Luxor

Luxor is the lightest dusting of syntactic sugar on Julia's Cairo graphics package (which should also be installed). It provides some basic vector drawing commands, and a few utilities for working with polygons, clipping masks, and turtle graphics.

The idea of Luxor is that it's slightly easier to use than Cairo, with shorter names, fewer underscores, default contexts, and simplified functions. It's for when you just want to draw something without too much ceremony. For a much more powerful graphics environment, try Compose.jl. Also worth looking at is Andrew Cooke's Drawing.jl package.

Colors.jl provides excellent color definitions and is also required.

I've only tried this on MacOS X. It will need some changes to work on Windows (but I can't test it).

Current status

It's been updated for Julia version 0.4 and for the modified Colors.jl.

SVG rendering currently seems unreliable — text placement generates segmentation faults.

Example usage

To install:

Pkg.clone(...)

"Hello World"

using Luxor, Colors
Drawing(1000, 1000, "/tmp/hello-world.png")
origin()
sethue("red")
fontsize(50)
text("hello world")
finish()
preview()

General Graphics

using Luxor, Colors
Drawing(1200, 1400, "/tmp/basic-test.png") # or PDF/SVG filename for PDF or SVG

origin() # move 0/0 to center
background("purple")

setopacity(0.7)     # opacity from 0 to 1
sethue(0.3,0.7,0.9) # sethue sets the color but doesn't change the opacity
setline(20) # line width

rect(-400,-400,800,800, :fill) # or :stroke, :fillstroke, :clip
randomhue()
circle(0, 0, 460, :stroke)

circle(0,-200,400,:clip)     # set a circular mask above the x axis
sethue("gold")
setopacity(0.7)
setline(10)

for i in 0:pi/36:2*pi - pi/36
    move(0, 0)
    line(cos(i) * 600, sin(i) * 600 )
    stroke()
end

clipreset()     # finish clipping

fontsize(60)
setcolor("turquoise")
fontface("Optima-ExtraBlack")     # a Mac OS X font
textwidth = textextents("Luxor")[5]
# move the text by half the width
text("Luxor", -textwidth/2, currentdrawing.height/2 - 400)

fontsize(18)
fontface("Avenir-Black")
# text on curve starting on an arc
textcurve("THIS IS TEXT ON A CURVE " ^ 14, 0, 0, 0, -10, 550)
finish()
preview() # on Mac OS X, opens in Preview

Turtle graphics

Some simple "turtle graphics" commands are included:

using Luxor, Colors

Drawing(1200, 1200, "/tmp/turtles.png")
origin()
background("black")

# let's have two turtles
raphael = Turtle(0, 0, true, 0, (1.0, 0.25, 0.25)) ; michaelangelo = Turtle(0, 0, true, 0, (1.0, 0.25, 0.25))

setopacity(0.95)
setline(6)

Pencolor(raphael, 1.0, 0.4, 0.2);       Pencolor(michaelangelo, 0.2, 0.9, 1.0)
Reposition(raphael, 500, -200);         Reposition(michaelangelo, 500, 200)
Message(raphael, "Raphael");            Message(michaelangelo, "Michaelangelo")
Reposition(raphael, 0, -200);           Reposition(michaelangelo, 0, 200)

pace = 10
for i in 1:5:400
    for turtle in [raphael, michaelangelo]
        Circle(turtle, 3)
        HueShift(turtle, rand())
        Forward(turtle, pace)
        Turn(turtle, 30 - rand())
        Message(turtle, string(i))
        pace += 1
    end
end

finish()
preview()

Sierpinski triangle

using Luxor, Colors

function draw_triangle(points::Array{Point}, degree::Int64)
    global triangle_count, cols
    setcolor(cols[degree+1])
    poly(points, :fill)
    triangle_count += 1
end

get_midpoint(p1::Point, p2::Point) = Point((p1.x + p2.x) / 2, (p1.y + p2.y) / 2)

function sierpinski(points::Array{Point}, degree::Int64)
    draw_triangle(points, degree)
    if degree > 0
        p1,p2,p3 = points
        sierpinski([p1, get_midpoint(p1, p2),
                        get_midpoint(p1, p3)], degree-1)
        sierpinski([p2, get_midpoint(p1, p2),
                        get_midpoint(p2, p3)], degree-1)
        sierpinski([p3, get_midpoint(p3, p2),
                        get_midpoint(p1, p3)], degree-1)
    end
end

@time begin
    depth = 8 # 12 is ok, 20 is right out
    cols = distinguishable_colors(depth+1)
    Drawing(400, 400, "/tmp/sierpinski.svg")
    origin()
    setopacity(0.5)
    triangle_count = 0
    my_points = [Point(-100,-50), Point(0,100), Point(100.0,-50.0)]
    sierpinski(my_points, depth)
    println("drew $triangle_count triangles")
end

finish()
preview()

# drew 9841 triangles
# elapsed time: 1.738649452 seconds (118966484 bytes allocated, 2.20% gc time)

n-gons

using Luxor, Colors
Drawing(1200, 1400)

origin()
cols = diverging_palette(60,120, 20) # hue 60 to hue 120
background(cols[1])
setopacity(0.7)
setline(2)

ngon(0, 0, 500, 8, 0, :clip)

for y in -500:50:500
    for x in -500:50:500
        setcolor(cols[rand(1:20)])
        ngon(x, y, rand(20:25), rand(3:12), 0, :fill)
        setcolor(cols[rand(1:20)])
        ngon(x, y, rand(10:20), rand(3:12), 0, :stroke)
    end
end

finish()
preview()

clipping masks

include("../examples/julia-logo.jl") # the julia logo coordinates

currentwidth = 500 # pts
currentheight = 500 # pts
Drawing(currentwidth, currentheight, "/tmp/clipping-tests.pdf")

function draw_logo_clip(x, y)
    foregroundcolors = diverging_palette(rand(0:360), rand(0:360), 200, s = 0.99, b=0.8)
    gsave()
    translate(x-100, y)
    julialogomask() # use julia logo as clipping mask
    clip()
    for i in 1:500
        sethue(foregroundcolors[rand(1:end)])
        circle(rand(-50:350), rand(0:300), 15, :fill)
    end
    grestore()
end

origin()
background("white")
setopacity(.4)
draw_logo_clip(0,0)

finish()
preview()

text clipping

Using a text path as a clipping region - here filled with names of Julia functions.

using Luxor, Colors

currentwidth = 1250 # pts
currentheight = 800 # pts
Drawing(currentwidth, currentheight, "/tmp/text-path-clipping.png")

origin()
background("darkslategray3")

fontsize(600) # big fontsize to use for clipping
fontface("Agenda-Black")
str = "julia" # string to be clipped
w, h = textextents(str)[3:4] # get width and height

translate(-(currentwidth/2) + 50, -(currentheight/2) + h)

textpath(str) # make text into a path
setline(3)
setcolor("black")
fillpreserve() # fill but keep
clip()  # clip

fontface("Monaco")
fontsize(10)
namelist = map(x->string(x), names(Base)) # list of names in Base.

x = -20
y = -h
while y < currentheight
    sethue(rand(7:10)/10, rand(7:10)/10, rand(7:10)/10)
    s = namelist[rand(1:end)]
    text(s, x, y)
    se = textextents(s)
    x += se[5] # move to the right
    if x > w
       x = -20 # next row
       y += 10
    end
end

finish()
preview()

Functions

Files

• Drawing() create a drawing, defaulting to PNG format, file called "/tmp/luxor-drawing.png", 800 pixels square
• Drawing(300,300) create a drawing 300 by 300 pixels, defaulting to PNG format, file called "/tmp/luxor-drawing.png",
• Drawing(300,300, "/tmp/my-drawing.pdf") create a PDF drawing in the file "/tmp/my-drawing.pdf", 300 by 300 pixels
• Drawing(800,800, "/tmp/my-drawing.svg") create an SVG drawing in the file "/tmp/my-drawing.svg", 800 by 800 pixels
• finish() finish the drawing
• preview() open the file in Preview (MacOS X only)

The global variable currentdrawing keeps a few parameters:

julia> fieldnames(currentdrawing)
10-element Array{Symbol,1}:
 :width
 :height
 :filename
 :surface
 :cr
 :surfacetype
 :redvalue
 :greenvalue
 :bluevalue
 :alpha

Axes and backgrounds

The origin (0/0) is at the top left, x axis runs left to right, y axis runs top to bottom

• origin() move the 0/0 origin to the centre of the image
• axes() draw axes at current 0/0
• background(color) fill background with a colored rectangle

Shapes and lines

For these functions, the action argument can be :nothing, :fill, :stroke, :fillstroke, or :clip, defaulting to :nothing.

• circle(x, y, r, action)

• arc(xc, yc, radius, angle1, angle2, action) add arc to current path centered at xc/yc starting at angle1 and ending at angle2 drawing arc clockwise

• carc(xc, yc, radius, angle1, angle2, action) add arc to current path centered at xc/yc starting at angle1 and ending at angle2, drawing arc counterclockwise.

• sector(innerradius, outerradius, startangle, endangle, action) draw a sector/track

Angles are measured from the positive x-axis to the positive y-axis in radians, clockwise.

• rect(xmin, ymin, w, h, action)

There is a 'current position':

• move(x, y) move to this position

• rmove(x, y) move relative to current position by x and y

• line(x, y) draw line from current position to the x/y position

• rline(x, y) draw line from current position by x and y

• curve(x1, y1, x2, y2, x3, y3) a cubic Bézier spline, starting at the current position, finishing at x3/y3, following two control points x1/y1 and x2/y2

There is a Point type (the only main type, apart from Drawing):

Point(12.0, 13.0)

Polygons are arrays of points.

• poly(list::Array, action = :nothing; close=false, reversepath=false) draws a polygon using array of Points. For example:

  poly(randompointarray(0,0,200,200, 85), :stroke)

• randompoint(lowx, lowy, highx, highy) returns a random point

• randompointarray(lowx, lowy, highx, highy, n) returns an array of random points. For example:

  poly(randompointarray(0,0,200,200, 85), :stroke)

Regular polygons, from triangles, pentagons, hexagons, septagons, heptagons, octagons, nonagons, decagons, and on-and-on-agons, with:

• ngon(xc, yc, radius, sides, angle, action=:nothing) draws a sides-sided polygon

Without an action, returns a poly (array of points) instead:

• ngon(xc, yc, radius, sides, angle)

Compare:

ngon(0, 0, 4, 4, 0) # returns the polygon's points

    4-element Array{Luxor.Point,1}:
     Luxor.Point(2.4492935982947064e-16,4.0)
     Luxor.Point(-4.0,4.898587196589413e-16)
     Luxor.Point(-7.347880794884119e-16,-4.0)
     Luxor.Point(4.0,-9.797174393178826e-16)

ngon(0, 0, 4, 4, 0, :close) # draws a polygon

Polygons can contain holes. The reversepath keyword changes the direction of the polygon. This draws an hexagonal bolt shape:

ngon(0, 0, 60, 6, 0, :path)
newsubpath()
ngon(0, 0, 40, 6, 0, :path, reversepath=true)
fillstroke()

Polygons can be simplified using the Douglas-Peucker algorithm (non-recursive version):

• simplify(polygon, tolerance) to delete points from an array of Points within the tolerance provided

• isinside(point, polygon) returns true if the point is inside the polygon

Styles

• setline(n) set line width

• setlinecap(s) set line ends to "butt", "round", or "square"

• setlinejoin(s) set line joins to "miter", "round", or "bevel"

• setdash(dashing) set line dashing to "solid", "dotted", "dot", "dotdashed", "longdashed", "shortdashed", "dash", "dashed", "dotdotdashed", or "dotdotdotdashed"

• fillstroke() fill and stroke the current path

• stroke() stroke the current path

• fill() fill the current path

• strokepreserve() stroke the path but keep it current

• fillpreserve() fill the path but keep it current

gsave() and grestore() should always be balanced in pairs. gsave() saves a copy of the current graphics settings (current axis rotation, position, scale, line and text settings, and so on). When the next grestore() is called, all changes you've made to the graphics settings will be discarded, and they'll return to how they were when you used gsave().

• gsave() save the graphics state

• grestore() restore the graphics state

Transforms

• scale(sx, sy) scale by sx and sy

• rotate(a) rotate clockwise (positive x-axis to positive y-axis) by a radians around current 0/0

• translate(tx, ty) translate by tx/ty

The current matrix is a six number array, perhaps like this:

[1, 0, 0, 1, 0, 0]

• getmatrix() gets the current matrix

• setmatrix(a) sets the matrix to array a

• transform(a) transform the current matrix by 'multiplying' it with matrix a. For example, to skew by 45 degrees in x and move by 20 in y direction:

  transform([1, 0, tand(45), 1, 0, 20])

Color and opacity

For color definitions and conversions, use Colors.jl.

The difference between the setcolor() and sethue() functions is that sethue() is independent of alpha opacity, so you can change the hue without changing the current opacity value (like in Mathematica).

• setcolor(color)

  setcolor"gold" (is a string macro, still experimental but might be quicker ...)

  setcolor("gold")

  setcolor("darkturquoise")

  setcolor(convert(Colors.HSV, Colors.RGB(0.5, 1, 1)))

• setcolor(r, g, b, alpha) eg:

  setcolor(.2, .3, .4, .5)

• setcolor(r, g, b)

• sethue(color) like setcolor

• sethue(r, g, b) like setcolor() but doesn't change opacity

• setopacity(alpha) change the alpha opacity (alpha is between 0 and 1)

• randomhue() choose a random color without changing current alpha opacity

• randomcolor() choose a random color

Paths

• newpath()

• newsubpath() used for example to make holes in shapes

• closepath()

• getpath() get the current path as an array of element types and points

• getpathflat() get the current path as an array of type/points with curves flattened to lines

Clipping

• clip() turn the current path into a clipping region, masking any graphics outside the path

• clippreserve() keep the current path, but also use it as a clipping region

• clipreset()

Text and fonts

• text(t, x, y) draw string t at x/y, or at 0/0 if x/y omitted

• textcentred(t, x, y) draw string t centred at x/y or 0/0

• textpath(t) make the string t into a graphic path suitable for fill(), stroke()...

• textcurve(str, x, y, xc, yc, r) draw string str on a circular arc of radius r centered at xc/yc starting on a line passing from xc/yc through x/y

• fontface(fontname) choose font fontname

• fontsize(n) set font size in points

• textextents(str) get array of dimensions of the string str, given current font:

  [xb, yb, width, height, xadvance, yadvance]