Archive for Linux

Qalculate!, My New Favorite Calculator

Over the past few years I acquired a bad habit of using search engines for basic calculations and conversions. I’m not talking about the stuff you should just do in your head — not quite that bad, but about the fact that most Linux distros don’t seem to ship with a calculator by default. So I finally got around to testing some programs and Qalculate! does all I want. You can install it on Debian using sudo apt install qalculate-gtk. There’s a list of features on the website. Enjoy a few screenshots.

qalculate-conversion-celsius-fs8
Celsius to Fahrenheit.
qalculate-conversion-km-fs8
Kilometer to mile.
qalculate-conversion-money-fs8
Euro to Dollar.

I hope you’ll like it too!

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Image Optimization Guide

On the forum I administer, I am forced to run a tight attachment policy. Disk space doesn’t grow on trees. Occasionally this leads to questions about the small attachment size limit of 50 KiB. This guide is intended to clarify that this is not nearly as tiny as you might think. Note that although I’ll mention commands without much explanation for the sake of brevity, you’re always recommended to further explore the possibilities offered by those commands with the --help flag as well as by running man the-command-here.

First you need to ask yourself what kind of file type is appropriate, if you have the choice. On screenshots, the main purpose of attachments on my forum, you’ll often encounter large areas of uniform background colors. PNG is therefore almost invariably the right choice. Crop out everything but what’s relevant. JPEG is appropriate for more dynamic pictures such as photographs. If you want to do a lot with photographs, you might want to consider an external hosting service. My wife likes SmugMug. Still, for thumbnails you might be able to do a fair bit more within a few hundred KiB than you might think. Finally, the vector graphics in SVG result in pictures that always look sharp. You’ll typically have drawn these in a program like Inkscape or Adobe Illustrator.

Table of Contents

  1. 1. Optimizing JPEG
  2. 2. Optimizing PNG
  3. 3. Optimizing SVG
  4. Addendum A: Scanned Documents
  5. Addendum B: Video

1. Optimizing JPEG

Often you’ll want to crop your file. Do not edit your JPEG followed by resaving it because this will result in reduced quality! You can crop losslessly with cropgui. On Windows you can use IrfanView.

If you don’t want to crop, and also potentially for some post-cropgui optimization, use jpegtran -copy none -progressive -optimize file.jpg > file-opt.jpg. Note that this will get rid of all metadata, which may be undesirable. If so, use jpegtran -copy all -progressive -optimize file.jpg > file-opt.jpg.

Of course if you want to scale down your JPEG there’s no point in mucking about with lossless cropping first. After scaling down, check how long your quality can go (also see a little helper script I wrote). In any case, you should avoid introducing any unnecessary compression steps with associated quality loss. Here are some results:

  • The original 11.jpg at 2.19 MB.
  • Losslessly cropped 11-crop.jpg at 1.11 MB.
  • Optimized with -copy all -progressive -optimize 11-crop-opt.jpg at 1.04 MB. -copy none would’ve saved an extra whopping 40-some KiB, which on this kind of filesize has little benefit, and besides, I quite like the metadata. For thumbnail-sized files the balance is likely to be different. For example, the 52.2 KiB SmugMug auto-generated thumbnail below can be insignificantly reduced to 51.1 KiB with --copy all, but to 48.2 KiB with --copy none. I think an 8% reduction is not too shabby, plus it brings the file size down to under the arbitrary 50 KiB limit on my forum.

2. Optimizing PNG

As I wrote in the introduction, for screenshots PNG is typically the right choice. If you want to use lossless PNG, use optipng -o7. In my experience it’s ever so slightly smaller than other solutions like pngcrush. But as long as you use a PNG optimizer it shouldn’t much matter which one you fancy. Also see this comparison.

If you don’t care about potentially losing some color accuracy, use pngquant instead. To top it off, if you really want to squeeze out your PNG, you can pass quality settings with --quality min-max, meaning you can pass --quality 30-50 or just --quality 10. Here are some quick results for the screenshot in the SVG section below, but be sure to check out the pngquant website for some impressive examples.


$ du -h --apparent-size inkscape-plain-svg.png
27K	inkscape-plain-svg.png

$ du -h --apparent-size inkscape-plain-svg-fs8\ default.png 
7.6K	inkscape-plain-svg-fs8 default.png

$ du -h --apparent-size inkscape-plain-svg-fs8\ quality\ 10.png 
4.3K	inkscape-plain-svg-fs8 quality 10.png

In this case there is no visual distinction between the original PNG and the default pngquant settings. The quality 10 result is almost imperceptibly worse unless you look closely, so I didn’t bother to include a sample.

3. Optimizing SVG

For using SVG on the web, I imagine I don’t have to tell you that in Inkscape, you should save your file as Plain SVG.

Save as Plain SVG in Inkscape.

What you may not know is that just like there are lossy PNGs, you can also create what amounts to lossy SVGs. There are some command-line tools to optimize SVGs, including (partially thanks to this SO answer):

  • Scour is probably the best command line tool for some quick optimization. You can just use the defaults like scour < in.svg > out.svg or scour -i in.svg -o out.svg. But I recommend you go further.
  • SVGO (SVG Optimizer)
  • SVG-optimiser (by Peter Collingridge)
  • SVG-editor (by Peter Collingridge

My personal preference for squeezing out every last byte goes toward the web-based version of the SVG-editor by Peter Collingridge. By running it in a browser with inferior SVG support such as Firefox, you’ll be sure that your optimized SVG still works properly afterward. The command line tools can only safely be used for basic optimizations, whereas the effects of going lossy (such as lowering precision) can only be fully appreciated graphically.

Addendum A: Scanned Documents

Scanned documents are a different item altogether. The best format for private use is DjVu, but for public sharing PDF is probably preferable. To achieve the best results, you should scan your documents in TIFF or PNG, followed by processing with unpaper or ScanTailor. If you’ve already got a PDF you’d like to improve, you can use pdfsandwich or my own readablepdf.

Addendum B: Video

I’m not aware of any lossless optimization for video compression such as offered by jpegtran, but you can often losslessly cut video. In the general purpose Avidemux, simply make sure both video and audio are set to copy. There is also a dedicated cross-platform app for lossless trimming of videos called, unsurprisingly, LosslessCut. If you do want to introduce loss for a smaller file size you can use the very same Avidemux with a different setting, ffmpeg, mpv, VLC, and so forth. You can get reasonable quality that’ll play many places with something like:

ffmpeg -i input-file.ext -c:v libx264 -crf 19 -preset slow -c:a libfaac -b:a 192k -ac 2 output-file.mp4

For the open WebM format, you can use along these lines:

ffmpeg -i input.mp4 -c:v libvpx -b:v 1M -c:a libvorbis output.webm

More examples on the ffmpeg wiki. Note that in many cases you should just copy the audio using -acodec copy, but of course that’s not always an option. Extra compression artifacts in audio detract significantly more from the experience than low-quality video.

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libGL error in Steam and Broken Age in Debian Stretch

After some update or other, Broken Age refused to start.

$ ./start.sh 
Running Broken Age
libGL error: unable to load driver: radeonsi_dri.so
libGL error: driver pointer missing
libGL error: failed to load driver: radeonsi
libGL error: unable to load driver: swrast_dri.so
libGL error: failed to load driver: swrast
X Error of failed request:  BadValue (integer parameter out of range for operation)
  Major opcode of failed request:  155 (GLX)
  Minor opcode of failed request:  3 (X_GLXCreateContext)
  Value in failed request:  0x0
  Serial number of failed request:  91
  Current serial number in output stream:  92

Oh well, let’s give it a little hand, shall we?

LD_PRELOAD='/usr/lib/i386-linux-gnu/libstdc++.so.6 /lib/i386-linux-gnu/libgpg-error.so.0' ./start.sh

This loads the included libraries before any others, in order to override the incompatible libraries shipped with the program in question. The same trick also works for Steam. If gaming is your goal, you should probably stick to whatever version of Ubuntu is supported best. I’m just pleased that I can play the occasional game like Oxenfree (no preloading required, mind you) or Broken Age on my workhorse without having to install any stability-reducing binary blobs.

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Fix No gksu(do) Permissions Prompt on Gparted, Synaptic, Mounting Drives, Etc. in Debian

I run Debian Stretch (testing) as my daily driver, and at some point I stopped being able to start programs like start Synaptic, Gparted, Synaptic etc. without manually typing gksu(do). The solution is as simple as it is seemingly unnecessary and stupid:

sudo apt install policykit-1-gnome

The problem is apparent upon reading the description:

This implementation was originally designed for GNOME 2, but most
GNOME-based desktop environments, including GNOME 3, GNOME Flashback,
MATE and Cinnamon, have their own built-in PolicyKit agents and no
longer use this one. The remaining users of this implementation
are XFCE and Unity.

Reported as Debian bug #843224. My first?


D’oh, I wrote this on November 5, 2016. I’ll still publish it anyway in case it’ll still help someone searching for a solution.

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Workarounds for Turning Off Your DisplayPort Monitor

Sometimes you jot down a few quick notes for yourself without bothering to turn them into a blogpost that might be useful to others. This is one of those notes. First, I’ll introduce my computer monitor workflow as it’s been since time immemorial, also known as ’95 or ’96. Just like how I turn off lights I don’t use, I’ve always turned off my monitor when I wanted it. This has never been a problem, until in early 2015 I had to use DisplayPort for the first time. If you want an UltraHD monitor, which you do if you care even the tiniest bit about sharpness and clarity, you have to use DisplayPort.

But DisplayPort isn’t nice. Turning off your monitor is treated the same as disconnecting it. In Windows this means everything resets itself to some absurdly low resolution, whereas in Linux the consequences can be even worse (like having to SSH in from another computer to run an xrandr command to reactivate the monitor). This means you either face a colossal waste of energy or continuous annoyance at the fact that your monitor has turned itself off yet again. In my view monitor timeouts should be at least twenty minutes, just as a failsafe in the extremely unlikely event that you forgot to turn it off. Luckily I found two reasonable workarounds within the first week or two of having acquired my UHD monitor.

The first?

xset dpms force off

This has the same effect as your monitor timeout, only at your volition. I tend to find the blinking light on the monitor somewhat annoying, but this nevertheless remains your best bet to quickly turn the screen off as part of your regular workflow.

The second method consists of actually turning the monitor off. Besides getting rid of the blinking light I figure it saves just a tiny bit more electricity to boot. Which is useful if you want to keep your computer active, but not your monitor. For this method you have to switch to TTY (Ctrl + Alt + F1-6) before turning your monitor off. Then when you turn your monitor back on, X won’t know it’s been missing. Switch back with Ctrl + Alt + F7.

I’m still hopeful that there might simply be an xorg.conf setting I’ve overlooked, but in any case these workarounds serve their purpose. Note that xset dpms force off is also tremendously useful on laptops that don’t have a function key for turning off the screen. Standby often just isn’t what you want.

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Scanning with an HP MFP (multi-function peripheral) on Debian

You need to install hplip. It looks like something’s still off about the colors compared to Ubuntu and Windows, and I can’t figure out what the difference is. Alas. :/ Also, don’t buy HP.

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Less is More

A minimal Debian install comes without the ability to view man pages. Fair enough, it’s minimal after all. But they can be quite useful. A sudo apt install man later results in man pages being shown. That’s all, folks? Unnfortunately not, because the man pages are shown using the more command, which doesn’t allow for scrolling up and down with the arrow keys or j and k, Pg Up and Pg Dn, and all the other usual niceties. To fix you need to sudo apt install less, a “pager program similar to more.” And better, at least on any machine with sufficient RAM. Meaning anything anyone is likely to use in 2016, or probably also in 1990 for that matter.

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Let’s Encrypt on Debian/Jessie

Wow, that was easy. I’ve been reading about Let’s Encrypt all over the place, and I wouldn’t like any snooping on my feeds password, now would I?

  1. Add the jessie-backports repository.
  2. sudo apt install -t jessie-backports certbot python-certbot-apache
  3. sudo letsencrypt --apache -d example.com [-d subdomain.example.com]

This stuff expires every 90 days, so you still need a cron job to renew.

sudo crontab -e

Let’s say 4 at night every Sunday.

* 4 * * 0 letsencrypt renew >> /var/log/letsencrypt-renew.log

Neat!

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Cloud, Kluit, Clod?

Just a quick demonstration of the power of openclipart.org. I dubbed my “personal cloud” experiment kluit: a Dutch word meaning both clod and the ball of earth around the roots of a tree. In other words, kluit is firmly grounded because you’ve got your own ground with you wherever you go. Be like Dracula. With a name in mind, I also wanted a matching logo. Following a quick search for leaves, root (or was it tree) and after a little initial play something like attraction, this is the quick and satisfying result.

A couple of floating leaves still connected with their roots. This arrangement symbolizes how creating your personal cloud keeps it grounded.

And of course the remix is free for all. Enjoy.

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Using Syncthing to Replace Dropbox on Android

According to the timestamp on Getting Started.pdf, I’ve been a happy Dropbox user since 2010. For probably equally many years, they’ve had the most obnoxious Android app. Perhaps I don’t want to put my whole Dropbox on my Android phone (although I’m not so sure I don’t), but obviously you should be able to select a whole directory to sync. Solutions like Dropsync are unfortunately super slow, probably because it seems to be mostly a clever hack that syncs files one by one.

Instead of a similar alternative, I’ve really always been irked by the lack of an easy to use Unison-like sync for my phone. Running Unison in a chroot just doesn’t quite cut it… The obvious solution is something like Syncthing or Bittorrent Sync, which works regardless whether or not there’s a remote server involved. And if there is, it’d be a remote server under my own control.

Syncthing isn’t ideal because of its lack of subdirectory selection. But since in reality it’s almost exclusively a one-way street anyway, it doesn’t matter so much. The main point is that this is all easier than running an FTP server on the device, plugging it in over USB, running a webserver on it to drop files into a browser window or whatever other overly complicated solutions might exist. To install Syncthing, get it on F-Droid. Or Google Play, if you don’t think it’s obnoxious.

You can get by almost entirely on F-Droid alone. In fact it’s where most of the best software is found.

Unfortunately Syncthing can’t sync wherever. Oh well, we’ll just sync within its own directory instead.

On my phone, Syncthing can’t handle the MicroSD card, but we can trick it.

It’ll make some things a touch more complicated. Maybe a symlink? Oh drat, FAT32 strikes again. Meh.

Aard Dictionary doesn’t care where it’s located.
Add a favorite, a shortcut, or both. It’ll be difficult to interact with the directory otherwise.

The sync problem isn’t really solved yet, but it’s sure a lot better. All in all, Android is still awful and you should probably consider getting an Ubuntu Phone instead. The end.

As for Syncthing, perhaps its most interesting property is that it can largely replace both Dropbox and Unison. In fact it can probably completely replace Unison for me, because I haven’t actually bothered replicating my stuff onto a separate physical HDD in years. And Syncthing definitely makes it easier to add more of my laptops and whatnot into the mix. On the flipside, the fact that I run Unison once a week or so forces a kind of built-in review of the changes I made, so I can undo them if desired. In this way it’s more like a backup. But of course, Syncthing can sync between more than two computers at once, while the changes are happening. It’s worth a look, if nothing else.

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