[Visualpython-users] Image Files and Animated Gifs from Vpython for Windows

[Ives, T. W. <tho...@hp...>]

VPython Community,
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I finally got tired of not being able to use my favorite graphics
routines to create image files for graphs for reporting and for creating
animations that I could transport to people without VPython, so I hacked
some useful stuff together. My apologies if someone already submitted
something similar.
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First, a clean and simple way to capture images for graphs, etc. The key
here is the use of PIL (Python Imaging Library) and importing ImageGrab
from that.
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	from visual import *
	from visual.graph import *
	import ImageGrab
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	ImageWidth =3D 640; ImageHeight =3D 480;=20
	oscillation =3D gdisplay(xtitle=3D't', ytitle=3D'Response', width =3D
ImageWidth, height =3D ImageHeight,=20
	    background =3D color.white, foreground =3D color.black)
	funct1 =3D gcurve(color=3Dcolor.magenta)
	funct2 =3D gvbars(delta=3D0.5, color=3Dcolor.red)
	funct3 =3D gdots(color=3Dcolor.orange)
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	for t in arange(-30, 70, 1):
	    funct1.plot( pos=3D(t, 5.0+5.0*cos(-0.2*t)*exp(0.015*t)) )
	    funct2.plot( pos=3D(t, 2.0+5.0*cos(-0.1*t)*exp(0.015*t)) )
	    funct3.plot( pos=3D(t, 5.0*cos(-0.03*t)*exp(0.015*t)) )
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	im =3D ImageGrab.grab((4,30,ImageWidth-4,ImageHeight-4))
	im.save("screen.gif")
	oscillation.display.visible =3D 0

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This places the window in the upper left corner of the screen. I had to
experiment with how much to take away from the grab, but it works
cleanly now for any width and height I specify.
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To create an animated gif, there is an extension of the above, below,
using a modification of the bounce2.py demo file. The new addition here
is WhirlGif from http://www.danbbs.dk/~dino/whirlgif/ which was very
easy compile and link with MinGW http://www.mingw.org/. This is a free
utility for creating animated gif files. The key factor in the file
below is to save the filenames into a string list to feed to the
os.system("command prompt script in a string") command. Also, the image
capture slows the animation down enough to turn off the rate setting, at
least on my machine :-). This method is also good for creating animated
surface plots.=20

	from visual import *
	import os
	import ImageGrab
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	ImageWidth =3D 300; ImageHeight =3D 300
	scene =3D display(width=3DImageWidth, height=3DImageHeight)
	scene.x =3D 0; scene.y =3D 0
	#scene.fullscreen =3D 1
	side =3D 4.0
	thk =3D 0.3
	s2 =3D 2*side - thk
	s3 =3D 2*side + thk
	wallR =3D box (pos=3D( side, 0, 0), length=3Dthk, height=3Ds2,
width=3Ds3,  color =3D color.red)
	wallL =3D box (pos=3D(-side, 0, 0), length=3Dthk, height=3Ds2,
width=3Ds3,  color =3D color.red)
	wallB =3D box (pos=3D(0, -side, 0), length=3Ds3,  height=3Dthk,
width=3Ds3,  color =3D color.blue)
	wallT =3D box (pos=3D(0,  side, 0), length=3Ds3,  height=3Dthk,
width=3Ds3,  color =3D color.blue)
	wallBK =3D box(pos=3D(0, 0, -side), length=3Ds2,  height=3Ds2,
width=3Dthk, color =3D (0.7,0.7,0.7))
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	ball =3D sphere (color =3D color.green, radius =3D 0.4)
	ball.mass =3D 1.0
	ball.p =3D vector (-0.15, -0.23, +0.27)
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	side =3D side - thk*0.5 - ball.radius
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	dt =3D 0.5
	t=3D0.0
	commandstring =3D "whirlgif -o bounce.gif "
	filelist =3D ""
	basename =3D "bounce_"; extname =3D ".gif"
	for i in range(200):
	  #rate(100)
	  t =3D t + dt
	  ball.pos =3D ball.pos + (ball.p/ball.mass)*dt
	  if not (side > ball.x > -side):
	    ball.p.x =3D -ball.p.x
	  if not (side > ball.y > -side):
	    ball.p.y =3D -ball.p.y
	  if not (side > ball.z > -side):
	    ball.p.z =3D -ball.p.z
	  im =3D ImageGrab.grab((4,30,ImageWidth-4,ImageHeight-4))
	  filename =3D basename+str(i)+extname
	  filelist +=3D filename + " "
	  im.save(filename)
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	scene.visible =3D 0
	os.system(commandstring + filelist)
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Hope these are helpful,
thom
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________________________________

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<http://www.hp.com/Redirect/gw/useng_welcome/logo/=3Dhttp://welcome.hp.co=
m
/country/us/eng/welcome.htm> 	 Thom Ives, Ph.D.

R&D Engineering Scientist=09
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tho...@hp...=20

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