Fix aspect ratio of logo image so it is not stretched or squashed

Also add two new tests that make sure logo stays the right aspect
ratio whether the canvas is tall/narrow or short/wide.

tests/test_vcs_draw_logo_on.py

@@ -14,3 +14,17 @@ def testDrawLogoOn(self):
         self.x.plot(a, bg=self.bg)
         fnm = "test_vcs_draw_logo_on.png"
         self.checkImage(fnm)
+
+        self.x.clear()
+        self.x.drawlogoon()
+        self.x.geometry(800, 400)
+        self.x.plot(a, bg=self.bg)
+        fnm = "test_vcs_draw_logo_on_wide.png"
+        self.checkImage(fnm)
+
+        self.x.clear()
+        self.x.drawlogoon()
+        self.x.geometry(400, 800)
+        self.x.plot(a, bg=self.bg)
+        fnm = "test_vcs_draw_logo_on_tall.png"
+        self.checkImage(fnm)

vcs/VTKPlots.py

@@ -215,6 +215,7 @@ def __init__(self, canvas, renWin=None,
         self.plotRenderers = set()
         # Maps priorities to renderers
         self.text_renderers = {}
+        self.logoContextArea = None
         self.logoContextItem = None
         self.logoContextItemPython = None
         self.renderer = None
@@ -576,6 +577,14 @@ def clear(self, render=True):
             self.contextView.GetScene().ClearItems()
             r, g, b = [c / 255. for c in self.canvas.backgroundcolor]
             self.contextView.GetRenderer().SetBackground(r, g, b)
+
+            if self.logoContextItem:
+                self.logoContextArea.ClearItems()
+                self.contextView.GetScene().RemoveItem(self.logoContextArea)
+                self.logoContextArea = None
+                self.logoContextItem = None
+                self.logoContextItemPython = None
+
         self._animationActorTransforms = {}
 
         self.showGUI(render=False)
@@ -1653,22 +1662,43 @@ def createLogo(self):
                 position = [0.895, 0.0]
                 position2 = [0.10, 0.05]
 
+                [renWinWidth, renWinHeight] = self.renWin.GetSize()
+                vpLowerLeftX = position[0] * renWinWidth
+                vpLowerLeftY = position[1] * renWinHeight
+                vpWidth = position2[0] * renWinWidth
+                vpHeight = position2[1] * renWinHeight
+
+                imgAspect = float(imgWidth) / imgHeight
+                vpAspect = vpWidth / vpHeight
+
+                if vpAspect > imgAspect:
+                    # We'll use the full vp height and adjust it's width so that it's
+                    # aspect ratio matches that of the image (so no stretching of the
+                    # image occurs).  The image should be centered, so we'll offset
+                    # position x value by half the difference.
+                    vpWidth = vpHeight * imgAspect
+                    halfDiff = ((position2[0] * renWinWidth) - vpWidth) / 2.0
+                    vpLowerLeftX += halfDiff
+                else:
+                    # Similar to above, but in this case we choose to keep the vp width
+                    # and adjust it's height.
+                    vpHeight = vpWidth / imgAspect
+                    halfDiff = ((position2[1] * renWinHeight) - vpHeight) / 2.0
+                    vpLowerLeftY += halfDiff
+
                 view = self.contextView
 
                 area = vtk.vtkContextArea()
                 view.GetScene().AddItem(area)
 
-                [renWinWidth, renWinHeight] = self.renWin.GetSize()
                 dataBounds = vtk.vtkRectd(0.0, 0.0, imgWidth, imgHeight)
-                screenGeom = vtk.vtkRecti(
-                    int(position[0] * renWinWidth),
-                    int(position[1] * renWinHeight),
-                    int(position2[0] * renWinWidth),
-                    int(position2[1] * renWinHeight))
+                screenGeom = vtk.vtkRecti(int(vpLowerLeftX), int(vpLowerLeftY),
+                                          int(vpWidth), int(vpHeight))
 
                 vcs2vtk.configureContextArea(area, dataBounds, screenGeom)
                 area.GetDrawAreaItem().AddItem(item)
 
+                self.logoContextArea = area
                 self.logoContextItem = item
                 self.logoContextItemPython = pythonItem