Most of the nicer looking images were generated using LaTeX, 12 pt font. Here's a brief sequence of commands: latex foo.tex; dvips -o foo.ps foo.dvi; ps2img.sh foo.ps foo.gif. Script ps2img.sh I found at http://hydro.iis.u-tokyo.ac.jp/~agata/archive/software/ps2img/ .
Unfortunately, the newer distribution of LaTeX, which I got with SUSE Linux, yields ugly-looking fonts, when going through Postscript as an intermediate step. If I directly convert to image, the font is too pale or thin and not very pleasing to an eye. Here's an alternative scheme which works. I used OpenOffice to type in numbers, one per line, using <Shift>-Enter to break the lines, font Century Schoolbook 16 pt (this is kind of similar to LaTeX's times font), the line spacing is “Fixed” at 0.28 in. From within OpenOffice, export file as pdf, then: pdfcrop -margins 10 foo.pdf (pdfcrop comes as part of LaTeX distribution); convert foo-crop.pdf foo.gif (convert is a part of ImageMagick package for Linux). I suspect something similar should work with Microsoft Word but I haven't experimented with it a lot.