():
+    assert ag.model_util.hilbert_pixels_from_pixel_scale(0.03) == 1500
+    assert ag.model_util.hilbert_pixels_from_pixel_scale(0.035) == 1500
+
+
+def test__hilbert_pixels_from_pixel_scale__below_003():
+    assert ag.model_util.hilbert_pixels_from_pixel_scale(0.02) == 1750
+    assert ag.model_util.hilbert_pixels_from_pixel_scale(0.01) == 1750
+
+
+def test__hilbert_pixels_from_pixel_scale__raises_for_non_positive():
+    with pytest.raises(ValueError):
+        ag.model_util.hilbert_pixels_from_pixel_scale(0.0)
+    with pytest.raises(ValueError):
+        ag.model_util.hilbert_pixels_from_pixel_scale(-0.05)
+
+
+def test__hilbert_pixels_from_pixel_scale__raises_for_non_finite():
+    with pytest.raises(ValueError):
+        ag.model_util.hilbert_pixels_from_pixel_scale(float("nan"))
+    with pytest.raises(ValueError):
+        ag.model_util.hilbert_pixels_from_pixel_scale(float("inf"))
+
+
+def test__hilbert_pixels_from_pixel_scale__boundary_values():
+    # Exactly 0.06 is NOT > 0.06, so falls to next branch (> 0.04 → 1250)
+    assert ag.model_util.hilbert_pixels_from_pixel_scale(0.06) == 1250
+    # Exactly 0.04 is NOT > 0.04, but IS >= 0.03 → 1500
+    assert ag.model_util.hilbert_pixels_from_pixel_scale(0.04) == 1500
+
+
 def test__mge_point_model_from__centre_prior_bounds():
     """
     When a custom centre is supplied the UniformPrior limits shift by ±0.1