covert shape-getting to method

src/astro_image_display_api/api_test.py

@@ -43,14 +43,17 @@ def wcs(self):
         return w
 
     @pytest.fixture
-    def catalog(self, wcs: WCS) -> Table:
+    def catalog(self, wcs: WCS, data: np.ndarray) -> Table:
         """
         A catalog fixture that returns an empty table with the
         expected columns.
         """
+        self.image.load_image(NDData(data=data, wcs=wcs))
+
         rng = np.random.default_rng(45328975)
-        x = rng.uniform(0, self.image.image_width, size=10)
-        y = rng.uniform(0, self.image.image_height, size=10)
+
+        x = rng.uniform(0, self.image.get_shape().width, size=10)
+        y = rng.uniform(0, self.image.get_shape().height, size=10)
         coord = wcs.pixel_to_world(x, y)
 
         cat = Table(
@@ -70,7 +73,7 @@ def setup(self):
         Subclasses MUST define ``image_widget_class`` -- doing so as a
         class variable does the trick.
         """
-        self.image = self.image_widget_class(image_width=250, image_height=100)
+        self.image = self.image_widget_class()
 
     def _assert_empty_catalog_table(self, table):
         assert isinstance(table, Table)
@@ -81,16 +84,10 @@ def _get_catalog_names_as_set(self):
         marks = self.image.get_catalog_names()
         return set(marks)
 
-    def test_width_height(self):
-        assert self.image.image_width == 250
-        assert self.image.image_height == 100
-
-        width = 200
-        height = 300
-        self.image.image_width = width
-        self.image.image_height = height
-        assert self.image.image_width == width
-        assert self.image.image_height == height
+    def test_width_height(self, data: np.ndarray):
+        self.image.load_image(NDData(data=data))
+        assert self.image.get_shape().width == 150
+        assert self.image.get_shape().height == 100
 
     @pytest.mark.parametrize("load_type", ["fits", "nddata", "array"])
     def test_load(self, data, tmp_path, load_type):

src/astro_image_display_api/image_viewer_logic.py

@@ -22,7 +22,7 @@
 from astropy.wcs.utils import proj_plane_pixel_scales
 from numpy.typing import ArrayLike
 
-from .interface_definition import ImageViewerInterface
+from .interface_definition import ImageViewerInterface, ImageShape
 
 
 @dataclass
@@ -48,6 +48,8 @@ class ViewportInfo:
     stretch: BaseStretch | None = None
     cuts: BaseInterval | tuple[numbers.Real, numbers.Real] | None = None
     colormap: str | None = None
+    image_width: int | None = None
+    image_height: int | None = None
 
 
 @dataclass
@@ -60,8 +62,6 @@ class ImageViewerLogic:
     # These are attributes, not methods. The type annotations are there
     # to make sure Protocol knows they are attributes. Python does not
     # do any checking at all of these types.
-    image_width: int = 0
-    image_height: int = 0
     zoom_level: float = 1
     _cuts: BaseInterval | tuple[float, float] = AsymmetricPercentileInterval(
         upper_percentile=95
@@ -198,6 +198,37 @@ def get_colormap(self, image_label: str | None = None) -> str:
 
     # The methods, grouped loosely by purpose
 
+
+    def get_shape(self, image_label: str | None = None) -> ImageShape:
+        """
+        Get the shape (i.e., width and height in pixels) of the image.
+
+        Parameters
+        ----------
+        image_label : optional
+            The label of the image to get the shape for. If not given and there is
+            only one image loaded, the shape for that image is returned. If there are
+            multiple images and no label is provided, an error is raised.
+
+        Returns
+        -------
+        shape : `ImageShape`, a 2-tuple of ints
+            A named tuple containing the width and height of the image in pixels. 
+
+        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.
+        """
+        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."
+            )
+        img = self._images[image_label]
+        return ImageShape(img.image_width, img.image_height)
+
     def get_catalog_style(self, catalog_label=None) -> dict[str, Any]:
         """
         Get the style for the catalog.
@@ -370,6 +401,9 @@ def _initialize_image_viewport_stretch_cuts(
 
         # Deal with the viewport first
         height, width = image_data.shape
+        self._images[image_label].image_width = width
+        self._images[image_label].image_height = height
+
         # Center the image in the viewport and show the whole image.
         center = (width / 2, height / 2)
         fov = max(image_data.shape)

src/astro_image_display_api/interface_definition.py

@@ -2,6 +2,7 @@
 import os
 from abc import abstractmethod
 from typing import Any, Protocol, runtime_checkable
+from collections import namedtuple
 
 from astropy.coordinates import SkyCoord
 from astropy.table import Table
@@ -10,17 +11,13 @@
 
 __all__ = [
     "ImageViewerInterface",
+    "ImageShape",
 ]
 
+ImageShape = namedtuple("ImageShape", ["width", "height"])
 
 @runtime_checkable
 class ImageViewerInterface(Protocol):
-    # These are attributes, not methods. The type annotations are there
-    # to make sure Protocol knows they are attributes. Python does not
-    # do any checking at all of these types.
-    image_width: int
-    image_height: int
-
     # The methods, grouped loosely by purpose
 
     # Method for loading image data
@@ -201,6 +198,31 @@ def get_colormap(self, image_label: str | None = None) -> str:
         """
         raise NotImplementedError
 
+    @abstractmethod
+    def get_shape(self, image_label: str | None = None) -> ImageShape:
+        """
+        Get the shape (i.e., width and height in pixels) of the image.
+
+        Parameters
+        ----------
+        image_label : optional
+            The label of the image to get the shape for. If not given and there is
+            only one image loaded, the shape for that image is returned. If there are
+            multiple images and no label is provided, an error is raised.
+
+        Returns
+        -------
+        shape : `ImageShape`, a 2-tuple of ints
+            A named tuple containing the width and height of the image in pixels. 
+
+        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
+
     # Saving contents of the view and accessing the view
     @abstractmethod
     def save(self, filename: str | os.PathLike, overwrite: bool = False) -> None: