New offset_by with new API

astrowidgets/core.py

@@ -6,9 +6,11 @@
 
 # THIRD-PARTY
 import numpy as np
+from astropy import units as u
 from astropy.coordinates import SkyCoord
 from astropy.io import fits
 from astropy.table import Table, vstack
+from astropy.utils.decorators import deprecated
 
 # Jupyter widgets
 import ipywidgets as ipyw
@@ -343,11 +345,14 @@ def center_on(self, point):
         else:
             self._viewer.set_pan(*(np.asarray(point) - self._pixel_offset))
 
+    @deprecated('0.3', alternative='offset_by')
     def offset_to(self, dx, dy, skycoord_offset=False):
         """
         Move the center to a point that is given offset
         away from the current center.
 
+        .. note:: This is deprecated. Use :meth:`offset_by`.
+
         Parameters
         ----------
         dx, dy : float
@@ -367,6 +372,28 @@ def offset_to(self, dx, dy, skycoord_offset=False):
         pan_x, pan_y = self._viewer.get_pan(coord=coord)
         self._viewer.set_pan(pan_x + dx, pan_y + dy, coord=coord)
 
+    def offset_by(self, dx, dy):
+        """
+        Move the center to a point that is given offset
+        away from the current center.
+
+        Parameters
+        ----------
+        dx, dy : float or `~astropy.unit.Quantity`
+            Offset value. Without a unit, assumed to be pixel offsets.
+            If a unit is attached, offset by pixel or sky is assumed from
+            the unit.
+
+        """
+        dx_val, dx_coord = _offset_is_pixel_or_sky(dx)
+        dy_val, dy_coord = _offset_is_pixel_or_sky(dy)
+
+        if dx_coord != dy_coord:
+            raise ValueError(f'dx is of type {dx_coord} but dy is of type {dy_coord}')
+
+        pan_x, pan_y = self._viewer.get_pan(coord=dx_coord)
+        self._viewer.set_pan(pan_x + dx_val, pan_y + dy_val, coord=dx_coord)
+
     @property
     def zoom_level(self):
         """
@@ -955,3 +982,18 @@ def save(self, filename):
         # to write that out to a file.
         with open(filename, 'wb') as f:
             f.write(self._jup_img.value)
+
+
+def _offset_is_pixel_or_sky(x):
+    if isinstance(x, u.Quantity):
+        if x.unit in (u.dimensionless_unscaled, u.pix):
+            coord = 'data'
+            val = x.value
+        else:
+            coord = 'wcs'
+            val = x.to_value(u.deg)
+    else:
+        coord = 'data'
+        val = x
+
+    return val, coord

astrowidgets/tests/test_api.py

@@ -2,9 +2,11 @@
 
 import pytest
 
+from astropy import units as u
 from astropy.io import fits
 from astropy.nddata import NDData
 from astropy.table import Table
+from astropy.utils.exceptions import AstropyDeprecationWarning
 
 from ginga.ColorDist import ColorDistBase
 
@@ -42,7 +44,26 @@ def test_offset_to():
     image = ImageWidget()
     dx = 10
     dy = 10
-    image.offset_to(dx, dy)
+    with pytest.warns(AstropyDeprecationWarning):
+        image.offset_to(dx, dy)
+
+
+def test_offset_by():
+    image = ImageWidget()
+
+    # Pixels
+    image.offset_by(10, 10)
+    image.offset_by(10 * u.pix, 10 * u.dimensionless_unscaled)
+    image.offset_by(10, 10 * u.pix)
+
+    # Sky
+    image.offset_by(1 * u.arcsec, 0.001 * u.deg)
+
+    with pytest.raises(u.UnitConversionError):
+        image.offset_by(1 * u.arcsec, 1 * u.AA)
+
+    with pytest.raises(ValueError, match='but dy is of type'):
+        image.offset_by(1 * u.arcsec, 1)
 
 
 def test_zoom_level():
@@ -271,10 +292,10 @@ def test_scroll_pan():
         assert image.scroll_pan is val
 
 
-def test_save():
+def test_save(tmp_path):
     image = ImageWidget()
     filename = 'woot.png'
-    image.save(filename)
+    image.save(tmp_path / filename)
 
 
 def test_width_height():

example_notebooks/ginga_widget.ipynb

@@ -185,7 +185,7 @@
    "outputs": [],
    "source": [
     "# Programmatically offset w.r.t. current center\n",
-    "w.offset_to(10, 10)"
+    "w.offset_by(10, 10)"
    ]
   },
   {
@@ -212,12 +212,14 @@
    "metadata": {},
    "outputs": [],
    "source": [
+    "from astropy import units as u\n",
+    "\n",
     "# Change the values if needed.\n",
-    "deg_offset = 0.001\n",
+    "deg_offset = 0.001 * u.deg\n",
     "\n",
     "# Programmatically offset (in degrees) w.r.t.\n",
     "# SkyCoord center\n",
-    "w.offset_to(deg_offset, deg_offset, skycoord_offset=True)"
+    "w.offset_by(deg_offset, deg_offset)"
    ]
   },
   {