pg.plot() and pg.PlotWidget() now accept background argument

ImageExporter correctly handles QBrush with style=NoBrush

pyqtgraph/__init__.py

@@ -281,7 +281,7 @@ def plot(*args, **kargs):
     #if len(args)+len(kargs) > 0:
         #w.plot(*args, **kargs)
         
-    pwArgList = ['title', 'labels', 'name', 'left', 'right', 'top', 'bottom']
+    pwArgList = ['title', 'labels', 'name', 'left', 'right', 'top', 'bottom', 'background']
     pwArgs = {}
     dataArgs = {}
     for k in kargs:

pyqtgraph/exporters/ImageExporter.py

@@ -17,7 +17,11 @@ class ImageExporter(Exporter):
             scene = item.scene()
         else:
             scene = item
-        bg = scene.views()[0].backgroundBrush().color()
+        bgbrush = scene.views()[0].backgroundBrush()
+        bg = bgbrush.color()
+        if bgbrush.style() == QtCore.Qt.NoBrush:
+            bg.setAlpha(0)
+            
         self.params = Parameter(name='params', type='group', children=[
             {'name': 'width', 'type': 'int', 'value': tr.width(), 'limits': (0, None)},
             {'name': 'height', 'type': 'int', 'value': tr.height(), 'limits': (0, None)},

pyqtgraph/widgets/PlotWidget.py

@@ -40,10 +40,12 @@ class PlotWidget(GraphicsView):
     For all 
     other methods, use :func:`getPlotItem <pyqtgraph.PlotWidget.getPlotItem>`.
     """
-    def __init__(self, parent=None, **kargs):
-        """When initializing PlotWidget, all keyword arguments except *parent* are passed
+    def __init__(self, parent=None, background='default', **kargs):
+        """When initializing PlotWidget, *parent* and *background* are passed to 
+        :func:`GraphicsWidget.__init__() <pyqtgraph.GraphicsWidget.__init__>`
+        and all others are passed
         to :func:`PlotItem.__init__() <pyqtgraph.PlotItem.__init__>`."""
-        GraphicsView.__init__(self, parent)
+        GraphicsView.__init__(self, parent, background=background)
         self.setSizePolicy(QtGui.QSizePolicy.Expanding, QtGui.QSizePolicy.Expanding)
         self.enableMouse(False)
         self.plotItem = PlotItem(**kargs)