#+LATEX_HEADER: \usepackage{tikz}

* Tikz test
Here's a tree, exported to both html and pdf.

#+header: :file (by-backend (latex "tree.tikz") (t "tree.png"))
#+header: :imagemagick yes :iminoptions -density 600 :imoutoptions -geometry 800
#+header: :results file raw
#+header: :fit yes
#+header: :headers '("\\usepackage{tikz}")
#+begin_src latex
  \usetikzlibrary{trees}
  \begin{tikzpicture}
    \node [circle, draw, fill=red!20] at (0,0) {1}
    child { node [circle, draw, fill=blue!30] {2}
      child { node [circle, draw, fill=green!30] {3} }
      child { node [circle, draw, fill=yellow!30] {4} }};
  \end{tikzpicture}
#+end_src

The same, with shorter syntax

#+header: :file (by-backend (latex "tree2.tikz") (t "tree2.png"))
#+begin_src tikz
  \usetikzlibrary{trees}
  \begin{tikzpicture}
    \node [circle, draw, fill=red!20] at (0,0) {1}
    child { node [circle, draw, fill=blue!30] {2}
      child { node [circle, draw, fill=green!30] {3} }
      child { node [circle, draw, fill=yellow!30] {4} }};
  \end{tikzpicture}
#+end_src

* COMMENT evaluate this first
#+begin_src emacs-lisp :results silent
(defmacro by-backend (&rest body)
  `(case org-export-current-backend ,@body))

(org-babel-do-load-languages
 'org-babel-load-languages
 '((latex . t)))

(defalias 'org-babel-execute:tikz 'org-babel-execute:latex)

(add-to-list 'org-src-lang-modes '("tikz" . latex))

(defvar org-babel-default-header-args:tikz
  '((:imagemagick . "yes")
    (:iminoptions . "-density 600")
    (:imoutoptions . "-geometry 300")
    (:results . "file raw")
    (:fit . "yes")
    (:headers . "'(\"\\\\usepackage{tikz}\")")))
#+end_src