Update allowed input types for stretch and cuts (astropy#44)

* Update allowed input types for stretch and cuts

* Remove autocut_options and stretch_options

* Change cuts/stretch from properties to set/get methods

Author: mwcraig

src/astro_image_display_api/dummy_viewer.py

@@ -8,6 +8,7 @@
 from astropy.table import Table, vstack
 from astropy.units import Quantity, get_physical_type
 from astropy.wcs import WCS
+from astropy.visualization import AsymmetricPercentileInterval, BaseInterval, BaseStretch, LinearStretch, ManualInterval
 from numpy.typing import ArrayLike
 
 from .interface_definition import ImageViewerInterface
@@ -25,12 +26,10 @@ class ImageViewer:
     image_width: int = 0
     image_height: int = 0
     zoom_level: float = 1
-    stretch_options: tuple = ("linear", "log", "sqrt")
-    autocut_options: tuple = ("minmax", "zscale", "asinh", "percentile", "histogram")
     _cursor: str = ImageViewerInterface.ALLOWED_CURSOR_LOCATIONS[0]
     marker: Any = "marker"
-    _cuts: str | tuple[float, float] = (0, 1)
-    _stretch: str = "linear"
+    _cuts: BaseInterval | tuple[float, float] = AsymmetricPercentileInterval(upper_percentile=95)
+    _stretch: BaseStretch = LinearStretch
     # viewer: Any
 
     # Allowed locations for cursor display
@@ -49,32 +48,24 @@ class ImageViewer:
     _wcs: WCS | None = None
     _center: tuple[float, float] = (0.0, 0.0)
 
-    @property
-    def stretch(self) -> str:
+    def get_stretch(self) -> BaseStretch:
         return self._stretch
 
-    @stretch.setter
-    def stretch(self, value: str) -> None:
-        if value not in self.stretch_options:
-            raise ValueError(f"Stretch option {value} is not valid. Must be one of {self.stretch_options}.")
+    def set_stretch(self, value: BaseStretch) -> None:
+        if not isinstance(value, BaseStretch):
+            raise ValueError(f"Stretch option {value} is not valid. Must be an Astropy.visualization Stretch object.")
         self._stretch = value
 
-    @property
-    def cuts(self) -> tuple:
+    def get_cuts(self) -> tuple:
         return self._cuts
 
-    @cuts.setter
-    def cuts(self, value: tuple) -> None:
-        if isinstance(value, str):
-            if value not in self.autocut_options:
-                raise ValueError(f"Cut option {value} is not valid. Must be one of {self.autocut_options}.")
-            # A real viewer would calculate the cuts based on the data
-            self._cuts = (0, 1)
-            return
-
-        if len(value) != 2:
-            raise ValueError("Cuts must have length 2.")
-        self._cuts = value
+    def set_cuts(self, value: tuple[float, float] | BaseInterval) -> None:
+        if isinstance(value, tuple) and len(value) == 2:
+            self._cuts = ManualInterval(value[0], value[1])
+        elif isinstance(value, BaseInterval):
+            self._cuts = value
+        else:
+            raise ValueError("Cuts must be an Astropy.visualization Interval object or a tuple of two values.")
 
     @property
     def cursor(self) -> str:

src/astro_image_display_api/interface_definition.py

@@ -6,6 +6,7 @@
 from astropy.nddata import NDData
 from astropy.table import Table
 from astropy.units import Quantity
+from astropy.visualization import BaseInterval, BaseStretch
 
 from numpy.typing import ArrayLike
 
@@ -30,13 +31,8 @@ class ImageViewerInterface(Protocol):
     image_width: int
     image_height: int
     zoom_level: float
-    stretch_options: tuple
-    autocut_options: tuple
     cursor: str
     marker: Any
-    cuts: Any
-    stretch: str
-    # viewer: Any
 
     # Allowed locations for cursor display
     ALLOWED_CURSOR_LOCATIONS: tuple = ALLOWED_CURSOR_LOCATIONS
@@ -65,6 +61,58 @@ def load_image(self, data: Any) -> None:
         """
         raise NotImplementedError
 
+    # Setting and getting image properties
+    @abstractmethod
+    def set_cuts(self, cuts: tuple | BaseInterval) -> None:
+        """
+        Set the cuts for the image.
+
+        Parameters
+        ----------
+        cuts : tuple or any Interval from `astropy.visualization`
+            The cuts to set. If a tuple, it should be of the form
+            ``(min, max)`` and will be interpreted as a
+            `~astropy.visualization.ManualInterval`.
+        """
+        raise NotImplementedError
+
+    @abstractmethod
+    def get_cuts(self) -> BaseInterval:
+        """
+        Get the current cuts for the image.
+
+        Returns
+        -------
+        cuts : `~astropy.visualization.BaseInterval`
+            The Astropy interval object representing the current cuts.
+        """
+        raise NotImplementedError
+
+    @abstractmethod
+    def set_stretch(self, stretch: BaseStretch) -> None:
+        """
+        Set the stretch for the image.
+
+        Parameters
+        ----------
+        stretch : Any stretch from `~astropy.visualization`
+            The stretch to set. This can be any subclass of
+            `~astropy.visualization.BaseStretch`.
+        """
+        raise NotImplementedError
+
+    @abstractmethod
+    def get_stretch(self) -> BaseStretch:
+        """
+        Get the current stretch for the image.
+
+        Returns
+        -------
+        stretch : `~astropy.visualization.BaseStretch`
+            The Astropy stretch object representing the current stretch.
+        """
+        raise NotImplementedError
+
     # Saving contents of the view and accessing the view
     @abstractmethod
     def save(self, filename: str | os.PathLike, overwrite: bool = False) -> None:

src/astro_image_display_api/widget_api_test.py

@@ -9,6 +9,7 @@
 from astropy.table import Table, vstack  # noqa: E402
 from astropy import units as u  # noqa: E402
 from astropy.wcs import WCS  # noqa: E402
+from astropy.visualization import AsymmetricPercentileInterval, LogStretch, ManualInterval
 
 __all__ = ['ImageWidgetAPITest']
 
@@ -268,37 +269,34 @@ def test_adding_markers_as_world(self, data, wcs):
                                    mark_coord_table['coord'].dec.deg)
 
     def test_stretch(self):
-        # Check that the stretch options is not an empty list
-        assert len(self.image.stretch_options) > 0
+        original_stretch = self.image.get_stretch()
 
-        original_stretch = self.image.stretch
-
-        with pytest.raises(ValueError, match='[mM]ust be one of'):
-            self.image.stretch = 'not a valid value'
+        with pytest.raises(ValueError, match=r'Stretch.*not valid.*'):
+            self.image.set_stretch('not a valid value')
 
         # A bad value should leave the stretch unchanged
-        assert self.image.stretch is original_stretch
+        assert self.image.get_stretch() is original_stretch
 
-        self.image.stretch = 'log'
+        self.image.set_stretch(LogStretch())
         # A valid value should change the stretch
-        assert self.image.stretch is not original_stretch
+        assert self.image.get_stretch() is not original_stretch
+        assert isinstance(self.image.get_stretch(), LogStretch)
 
     def test_cuts(self, data):
-        with pytest.raises(ValueError, match='[mM]ust be one of'):
-            self.image.cuts = 'not a valid value'
-
-        with pytest.raises(ValueError, match='must have length 2'):
-            self.image.cuts = (1, 10, 100)
+        with pytest.raises(ValueError, match='[mM]ust be'):
+            self.image.set_cuts('not a valid value')
 
-        assert 'histogram' in self.image.autocut_options
+        with pytest.raises(ValueError, match='[mM]ust be'):
+            self.image.set_cuts((1, 10, 100))
 
         # Setting using histogram requires data
         self.image.load_image(data)
-        self.image.cuts = 'histogram'
-        assert len(self.image.cuts) == 2
+        self.image.set_cuts(AsymmetricPercentileInterval(0.1, 99.9))
+        assert isinstance(self.image.get_cuts(), AsymmetricPercentileInterval)
 
-        self.image.cuts = (10, 100)
-        assert self.image.cuts == (10, 100)
+        self.image.set_cuts((10, 100))
+        assert isinstance(self.image.get_cuts(), ManualInterval)
+        assert self.image.get_cuts().get_limits(data) == (10, 100)
 
     @pytest.mark.skip(reason="Not clear whether colormap is part of the API")
     def test_colormap(self):