"""

Masked drawing operations.

PlotDevice can use any Bezier path as a "stencil" to mask-out any

shapes you draw to the canvas. The clip() and mask() commands work with

drawing primitives as well as text and images.

"""

size(300,300)

# ---- Clipping with Primitive Shapes ---- #

# Transformation commands can have an effect on the clipped path, the

# drawing that occurs within the clipping mask, or both. In this case

# we only want our arrow-shaped mask to be rotated (not its contents).

# So we'll generate its Bezier inside a `with rotate' block.

# Rotate the arrow to let it point down.

with rotate(-90):

# The last parameter instructs the command to return the arrow shape

# as a Bezier object rather than drawing it to the canvas.

p = arrow(250, 100, 200, plot=False)

# Beziers have a particularly useful property called `bounds` that returns

# the dimensions of the "bounding box". We'll use these coordinates to

# figure out where to draw ovals so they lie inside the visible portion.

(x,y), (w,h) = p.bounds

# All drawing commands inside of the `with clip()' block are clipped

# according to the given path (in this case the arrow we just defined).

with clip(p):

# draw 200 randomly-rotated lines (actually rectangles with a height of 1)

# positioned within the bounds of the clipping mask

for i in range(400):

fill(random(), random(), 0, random())

s = random(30, 120)

with rotate(random(45, 135)):

rect(x+random(w)-s/2, y+random(h), s, 1)

# ---- Clipping with Text ---- #

# Clipping with text works just like clipping with shapes. The clip() and

# mask() commands can both work with text() objects, but in this case we'll

# use textpath() to generate a Bezier instead (since we need to access its

# `bounds` property).

# Set the font. Note that all state operations work as expected for the

# textpath() command just as they would with text()

font("Didot", "bold", 72)

align(CENTER)

# Return a path that can be used for clipping. Textpaths never draw on screen.

p = textpath("Stencil", WIDTH/2, 270)

# As before, we'll use the Bezier path's bounds to position our clipped contents

(x,y), (w,h) = p.bounds

# use the text's boundaries as a clipping mask

with clip(p):

# Draw 200 rects of a random size and position them within the bounds

for i in range(200):

fill(random(), 0.7, 0, random())

s = random(20)

arc(x+random(w), y+random(h), s)