Simple examples
The obligatory "Hello World"
Here's the "Hello world":
using Luxor
Drawing(1000, 1000, "hello-world.png")
origin()
background("black")
sethue("red")
fontsize(50)
text("hello world")
finish()
preview()
Drawing(1000, 1000, "hello-world.png")
defines the width, height, location, and type of the finished image. origin
moves the 0/0 point to the centre of the drawing surface (by default it's at the top left corner). Thanks to Colors.jl
we can specify colors by name as well as by numeric value: background("black")
defines the color of the background of the drawing. text("helloworld")
draws the text. It's placed at the current 0/0 point and left-justified if you don't specify otherwise. finish
completes the drawing and saves the PNG image in the file. preview
tries to display the saved file, perhaps using another application (eg Preview on macOS).
The macros @png
, @svg
, @pdf
, @draw
, and @imagematrix
provide shortcuts for making and previewing graphics without you having to provide the usual set-up and finish instructions:
# using Luxor
@png begin
fontsize(50)
circle(Point(0, 0), 150, :stroke)
text("hello world", halign=:center, valign=:middle)
end
@svg begin
sethue("red")
randpoint = Point(rand(-200:200), rand(-200:200))
circle(randpoint, 2, :fill)
sethue("black")
foreach(f -> arrow(f, between(f, randpoint, .1), arrowheadlength=6),
first.(collect(Table(fill(20, 15), fill(20, 15)))))
end
The @draw
and drawsvg
macros are useful if you work in Juno/VS Code IDEs or a notebook environment such as Jupyter or Pluto and don't need to always save your work in files. They create a PNG or SVG format drawing in memory, rather than saved in a file. It's displayed in the plot pane or in an adjacent cell.
@draw begin
setopacity(0.85)
steps = 20
gap = 2
for (n, θ) in enumerate(range(0, step=2π/steps, length=steps))
sethue([Luxor.julia_green,
Luxor.julia_red,
Luxor.julia_purple,
Luxor.julia_blue][mod1(n, 4)])
sector(Point(0, 0), 50, 250 + 2n, θ, θ + 2π/steps - deg2rad(gap), :fill)
end
end
The Julia logos
Luxor contains built-in functions that draw the Julia logo, either in color or a single color, and the three Julia circles.
using Luxor
Drawing(600, 400, "../assets/figures/julia-logos.png")
origin()
background("white")
for θ in range(0, step=π/8, length=16)
gsave()
scale(0.2)
rotate(θ)
translate(350, 0)
julialogo(action=:fill, bodycolor=randomhue())
grestore()
end
gsave()
scale(0.3)
juliacircles()
grestore()
translate(150, -150)
scale(0.3)
julialogo()
finish()
# preview()
nothing # hide
The gsave
function saves the current drawing environment temporarily, and any subsequent changes such as the scale
and rotate
operations are discarded when you call the next grestore
function.
Use the extension to specify the format: for example, change julia-logos.png
to julia-logos.svg
or julia-logos.pdf
or julia-logos.eps
to produce SVG, PDF, or EPS format output.
Something a bit more complicated: a Sierpinski triangle
Here's a version of the Sierpinski recursive triangle, clipped to a circle.
# using Luxor, Colors
# Drawing()
# background("white")
# origin()
function triangle(points, degree)
sethue(cols[degree])
poly(points, :fill)
end
function sierpinski(points, degree)
triangle(points, degree)
if degree > 1
p1, p2, p3 = points
sierpinski([p1, midpoint(p1, p2),
midpoint(p1, p3)], degree-1)
sierpinski([p2, midpoint(p1, p2),
midpoint(p2, p3)], degree-1)
sierpinski([p3, midpoint(p3, p2),
midpoint(p1, p3)], degree-1)
end
end
function draw(n)
circle(Point(0, 0), 75, :clip)
points = ngon(Point(0, 0), 150, 3, -π/2, vertices=true)
sierpinski(points, n)
end
depth = 8 # 12 is ok, 20 is right out (on my computer, at least)
cols = distinguishable_colors(depth) # from Colors.jl
draw(depth)
# finish()
# preview()
The Point type is an immutable composite type containing x
and y
fields that specify a 2D point.
Simple numberlines
tickline()
is useful for generating spaced points along a line:
@drawsvg begin
background("black")
fontsize(12)
sethue("white")
tickline(Point(-350, 0), Point(350, 0),
finishnumber=100,
log=true,
major=7)
end 800 150
The arrow
functions let you add decoration to the arrow shafts, so it's possible to use this function to create more complicated spacings. Here's how a curved number line could be made:
@drawsvg begin
background("antiquewhite")
_counter() = (a = -1; () -> a += 1)
counter = _counter() # closure
fontsize(15)
arrow(O + (0, 100), 200, π, 2π,
arrowheadlength=0,
decoration=range(0, 1, length=61),
decorate = () -> begin
d = counter()
if d % 5 == 0
text(string(d), O + (0, -20), halign=:center)
setline(3)
end
line(O - (0, 5), O + (0, 5), :stroke)
end
)
end 800 300
The decorate
function here adds graphics and text at the origin, which is located at each point along the shaft.
Draw a matrix
To draw a matrix, you can use a Table to generate the positions.
It's sometimes useful to be able to highight particular cells. Here, numbers that have already been used once are drawn in orange.
using Luxor
function drawmatrix(A::Matrix;
cellsize = (10, 10))
table = Table(size(A)..., cellsize...)
used = Set()
for i in CartesianIndices(A)
r, c = Tuple(i)
if A[r, c] ∈ used
sethue("orange")
else
sethue("purple")
push!(used, A[r, c])
end
text(string(A[r, c]), table[r, c],
halign=:center,
valign=:middle)
sethue("white")
box(table, r, c, :stroke)
end
end
A = rand(1:99, 5, 8)
@drawsvg begin
background("black")
fontsize(30)
setline(0.5)
sethue("white")
drawmatrix(A, cellsize = 10 .* size(A))
end