More examples

One place to look for examples is the Luxor/test directory.

"tiled images"

Illustrating this document

This documentation was built with Documenter.jl, which is an amazingly powerful and flexible documentation generator written in Julia. The illustrations are mostly created when the HTML pages are built: the Julia source for the image is stored in the Markdown source document, and the code to create the images runs each time the documentation is generated.

The Markdown markup looks like this:

```@example
using Luxor, Random # hide
Drawing(600, 250, "../assets/figures/polysmooth-pathological.png") # hide
origin() # hide
background("white") # hide
setopacity(0.75) # hide
Random.seed!(42) # hide
setline(1) # hide
p = star(O, 60, 5, 0.35, 0, vertices=true)
setdash("dot")
sethue("red")
prettypoly(p, close=true, :stroke)
setdash("solid")
sethue("black")
polysmooth(p, 40, :fill, debug=true)
finish() # hide
```

![polysmooth](../assets/figures/polysmooth-pathological.png)

and after you run Documenter's build process the HTML output looks like this:

p = star(O, 60, 5, 0.35, 0, vertices=true)
setdash("dot")
sethue("red")
prettypoly(p, close=true, :stroke)
setdash("solid")
sethue("black")
polysmooth(p, 40, :fill, debug=true)

polysmooth

Why turtles?

An interesting application for turtle-style graphics is for drawing Lindenmayer systems (l-systems). Here's an example of how a complex pattern can emerge from a simple set of rules, taken from Lindenmayer.jl:

penrose

The definition of this figure is:

penrose = LSystem(Dict("X"  =>  "PM++QM----YM[-PM----XM]++t",
                       "Y"  => "+PM--QM[---XM--YM]+t",
                       "P"  => "-XM++YM[+++PM++QM]-t",
                       "Q"  => "--PM++++XM[+QM++++YM]--YMt",
                       "M"  => "F",
                       "F"  => ""),
                  "1[Y]++[Y]++[Y]++[Y]++[Y]")

where some of the characters—eg "F", "+", "-", and "t"—issue turtle control commands, and others—"X,", "Y", "P", and "Q"—refer to specific components of the design. The execution of the l-system involves replacing every occurrence in the drawing code of every dictionary key with the matching values.

Strange

It's usually better to draw fractals and similar images using pixels and image processing tools. But just for fun it's an interesting experiment to render a strange attractor image using vector drawing rather than placing pixels.

using Luxor, Colors
function strange(dotsize, w=800.0)
    xmin = -2.0; xmax = 2.0; ymin= -2.0; ymax = 2.0
    Drawing(w, w, "../assets/figures/strange-vector.png")
    origin()
    background("grey5")
    xinc = w / (xmax - xmin)
    yinc = w / (ymax - ymin)
    # control parameters
    a = 2.24
    b = 0.43
    c = -0.65
    d = -2.43
    e1 = 1.0
    x = y = z = 0.0
    wover2 = w / 2 - 50 # margin
    for j = 1:w
        for i = 1:w
            xx = sin(a * y) - z * cos(b * x)
            yy = z * sin(c * x) - cos(d * y)
            zz = e1 * sin(x)
            x = xx
            y = yy
            z = zz
            if xx < xmax && xx > xmin
                if yy < ymax && yy > ymin
                    xpos = rescale(
                        xx,
                        xmin,
                        xmax,
                        -wover2,
                        wover2,
                    ) # scale to range
                    ypos = rescale(
                        yy,
                        ymin,
                        ymax,
                        -wover2,
                        wover2,
                    ) # scale to range
                    rcolor = rescale(xx, -1, 1, 0.0, 0.6)
                    gcolor = rescale(yy, -1, 1, 0.2, 0.5)
                    bcolor = rescale(zz, -1, 1, 0.6, 0.9)
                    setcolor(rcolor, gcolor, bcolor)
                    move(Point(xpos, ypos))
                    line(Point(xpos + dotsize, ypos))
                    line(Point(
                        xpos + dotsize,
                        ypos + dotsize,
                    ))
                    line(Point(xpos, ypos + dotsize))
                    fillpath()
                end
            end
        end
    end
    finish()
end

strange(.5, 800)

strange attractor in vectors

This example generates about 650,000 paths, which is why it’s better to target PNG rather than SVG or PDF for this example. Also for speed, the “dots” are actually simple paths, which are slightly quicker to draw than circles or polygons.

More animations

strange attractor in vectors

Most of the animations on this YouTube channel are made with Luxor.

using Luxor, Colors

function set_gold_blend()
    gblend = blend(O, 0, O, 250, "gold2", "gold3")
    setblend(gblend)
end

function draw_scarab_legs(pos)
    translate(pos)
    # legs
    @layer begin
        for i in 1:2
            move(O)
            rline.((polar(80, -π/6),
                polar(70, -π/2),
                polar(12, -5π/6),
                polar(60, -π/4)))

            #middle leg
            move(0, 40)
            rline.((
                polar(120, -π/6),
                polar(40, π/2)))

            #back leg
            move(0, 100)
            rline.((
                polar(130, -π/6),
                polar(110, π/2)))

            # flip for other leg
            transform([-1 0 0 1 0 0])
        end
    end
end

function draw_scarab_body()
    @layer begin
        squircle(Point(0, -25), 26, 75, action=:path)
        squircle(Point(0, 0), 50, 70, action=:path)
        squircle(Point(0, 40), 65, 90, action=:path)
    end
end

function draw()
    @drawsvg begin
    setopacity(1.0)
    setline(20)
    setlinecap("butt")
    setlinejoin("round")
    width = 180
    height= 240

    sethue("black")
    squircle(O, width, height-5, rt=0.4, action=:fill)

    set_gold_blend()
    squircle(O, width, height-5, rt=0.4, action=:path)
    translate(0, 50)
    draw_scarab_legs(O)
    strokepath()
    draw_scarab_body()
    fillpath()

    # julia dots === Ra egyptian sun deity
    @layer begin
        translate(0, -190)
        circle(O, 48, action=:fill)
        juliacircles(20)
    end

    clipreset()
    end
end

draw()

A Japanese-style Temple scene

This code was created by kfung, a student that participated in Google Code-in 2019 competition.

using Luxor
Drawing(1280, 720, "../assets/figures/temple.png")
origin()
setblend(blend(Point(0, -200), Point(0, 300), "#F38070", "#F3C3BC"))
box(O, 1280, 720, :fill)
sethue("#F7C5BC")
setopacity(0.3)
sun = Point(450, -225)
poly([sun, Point(400, 400), Point(640, 400), sun], :fill)
poly([sun, Point(-150, 400), Point(150, 400), sun], :fill)
poly([sun, Point(-640, 400), Point(-640, 0), sun], :fill)
poly([sun, Point(-640, -150), Point(-640, -450), sun], :fill)
poly([sun, Point(100, -360), Point(300, -360), sun], :fill)
poly([sun, Point(375, -400), Point(475, -400), sun], :fill)
poly([sun, Point(585, -400), Point(775, -400), sun], :fill)
poly([sun, Point(640, -265), Point(640, -175), sun], :fill)
poly([sun, Point(640, -100), Point(640, 125), sun], :fill)
sethue("#C02C20")
setopacity(1)
circle(450, -225, 40, :fill)
sethue("white")
setopacity(0.98)
ellipse(20, -275, 150, 75, :fill)
ellipse(-20, -240, 150, 50, :fill)
ellipse(60, -245, 150, 50, :fill)
ellipse(-450, -240, 150, 50, :fill)
ellipse(-350, -250, 150, 50, :fill)
ellipse(430, -90, 200, 10, :fill)
ellipse(470, -95, 200, 10, :fill)
setopacity(0.8)
ellipse(-450, -130, 200, 10, :fill)
ellipse(-490, -135, 200, 10, :fill)
setopacity(1)
sethue("#2E951A")
drawbezierpath(makebezierpath([Point(-780, 500), Point(-640, 100), Point(-560, -20), Point(-480, -80), Point(-400, -80), Point(-320, -20), Point(-240, 100), Point(-240, 500)]), :fill, close=false)
sethue("#37C61B")
drawbezierpath(makebezierpath([Point(-780, 500), Point(-640, 200), Point(-560, 100), Point(-480, 40), Point(-400, 30), Point(-320, 70), Point(-240, 150), Point(-240, 500)]), :fill, close=false)
sethue("#23AE34")
setopacity(1)
ellipse(530, 90, 100, 100, :fill)
ellipse(490, 150, 80, 80, :fill)
ellipse(570, 150, 80, 80, :fill)
sethue("#713D1D")
box(530, 220, 15, 290, :fill)
setline(15)
line(Point(530,180), Point(565, 125), :stroke)
line(Point(530,140), Point(495, 105), :stroke)
sethue("#E13705")
circle(480, 150, 8, :fill)
circle(560, 100, 8, :fill)
circle(510, 70, 8, :fill)
circle(580, 160, 8, :fill)
[circle(544+16*(i-1), 292, 8, :fill) for i in 1:3]
circle(552, 278, 8, :fill)
circle(512, 292, 8, :fill)
circle(496, 292, 8, :fill)
sethue("white")
setline(10)
line(Point(440, 300), Point(440, 250), :stroke)
poly([Point(410, 250), Point(395, 235), Point(410, 220), Point(465, 220), Point(465, 250)], :fill)
sethue("black")
fontsize(12)
fontface("Arial")
text("THIS WAY", Point(434, 241), halign=:center,  valign = :center)
setopacity(1)
sethue("#2A3A4A")
box(0, 330, 1280, 60, :fill)
setline(20)
setopacity(1)
drawbezierpath(makebezierpath([Point(-570, 320), Point(-500, 270), Point(-400, 230), Point(-550, 200), Point(-360, 160), Point(-460, 110), Point(-342, 70), Point(-340, 70)]), :stroke, close=false)
circle(-340, 69, 10, :fill)
circle(-336, 67, 10, :fill)
setopacity(1)
sethue("white")
[box(-600+100*(i-1), 330, 50, 5, :fill) for i in 1:13]
sethue("#E7D1BC")
box(0, 240, 700, 120, :fill)
box(0, 150, 300, 120, :fill)
box(0, 40, 500, 120, :fill)
sethue("#EE766B")
[circle((-400+20*(i-1)), 180, 10, :fill) for i in 1:41]
[circle((-270+20*(i-1)), -20, 10, :fill) for i in 1:28]
sethue("#D14A3E")
poly([Point(-420, 180), Point(420, 180), Point(250, 70), Point(-250, 70), Point(-420, 180)], :fill)
poly([Point(-290, -20), Point(290, -20), Point(150, -120), Point(-150, -120), Point(-290, -20)], :fill)
circle(0, 58, 10, :fill)
circle(0, 45, 4, :fill)
sethue("#B71909")
poly([Point(0, 55), Point(140, 180), Point(-140, 180), Point(0, 55)], :fill)
sethue("#E7D1BC")
poly([Point(0, 70), Point(159, 210), Point(-159, 210), Point(0, 70)], :fill)
sethue("black")
[box(-180+120*(i-1), 30, 20, 40, :fill) for i in 1:4]
box(-300, 240, 20, 40, :fill)
box(-200, 240, 20, 40, :fill)
box(200, 240, 20, 40, :fill)
box(300, 240, 20, 40, :fill)
sethue("#C99A6F")
box(-130, 240, 10, 120, :fill)
box(130, 240, 10, 120, :fill)
poly([Point(0, 85), Point(91, 165), Point(-91, 165), Point(0, 85)], :fill)
sethue("black")
box(0, 258, 88, 84, :fill)
sethue("#C99A6F")
box(-20, 260, 38, 80, :fill)
box(20, 260, 38, 80, :fill)
sethue("black")
circle(-10, 260, 4, :fill)
circle(10, 260, 4, :fill)
finish()

temple