we used to have two path for rendering a frame

[doutriaux1]

the one saving pngs was broken and not preserving pngs
two paths are now unified
this also fixes zoom on animations.
fix #1845

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This change is

[doutriaux1]

@aashish24 @chaosphere2112

[doutriaux1]

@danlipsa

[aashish24]

How do we test it @doutriaux1 ?

[doutriaux1]

import vcs
import cdms2
import os

f=cdms2.open(os.path.join(vcs.sample_data,"clt.nc"))
s=f("clt",slice(0,12))

x=vcs.init(geometry=(800,600))
x.colormap = "AMIP" 
x.plot(s)       
x.animate.create(thread_it=1)
x.animate.zoom(2)
#x.animate.run()
raw_input("Press enter")
x.animate.save("crap.mp4")

[danlipsa]

@doutriaux1 Do we have a test that failed before and passes with this change?

[doutriaux1]

nope. and animation testing are such a pain... I guess we could edit all of our exisiting animation test and force them to have a different colormap.

[danlipsa]

@doutriaux1 Probably its enough if you only change one. If its easy to do it may be worth it - if not, its fine.

[aashish24]

LGTM 👍 but I didn't run testing.

[aashish24]

@doutriaux1 @danlipsa can we merge this now?