wezm.net/content/technical/2011/08/monochrome-thumbnails.html

Ever since this version of my site went live I've been meaning to
post about the generation of the monochrome thumbnails on the [front page](/).
When I was building the site I wanted to include recent items
from my Flickr photostream. However with the predominantly monochrome
design I didn't like the look of all the colour they added. So I looked into
having monochrome versions of the thumbnails shown.

The first thing I investigated was Javascript image processing libraries. The
only main contender in that space was [Pixastic]. It worked but its cross browser
support wasn't great at the time. So I moved on to writing a tool that I
could run locally.

[Pixastic]: http://pixastic.com/

I decided the tool should generate a single image with
both the colour and monochrome versions in it (a technique known as spriting).
Using a single image means only one HTTP request instead of forty. Being a
programmer with an interest in Cocoa programming I created a small command line
tool that used the Flickr API to get the details of the last twenty images in
my photostream, fetch them and then use Core Image to convert them to
monochrome, add both the colour and monochrome versions to the output image and
finally save the result.

This worked great, however when I stopped hosting my site on my Mac I thought I
would need to run the process periodically on my Linux server, which ruled out
Core Image. I took this as another opportunity to learn something new and
rewrote it in Lua using imlib2 bindings. I had to make some additions to the
imlib bindings, which are [published on GitHub][luaimlib].

[luaimlib]: https://github.com/wezm/lua-imlib2

I used the Lua version for some time but never bothered to set it up
on the server. I wasn't uploading photos all that frequently and it
was simple enough to run locally and rsync the result. I've recently
switched back to the Mac version as it was simpler to get up and running
on my new laptop.

The [code is on GitHub][code] if anyone wants to do something similar. The
Cocoa version is on the master branch, the Lua version is on the
[lua branch][lua-branch].

[code]: https://github.com/wezm/monothumb
[lua-branch]: https://github.com/wezm/monothumb/tree/lua

The current version of the processed thumbnails is shown below.

<div style="overflow-x: auto; overflow-y: hidden;">
  <img src="/images/photos.jpg"  />
</div>