Windows + Pygame + VidCap

So I thought I would try out the pycam module on windows.

First of all it seems windows comes with nothing, not even python. So after installing python I still needed this: http://videocapture.sourceforge.net/

and this: http://pygame.org/ftp/pygame-1.9.1.win32-py2.5.msi

Vid cap itself is so easy:

from VideoCapture import Device cam = Device() cam.saveSnapshot('image.jpg')

To get just the most basic stuff going, for some reason the VidCap module wouldn't let me open a camera unless the size was set at (160, 120) and the Camera class seemed to change going to windows... anyhow if you want to play with this grab it from the repo here.

This is using the pygame edge detect, just tried the scipy one - appears to be a problem mapping surface to numpy array... from memory there was a hack to get around something so maybe thats no longer required.

The "greenscreen" example and the simple threshold.

Couldn't immediatly see how to get the python wrappings for swig going on windows, and all the face detection stuff won't work untill they are installed correctly. I did rebuild opencv in visual studio and all the C examples work fine, Windows and Python don't seem to get along that well. Anyhow I don't plan on looking into it in a hurry. Do people actually still use windows? (Why?)

Homomorphic encryption using RSA

I recently had cause to briefly look into Homomorphic Encryption , the process of carrying out computations on encrypted data. This technique allows for privacy preserving computation. Fully homomorphic encryption (FHE) allows both addition and multiplication, but is (currently) impractically slow. Partially homomorphic encryption just has to meet one of these criteria and can be much more efficient. An unintended, but well-known, malleability in the common RSA algorithm means that the multiplication of ciphertexts is equal to the multiplication of the original messages. So unpadded RSA is a partially homomorphic encryption system. RSA is beautiful in how simple it is. See wikipedia to see how to generate the public ( e , m ) and private keys ( d , m ). Given a message x it is encrypted with the public keys it to get the ciphertext C ( x ) with: C ( x ) = x e mod m To decrypt a ciphertext C ( x ) one applies the private key: m = C ( x ) d mod m The homomorphic prop...

Matplotlib in Django

The official django tutorial is very good, it stops short of displaying data with matplotlib - which could be very handy for dsp or automated testing. This is an extension to the tutorial. So first you must do the official tutorial! Complete the tutorial (as of writing this up to part 4). Adding an image to a view To start with we will take a static image from the hard drive and display it on the polls index page. Usually if it really is a static image this would be managed by the webserver eg apache. For introduction purposes we will get django to serve the static image. To do this we first need to change the template. Change the template At the moment poll_list.html probably looks something like this: <h1>Django test app - Polls</h1> {% if object_list %} <ul> {% for object in object_list %} <li><a href="/polls/{{object.id}}">{{ object.question }}</a></li> {% endfor %} </ul> {% else %} <p>No polls...

Python and Gmail with IMAP

Today I had to automatically access my Gmail inbox from Python. I needed the ability to get an unread email count, the subjects of those unread emails and then download them. I found a Gmail.py library on sourceforge, but it actually opened the normal gmail webpage and site scraped the info. I wanted something much faster, luckily gmail can now be accessed with both pop and imap. After a tiny amount of research I decided imap was the better albiet slightly more difficult protocol. Enabling imap in gmail is straight forward, it was under labs. The address for gmail's imap server is: imap.gmail.com:993 Python has a library module called imaplib , we will make heavy use of that to access our emails. I'm going to assume that we have already defined two globals - username and password. To connect and login to the gmail server and select the inbox we can do: import imaplib imap_server = imaplib . IMAP4_SSL ( "imap.gmail.com" , 993 ) imap_server . login ( use...

Bits of py

Search This Blog