Module: Calculus::Latex

Included in:
Expression
Defined in:
lib/calculus/latex.rb

Overview

Renders expression to PNG image using latex<tt> and <tt>dvipng

Constant Summary collapse

TEMPLATE =

Basic latex template which use packages amsmath and amssymb from standard distributive and set off expression with $$.

<<-EOT.gsub(/^\s+/, '')
  \\documentclass{article}
  \\usepackage{amsmath,amssymb}
  \\begin{document}
  \\thispagestyle{empty}
  $$ # $$
  \\end{document}
EOT

Instance Method Summary collapse

Instance Method Details

#missing_commands ⇒ Object

Check LaTeX toolchain availability and returns array of missing tools



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# File 'lib/calculus/latex.rb', line 49

def missing_commands
  commands = []
  commands << "latex" unless can_run?("latex -v")
  commands << "dvipng" unless can_run?("dvipng -v")
  commands
end

#to_png(background = 'White', density = 700) ⇒ Object

Render image from source expression string. It is possible to pass background color (default: 'White') and density (default: 700). See dvipng(1) page for details.

Raises CommandNotFound exception when some tools not available.

Returns path to images. Note that caller should take care about this file.



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# File 'lib/calculus/latex.rb', line 31

def to_png(background = 'White', density = 700)
  raise CommandNotFoundError, "Required commands missing: #{missing_commands.join(', ')} in PATH. (#{ENV['PATH']})" unless missing_commands.empty?

  temp_path = Dir.mktmpdir
  Dir.chdir(temp_path) do
    File.open("#{sha1}.tex", 'w') do |f|
      f.write(TEMPLATE.sub('#', self.to_s))
    end
    `latex -interaction=nonstopmode #{sha1}.tex && dvipng -q -T tight -bg #{background} -D #{density.to_i} -o #{sha1}.png #{sha1}.dvi`
  end
  return File.join(temp_path, "#{sha1}.png") if $?.exitstatus.zero?
ensure
  File.unlink("#{sha1}.tex") if File.exists?("#{sha1}.tex")
  File.unlink("#{sha1}.dvi") if File.exists?("#{sha1}.dvi")
end