Give control over bbox_inches and rendering format.

baukit/labwidget.py

@@ -993,13 +993,16 @@ class Image(Widget):
         """Clears the image."""
         self.src = ''
 
-    def render(self, obj):
+    def render(self, obj, **kwargs):
         buf = io.BytesIO()
+        if 'format' not in kwargs:
+            kwargs['format'] = 'png'
+        image_format = kwargs['format']
         if hasattr(obj, 'save'): # Like a PIL.Image.Image
-            obj.save(buf, format='png')
+            obj.save(buf, **kwargs)
         elif hasattr(obj, 'savefig'): # Like a matplotlib.figure.Figure
-            obj.savefig(buf, format='png', bbox_inches='tight')
-        self.src= 'data:image/png;base64,' + (
+            obj.savefig(buf, **kwargs)
+        self.src= f'data:image/{image_format};base64,' + (
             base64.b64encode(buf.getvalue()).decode('utf-8'))
         buf.close()
 

baukit/plotwidget.py

@@ -27,6 +27,7 @@ class PlotWidget(Image):
     def __init__(self, redraw_rule, rc=None, **kwargs):
         super().__init__()
         init_args = dict(kwargs)
+        render_args = dict()
         self.rc = {} if rc is None else rc
         
         all_names = []
@@ -34,7 +35,7 @@ class PlotWidget(Image):
             if i == 0:
                 assert p.default == inspect._empty, 'First arg of redraw rule should be the figure'
             else:
-                if name in kwargs:
+                if name in init_args:
                     default = init_args.pop(name)
                 else:
                     assert p.default != inspect._empty, 'Arguments must have default values'
@@ -42,6 +43,11 @@ class PlotWidget(Image):
                 setattr(self, name, Property(default))
                 all_names.append(name)
 
+        for name in ['format', 'metadata', 'bbox_inches', 'pad_inches',
+                'facecolor', 'edgecolor', 'backend']:
+            if name in init_args:
+                render_args[name] = init_args.pop(name)
+
         with matplotlib.pyplot.rc_context(rc=self.rc):
             old_backend = matplotlib.pyplot.get_backend()
             matplotlib.pyplot.switch_backend('agg')
@@ -57,6 +63,6 @@ class PlotWidget(Image):
                 for name in all_names:
                     args.append(getattr(self, name))
                 redraw_rule(*args)
-                self.render(self.fig)
+                self.render(self.fig, **render_args)
         self.on(' '.join(all_names), invoke_redraw)
         invoke_redraw()