TL;DR: Where’s the code?

Hi impatient person, it’s here: and the gThumb plugin is here:


Google killed off Picasa desktop, which Phil has been using for a number of years, in particular because of it’s ability to recognise faces and tag / group them. With over 20000 photos, and 200+ people tagged, it’s time to get out before losing all that knowledge.

Data escape

Provided the appropriate option is ticked, Picasa will save a .picasa.ini file in each folder it knows about, containing rectangles that locate faces in image files, and where those faces have been tagged, the name tag used. While this preserves the output data, it does not include the trained recognition model Picasa is using to accurately match faces, this is buried in a custom binary database, and unlikely to make any sense outside of the particular recognition engine used, so we need to start again for this…

New recogniser tech

After a bit of rummaging Phil found the excellent face_recognition project from Adam Geitgey: and his clear blog series explaining stuff:, fabulous job Adam!

Armed with this code, and after a fair amount of trial & error getting dependencies working (see below), some testing showed that careful tuning of image size and algorithm selection could result in decent face detection & landmark extraction through a batch of images without eating vast compute time.

Sane storage

Because I intend to save overnight image processing results in a format that can be easily queried by other tools on multiple systems, I need portability, indexing and structure, preferably without a lot more installation / maintenance pain: step forward SQLite :)

The current database schema supports two distinct jobs:

- keeping a record of all files (images or not) in the searched areas, detecting changes and duplicates (via file hashes). - keeping a record of facial co-ordinates in each image (file hash), grouping them into similar clusters and labelling clusters.

Bootstrapping the clustering

Since I already have tags from Picasa, on some image files, I can pre-load clusters from this Picasa data (including the multiple groups per label), which gives me a starting point for clustering unknown faces too.

Sage advice

Having got this far, I ran off the end of the tutorials from Adam and was unsure on how to approach the classification / training stages, so I asked my friend and colleague, GBG’s resident data scientist Ian. After my poor problem description, Ian wisely suggested that I probably didn’t have enough training data to get a good machine learning model, it may well ‘overfit’ and have problems, besides that’s all hard work with new libraries (Scikit probably), and there are effective simpler means to an end: analysis!

Encoding analysis

Ian suggested I try and improve the basic face matcher that comes in the face_recognition package, by looking at the variance of the elements in a facial encoding (128 of them) across my data set, and weighting towards those with higher variance when doing simple vector (euclidean) distance measures. He also thought it would speed up the comparison if I reduced the n(n-1) complexity back to n by averaging the already labelled/grouped Picasa faces and comparing new data to those averages, rather than every member of a group. Good advice, thanks Ian!

gThumb as a viewer

I went looking for a way to visualise outputs as it’s tedious picking through log files and firing up eog for sample images. After some initial rummaging at I installed gThumb from the standard distro and started work on a plugin, which currently intercepts image loading to draw red markers on images, and extends the tree menu with a Faces tree showing all images that contain labelled faces.

face_recognition install

Adam provides instructions on installing the C library used (dlib) from source here:

Having been through this, I discovered that the python package manager does just as well, so my final install list to get this working was:

# aptitude install python-pip python-setuptools python-numpy libboost-python-dev libjpeg-dev cmake
# pip install dlib
# pip install face_recognition

Speeding it all up

With everything in place and mostly working, I started running lots of image files through.. which is when I discovered the need to tune face detection settings to get any workable speed. Unfortunately the current tuning misses a lot of faces that aren’t square-on (it relies on HOG first, only running CNN if nothing turns up, or not at all). I need GPU power to make this all go faster!

Fortunately Simon has just upgraded our desktop PC which means there is a spare AMD Turks (6670) device and the Xeon / Haswell integrated Intel graphics device I could use.. Cue installation montage of AMD card into my server and BIOS poking to stop it disabling the Intel GPU when the AMD was plugged in :)

NB: If you want both integrated and extension GPUs working in a Dell machine - you must [enable ‘Multi-Display’ in the BIOS] ( and you must have a VGA device (or emulator) plugged into the VGA port at boot - otherwise the BIOS turns off the integrated chip.

Now it gets fun again - I’ve never written any GPGPU code, and it looks like I may have to port the underlying dlib library from CUDA to OpenCL, since there is no CUDA for AMD or Intel devices (kind of..).

I thus started from zero: got a demo working, then got an FIR filter implementation working (thanks gr-clenabled) then started comparing performance between CPU, Xeon GPU, AMD GPU and was surprised that the Xeon GPU only just outperforms the CPU, while the AMD GPU is slower, due to data shifting delays across PCI. Hmmn. I’m still looking at tuning the code for AMD, since I was hoping for at least 10x over the CPU, perhaps an FIR filter isn’t a reasonable testbed?

A word of caution here: at one point I wrote some bad GPGPU code which didn’t specify resources correctly, and didn’t release them either - running this a few times started producing errors, then hard locked my whole server when it crashed on the Intel GPU - eek!