Scatterplot: Use opacity for contrast

Orange/widgets/visualize/owscatterplotgraph.py

@@ -23,7 +23,6 @@
 from Orange.widgets import gui
 from Orange.widgets.settings import Setting
 from Orange.widgets.utils import classdensity, colorpalettes
-from Orange.widgets.utils.plot import OWPalette
 from Orange.widgets.visualize.utils.customizableplot import Updater, \
     CommonParameterSetter
 from Orange.widgets.visualize.utils.plotutils import (
@@ -534,9 +533,7 @@ def get_size_data(self):
     DarkerValue = 120
     UnknownColor = (168, 50, 168)
 
-    COLOR_NOT_SUBSET = (128, 128, 128, 0)
-    COLOR_SUBSET = (128, 128, 128, 255)
-    COLOR_DEFAULT = (128, 128, 128, 255)
+    COLOR_DEFAULT = (128, 128, 128)
 
     MAX_VISIBLE_LABELS = 500
 
@@ -1025,7 +1022,7 @@ def get_colors(self):
         else:
             return self._get_discrete_colors(c_data, subset)
 
-    def _get_same_colors(self, subset):
+    def _get_same_colors(self, subset, color=COLOR_DEFAULT):
         """
         Return the same pen for all points while the brush color depends
         upon whether the point is in the subset or not
@@ -1038,21 +1035,17 @@ def _get_same_colors(self, subset):
         Returns:
             (tuple): a list of pens and list of brushes
         """
-        color = self.plot_widget.palette().color(OWPalette.Data)
-        pen = [_make_pen(color, 1.5)] * self.n_shown  # use a single QPen instance
-
-        # Prepare all brushes; we use the first two or the last
-        brushes = []
-        for c in (self.COLOR_SUBSET, self.COLOR_NOT_SUBSET, self.COLOR_DEFAULT):
-            color = QColor(*c)
-            if color.alpha():
-                color.setAlpha(self.alpha_value)
-            brushes.append(QBrush(color))
 
         if subset is not None:
-            brush = np.where(subset, *brushes[:2])
+            colors = [QColor(*color, alpha)
+                      for alpha in self._alpha_for_subsets()]
+            brushes = [QBrush(color) for color in colors]
+            brush = np.where(subset, *brushes)
         else:
-            brush = brushes[-1:] * self.n_shown  # use a single QBrush instance
+            qcolor = QColor(*color, self.alpha_value)
+            brush = np.full(self.n_shown, QBrush(qcolor))
+        qcolor = QColor(*color, self.alpha_value)
+        pen = [_make_pen(qcolor, 1.5)] * self.n_shown
         return pen, brush
 
     def _get_continuous_colors(self, c_data, subset):
@@ -1066,18 +1059,18 @@ def _get_continuous_colors(self, c_data, subset):
 
         if np.isnan(c_data).all():
             self.palette = palette
-            return self._get_continuous_nan_colors(len(c_data))
+            return self._get_same_colors(subset, self.palette.nan_color)
 
         self.scale = DiscretizedScale(np.nanmin(c_data), np.nanmax(c_data))
         bins = self.scale.get_bins()
         self.palette = \
             colorpalettes.BinnedContinuousPalette.from_palette(palette, bins)
         colors = self.palette.values_to_colors(c_data)
-        brush = np.hstack(
-            (colors,
-             np.full((len(c_data), 1), self.alpha_value, dtype=np.ubyte)))
-        pen = (colors.astype(dtype=float) * 100 / self.DarkerValue
-               ).astype(np.ubyte)
+        alphas = np.full((len(c_data), 1), self.alpha_value, dtype=np.ubyte)
+        brush = np.hstack((colors, alphas))
+        pen = np.hstack(
+            ((colors.astype(dtype=float) * 100 / self.DarkerValue).astype(np.ubyte),
+             alphas))
 
         # Reuse pens and brushes with the same colors because PyQtGraph then
         # builds smaller pixmap atlas, which makes the drawing faster
@@ -1093,27 +1086,21 @@ def create_pen(col):
         def create_brush(col):
             return QBrush(QColor(*col))
 
-        cached_pens = {}
-        pen = [reuse(cached_pens, create_pen, *col) for col in pen.tolist()]
-
         if subset is not None:
+            alpha_subset, alpha_unset = self._alpha_for_subsets()
             brush[:, 3] = 0
-            brush[subset, 3] = self.alpha_value
+            brush[subset, 3] = alpha_subset
+            pen[:, 3] = alpha_unset
+            brush[subset, 3] = alpha_subset
 
+        cached_pens = {}
+        pen = [reuse(cached_pens, create_pen, *col) for col in pen.tolist()]
         cached_brushes = {}
         brush = np.array([reuse(cached_brushes, create_brush, *col)
                           for col in brush.tolist()])
 
         return pen, brush
 
-    def _get_continuous_nan_colors(self, n):
-        nan_color = QColor(*self.palette.nan_color)
-        nan_pen = _make_pen(nan_color.darker(1.2), 1.5)
-        pen = np.full(n, nan_pen)
-        nan_brush = QBrush(nan_color)
-        brush = np.full(n, nan_brush)
-        return pen, brush
-
     def _get_discrete_colors(self, c_data, subset):
         """
         Return the pens and colors whose color represent an index into
@@ -1126,20 +1113,44 @@ def _get_discrete_colors(self, c_data, subset):
         c_data[np.isnan(c_data)] = len(self.palette)
         c_data = c_data.astype(int)
         colors = self.palette.qcolors_w_nan
-        pens = np.array(
-            [_make_pen(col.darker(self.DarkerValue), 1.5) for col in colors])
-        pen = pens[c_data]
-        if self.alpha_value < 255:
+        if subset is None:
             for col in colors:
                 col.setAlpha(self.alpha_value)
-        brushes = np.array([QBrush(col) for col in colors])
-        brush = brushes[c_data]
+            pens = np.array(
+                [_make_pen(col.darker(self.DarkerValue), 1.5)
+                 for col in colors])
+            pen = pens[c_data]
+            brushes = np.array([QBrush(col) for col in colors])
+            brush = brushes[c_data]
+        else:
+            subset_colors = [QColor(col) for col in colors]
+            alpha_subset, alpha_unset = self._alpha_for_subsets()
+            for col in subset_colors:
+                col.setAlpha(alpha_subset)
+            for col in colors:
+                col.setAlpha(alpha_unset)
 
-        if subset is not None:
+            pens, subset_pens = (
+                np.array(
+                    [_make_pen(col.darker(self.DarkerValue), 1.5)
+                     for col in cols])
+                for cols in (colors, subset_colors))
+            pen = np.where(subset, subset_pens[c_data], pens[c_data])
+
+            brushes = np.array([QBrush(col) for col in subset_colors])
+            brush = brushes[c_data]
             black = np.full(len(brush), QBrush(QColor(0, 0, 0, 0)))
             brush = np.where(subset, brush, black)
         return pen, brush
 
+    def _alpha_for_subsets(self):
+        a, b, c = 1.2, -3.2, 3
+        x = self.alpha_value / 255
+        alpha_subset = 31 + int(224 * (a * x ** 3 + b * x ** 2 + c * x))
+        x = 1 - x
+        alpha_unset = int(255 - 224 * (a * x ** 3 + b * x ** 2 + c * x))
+        return alpha_subset, alpha_unset
+
     def update_colors(self):
         """
         Trigger an update of point colors

Orange/widgets/visualize/tests/test_owscatterplotbase.py

@@ -635,12 +635,12 @@ def run_tests():
             self.master.get_subset_mask = lambda: np.arange(10) >= 5
             graph.update_colors()
             brushes = graph.scatterplot_item.data["brush"]
-            self.assertEqual(brushes[0].color().alpha(), 0)
-            self.assertEqual(brushes[1].color().alpha(), 0)
-            self.assertEqual(brushes[4].color().alpha(), 0)
-            self.assertEqual(brushes[5].color().alpha(), 123)
-            self.assertEqual(brushes[6].color().alpha(), 123)
-            self.assertEqual(brushes[7].color().alpha(), 123)
+            a0 = brushes[0].color().alpha()
+            self.assertEqual(brushes[1].color().alpha(), a0)
+            self.assertEqual(brushes[4].color().alpha(), a0)
+            self.assertGreater(brushes[5].color().alpha(), a0)
+            self.assertGreater(brushes[6].color().alpha(), a0)
+            self.assertGreater(brushes[7].color().alpha(), a0)
 
         graph = self.graph