Introduce precise drawing algorithm

hips/draw/paint.py

@@ -17,8 +17,6 @@
 ]
 
 
-# TODO for Adeel: add option "precise".
-# Should be default "true" eventually, for now, can use "false" if it's very slow.
 class HipsPainter:
     """Paint a sky image from HiPS image tiles.
 
@@ -34,6 +32,8 @@ class HipsPainter:
         HiPS survey properties
     tile_format : {'fits', 'jpg', 'png'}
         Format of HiPS tile
+    precise : bool
+        Use the precise drawing algorithm
 
     Examples
     --------
@@ -56,10 +56,11 @@ class HipsPainter:
     (1000, 2000)
     """
 
-    def __init__(self, geometry: WCSGeometry, hips_survey: Union[str, HipsSurveyProperties], tile_format: str) -> None:
+    def __init__(self, geometry: WCSGeometry, hips_survey: Union[str, HipsSurveyProperties], tile_format: str, precise: bool = False) -> None:
         self.geometry = geometry
         self.hips_survey = HipsSurveyProperties.make(hips_survey)
         self.tile_format = tile_format
+        self.precise = precise
         self._tiles = None
         self.float_image = None
         self._stats: Dict[str, Any] = {}
@@ -161,21 +162,23 @@ def run(self) -> np.ndarray:
         # Other useful info: number of tiles fetched
 
     def make_tile_list(self):
-        # Fetch all tiles needed
         parent_tiles = self.tiles
 
-        # TODO for Adeel: implement distortion correction here.
-        # Create new list of tiles, where some have been replaced by 4 children.
         # Suggestion: for now, just split once, no recursion.
         # Leave TODO, to discuss with Thomas next week.
         # See also: https://github.com/hipspy/hips/issues/92
 
-        # For now, we just create a 1:1 copy
-        tiles = []
-        for tile in parent_tiles:
-            tiles.append(tile)
-
-        self.draw_tiles = tiles
+        if self.precise == True:
+            tiles = []
+            for tile in parent_tiles:
+                corners = tile.meta.skycoord_corners.to_pixel(self.geometry.wcs)
+                if is_tile_distorted(corners):
+                    tiles.append(tile.children)
+                else:
+                    tiles.append(tile)
+            self.draw_tiles = [tile for children in tiles for tile in children]
+        else:
+            self.draw_tiles = parent_tiles
 
     def _make_empty_sky_image(self):
         shape = compute_image_shape(
@@ -207,7 +210,7 @@ def plot_mpl_hips_tile_grid(self) -> None:
         not something end-users will call or need to know about.
         """
         import matplotlib.pyplot as plt
-        for tile in self.tiles:
+        for tile in self.draw_tiles:
             corners = tile.meta.skycoord_corners.transform_to(self.geometry.celestial_frame)
             ax = plt.subplot(projection=self.geometry.wcs)
             opts = dict(color='red', lw=1, )

hips/draw/tests/test_ui.py

@@ -16,7 +16,8 @@
         data_2=2296,
         data_sum=8756493140,
         dtype='>i2',
-        repr='HipsDrawResult(width=1000, height=2000, channels=2, dtype=>i2, format=fits)'
+        repr='HipsDrawResult(width=1000, height=2000, channels=2, dtype=>i2, format=fits)',
+        precise=False
     ),
     dict(
         file_format='jpg',
@@ -26,7 +27,19 @@
         data_2=[137, 116, 114],
         data_sum=828908873,
         dtype='uint8',
-        repr='HipsDrawResult(width=1000, height=2000, channels=3, dtype=uint8, format=jpg)'
+        repr='HipsDrawResult(width=1000, height=2000, channels=3, dtype=uint8, format=jpg)',
+        precise=False
+    ),
+    dict(
+        file_format='jpg',
+        shape=(1000, 2000, 3),
+        url='https://raw.githubusercontent.com/hipspy/hips-extra/master/datasets/samples/FermiColor/properties',
+        data_1=[139, 114, 115],
+        data_2=[142, 113, 110],
+        data_sum=825148172,
+        dtype='uint8',
+        repr='HipsDrawResult(width=1000, height=2000, channels=3, dtype=uint8, format=jpg)',
+        precise=True
     ),
     dict(
         file_format='png',
@@ -36,7 +49,8 @@
         data_2=[227, 217, 205, 255],
         data_sum=1635622838,
         dtype='uint8',
-        repr='HipsDrawResult(width=1000, height=2000, channels=3, dtype=uint8, format=png)'
+        repr='HipsDrawResult(width=1000, height=2000, channels=3, dtype=uint8, format=png)',
+        precise=False
     ),
 ]
 
@@ -47,7 +61,7 @@ def test_make_sky_image(tmpdir, pars):
     hips_survey = HipsSurveyProperties.fetch(url=pars['url'])
     geometry = make_test_wcs_geometry()
 
-    result = make_sky_image(geometry=geometry, hips_survey=hips_survey, tile_format=pars['file_format'])
+    result = make_sky_image(geometry=geometry, hips_survey=hips_survey, tile_format=pars['file_format'], precise=pars['precise'])
 
     assert result.image.shape == pars['shape']
     assert result.image.dtype == pars['dtype']

hips/draw/ui.py

@@ -15,7 +15,7 @@
 
 
 def make_sky_image(geometry: WCSGeometry, hips_survey: Union[str, 'HipsSurveyProperties'],
-                   tile_format: str) -> 'HipsDrawResult':
+                   tile_format: str, precise: bool = False) -> 'HipsDrawResult':
     """Make sky image: fetch tiles and draw.
 
     The example for this can be found on the :ref:`gs` page.
@@ -29,13 +29,15 @@ def make_sky_image(geometry: WCSGeometry, hips_survey: Union[str, 'HipsSurveyPro
     tile_format : {'fits', 'jpg', 'png'}
         Format of HiPS tile to use
         (some surveys are available in several formats, so this extra argument is needed)
+    precise : bool
+        Use the precise drawing algorithm
 
     Returns
     -------
     result : `~hips.HipsDrawResult`
         Result object
     """
-    painter = HipsPainter(geometry, hips_survey, tile_format)
+    painter = HipsPainter(geometry, hips_survey, tile_format, precise)
     painter.run()
     return HipsDrawResult.from_painter(painter)
 

hips/tiles/tile.py

@@ -12,7 +12,6 @@
 from astropy.coordinates import SkyCoord
 from astropy.io import fits
 from ..utils import healpix_pixel_corners
-from .io import tile_default_url, tile_default_path
 
 __all__ = [
     'HipsTileMeta',
@@ -231,10 +230,10 @@ def children(self) -> List['HipsTile']:
         """Create four children tiles from parent tile."""
         w = self.data.shape[0] // 2
         data = [
-            self.data[0: w, 0: w],
-            self.data[0: w, w: w * 2],
             self.data[w: w * 2, 0: w],
-            self.data[w: w * 2, w: w * 2]
+            self.data[0: w, 0: w],
+            self.data[w: w * 2, w: w * 2],
+            self.data[0: w, w: w * 2]
         ]
 
         tiles = []
@@ -243,7 +242,8 @@ def children(self) -> List['HipsTile']:
                 self.meta.order + 1,
                 self.meta.ipix * 4 + idx,
                 self.meta.file_format,
-                self.meta.frame
+                self.meta.frame,
+                len(data[0])
             )
             tile = self.from_numpy(meta, data[idx])
             tiles.append(tile)