Re: [Matplotlib-users] image blitted onto an axes is not showing up

[Benjamin R. <ben...@ou...>]

On Wednesday, November 2, 2011, John Jameson <jw...@gm...> wrote:
> Hi,
> I am trying to do an animation in two axes (subplots) and I can get it to
work so-so if I do it the "wrong way" but when I do it the "right way" I
don't see anything in my second subplot.
> The first subplot (ax1) shows a bunch of moving line segments ("sticks")
and the second one (ax2) shows a low resolution (pixellated) view of the
first subplot. The latter (ax2) uses imshow() but when I update it through
setarray() and blit it onto the canvas it doesn't show up (although the
sticks in the ax1 show up fine). However, if I insert the line
canvas.draw() after the ax2 blit it works but it makes the ax1 animation
very jittery.
> Can someone tell me the correct way to do this?  I'm still a tenderfoot
in Matplotlib ;-(
> thanks!
> John
>
>
>
>
>
>
> class Sticks_animator():
>
>     x_offset = 0.0
>
>     def __init__(self, n_sticks_tot, n_pixels_horizontal=0,
>
>             n_pixels_vertical=0 ):
>
> .
> .
> .
> .
> .
>
>    def reset(self):
>
>         self.background1 = None
>
>         self.background2 = None
>
>         self.start = 1
>
>     def draw_sticks(self):
>
>         if self.start:
>
>             self.poly = []
>
>             for i in range( self.n_sticks_tot):
>
>                 x_stick = array([ [self.x1[i], self.y1[i]],
>
>                                   [self.x2[i], self.y2[i]] ] )
>
>
>
>                 self.poly.append( Polygon( x_stick, animated=True,
>
>                                            lw=2, fill=False) )
>
>                 self.ax1.add_patch(self.poly[i])
>
>                 self.ax1.draw_artist(self.poly[i])
>
>
>
>         else:
>
>             for i in range( self.n_sticks_tot):
>
>                 x_stick = array([ [self.x1[i], self.y1[i]],
>
>                                   [self.x2[i], self.y2[i]] ] )
>
>                 self.poly[i].set_xy(x_stick)
>
>                 self.ax1.draw_artist(self.poly[i])
>
>     def draw_retina(self):
>
>         if self.start:
>
>             self.img = self.ax2.imshow(self.inten,
interpolation='nearest')
>
>         else:
>
>             self.img.set_array(self.inten)
>
>
>
>     def step_it(self):
>
>         self.inten, self.n_sticks_tot, self.x1, self.y1, \
>
>                        self.x2, self.y2, done = self.stks.Step_it()
>
>
> # self.stks.Step_it() is finds all the stick coordinates
>
> #   and inten is a NXN array of a pixellated (low res) view
>
> #   of all the sticks
>
>
>
> if self.background1 is None:
>
>             self.background1 = self.canvas.copy_from_bbox(self.ax1.bbox)
>
>         self.canvas.restore_region(self.background1)
>
>         self.draw_sticks()
>
>         self.canvas.blit(self.ax1.bbox)
>
>         if self.add_retina_view:
>
>             self.draw_retina()
>
>             self.canvas.blit(self.ax2.bbox)
>
> #            self.canvas.draw()   IF I UNCOMMENT THIS IT "WORKS"
>
>         self.start = 0
>
>
>
>         if done:
>
>             gtk.main_quit()
>
>             raise SystemExit
>
>         return True
>
>     def mainer( self, stks ):
>
>  self.stks = stks
>
>         if isinteractive():
>
>             ioff()
>
>         def start_anim(event):
>
>             gobject.idle_add( self.step_it )
>
>             self.canvas.mpl_disconnect(start_anim.cid)
>
>
>
>         start_anim.cid = self.canvas.mpl_connect('draw_event', start_anim)
>
>         plt.show()
>

Which version of mpl are you using?  v1.1.0 comes with an animation module
to handle most of this for you.  Check out the animation examples on the
website.

Note, very often, when blitting, the issue can be that the individual
artists were not sett as animated.  Note that (counter-intuitively) the new
animation module does not fully work if animate=True, so I'd using
animate.py, don't set animate=True.

Hopefully, that wasn't too confusing...
Ben Root