Imviz: Add zoom and zoom_level API

jdaviz/configs/imviz/helper.py

@@ -209,6 +209,80 @@ def offset_by(self, dx, dy):
                 viewer.state.x_max = viewer.state.x_min + width
                 viewer.state.y_max = viewer.state.y_min + height
 
+    @property
+    def zoom_level(self):
+        """Zoom level:
+
+        * 1 means real-pixel-size.
+        * 2 means zoomed in by a factor of 2.
+        * 0.5 means zoomed out by a factor of 2.
+        * 'fit' means zoomed to fit the whole image width into display.
+
+        """
+        viewer = self.app.get_viewer("viewer-1")
+        if viewer.shape is None:  # pragma: no cover
+            raise ValueError('Viewer is still loading, try again later')
+
+        screenx = viewer.shape[1]
+        screeny = viewer.shape[0]
+        zoom_x = screenx / (viewer.state.x_max - viewer.state.x_min)
+        zoom_y = screeny / (viewer.state.y_max - viewer.state.y_min)
+
+        return max(zoom_x, zoom_y)  # Similar to Ginga get_scale()
+
+    # Loosely based on glue/viewers/image/state.py
+    @zoom_level.setter
+    def zoom_level(self, val):
+        if ((not isinstance(val, (int, float)) and val != 'fit') or
+                (isinstance(val, (int, float)) and val <= 0)):
+            raise ValueError(f'Unsupported zoom level: {val}')
+
+        viewer = self.app.get_viewer("viewer-1")
+        image = viewer.state.reference_data
+        if (image is None or viewer.shape is None or
+                viewer.state.x_att is None or viewer.state.y_att is None):  # pragma: no cover
+            return
+
+        # Zoom on X and Y will auto-adjust.
+        if val == 'fit':
+            # Similar to ImageViewerState.reset_limits() in Glue.
+            new_x_min = 0
+            new_x_max = image.shape[viewer.state.x_att.axis]
+        else:
+            cur_xcen = (viewer.state.x_min + viewer.state.x_max) * 0.5
+            new_dx = viewer.shape[1] * 0.5 / val
+            new_x_min = cur_xcen - new_dx
+            new_x_max = cur_xcen + new_dx
+
+        with delay_callback(viewer.state, 'x_min', 'x_max'):
+            viewer.state.x_min = new_x_min - 0.5
+            viewer.state.x_max = new_x_max - 0.5
+
+        # We need to adjust the limits in here to avoid triggering all
+        # the update events then changing the limits again.
+        viewer.state._adjust_limits_aspect()
+
+    # Discussion on why we need two different ways to set zoom at
+    # https://github.com/astropy/astrowidgets/issues/144
+    def zoom(self, val):
+        """Zoom in or out by the given factor.
+
+        Parameters
+        ----------
+        val : int or float
+            The zoom level to zoom the image.
+            See `zoom_level`.
+
+        Raises
+        ------
+        ValueError
+            Invalid zoom factor.
+
+        """
+        if not isinstance(val, (int, float)):
+            raise ValueError(f"zoom only accepts int or float but got '{val}'")
+        self.zoom_level = self.zoom_level * val
+
     @property
     def marker(self):
         """Marker to use.

jdaviz/configs/imviz/tests/test_astrowidgets_api.py

@@ -65,6 +65,59 @@ def test_center_offset_sky(self):
             self.imviz.offset_by(dsky, dsky)
 
 
+class TestZoom(BaseImviz_WCS_NoWCS):
+
+    @pytest.mark.parametrize('val', (0, -0.1, 'foo', [1, 2]))
+    def test_invalid_zoom_level(self, val):
+        with pytest.raises(ValueError, match='Unsupported zoom level'):
+            self.imviz.zoom_level = val
+
+    def test_invalid_zoom(self):
+        with pytest.raises(ValueError, match='zoom only accepts int or float'):
+            self.imviz.zoom('fit')
+
+    def assert_zoom_results(self, zoom_level, x_min, x_max, y_min, y_max, dpix):
+        assert_allclose(self.imviz.zoom_level, zoom_level)
+        assert_allclose((self.viewer.state.x_min, self.viewer.state.x_max,
+                         self.viewer.state.y_min, self.viewer.state.y_max),
+                        (x_min + dpix, x_max + dpix,
+                         y_min + dpix, y_max + dpix))
+
+    @pytest.mark.parametrize('is_offcenter', (False, True))
+    def test_zoom(self, is_offcenter):
+        if is_offcenter:
+            self.imviz.center_on((0, 0))
+            dpix = -4.5
+        else:
+            self.imviz.center_on((4.5, 4.5))
+            dpix = 0
+
+        self.assert_zoom_results(10, -0.5, 9.5, -0.5, 9.5, dpix)
+
+        # NOTE: Not sure why X/Y min/max not exactly the same as aspect ratio 1
+        self.imviz.zoom_level = 1
+        self.assert_zoom_results(1, -46, 54, -45.5, 54.5, dpix)
+
+        self.imviz.zoom_level = 2
+        self.assert_zoom_results(2, -21.5, 28.5, -20.5, 29.5, dpix)
+
+        self.imviz.zoom(2)
+        self.assert_zoom_results(4, -9.5, 15.5, -8.0, 17.0, dpix)
+
+        self.imviz.zoom(0.5)
+        self.assert_zoom_results(2, -22.5, 27.5, -20.5, 29.5, dpix)
+
+        self.imviz.zoom_level = 0.5
+        self.assert_zoom_results(0.5, -98, 102, -95.5, 104.5, dpix)
+
+        # This fits the whole image on screen, regardless.
+        # NOTE: But somehow Y min/max auto-adjust does not work properly
+        # in the unit test when off-center. Works in notebook though.
+        if not is_offcenter:
+            self.imviz.zoom_level = 'fit'
+            self.assert_zoom_results(10, -0.5, 9.5, -0.5, 9.5, 0)
+
+
 class TestMarkers(BaseImviz_WCS_NoWCS):
 
     def test_invalid_markers(self):

jdaviz/configs/imviz/tests/utils.py

@@ -1,38 +1,42 @@
-import numpy as np
-import pytest
-from astropy.io import fits
-from astropy.wcs import WCS
-
-__all__ = ['BaseImviz_WCS_NoWCS']
-
-
-class BaseImviz_WCS_NoWCS:
-    @pytest.fixture(autouse=True)
-    def setup_class(self, imviz_app):
-        hdu = fits.ImageHDU(np.zeros((10, 10)), name='SCI')
-
-        # Apply some celestial WCS from
-        # https://learn.astropy.org/rst-tutorials/celestial_coords1.html
-        hdu.header.update({'CTYPE1': 'RA---TAN',
-                           'CUNIT1': 'deg',
-                           'CDELT1': -0.0002777777778,
-                           'CRPIX1': 1,
-                           'CRVAL1': 337.5202808,
-                           'NAXIS1': 10,
-                           'CTYPE2': 'DEC--TAN',
-                           'CUNIT2': 'deg',
-                           'CDELT2': 0.0002777777778,
-                           'CRPIX2': 1,
-                           'CRVAL2': -20.833333059999998,
-                           'NAXIS2': 10})
-
-        # Data with WCS
-        imviz_app.load_data(hdu, data_label='has_wcs')
-
-        # Data without WCS
-        imviz_app.load_data(hdu, data_label='no_wcs')
-        imviz_app.app.data_collection[1].coords = None
-
-        self.wcs = WCS(hdu.header)
-        self.imviz = imviz_app
-        self.viewer = imviz_app.app.get_viewer('viewer-1')
+import numpy as np
+import pytest
+from astropy.io import fits
+from astropy.wcs import WCS
+
+__all__ = ['BaseImviz_WCS_NoWCS']
+
+
+class BaseImviz_WCS_NoWCS:
+    @pytest.fixture(autouse=True)
+    def setup_class(self, imviz_app):
+        hdu = fits.ImageHDU(np.zeros((10, 10)), name='SCI')
+
+        # Apply some celestial WCS from
+        # https://learn.astropy.org/rst-tutorials/celestial_coords1.html
+        hdu.header.update({'CTYPE1': 'RA---TAN',
+                           'CUNIT1': 'deg',
+                           'CDELT1': -0.0002777777778,
+                           'CRPIX1': 1,
+                           'CRVAL1': 337.5202808,
+                           'NAXIS1': 10,
+                           'CTYPE2': 'DEC--TAN',
+                           'CUNIT2': 'deg',
+                           'CDELT2': 0.0002777777778,
+                           'CRPIX2': 1,
+                           'CRVAL2': -20.833333059999998,
+                           'NAXIS2': 10})
+
+        # Data with WCS
+        imviz_app.load_data(hdu, data_label='has_wcs')
+
+        # Data without WCS
+        imviz_app.load_data(hdu, data_label='no_wcs')
+        imviz_app.app.data_collection[1].coords = None
+
+        self.wcs = WCS(hdu.header)
+        self.imviz = imviz_app
+        self.viewer = imviz_app.app.get_viewer('viewer-1')
+
+        # Since we are not really displaying, need this to test zoom.
+        self.viewer.shape = (100, 100)
+        self.viewer.state._set_axes_aspect_ratio(1)

notebooks/ImvizExample.ipynb

@@ -387,6 +387,54 @@
     "imviz.offset_by(0.5 * u.arcsec, -1.5 * u.arcsec)"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "id": "e2744c0c-8721-480a-811e-87904373e66f",
+   "metadata": {},
+   "source": [
+    "You can programmatically zoom in and out.\n",
+    "\n",
+    "Zoom level:\n",
+    "\n",
+    "* 1 means real-pixel-size.\n",
+    "* 2 means zoomed in by a factor of 2.\n",
+    "* 0.5 means zoomed out by a factor of 2.\n",
+    "* 'fit' means zoomed to fit the whole image width into display."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "1bad9bdf-b959-4b74-9a77-07212095c2ce",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "# Get the current zoom level.\n",
+    "imviz.zoom_level"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "7a834bcf-7d5a-492b-bc54-740e1500a2f4",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "# Set the zoom level directly.\n",
+    "imviz.zoom_level = 1"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "32288b81-1817-4549-b2e4-5e7f55b0ee3d",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "# Set the relative zoom based on current zoom level.\n",
+    "imviz.zoom(2)"
+   ]
+  },
   {
    "cell_type": "markdown",
    "id": "11fab067-7428-4ce4-bc9b-f5462fe52e2a",