Python Adventures

Today I found an interesting post: Face Detection in Static Images with Python. You give an image as input and the program draws a rectangle around the face(s) on the image.

Installation

sudo apt-get install python-opencv libcv-dev opencv-doc

Under Ubuntu 11.04, the required XML is in the opencv-doc package at a different location, thus you need to modify the source code:

...
cascade = cvLoadHaarClassifierCascade(
    '/usr/share/doc/opencv-doc/examples/haarcascades/haarcascades/haarcascade_frontalface_default.xml.gz',
    cvSize(1,1))
...

See the full (patched) source code here.

Lesson learned
You can draw a rectangle on an image the following way:

convert original.jpg -stroke red -fill none -draw "rectangle 50,36 115,101" output.jpg

Where 50,36 is the top left, 115,101 is the bottom right coordinates.

_{/ @reddit /}