color assimilation grid illusion

The image [..] is a visual/artistic experiment playing with simultanous contrast resulting from other experiments these days. An over-saturated colored grid overlayed on a  grayscale image causes the grayscale cells to be perceived as having color.
The processing needed to create the above image happened along with unrelated but significant code improvements In the last couple of weeks. I have been visiting mitch – a prolific GIMP contributors for collaboration – and lots of progress has been – and is still – being made on babl, GEGL and GIMP.

original article
See the effect in a video

You can now play with this effect and experiment for yourself. Get Gimp and enjoy!

host GIT repositories painlessly

As people around me discuss what to go for in regards to manage their growing number of private GIT repositories I joined their discussion.

A couple of years ago I assessed how I would want to store my collection of almost 100 GIT private repositories and all those cloned mirrors I want to keep for archival and sentimental reasons.

An option was to pay for GitHub. Another option, which most seemed to prefer, was going for a local Gitlab set-up.

All seemed not desirable. Like chaining my workflows to GitHub as a provider or adopting a new hobby to operate and maintain a private GitLab server. And as it might have become easier to operate a GitLab server with the introduction of container management systems. But I’ve always seemed to have to update to a new version when I actually wanted to use it.

So this was when I had to make the call for my own set-up about 4 years ago. We were using a rather well working GitLab set-up for work back then. But it all seemed overkill to me also back then.

So I found:

It runs with one command, the only dependency is two file system directories with (a) the settings of gogs and (b) your repositories.

It’ll deploy as literally a SINGLE BINARY without any other things to consider. With the provided dockerfile you are up and running in seconds.

It has never let me down. It’s running and providing it’s service. And that’s the end of it.

I am using it, as said, for 95 private repositories and a lot of additionally mirrored GIT repositories. Gogs will support you by keeping those mirrors in sync for you in the background. It’s even multi-user multi-organization.

code autocomplete with deep learning

When you are writing code the patterns seem to repeat every once in a while. Not only the patterns but also the occasion you are going to apply certain code styles and methods while developing.

To support a developer with this creative work the tedious and repetitious tasks of typing out what is thought can be supported by machine learning.

Chances are your favourite IDE already supports an somehow AI driven code autocomplete feature. And if it does not, read on as there are ways to integrate products like TabNine into any editor you can think of…

Visual Studio IntelliCode is a set of AI-assisted capabilities that improve developer productivity with features like contextual IntelliSense, argument completion, code formatting, and style rule inference.

IntelliCode augments existing developer workflows with machine-learning services that provide an understanding of code and its context. It’s applicable for C#, C++ (in preview), JavaScript/TypeScript (in preview), and XAML code today, and will be updated in the future to support more languages.

Visual Studio IntelliCode

Of course there are some new contenders to the scene, like TabNine:

TL;DR: TabNine is an autocompleter that helps you write code faster. We’re adding a deep learning model which significantly improves suggestion quality. You can see videos below and you can sign up for it here.


Deep TabNine requires a lot of computing power: running the model on a laptop would not deliver the low latency that TabNine’s users have come to expect. So we are offering a service that will allow you to use TabNine’s servers for GPU-accelerated autocompletion. It’s called TabNine Cloud, …


fiddle with .NET in your browser

There are a lot of different “fiddles”. There’s JSFiddle, SQLFiddle, HTMLFiddle, RegExFiddle, PythonFiddle, R-Fiddle, GoFiddle. There is even a page that curates a list of fiddles.

For .NET there’s one too. It supports C#, F# and VB.NET. For trying something quickly or sharing it online this is a nice way to do it:

Hello World C#
MVC even

retrofit an old printer to be available on the network

In 2007 I had become proud owner of a Samsung ML-2010 mono laser printer. It’s done a great job ever since and I can recall changing the toner just once so far.

So you can tell: I am not a heavy printer user. Every so often I gotta print out a sheet of paper to put on a package or to fill out a form. A laser printer is the perfect fit for this pattern as it’s toner is not going-bad or evaporating like ink does in ink-printers.

So I still like the printer and it’s in perfect working condition. I’ve just recently filled up the toner for almost no money. But – but this printer needs to be physically connected to the computer that wants to print.

As the usage patterns have significantly changed in the last 12 years this printer needs to be brought into todays networked world.

Replacing it with a new printer is not an option. All printers I could potentially purchase are both more expensive to purchase and the toner is much more expensive to refill. No-can-do.

If only there was an easy way to get the printer network ready. Well, turns out, there is!

First let’s start introducing an opensource project: CUPS

CUPS (formerly an acronym for Common UNIX Printing System) is a modular printing system for Unix-like computer operating systems which allows a computer to act as a print server. A computer running CUPS is a host that can accept print jobs from client computers, process them, and send them to the appropriate printer.


A good, cheap and energy-efficient way to run a CUPS host is a Raspberry Pi. I do own several first-generation models that have been replaced by much more powerful ones in the previous years.

So I’ve taken one Raspberry Pi and did the set-up steps: Installing the Raspberry Pi Print Server Software.

And now – what did I get?

I got a networked Samsung Laser Printer. No thrills, no problems at all.

the CUPS web interface
the printer shows up on Linux (Ubuntu here)
on iOS and macOS the printer magically appears
on Windows 10.

TAICHI: opensource computer graphics library

I am following the proceedings of ACM SIGGRAPH conferences for more than 20 years now and with the recent years development in computational capacity it seems that many more algorithms and ideas make it to an application near you.

Take this one contribution by Yuanming Hu for example – the Taichi open source computer graphics library:

Taichi is an open-source computer graphics library that aims to provide easy-to-use infrastructures for computer graphics R&D. It’s written in C++14 and wrapped friendly with Python.

Yuanming Hu has been working on the development of Taichi since his third undergrad year (2016), mainly in his spare time. He would like to thank Prof. Toshiya Hachisuka and Prof. Seiichi Koshizukafor making possible his internship at UTokyo, where the initial parts of Taichi were developed.

Taichi: About

Also interesting, trivia about the name:

Tool: Partition Recovery and Undelete – Testdisk

Mass storage hardware breaks all the time. Sometimes it’s hardware that breaks, but sometimes it’s the software that breaks. If it’s the software (or own talent) that made the data go boom, TestDisk is a tool you should know about.

DISCLAIMER: If the data you are trying so recover is actually worth anything you might want to reserve to a professional data recovery service rather than trying to train-on-the-job.

Apart from the availability of pre-compiled packages for most operating systems you can also grab a bootable LiveCD when everything seems gone and lost.

The process itself is rather exciting (if you want the data back) and may require a fresh pair of pants upfront, throughout and after.

Thankfully there’s a great wiki and documentation of how to go about the business of data recovery.

TestDisk is powerful free data recovery software! It was primarily designed to help recover lost partitions and/or make non-booting disks bootable again when these symptoms are caused by faulty software: certain types of viruses or human error (such as accidentally deleting a Partition Table). Partition table recovery using TestDisk is really easy.

  • TestDisk can
    • Fix partition table, recover deleted partition
    • Recover FAT32 boot sector from its backup
    • Rebuild FAT12/FAT16/FAT32 boot sector
    • Fix FAT tables
    • Rebuild NTFS boot sector
    • Recover NTFS boot sector from its backup
    • Fix MFT using MFT mirror
    • Locate ext2/ext3/ext4 Backup SuperBlock
    • Undelete files from FAT, exFAT, NTFS and ext2 filesystem
    • Copy files from deleted FAT, exFAT, NTFS and ext2/ext3/ext4 partitions.

TestDisk has features for both novices and experts. For those who know little or nothing about data recovery techniques, TestDisk can be used to collect detailed information about a non-booting drive which can then be sent to a tech for further analysis. Those more familiar with such procedures should find TestDisk a handy tool in performing onsite recovery.

And if you give up, think about writing an article of you actually digging deeper:

Wireless Network Mapping – data source and data sink

When you work with wireless networks and you do programming and mobile app development that works with things like user location you might find this useful.

Take thousands of users and you’ve got the worlds wifi networks mapped…

WiGGLE (Wireless Geographic Logging Engine) is a project which takes wireless network data + location and puts it into a big database. On top of storage it’s giving you access to that data.

We consolidate location and information of wireless networks world-wide to a central database, and have user-friendly desktop and web applications that can map, query and update the database via the web.

So what’s my use-case? Apart from the obvious I will make use of this by finding out more about those fellow travelers around me. Many people probably to the same as me: Travel with a small wifi / 4g access point. Whenever this accesspoints shows up in scans the path will be traceable.

I am curious to see which access point around me is in the million-mile club yet…

full website screenshots from your commandline

Think of this: You want to capture a whole, multi-scroll-pages, web-page into one image.

This can be difficult without the right tools. It surely will be a lot of work to accomplish a 10th of thousand pixel height screenshot put together from multiple single screenshots…

CutyCapt is there to help! It’s a command line tool encapsulating the very powerful WebKit browser engine to render a full page and then create a single file screenshot of the whole page for you.

By example, this is what it did when told to screenshot this website:

PixelFed – Federated Image Sharing

In search of alternatives to the traditional centralized hosted social networks a lot of smart people have started to put time and thought into what is called “the-federation”.

The Federation refers to a global social network composed of nodes that talk to each other. Each of them is an installation of software which supports one of the federated social web protocols.

What is The Federation?

You may already have heard about projects like Mastodon, Diaspora*, Matrix (Synapse) and others.

The PixelFed project seems to gain some traction as apparently the first documentation and sources are made available.

PixelFed is a federated social image sharing platform, similar to instagram. Federation is done using the ActivityPub protocol, which is used by Mastodon, PeerTube, Pleroma, and more. Through ActivityPub PixelFed can share and interact with these platforms, as well as other instances of PixelFed.


I am posting this here as to my personal logbook.

Given that there’s already a Dockerfile I will give it a try as soon as possible.

WiFi QR Code Generator

Whenever we arrive at a place that we have not been before it is important to get properly connected to the internet.

Finding wifi SSIDs and typing passwords is tedious and prone to errors. There is an easier way of course!

The owner of the wireless network can generate a QR code that you can easily take a photo of and your phone will automatically prompt you to log into the wireless network without you having to type anything.

On your phone it looks like this:

To generate these QR codes that contain all information for visitors/new users to connect this simple tool / online generator can be used:

Ever wanted to create a cool QR code for your guests? But never wanted to type in your WiFi credentials into a form that submits them to a remote webserver to render the QR code? QiFi for the rescue! It will render the code in your browser, on your machine, so the WiFi stays as secure as it was before (read the code if you do not trust text on the internet :-))!

Don’t worry: your access point information is not transferred over the internet. As this is open source at the time of writing the data was held in HTML 5 local storage on the local browser only and not transferred out.

bridge the openvpn-status.log to MQTT

For big parts of my VPN needs I use OpenVPN. Especially on iOS devices the deep integration just works. Even to a degree that you enable the VPN once and the device will transparently keep it up / reestablish connections when required.

OpenVPN protocol has emerged to establish itself as a de- facto standard in the open source networking space with over 50 million downloads. OpenVPN is entirely a community-supported OSS project which uses the GPL license.


I am using the dockerized version of OpenVPN. From there I’ve got several ways to get telemetry data (like connections, traffic, …) out of it. One way is the management interface provided by OpenVPN. Another way is by using the default openvpn-status.log file.

Since the easiest way out-of-the-box was to use the logfile I sat down and wrote a little 2mqtt bridge for the contents of the logfile.

It’s also dockerized so you can easily set it up by pointing the openvpn-status.log to the right volume/mount-point.

When done it’ll produce MQTT messages like this:

The set-up and start-up is rather simple:

docker run -d --restart=always --volume /openvpnstatus2mqttconfiglocation/:/configuration --volume /openvpnstatusloglocation/:/openvpn openvpn-status2mqtt

MQTT Broker, Topic-Prefix and so on are configured with the .json configuration file found along the project.

Of course everything I wrote is available on GitHub as open-source.

The immediate outcome of this is that with the always-on VPN I am now getting statistics about, for example, the data consumption of my iPhone.

The big traffic spike at 1 AM is the backup that my iPhone does every night. Very interesting also how often the connection is closed and opened again even without me using the phone…

online archeology: to be young and online in 1987 is the place to find out about our common internet past. It’s the another project, besides Wikipedia and …, that started it’s life with a bold claim it so far holds true to:

The Internet Archive, a 501(c)(3) non-profit, is building a digital library of Internet sites and other cultural artifacts in digital form. Like a paper library, we provide free access to researchers, historians, scholars, the print disabled, and the general public. Our mission is to provide Universal Access to All Knowledge.

Internet Archive: About IA

And when you freely roam around the archive you will find many gems, like this one:

Another recommendation / starting point on the archive would be Computer Chronicles:

There’s countless hours of material to dig into and be amazed!

terminates the calling process if buffer is not a valid userspace pointer.

How to build security into your software? It’s always simple to find examples where things gone wrong. Where security was compromised and things did not work out as the software authors envisioned.

As always there are new concepts and operating systems being implemented.

A particularly interesting example of security software design can be observed here:

Fuchsia is an open source capability-based operating system currently being developed by Google.

In contrast to prior Google-developed operating systems such as Chrome OS and Android, which are based on the Linux kernel, Fuchsia is based on a new microkernel called Zircon. The name Zircon refers to the mineral of the same name.

Google Fuchsia

So you now know what Fuchsia is. Now on to the actual example. For this we have to take a look into the developer documentation of Zircon:

So this describes a method to get random numbers from the systems cryptocraphically-secure-random-number-generator (CPRNG). It takes a pointer to a memory location as a parameter.

Now. What’s secure about that? It’s the behaviour of the method when it is encountering an unsecure situation:

It’ll kill the calling process when the pointer is not valid.

automated downloads

Hmm… I’ve set-up a script to automatically download a TV show about a year ago and just remembered it…

Apparently 1 year of this show is 167 Gbyte…

For completeness the download script – ignore my bad scripting:


# parameter 1: month
# parameter 2: from day
# parameter 3: to day
# parameter 4: year

# data -dmonday +%d

next_monday=$(date -dmonday +%d)
next_monday_month=$(date -dmonday +%m)
next_monday_year=$(date -dmonday +%y)

previous_monday=$(date -d'monday-7 days' +%d)
previous_monday_month=$(date -d'monday-7 days' +%m)
previous_monday_year=$(date -d'monday-7 days' +%y)

next_friday=$(date -dfriday +%d)
next_friday_month=$(date -dfriday +%m)
next_friday_year=$(date -dfriday +%y)

previous_friday=$(date -d'friday-7 days' +%d)
previous_friday_month=$(date -d'friday-7 days' +%m)
previous_friday_year=$(date -d'friday-7 days' +%y)

for i in `seq 1 7`;
        day=$(date -d'today+'$i' days' +%d)
        month=$(date -d'today+'$i' days' +%m)
        year=$(date -d'today+'$i' days' +%y)
        wget -c ""$year"/"$month"/"$year$month$day"_sendung_dku/1/"$year$month$day"_sendung_dku_3328k_p36v14.mp4"


Picture yourself in this situation. You connect to a network and nothing works. Except for this:

It is quite common to have DNS working in networks while everything else is not. Sometimes the network requires a log-in to give you access to a small portion of the internet.

Now, with the help of a tool called iodine, you can get access to the full internet with only DNS working in your current network:

iodine lets you tunnel IPv4 data through a DNS server. This can be usable in different situations where internet access is firewalled, but DNS queries are allowed. 

It runs on Linux, Mac OS X, FreeBSD, NetBSD, OpenBSD and Windows and needs a TUN/TAP device. The bandwidth is asymmetrical with limited upstream and up to 1 Mbit/s downstream. 


Setting it up is a bit of work but given that you are anyway having access to a well connected server on the free portion of the internet it can be easily done.

Of course the source is on github.

making ICs at home

Try to wrap your head around this: There are people out there that take the term “Maker” to new levels. People Like Sam Zeloof. He went out and created his very own integrated circuit designs and then he built them. Like the actual silicon, the die, the bonded chip, the IC. The real thing.

Be inspired:

I am very excited to announce the details of my first integrated circuit and share the journey that this project has taken me on over the past year. I hope that my success will inspire others and help start a revolution in home chip fabrication. When I set out on this project I had no idea of what I had gotten myself into, but in the end I learned more than I ever thought I would about physics, chemistry, optics, electronics, and so many other fields. Furthermore, my efforts have only been matched with the most positive feedback and support from the world; I owe a sincere thanks to everyone who has helped me, given me advice, and inspired me on this project. Especially my amazing parents, who not only support and encourage me in any way they can but also give me a space to work in and put up with the electricity costs… Thank you!

Sam Zeloof

Decoding history, the hard way (and with machine learning)

Imagine you’ve got this ancient piece of technology in front of you. You clearly understand how the hardware works and you are even able to emulate the hardware on your modern-world computer.

Unfortunately hardware is only one half of the story. Software is the other half. And software at this time of the past was burned into chips which do not easily give their secret software away.

But let’s start with the hardware:

The IBM 5100 Portable Computer is a portable computer (one of the first) introduced in September 1975, six years before the IBM Personal Computer. It was the evolution of a prototype called the SCAMP (Special Computer APL Machine Portable) that was developed at the IBM Palo Alto Scientific Center in 1973. In January 1978, IBM announced the IBM 5110, its larger cousin, and in February 1980 IBM announced the IBM 5120. The 5100 was withdrawn in March 1982.

When the IBM PC was introduced in 1981, it was originally designated as the IBM 5150, putting it in the “5100” series, though its architecture was not directly descended from the IBM 5100.

And now on to the software:

The IBM 5100 portable computer came with some of its built-in programs stored in a read-only memory called the “non-executable ROS”. (ROS = “read-only storage”.) In contrast with the “executable ROS”, which supplies instructions to the 5100’s processor directly, the non-executable ROS is accessed using sequential I/O operations, a bit like a tape.

Most notably, the non-executable ROS holds the interactive interpreters for the APL and BASIC programming languages. These are not “native” 5100 programs but were expressed instead in System/370 mainframe and System/3 minicomputer machine code respectively. The 5100 runs emulator programs for those computers in order to host the interpreters, so perhaps it’s just as well that the non-executable ROS is non-executable.


So this write-up is all about how the bits where pushed to the screen and recorded as pictures of the said screen. The characters in these pictures then where analyzed and with the help of machine learning the data could be successfully extracted. It is mind-boggling. And it is all on Github.

Bitmap & tilemap generation with the help of ideas from quantum mechanics

You can get a grasp at the beautiful side of science with visualizations and algorithms that output visual results.

This is the example of producing lots and lots of complex data (houses!) from a small set of input data. It is widely used in game development but also can be helpful to generate parameterized test and simulation environments for machine learning.

So before sending you over to the more detailed explanation the visual example:

This is a lot of different house images. Those are generated using a program called WaveFunctionCollapse:

WFC initializes output bitmap in a completely unobserved state, where each pixel value is in superposition of colors of the input bitmap (so if the input was black & white then the unobserved states are shown in different shades of grey). The coefficients in these superpositions are real numbers, not complex numbers, so it doesn’t do the actual quantum mechanics, but it was inspired by QM. Then the program goes into the observation-propagation cycle:

On each observation step an NxN region is chosen among the unobserved which has the lowest Shannon entropy. This region’s state then collapses into a definite state according to its coefficients and the distribution of NxN patterns in the input.

On each propagation step new information gained from the collapse on the previous step propagates through the output.

On each step the overall entropy decreases and in the end we have a completely observed state, the wave function has collapsed.

It may happen that during propagation all the coefficients for a certain pixel become zero. That means that the algorithm has run into a contradiction and can not continue. The problem of determining whether a certain bitmap allows other nontrivial bitmaps satisfying condition (C1) is NP-hard, so it’s impossible to create a fast solution that always finishes. In practice, however, the algorithm runs into contradictions surprisingly rarely.

Wave Function Collapse algorithm has been implemented in C++PythonKotlinRustJuliaGoHaxeJavaScript and adapted to Unity. You can download official executables from or run it in the browser. WFC generates levels in Bad NorthCaves of Qudseveral smaller games and many prototypes. It led to new research. For more related workexplanationsinteractive demosguidestutorials and examples see the ports, forks and spinoffs section.

useful CSS Grid Generator

This project is a way for people to use CSS Grid features quickly to create dynamic layouts.

You can set the numbers, and units of your columns and rows, and I’ll generate a CSS grid for you! Drag within the boxes to create divs placed within the grid.

I noticed a lot of people weren’t using Grid because they felt it was too complicated and they couldn’t understand it. Grid is capable of so much, and this small generator only touches on a fraction of the features. The purpose of this is so people get up and running quickly, and create more interesting layouts.

Once you work with this a bit, I suggest checking out resources by Rachel AndrewJen Simmons, and Dave Geddes to dive deeper. There is also a CSS Grid Guide on CSS-Tricks, and a fun little game called Grid Garden to help you learn more!


Craft Beer in Tokyo (Kanto)

There are lists of things all over the internet. I’ve linked to some of these food related lists and maps already on this blog.

And of course there’s this list of craft beer breweries missing:

microbrewery or craft brewery is a brewery that produces small amounts of beer, typically much smaller than large-scale corporate breweries, and is independently owned. Such breweries are generally characterized by their emphasis on quality, flavor and brewing technique.


seen: properly scrolling through code

When working on source files with wide-ranging scopes, I wish source editors could pin the declaration lines to the top of the window like section headers, something like this…

Joe Groff on Twitter

This looks like something that would really make a difference when editing code. Let’s see how long until we get something like that in modern editors…

I/O Is Faster Than the CPU

I/O is getting faster in servers that have fast programmable NICs and non-volatile main memory operating close to the speed of DRAM, but single-threaded CPU speeds have stagnated. Applications cannot take advantage of modern hardware capabilities when using interfaces built around abstractions that assume I/O to be slow. We therefore propose a structure for an OS called parakernel, which eliminates most OS abstractions and provides interfaces for applications to leverage the full potential of the underlying hardware. The parakernel facilitates application-level parallelism by securely partitioning the resources and multiplexing only those resources that are not partitioned.

“are you still watching?” – tailfix

drop in replacement for tail -F that asks you if you are still watching

Just like Laura I am also was having a moment when I stumbled across tailflix.

For those not understanding the reference: At the end of an episode you’ve watched on Netflix you will be shown another one, and so on, and so on. Until if you have not touched the remote at all for several episodes Netflix will ask you “Are you still watching?”.

serve live interactive Jupyter notebooks

The Jupyter Notebook is an open-source web application that allows you to create and share documents that contain live code, equations, visualizations and narrative text. Uses include: data cleaning and transformation, numerical simulation, statistical modeling, data visualization, machine learning, and much more.


Voila serves live Jupyter notebook including Jupyter interactive widgets.

Unlike the usual HTML-converted notebooks, each user connecting to the Voila tornado application gets a dedicated Jupyter kernel which can execute the callbacks to changes in Jupyter interactive widgets.

Look me in the eye

As tools get better artists really polish out what technology enables them to do with computers nowadays.

This eye above made me awww. It’s from a user “ChrisJones” in the Blender Forum who posted his progress on modelling a human head in upmost detail.

Go there and be awwd as well. And while you’re there grab a copy of Blender and give it a go.

clone files from and to the cloud

Rclone is a command line program to sync files and directories to and from:

Alibaba Cloud (Aliyun) Object Storage System (OSS), Amazon Drive, Amazon S3, Backblaze B2, Box, Ceph, DigitalOcean Spaces, Dreamhost, Dropbox, FTP, Google Cloud Storage, Google Drive, HTTP, Hubic, Jottacloud, IBM COS S3, Koofr, Memset Memstore, Mega, Microsoft Azure Blob Storage, Microsoft OneDrive, Minio, Nextcloud, OVH, OpenDrive, Openstack Swift, Oracle Cloud Storage, ownCloud, pCloud,, QingStor, Rackspace Cloud Files, Scaleway, SFTP, Wasabi, WebDAV, Yandex Disk, The local filesystem

Whenever you would need to move large and/or many files between cloud storages you should give rClone a try.

technical visualization tools

There’s so much happening in this field as visualizations become more powerful and easier to create.


WaveDrom draws your Timing Diagram or Waveform from simple textual description. It comes with description language, rendering engine and the editor.

WaveDrom editor works in the browser or can be installed on your system. Rendering engine can be embeded into any webpage.


Generation of diagrams and flowcharts from text in a similar manner as markdown.

Ever wanted to simplify documentation and avoid heavy tools like Visio when explaining your code?

This is why mermaid was born, a simple markdown-like script language for generating charts from text via javascript. Try it using our editor.