Make StackOverflow ad for Julia

## stackad.jl
#!/usr/bin/env julia

using Luxor, Colors

Drawing(600, 500, "/tmp/stackad.png")
origin()
background("white")

# background textifying, not for reading, fortunately
function background_text(str_array, fontsz, beginning::Point, ending::Point)
    gsave()
    sethue("grey75")
    x = beginning.x
    y = beginning.y
    fontsize(fontsz)
    counter=1
    while y < ending.y
        s = str_array[counter] *  " "
        text(s, x, y)
        counter = mod1(counter + 1, length(str_array))
        se = textextents(s)
        x += se[5] # move to the right
        if x > ending.x
           x = beginning.x # next row
           y += fontsz # no linespacing required
        end
        # fade text gradually as we descend
        setopacity(rescale(y, (beginning.y, ending.y), (1.0, 0.0)))
    end
    grestore()
end

# packages are scraped from https://juliaobserver.com 2017-05-11 08:35:33 Top packages
top30packages = ["IJulia:", "Julia", "kernel", "and", "magics", "for", "Jupyter", "Gadfly:", "Crafty", "statistical", "graphics", "Mocha:", "Deep", "Learning", "framework", "for", "Julia", "DataFrames:", "library", "for", "working", "with", "tabular", "data", "DSGE:", "Solve", "and", "estimate", "Dynamic", "Stochastic", "General", "Equilibrium", "models", "JuMP:", "Modeling", "language", "for", "Mathematical", "Optimization", "PyCall:", "Package", "to", "call", "Python", "functions", "Cxx:", "The", "Julia", "C++", "Interface", "Escher:", "Composable", "Web", "UIs", "Plots:", "Powerful", "convenience", "visualizations", "and", "data", "analysis", "Distributions:", "probability", "distributions", "Optim:", "Optimization", "functions", "MXNet", "MXNet:", "flexible", "and", "efficient", "deep", "learning", "ParallelAccelerator:", "The", "ParallelAccelerator", "package", "part", "of", "the", "High", "Performance", "Scripting", "project", "at", "Intel", "Labs", "Knet:", "Koç", "University", "deep", "learning", "framework", "DifferentialEquations:", "suite", "for", "high-performance", "solvers", "of", "differential", "equations", "Convex:", "disciplined", "convex", "programming", "Interact:", "Interactive", "widgets", "Bio:", "Bioinformatics", "and", "Computational", "Biology", "Infrastructure", "Graphs:", "Working", "with", "graphs", "PyPlot:", "Plotting", "based", "on", "matplotlib.pyplot", "Images:", "An", "image", "library", "Lazy:", "Functional", "programming", "GLM:", "Generalized", "linear", "models", "QuantEcon:", "Julia", "implementation", "of", "QuantEcon", "routines", "Winston:", "2D", "plotting", "OpenCL:", "OpenCL", "bindings", "Klara:", "MCMC", "inference", "HDF5:", "Saving", "and", "loading", "data", "in", "the", "HDF5", "file", "format"]

background_text(top30packages, 18, Point(-295, -235), Point(295, 160))

# julia logo (of course)
gsave()
scale(1.2, 1.2)
translate(Point(-170, -190))
julialogo()
grestore()

# slogans
sethue("darkslateblue")
box(Point(0, 120), 600, 100, :fill)
sethue("white")
fontsize(26)
fontface("GothamBold")
text("modern, fast, and open source", 0, 112, halign=:center)
fontsize(19)
text("for data science and technical computing", Point(0, 145), halign=:center)

# github logo file GitHub-Mark-32px.png will need to be downloaded from
# https://github.com/logos
githublogo = readpng("GitHub-Mark-32px.png")
sethue("black")
fontsize(28)
text("Contribute on Github", Point(-10, 220), halign=:center)
placeimage(githublogo, Point(150, 195))

# don't forget that 2 pixel black border
sethue("black")
setline(4) # ! aargh, at this low res, we've got pixel antialiasing problems...
box(O, 600, 500, :stroke)

finish()
preview()