standalone package: reconstruction of the command line

Question

With current version of ImageMagick, ImageMagick 7.0.7-21 Q16 x64 2018-01-06 application filename is long ago magick so the standalone package should be invoked by something like this:

\documentclass[convert={convertexe=magick,density=200,outext=.png}]{standalone} 

which sends command

magick -density 200 filename.pdf filename.png

to the prompt. Now this procedure results with PNGs with a transparent background. To avoid transparence prompt command should be changed to

magick -density 200 filename.pdf -alpha remove filename.png

that is, -alpha remove should be put between two filenames. This means that -alpha remove cannot be simply attacked to density=200, as proposed elsewhere: converting a table to png using standalone.

I went through the standalone package, and Pg. 17 of the manual suggests that command prompt could be reconstructed using sub-option command. So what I actually tried to do is this:

\documentclass[tikz,convert={convertexe=magick,density=200,outext=.png,command={\convertexe\space -density \density\space \infile\space -alpha remove\space \outfile}}]{standalone}

However, it seems that command reconstruction does not work, as PdfLatex compiler from Miktex returns ! Undefined control sequence. upon invoking \convertexe.

The example in the manual reads:

command={\convertexe\space -density \density\space \infile\space \ifx\size\empty\else -resize \size\fi\space -quality 90 \outfile}

What is wrong? Did I misread the instructions?

Answer 1

If I have the following test.tex file

\documentclass[tikz,convert]{standalone}

\begin{document} 

\begin{tikzpicture}
\draw (0,0) rectangle (2,1) node [midway] {Example};
\end{tikzpicture}

\end{document}

along with the following standalone.cfg file in the same directory

\standaloneconfig{
  multi=false,
  crop,
  convert={
    convertexe=magick,
    density=200,
    outext=.png,
    command={%
      \convertexe\space
      -density \density\space
      \infile\space
      -alpha remove\space
      \outfile
    }
  }
}

then running

pdflatex -shell-escape test

results in calling the external program

magick -density 200 test.pdf -alpha remove test.png

as can be seen in the test.log file by looking for runsys. Indeed, if I ask for information about the file, I get

> file test.png
test.png: PNG image data, 1700 x 2200, 4-bit grayscale, non-interlaced

Update

You can specify the commands also in the options, but with a small tweak:

\documentclass[
  tikz,
  multi=false,
  crop,
  convert={
    convertexe=magick,
    density=200,
    outext=.png,
    command=\unexpanded{%
      \convertexe\space
      -density \density\space
      \infile\space
      -alpha remove\space
      \outfile
    },
  },
]{standalone}

\begin{document} 

\begin{tikzpicture}
\draw (0,0) rectangle (2,1) node [midway] {Example};
\end{tikzpicture}

\end{document}

In the log file I find

runsystem(magick -density 200 conv.pdf -alpha remove conv.png)...executed.

and the generated file reports

> identify test.png
test.png PNG 159x80 159x80+0+0 8-bit Gray 16c 900B 0.000u 0:00.000