Emit axes for unbound colorbars

Fixes nschloe#606

Not sure if this is the best way to do it, since it seems a bit kludgy,
but it seems to work.

src/tikzplotlib/_axes.py

@@ -10,25 +10,26 @@ def __init__(self, data, obj):  # noqa: C901
         """Returns the PGFPlots code for an axis environment."""
         self.content = []
 
-        # Are we dealing with an axis that hosts a colorbar? Skip then, those are
-        # treated implicitily by the associated axis.
-        self.is_colorbar = _is_colorbar_heuristic(obj)
-        if self.is_colorbar:
-            return
-
         # instantiation
         self.nsubplots = 1
         self.subplot_index = 0
         self.is_subplot = False
 
-        if isinstance(obj, mpl.axes.Subplot):
+        self.axis_options = []
+
+        # Are we dealing with an axis that hosts a colorbar? Skip then, those are
+        # treated implicitily by the associated axis.
+        self.is_colorbar = _is_colorbar_heuristic(obj)
+
+        if isinstance(obj, mpl.axes.Subplot) and not self.is_colorbar:
             self._subplot(obj, data)
 
         self.axis_options = []
         self.is_visible = obj.get_visible()
 
         # check if axes need to be displayed at all
-        if not (obj.axison and self.is_visible):
+        # unassociated colorbars should have hidden axes; colorbars associated to axes will be printed by the axis
+        if not (obj.axison and self.is_visible) or self.is_colorbar:
             self.axis_options.append("hide x axis")
             self.axis_options.append("hide y axis")
 
@@ -147,10 +148,9 @@ def __init__(self, data, obj):  # noqa: C901
         if col != "white":
             self.axis_options.append(f"axis background/.style={{fill={col}}}")
 
-        # find color bar
-        colorbar = _find_associated_colorbar(obj)
-        if colorbar:
-            self._colorbar(colorbar, data)
+        self.colorbar = _find_associated_colorbar(obj)
+        if self.colorbar:
+            self._colorbar(self.colorbar, data)
 
         if self.is_subplot:
             self.content.append("\n\\nextgroupplot")
@@ -798,7 +798,7 @@ def _handle_listed_color_map(cmap, data):
     if cmap.N is None or cmap.N == len(cmap.colors):
         colors = [
             f"rgb({k}{unit})=({rgb[0]:{ff}},{rgb[1]:{ff}},{rgb[2]:{ff}})"
-            for k, rgb in enumerate(cmap.colors)
+            for k, rgb in enumerate(map(mpl.colors.to_rgb, cmap.colors))
         ]
     else:
         reps = int(float(cmap.N) / len(cmap.colors) - 0.5) + 1
@@ -856,6 +856,12 @@ def _find_associated_colorbar(obj):
     next axis environment, and see if it is de facto a color bar; if yes, return the
     color bar object.
     """
+    try:
+        cbar = obj._colorbar
+        if cbar is not None:
+            return cbar
+    except AttributeError:
+        pass
     for child in obj.get_children():
         try:
             cbar = child.colorbar

src/tikzplotlib/_save.py

@@ -328,6 +328,9 @@ def _recurse(data, obj):
     """Iterates over all children of the current object, gathers the contents
     contributing to the resulting PGFPlots file, and returns those.
     """
+    # bound_colorbars holds colorbars that are associated to axes
+    # we don't add axes from colorbars if they come after the axis to which they were associated
+    bound_colorbars = []
     content = _ContentManager()
     for child in obj.get_children():
         # Some patches are Spines, too; skip those entirely.
@@ -338,17 +341,20 @@ def _recurse(data, obj):
         if isinstance(child, mpl.axes.Axes):
             ax = _axes.Axes(data, child)
 
-            if ax.is_colorbar:
+            if ax.is_colorbar and any(ax.colorbar is cb for cb in bound_colorbars):
                 continue
 
+            if not ax.is_colorbar and ax.colorbar is not None:
+                bound_colorbars.append(ax.colorbar)
+
             # add extra axis options
             if data["extra axis options [base]"]:
                 ax.axis_options.extend(data["extra axis options [base]"])
 
             data["current mpl axes obj"] = child
             data["current axes"] = ax
 
-            if ax.is_visible:
+            if ax.is_visible and not ax.is_colorbar:
                 # Run through the child objects, gather the content.
                 data, children_content = _recurse(data, child)
             else:

tests/test_colorbars_reference.tex

@@ -2,6 +2,70 @@
 
 \definecolor{darkgray176}{RGB}{176,176,176}
 
+\begin{axis}[
+colorbar horizontal,
+colormap={mymap}{[1pt]
+  rgb(0pt)=(0,1,1);
+  rgb(1pt)=(1,0,1)
+},
+hide x axis,
+hide y axis,
+point meta max=10,
+point meta min=-5,
+tick align=outside,
+tick pos=left,
+x grid style={darkgray176},
+xlabel={Some Units},
+xmin=-5, xmax=10,
+xtick style={color=black},
+ymin=0, ymax=1
+]
+\end{axis}
+
+\begin{axis}[
+colorbar horizontal,
+colormap={mymap}{[1pt]
+ rgb(0pt)=(1,0,0);
+  rgb(1pt)=(0,0.5,0);
+  rgb(2pt)=(0,0,1);
+  rgb(3pt)=(0,0.75,0.75)
+},
+hide x axis,
+hide y axis,
+point meta max=8,
+point meta min=1,
+tick align=outside,
+tick pos=left,
+x grid style={darkgray176},
+xlabel={Discrete intervals, some other units},
+xmin=1, xmax=8,
+xtick style={color=black},
+ymin=0, ymax=1
+]
+\end{axis}
+
+\begin{axis}[
+colorbar horizontal,
+colormap={mymap}{[1pt]
+ rgb(0pt)=(0,0.4,1);
+  rgb(1pt)=(0,0.8,1);
+  rgb(2pt)=(1,0.8,0);
+  rgb(3pt)=(1,0.4,0)
+},
+hide x axis,
+hide y axis,
+point meta max=1,
+point meta min=-1,
+tick align=outside,
+tick pos=left,
+x grid style={darkgray176},
+xlabel={Custom extension lengths, some other units},
+xmin=-1, xmax=1,
+xtick style={color=black},
+ymin=0, ymax=1
+]
+\end{axis}
+
 \begin{groupplot}[group style={group size=1 by 4}]
 \nextgroupplot[
 colorbar horizontal,