Using LaTeX to generate .png images of an equation

Question

I am familiar with using LaTeX on online websites (like MathOverflow or Physicsforums). My input is rendered using MathJax. However, I do not understand the LaTeX environment in its native OS form. I have downloaded MacTeX, and all I would like to do is make tiny little .png or .jpg files that each contain one equation.

After some Googling, I have tried something along the lines of:

\documentclass[preview]{standalone}
\begin{document}
\begin{equation}
\frac{1}{2} = 0.5
\end{equation}
\end{document}

followed by

pdflatex equation.tex
convert -density 300 equation.pdf -quality 95 equation.png

(using ImageMagick's convert program), but the output contains a number next to my equation that I can't seem to get rid of. Also, this seems like a lot of work, and I don't need a whole documentclass just for one equation. Not to mention pdflatex produces a bunch of other auxiliary files that clutter up my directory during the conversion process. Is there some way I can just easily go from a file containing

\frac{1}{2} = 0.5

to equation.png? Better yet, is there a simple way I can take a file containing a list of equations and have each of them converted into their own little .png image?

Answer 1

standalone class is sufficient. You can enable the multi option, so that the contents of each (math) environment is cropped to its own page in a PDF file. Then you can either save each page directly as a .png image (Acrobat Pro, and perhaps Adobe Reader, allows you to do it in one go), or you can use the convert functionality (need Image Magick) provided with standalone. For the latter method, see Section 4.6 of the standalone documentation.

In the example below I define a new environment mymath, which is basically inline math with display style.

MWE

\documentclass[multi={mymath},border=1pt]{standalone}
% \usepackage{amsmath}
\newenvironment{mymath}{$\displaystyle}{$}

\begin{document}

\begin{mymath}
  \frac{1}{2}=0.5
\end{mymath}

\begin{mymath}
  a^2 + b^2 = c^2
\end{mymath}

\end{document}

Output

Answer 2

Here's what I do to go from a file of equations to png files using asymptote. You'll need the following 3 files in a directory.

sample.bat - change the "5" to alter the png resolution

asy sample -noV -render 5 -f png
pause

sample.dat - this file holds your equations.

\frac{1}{2} = 0.5
y = \sin{x}
a^2 + b^2 = c^2

sample.asy - this is the asymptote code

file fin = input("sample.dat").line();
int index = 1;
while (!eof(fin))
{
    string s = fin;
    if (s == "") { continue; }
    label("$\displaystyle " + s + "$", (0,0));
    shipout("eq"+string(index));
    erase();
    ++index;
}

Running the batch file will create the following 3 png files.

Answer 3

Since you have MacTeX, use LaTeXiT, which lets you convert equations to images in several formats, including PDF and PNG. There is no need to write LaTeX support code: just enter the equation in the input box and press "LaTeX it!".

If you want to convert equations in batch, you can write a simple script that adds the equation to a template based on the standalone class, runs latex, and then dvipng.

There are also web services, such as Roger's Online Equation Editor.

Answer 4

The problem appears to be that latex automatically numbers equations in the equation environment. This default behavior of latex's is likely because authors often need to refer to equations. An easy solution is to remove numbering by using

\begin{equation*}
YOUR EQUATION GOES HERE
\end{equation*}

Answer 5

I want to add my two cents here. I wasn't satisfied with the current solutions so I wrote a script. You can find it here, pnglatex. In its simplest form you can use it like this:

pnglatex -f '\frac{1}{2}'

To get a full list of options use pnglatex -h.

Answer 6

I am missing the reputation to add a comment to Herr K.'s answer...

In order to generate individual PNG files on Windows, you may need to specify the actual convert executable on your path (standalone assumes this to be imgconvert on Windows, instead of convert).

MWE:

\documentclass[
  multi={mymath},
  border=2pt,
  convert={convertexe={convert},density=300,outext=.png}
  ]{standalone}
% \usepackage{amsmath}
\newenvironment{mymath}{$\displaystyle}{$}

\begin{document}

\begin{mymath}
  \frac{1}{2}=0.5
\end{mymath}

\begin{mymath}
  a^2 + b^2 = c^2
\end{mymath}

\end{document}

This generates to following two PNG files:

Answer 7

If you use DMelt (http://jwork.org/dmelt) version 2 and above, you can make PNG file from equation using Python syntax:

from jhplot import *
eq="\\frac{\sin(x*2)}{\int^{100}_{i=0} F(x) dx}"
image="/tmp/equation.png" # output file
# create equation 
q1=HLatexEq(eq, 64)       # font size 64 
q1.export(image)
print "Created :",image
IView(image)              # View this image