Turns a math expression in Latex-format into a png to be used in a markdown document

latex-picture.el

;; Turn region into Latex-picture
(defun latex-picture (start end)
  (interactive "r")
  (let ((hex-string (url-hexify-string 
		   (filter-buffer-substring start end))))
    (delete-region start end)
    (insert (concat "![](http://www.sitmo.com/gg/latex/latex2png.2.php?z=100&eq="
		    hex-string
		    ")"))))