The p-Code Machine

I’ve been posting a fair amount of photography, imaging and color management lately. While colorimetry can be a good solution to display issues, but a lot of people don’t want to take it that far.

So say you’ve just gotten a new notebook, and like many notebooks the display looks a tad blueish, and you don’t want to invest in a full blown color management solution. There is a fairly simple way to address this issue at least to an extent, and it’s called xgamma (please note that xgamma might not work if your X11 setup is in 16bit mode, which is very unlikely on a modern system).

Now before making any changes it’s a good idea to get a good image to evaluate any changes with. I can highly recommend the Smugmug Calibration Print. So open the calibration print in your favorite image viewer, and do:

# xgamma -rgamma 1.0 -ggamma 1.0 -bgamma 0.9

You should see your display shift in color. Lots of notebook display also tend to lack contrast, so in theory you can use xgamma to compensate for that too:

# xgamma -rgamma 0.9 -ggamma 0.9 -bgamma 0.8

Again check the calibration print again, make sure you can clearly distinguish all the grey patches at the top of the image.

Now when you reboot your machine these settings will be lost. The best way I’ve found to automatically apply these settings seem to be via what’s called XDG Autostart, it’s basically a set of .desktop files that are run during session startup. Most big desktop environments (GNOME/XFCE/KDE) support these.

So, put the following into /etc/xdg/autostart/xgamma.desktop

[Desktop Entry]
Encoding=UTF-8
Name=Set display gamma corrections
GenericName=Set display gamma corrections
Comment=Applies display gamma corrections at session startup
Exec=xgamma -rgamma 0.9 -ggamma 0.9 -bgamma 0.8
Terminal=false
Type=Application
Categories=

Now reboot, and see your gamma settings being applied at during each new X11 login.

Please beware that the above correction are ballpark corrections, for real accuracy you really need to do proper color management.

Usually I don’t do a lot of “real” coding for Darktable, but I had some time on my hands today, and I implemented basic Unity integration for Darktable. Since I wasn’t familiar with libunity, nor was I really familiar with the depths of Darktable code let alone CMake, the implementation took me about 2 hours.

That said, have a look at the results:

You can also download the video for offline viewing if you prefer.

By the way, the bug I mentioned at the end of the video has been mitigated, which is a chic way of saying I kludged it so you won’t be bothered by it. But it’s not truely fixed.

Since I did my last darktable 0.7 screencast library, some things have changed. So at the very least this warranted an update screencast.

The downside is that I was recovering from a cold, so these screencasts sound a bit rough:

Darktable 0.9 Update (download)

Darktable B&W Film Emulation (download)

Darktable Denoising (download)

Darktable Spot Removal (download)

Small mistake, it’s actually possible to remove spots by rightclicking them.

There are millions of black & white photo plugins available. Some simple, some complex. When I recently got back a batch of real developed black & white film, I tried to investigate my scans to see how to emulate the effect (and possibly how to automate it).

The simplest approach I’ve been able to come up with involves blurring and decreasing contrast (with output levels). It can be automated with ImageMagick like so:

# convert -gaussian-blur 1x1 -filter triangle -resize 3000x2000 -level \!15%,\!95%,1.0 -colorspace gray -gaussian-blur 5x1 input.jpg output.jpg

Please note that doesn’t involve noise simulation yet, which seems to be hard to do with ImageMagick (tips are welcome). Please do note that I’m resampling to 6MPixels for convenience, you can use any resolution assuming you roughly scale along the 5 pixel Gaussian blur.

Recently I’ve been fiddling a bit with Upstart, and in general I’m positive about the experience. Upstart offers a lot of flexibility and simple but very welcome features like real service supervision with respawning capabilities. There are a few downsides:

Relatively few SysV init scripts have been converted to Upstart jobs. This is logical since there are a lot of scripts to convert and all of them need testing before considering them production ready. That said, the progress over time in this area isn’t particularly overwhelming either.

Upstart is much harder to troubleshoot when unexpected things happen, this is to a degree inherent to Upstart’s parallel/event-based nature. Adding the following options to your kernel parameters does help a bit: ‘nosplash INIT_VERBOSE=yes init=/sbin/init noplymouth -v’.

As far as I know there is no way to have SysV init scripts depend on Upstart jobs. While this was to be expected since this is pretty hard to implement sensibly. But considering my first point (the fact that lots of SysV scripts still have be converted), this can be annoying. My advice, don’t fiddle with the the rc job! I did, and it gave me grief (Upstart hung on reboots), causing me to waste a day figuring out what went wrong. If you need a SysV script to depend on an Upstart job, remove the SysV script and convert it to an Upstart job yourself.

As some of you may know configuring LDAP on Ubuntu Lucid can be a bit of a pain in the ass, especially getting it consistent throughout your infrastructure. So here’s way to relatively easily configure LDAP via Debconf preseeding.

First install debconf (it’s likely already installed, but doublecheck this):

# apt-get install debconf

Then put the following lines into debconf-ldap-preseed.txt so we can feed it to debconf later (obviously you need to adapt this configuration file to your own situation):

ldap-auth-config    ldap-auth-config/binddn    string    cn=proxyuser,dc=yourdomain,dc=com
ldap-auth-config    ldap-auth-config/bindpw    password    
ldap-auth-config    ldap-auth-config/dblogin    boolean    false
ldap-auth-config    ldap-auth-config/dbrootlogin    boolean    true
ldap-auth-config    ldap-auth-config/ldapns/base-dn    string    dc=yourdomain,dc=com
ldap-auth-config    ldap-auth-config/ldapns/ldap-server    string    ldap://10.10.10.10/
ldap-auth-config    ldap-auth-config/ldapns/ldap_version    select    3
ldap-auth-config    ldap-auth-config/move-to-debconf    boolean    true
ldap-auth-config    ldap-auth-config/override    boolean    true
ldap-auth-config    ldap-auth-config/pam_password    select    crypt
ldap-auth-config    ldap-auth-config/rootbinddn    string    cn=manager,dc=yourdomain,dc=com
ldap-auth-config    ldap-auth-config/rootbindpw    password    
libnss-ldap    libnss-ldap/binddn    string    cn=proxyuser,dc=yourdomain,dc=com
libnss-ldap    libnss-ldap/bindpw    password    
libnss-ldap    libnss-ldap/confperm    boolean    false
libnss-ldap    libnss-ldap/dblogin    boolean    false
libnss-ldap    libnss-ldap/dbrootlogin    boolean    true
libnss-ldap    libnss-ldap/nsswitch    note    
libnss-ldap    libnss-ldap/override    boolean    true
libnss-ldap    libnss-ldap/rootbinddn    string    cn=manager,dc=yourdomain,dc=com
libnss-ldap    libnss-ldap/rootbindpw    password    
libnss-ldap    shared/ldapns/base-dn    string    dc=yourdomain,dc=com
libnss-ldap    shared/ldapns/ldap-server    string    ldap://10.10.10.10/
libnss-ldap    shared/ldapns/ldap_version    select    3
libpam-ldap    libpam-ldap/binddn    string    cn=proxyuser,dc=yourdomain,dc=com
libpam-ldap    libpam-ldap/bindpw    password    
libpam-ldap    libpam-ldap/dblogin    boolean    false
libpam-ldap    libpam-ldap/dbrootlogin    boolean    false
libpam-ldap    libpam-ldap/override    boolean    true
libpam-ldap    libpam-ldap/pam_password    select    crypt
libpam-ldap    libpam-ldap/rootbinddn    string    cn=manager,dc=yourdomain,dc=com
libpam-ldap    libpam-ldap/rootbindpw    password    
libpam-ldap    shared/ldapns/base-dn    string    dc=yourdomain,dc=com
libpam-ldap    shared/ldapns/ldap-server    string    ldap://10.10.10.10/
libpam-ldap    shared/ldapns/ldap_version    select    3
libpam-runtime    libpam-runtime/profiles    multiselect    unix, ldap

Now we feed the above file to debconf:

# cat debconf-ldap-preseed.txt | debconf-set-selections

And finally we need to switch nss to include LDAP lookups:

# auth-client-config -p lac_ldap -t nss

Optionally make sure homedirs are created on login:

# echo -e 'session required\t\t\tpam_mkhomedir.so' >> /etc/pam.d/common-session

One of the other advantages is that this may also benefit future upgrades, since all the settings are preseeded through debconf it’s less likely a future update/upgrade will break your setup. This is purely speculative since I haven’t done any actual upgrades yet.

When compressing data we all know we have several options, gzip most commonly used or bzip2 when we need better ratios. Recently we have also seen the introduction of lzma, which is horribly slow by default but gets us amazing ratios.

That said, when compressing your next file, you might want to consider trying lzma -2, it compresses slightly better than bzip2 –best, while still being approximately as fast as gzip –best… Seems like a nice trade off…

Recently I’ve been re-entering the world of electronics, and more particularly microcontrollers. Back in the day I had some introductory experience with Parallax’s BASIC Stamp, which wasn’t that great. Only recently I discovered the Arduino project, which is absolutely awesome.

The original Arduino IDE is written in Java however, and that makes for poor integration on the Linux platform, particularly with Ubuntu Unity. Luckily enough someone has been busy to do a simple rewrite of the original IDE in Python and GTK, making a fully Linux native IDE, and it’s called Gnoduino, and I even have a PPA for it.

I did a screencast on the general topic of Arduino and the differences between the original IDE and the Gnoduino IDE:

You can also download the video for offline viewing if you prefer.

So today I was migrating our HP SSSU utility from an x86 to an x86-64 machine, only to find our I couldn’t execute the utility anymore because it was on a x86-64 machine, I wanted to lookup the version number of the utility to find a matching x86-64 version. So I was too lazy to log onto the old machine, so I used strings to find it’s version number, only to find a crazy surprise:

SSSU for HP StorageWorks Command View EVA
9.2.0
Version: %s
Build: %s
Error closing https connection
Error closing https connection
Total regression differences = %u
Press return to exit
%.6d%c
                           oooo$$$$$$$$$$$$oooo
                      oo$$$$$$$$$$$$$$$$$$$$$$$$o
                   oo$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$o         o$   $$ o$
   o $ oo        o$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$o       $$ $$ $$o$
oo $ $ '$      o$$$$$$$$$    $$$$$$$$$$$$$    $$$$$$$$$o       $$$o$$o$
'$$$$$$o$     o$$$$$$$$$      $$$$$$$$$$$      $$$$$$$$$$o    $$$$$$$$
  $$$$$$$    $$$$$$$$$$$      $$$$$$$$$$$      $$$$$$$$$$$$$$$$$$$$$$$
  $$$$$$$$$$$$$$$$$$$$$$$    $$$$$$$$$$$$$    $$$$$$$$$$$$$$  '''$$$
   '$$$''''$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$     '$$$
    $$$   o$$$$$$$$M$i$c$h$e$l$&$R$o$g$e$r$$$$$$$$$$$$$$$$$$$     '$$$o
   o$$'   $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$       $$$o
   $$$    $$$$$$$$$$$$$$$$$$w$e$r$e$$$$$$$$$$$$$$$$$$$$' '$$$$$$ooooo$$$$o
  o$$$oooo$$$$$  $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$   o$$$$$$$$$$$$$$$$$
  $$$$$$$$'$$$$   $$$$$$$$$$$$$$$h$e$r$e$$$$$$$$$$$$     $$$$''''''''
 ''''       $$$$    '$$$$$$$$$$$$$$$$$$$$$$$$$$$$'      o$$$
            '$$$o     '''$$$$$$$$$$$$$$$$$$'$$'         $$$
              $$$o          '$$''$$$$$$''''           o$$$
               $$$$o                                o$$$'
                '$$$$o      o$$$$$$o'$$$$o        o$$$$
                  '$$$$$oo     ''$$$$o$$$$$o   o$$$$''
                     ''$$$$$oooo  '$$$o$$$$$$$$$'''
                        ''$$$$$$$oo $$$$$$$$$$
                                ''''$$$$$$$$$$$
                                    $$$$$$$$$$$$
                                     $$$$$$$$$$'
                                      '$$$''

This is obviously a reference to The Hitchhiker’s Guide to the Galaxy (why?).

So like many I feared Unity, now having met it, and giving a seriously go I’m slowly starting to like it. And I’m sticking with it for at least a few weeks before passing final judgement. That said, here are a few small tips:

Currently by default the icons in the Launcher are all “backlit” with a background color, you can turn that off, to only have running programs backlit (to make that fact extra obvious). You can make this the system-wide default like so:

$ sudo  gconftool-2 --direct \

  --config-source xml:readwrite:/etc/gconf/gconf.xml.defaults \

  --type int --set /apps/compiz-1/plugins/unityshell/screen0/options/backlight_mode 1

Next, the Launcher auto-hides whenever you move a window into it (for example maximize a window). I don’t really like that, since I have too much horizontal screen estate anyhow, so I’d like to Launcher to permanently claim it’s space (again as a system-wide default):

$ sudo  gconftool-2 --direct \

  --config-source xml:readwrite:/etc/gconf/gconf.xml.defaults \

  --type int --set /apps/compiz-1/plugins/unityshell/screen0/options/launcher_hide_mode 0

Some other tips, you might find handy:

If you want to move Launcher buttons around on the Launcher you need to drag button off before you can move it. This makes moving buttons around a very conscious action, preventing the mouse-challenged people from accidentally moving them around.

Also you might have noticed that left clicking a Launcher button will only start an application once. So for apps you might want to start multiple times like a Terminal you’d need to search for the app to start it a second time, which would be rather time consuming. Luckily the Unity designer thought about this, so left click will start an application once (prevent people from accidentally starting most apps twice). But if you do want to start an app twice or thrice you can just middle click the Launcher button.

And last but not least, this wallpaper may be of use to you.