Alchemy app released (in beta)

I've finally published the beta version of Alchemy on the play store. It's still in beta, but it seems to be working well. Give it a shot if you're looking for a different way to donate to charity!

Memory leak with android linearlayout and Picasso

I recently ran into an issue using Picasso with Android's linearlayout. I was using Picasso to load images from a url into a linearlayout, handling errors with Picasso's build object as follows:

Picasso.Builder builder = new Picasso.Builder(this.mContext);
builder.listener(new Picasso.Listener()
{
    @Override
    public void onImageLoadFailed(Picasso picasso, Uri uri, Exception exception)
    {
      picasso.load(mThumbIds[0]).into(imageView); // on failure just load the default image
    }
});
Picasso picasso= builder.build();

I was recycling the images correctly with convertView (using a viewholder class), but I couldn't track down the source of a memory leak which occured every time a new image was loaded - eventually causing the app to crash. The leak however when away when I stopped using Picasso's builder, instead just using a simple try catch setup.

try{
    Picasso.with(mContext).load(logo_url).placeholder(R.drawable.alchemy).into(holder.imageView);
}
catch (Throwable e){
     Picasso.with(mContext).load(R.drawable.alchemy).into(holder.imageView);
}


Installing OpenCV3 for Python 3 on Windows

I need to use python for face recognition as part of the server for a charity app I'm working on. The app is supposed to show charity logos, but in the case of smaller charities, sometimes the google custom search I use to search for the logos returns instead a picture with a person in it. I need to identify cases where this happens and use a placeholder image instead.

My first attempt to install opencv was through pip from anaconda:

pip install opencv-python

However this gave me the following error when I tried to import cv2:

ImportError: DLL load failed: The specified module could not be found.

I uninstalled the anaconda version and found a 64 bit wheel of opencv for python 3.6 at http://www.lfd.uci.edu/~gohlke/pythonlibs/#opencv. Downloading this and installing it with pip worked perfectly. I don't know why the original error occured, but it looks like python 3 support might not be great with opencv at the moment.

Using Python 3 to extract files from an encrypted archive with a password

Recently I needed to use python to extract the contents of a password-protected zip archive and I came across a few issues I thought would be good to document.

Python has a build in zipfile library that is really good at handling zip files, but unfortunately has a few limitations when it comes to encrypted zip files. This is how Python3 can be used to extract a file from an encrypted zip archive:


The first issue that I came across was some unclear documentation for the "open" method of zipfile in Python 3. The open method uses the "pwd" argument to pass the password for the file, but in Python 3 you need to convert this to bytes before calling open. Unfortunately, the library only seems to support CRC-32 based encryption  - meaning that the default linux zip encryption will work, but AES will not. I was also unable to get this to work with 7zip and WinZip.

New website design

It had been a while since I updated my website so I found a new template from http://themes.3rdwavemedia.com and redesigned the whole site. I particularly like the github and blog integration with the new theme - hopefully that will encourage me to write more here too, especially as I'm working on the new Alchemy app.

New LOFAR baseline comparison tool

I've written a new tool for comparing the lengths of different baselines to a single LOFAR station. It should be useful when looking for delay and rate solutions with FRING or a similar task. The tool is located at http://www.colmcoughlan.com/lofar.html.

Installing AIPS on Ubuntu 16.04

I've recently installed AIPS (version 31DEC16) on Ubuntu 16.04. Here are my notes on the installation experience. Due to recent compiler work on AIPS this was a much better experience than on recent new versions of Ubuntu. Note that this was a "text" (compile-from-source) install - if you just need to use AIPS you will likely get a faster experience using the pre-compiled binaries available from the binary installation (see http://www.aips.nrao.edu/dec16.shtml for full instructions)


As before, the Ubuntu dependencies are:


        libx11-dev and its dependancies
        x11proto-xext-dev
        libxext-dev
        libxpm-dev
        libncurses5-dev
        libncursesw5-dev
        libbsd-dev
        libedit-dev


I use gcc and gfortran to compile AIPS - you need to specify their location in the AIPS installer (/usr/bin/gfortran is both the fortran compiler and the linker for me, while /usr/bin/gcc compiles for C). I also have trouble with the fortran compiler flags -axWPT and -ip options, so I turn them off both for gfortran and gcc. XAS isn't built using these directives however, so you need to go to Y/SERVERS and edit XAS.SHR to remove the use of the axWPT and -ip flags when compiling the TV server.


A new problem with this combination of Ubuntu and AIPS is an errant "-c" ending up in the link command for making XAS after XAS.SHR is run. This means you will get an error that XAS failed to link, but if you open the makefile at Y/SERVERS/XAS/makefile and remove the "-c" option from the LOCALOPTS_LNX64 variable, then you can just type "make" to correctly make and set up XAS (I did this in a separate terminal while the rest of the installation was proceeding). Make sure the executable xas file has been successfully moved to LNX64/LOAD.


Make sure to add


        sssin        5000/tcp    SSSIN        # AIPS TV
        ssslock        5002/tcp    SSSLOCK        # AIPS TV Lock
        msgserv        5008/tcp    MSGSERV        # AIPS Message Server
        tekserv        5009/tcp    TEKSERV        # AIPS TekServer
        aipsmt0        5010/tcp    AIPSMT0
        aipsmt1        5011/tcp    AIPSMT1
        aipsmt2        5012/tcp    AIPSMT2
        aipsmt3        5013/tcp    AIPSMT3
        aipsmt4        5014/tcp    AIPSMT4
        aipsmt5        5015/tcp    AIPSMT5
        aipsmt6        5016/tcp    AIPSMT6
        aipsmt7        5017/tcp    AIPSMT7


to /etc/services to get AIPS to run properly. To do this you may need to open the file as root.


One last thing - add the aips path to your profile so you can run it straight from the terminal. For me the line was ". /home/colm/aips/LOGIN.SH; $CDTST". The CDTST bit at the end is needed if you intend to compile custom AIPS tasks.