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Older articles (2/18)

  1. Attempting a conky replacement in Python (part 2)

    In part 1 we say that a simple replacement for conky for generating a statusline for i3 can be achieved. But since it uses the subprocess module to call external programs it is pretty CPU intensive.

    The question now is if we can reduce that? For that we’re going to use mmap to look at the mailbox, and call sysctlbyname(3) using ctypes to get the remaining system information. Note that sysctl et al and the names used are specific to FreeBSD.

  2. Adding text or graphics to a PDF file (again)

    In an earlier article I talked about using a picture environment in LaTeX to add lines and text over an image. In another article I showed how to draw with PostScript, including using Encapsulated PostScript to include arbitrary images.

    In this article I want to cover the pros and cons of these methods and introduce a third method: TikZ.

  3. ImageMagick: convert vs Wand

    The ImageMagick suite has been in my software toolbox for years. It is my go-to tool for manipulating bitmap images. Over the years I have written several front-ends for specific tasks for in Python.

    In general, I have used the subprocess module to launch convert or mogrify from Python.

    With the release of Wand 0.5.0 which supports ImageMagick 7, I decided to try that by porting one of my scripts (foto4lb) to it.

  4. 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 tell you that this is definitely an improvement.

    Although I use LaTeX for things that require high-quality typesetting, these days almost all my other writings are in reStructuredText.

    The previous pelican version 3.7 was basically the last Python 2.7 application that I use. So now that pelican supports Python 3, I’m switching. Since Pelican 4 is not in the FreeBSD ports tree yet, I’m installing it myself.

    Note

    As of 4.0.1, Pelican is now in the FreeBSD ports tree and I’m using the port www/py-pelican. At the moment I’m still installing typogrify and smartypants by hand.

  5. 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 weighing them.

    For those familiar with gelcoat spraying, this is not a system with coupled gelcoat and peroxide pumps. But rather an external mixing spray gun where the peroxide is simply fed from a pressurized container to the spray gun.

    Since we’re handling resins, solvents and peroxide, protective equipment including gloves is a must. That makes it cumbersome to whip out a smartphone to use it as a calculator to check the ratio. Since you don’t want to get gelcoat or peroxide on your expensive phone, you have to take off your gloves to handle it. This would have to be repeated several times.

    So I decided to make a diagram where one could relatively easy read off the peroxide percentage given the quantities of both components. This can be printed and laminated between plastic to make it resistant against stains.

    The whole thing can be found in a github repo.

  6. 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 a sense, I’ve always been dissatisfied with them.

    When the book Mathematical Illustrations was mentioned on hacker news, this re-kindled my interest in PostScript. And I learned some valuable lessons from it.

  7. 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.


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