Roland's homepage

My random knot in the Web


This is my home in the virtual world, where I write about things that I want to share. The freely available software that I've written as well as some of the photographs I've taken over the years can also be found here. Please use the navigation links on the right if you are looking for something.

Recent articles

  1. Installing Pelican 4

    Pelican is the static site generator that I use for my website. This allows me to write my website posts in almost plain text (actually a light-weight markup language named reStructuredText), which are then translated into HTML. As someone who has written his webpages in HTML by hand, I can …

  2. Creating a nomogram with Python and Postscript

    At work I needed a suitable way to check the calibration of gelcoat spray equipment. Gelcoat requires an initiator (often called “catalyst”) in the form of a peroxide to cure. The peroxide/gelcoat ratio is important, so it is checked regularly by spraying the separate components into suitable containers and …

  3. Drawing with PostScript

    PostScript (in the form of ghostscript) was for me the first way to generate vector graphics outside of a CAD program. I have several hundreds of figures written in PostScript for inclusion in e.g. LaTeX document.

    Later I’ve started using other programs like metapost and asymptote. But in …

  4. TeXLive 2018 update

    Today I updated my TeXLive install to 2018. Although the install went fine, there was a problem with the binaries.

    Both asymptote and xetex were linked to different versions of some libraries than those that are supplied by ports. So I had to rebuild them.


    Some might wonder why …

  5. Measuring particulate matter with the PMS5003

    This article details how I used the Plantower PMS5003 particulate matter (“PM”) sensor on a PC or laptop, using an FT232H breakout board to make the connection.


    My reasons for buying this device are so that I can measure airborne particulate matter at home and at work. So I …

  6. Storing and graphing time-based data

    In this article we will look into the best way to store time-based data and use it with gnuplot.


    The first thing to realize is that we should specify a timezone when specifying dates and times (“datetimes”). To prevent calculations, I tend to use datetimes in UTC.


    Next …

  7. Video manipulation with ffmpeg

    Serveral useful recipes for manipulation video with ffmpeg.

    Note that a name within angle brancket (like <this>) represents a generic input or output file.

    Extracting raw audio

    The following recipe extracts the audio from a video file and converts it to WAV format.

    ffmpeg -y -hide_banner -i <input> -vn -c …

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