Getting an Xcode framework version of OpenCV built used to be a pretty hair-raising exercise in yak-shaving. It’s gotten a whole lot easier lately.

First, check out the OpenCV sources:

cd ~
git clone https://github.com/Itseez/opencv.git
cd opencd/
git checkout 3.0.0

You’ll need to make a symbolic link to Xcode’s developer tools so everyone can find things:

cd /
sudo ln -s /Applications/Xcode.app/Contents/Developer/ Developer
cd ~/opencv

All you need to do is have python run the build. Works flawlessly.

python platforms/ios/build_framework.py ios

Walk away from the keyboard for half an hour, when you get back, you’ll have a nice opencv2.framework in ~/opencv/ios/…

If you’re running CentOS 6 on a virtual server, you may run into the following problem when you try to restart iptables:

# service iptables restart
iptables: Setting chains to policy ACCEPT: security raw nat[FAILED]filter 
iptables: Flushing firewall rules:                         [  OK  ]
iptables: Unloading modules:                               [  OK  ]
iptables: Applying firewall rules:                         [  OK  ]

It’s a fairly simple fix. First, open up /etc/init.d/iptables in your favorite text editor, and look for this section of code:

   echo -n $"${IPTABLES}: Setting chains to policy $policy: "
    ret=0
    for i in $tables; do
        echo -n "$i "
        case "$i" in
            raw)
                $IPTABLES -t raw -P PREROUTING $policy \
                    && $IPTABLES -t raw -P OUTPUT $policy \
                    || let ret+=1
                ;;

After the “case” line, and before the “raw)” line — i.e. between lines 5 and 6, above — add the following:

           security)
               $IPTABLES -t filter -P INPUT $policy \
                   && $IPTABLES -t filter -P OUTPUT $policy \
                   && $IPTABLES -t filter -P FORWARD $policy \
                   || let ret+=1
               ;;

When you’re done, the whole section should look like this:

   echo -n $"${IPTABLES}: Setting chains to policy $policy: "
    ret=0
    for i in $tables; do
        echo -n "$i "
        case "$i" in
            security)
                $IPTABLES -t filter -P INPUT $policy \
                    && $IPTABLES -t filter -P OUTPUT $policy \
                    && $IPTABLES -t filter -P FORWARD $policy \
                    || let ret+=1
                ;;
            raw)
                $IPTABLES -t raw -P PREROUTING $policy \
                    && $IPTABLES -t raw -P OUTPUT $policy \
                    || let ret+=1
                ;;

Then, restart iptables, and things should be fine.

# service iptables restart
iptables: Setting chains to policy ACCEPT: security raw nat[  OK  ]filter 
iptables: Flushing firewall rules:                         [  OK  ]
iptables: Unloading modules:                               [  OK  ]
iptables: Applying firewall rules:                         [  OK  ]

Technology

• SolidRun has released the HummingBoard, a souped-up version of the Raspberry Pi, available at a couple of performance levels and in a couple of form-factors. Looks very interesting for the “Internet of Things” applications…
• Got a really old PC or laptop? Turn it into something useful with LXLE, a remastered version of Ubuntu LTS designed to give even severely underpowered machines (by today’s standards) a pretty kickass and highly functional desktop.
• The Obama Administration has killed the nomination of pharmaceutical executive Phil Johnson after an outcry from the tech sector and a public statement from Sen. Chuck Schumer (D-NY) that he wouldn’t support the nomination.

Design

• The Benefits of Sketching by Hand: This is something I’ve been working on for a while, and practice definitely pays off. Wish I’d started sooner.
• Getting Real Survey Answers Out of Smart, Busy People: How Quartz got almost a thousand high-level executive to provide meaningful survey data on advertising.

Culture

A Conversation with Alejandro Jodorowsky at SXSW 2014

Current Events

• The State Legislature of Vermont has become the first in the country to call for a Constitutional Convention to overturn the Citizens United decision and get money as a form of “speech” out of the political process.