Add get_image and get_image_label

src/astro_image_display_api/api_test.py

@@ -797,3 +797,28 @@ def test_save_overwrite(self, tmp_path):
 
         # Using overwrite should save successfully
         self.image.save(filename, overwrite=True)
+
+    def test_get_image_labels(self, data):
+        # the test viewer begins with a default empty image
+        assert len(self.image.get_image_labels()) == 1
+        assert self.image.get_image_labels()[0] is None
+        assert isinstance(self.image.get_image_labels(), tuple)
+
+        self.image.load_image(data, image_label="test")
+        assert len(self.image.get_image_labels()) == 2
+        assert self.image.get_image_labels()[-1] == "test"
+
+    def test_get_image(self, data):
+        self.image.load_image(data, image_label="test")
+
+        # currently the type is not specified in the API
+        assert self.image.get_image() is not None
+        assert self.image.get_image(image_label="test") is not None
+
+        retrieved_image = self.image.get_image(image_label="test")
+
+        self.image.load_image(retrieved_image, image_label="another test")
+        assert self.image.get_image(image_label="another test") is not None
+
+        with pytest.raises(ValueError, match="[Ii]mage label.*not found"):
+            self.image.get_image(image_label="not a valid label")

src/astro_image_display_api/image_viewer_logic.py

@@ -50,6 +50,7 @@ class ViewportInfo:
     stretch: BaseStretch | None = None
     cuts: BaseInterval | tuple[numbers.Real, numbers.Real] | None = None
     colormap: str | None = None
+    data: ArrayLike | NDData | CCDData | None = None
 
 
 @dataclass
@@ -332,6 +333,17 @@ def load_image(
         # working with the new image.
         self._wcs = self._images[image_label].wcs
 
+    def get_image(self, image_label: str | None = None):
+        image_label = self._resolve_image_label(image_label)
+        if image_label not in self._images:
+            raise ValueError(
+                f"Image label '{image_label}' not found. Please load an image first."
+            )
+        return self._images[image_label].data
+
+    def get_image_labels(self):
+        return tuple(self._images.keys())
+
     def _determine_largest_dimension(self, shape: tuple[int, int]) -> int:
         """
         Determine which index is the largest dimension.
@@ -401,6 +413,7 @@ def _initialize_image_viewport_stretch_cuts(
     def _load_fits(self, file: str | os.PathLike, image_label: str | None) -> None:
         ccd = CCDData.read(file)
         self._images[image_label].wcs = ccd.wcs
+        self._images[image_label].data = ccd
         self._initialize_image_viewport_stretch_cuts(ccd.data, image_label)
 
     def _load_array(self, array: ArrayLike, image_label: str | None) -> None:
@@ -416,6 +429,7 @@ def _load_array(self, array: ArrayLike, image_label: str | None) -> None:
         self._images[image_label].largest_dimension = self._determine_largest_dimension(
             array.shape
         )
+        self._images[image_label].data = array
         self._initialize_image_viewport_stretch_cuts(array, image_label)
 
     def _load_nddata(self, data: NDData, image_label: str | None) -> None:
@@ -428,6 +442,7 @@ def _load_nddata(self, data: NDData, image_label: str | None) -> None:
             The NDData object to load.
         """
         self._images[image_label].wcs = data.wcs
+        self._images[image_label].data = data
         self._images[image_label].largest_dimension = self._determine_largest_dimension(
             data.data.shape
         )

src/astro_image_display_api/interface_definition.py

@@ -48,6 +48,50 @@ def load_image(self, data: Any, image_label: str | None = None) -> None:
         raise NotImplementedError
 
     # Setting and getting image properties
+    @abstractmethod
+    def get_image(
+        self,
+        image_label: str | None = None,
+    ) -> Any:
+        """
+        Parameters
+        ----------
+        image_label : optional
+            The label of the image to set the cuts for. If not given and there is
+            only one image loaded, that image is returned.
+
+        Returns
+        -------
+        image_data : Any
+            The data of the loaded image. The exact type of the data is not specified,
+            and different backends may return different types. A return type compatible
+            with `astropy.nddata.NDData` is preferred, but not required. It is expected
+            that the returned data can be re-loaded into the viewer using
+            `load_image`, however.
+
+        Raises
+        ------
+        ValueError
+            If the `image_label` is not provided when there are multiple images loaded,
+            or if the `image_label` does not correspond to a loaded image.
+
+        """
+        raise NotImplementedError
+
+    @abstractmethod
+    def get_image_labels(
+        self,
+    ) -> tuple[str]:
+        """
+        Get the labels of the loaded images.
+
+        Returns
+        -------
+        image_labels: tuple of str
+            The labels of the loaded images.
+        """
+        raise NotImplementedError
+
     @abstractmethod
     def set_cuts(
         self,