"""

Getting meta with the canvas.

PlotDevice allows you to query the current state of the canvas,

and even use its contents as an image. This allows for some trippy

feed-back effects.

"""

size(500, 500)

# By default, the canvas draws a white background, so as we overlay

# each copy it replaces everything below it. Try uncommenting the

# next line to use a transparent background instead:

# background(None)

# Draw some ovals on screen, just to get something to display.

for i in range(1000):

oval(random(WIDTH), random(HEIGHT), 20, 20, fill=(random(), random(), 0, random()))

# Now do the feedback ten times.

for i in range(10):

# Scale each copy down a bit and rotate it. This gives the familiar

# betacam-pointing-at-a-television feedback effect. You can play with

# these parameters to get other effects.

scale(0.98)

rotate(1)

# Here's the tricky bit. We call the image() command but rather than

# passing it the path to an image file, we use the contents of the

# canvas itself (using the `canvas` variable in the local namespace).

# Try blurring the image by addding: alpha=0.8

image(canvas, random(-50,49), random(-50,49))