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Using exiftool to reduct EXIF metadata in some JPEGs

January 9, 2011 1 comment

After spending way to much time trying to edit some EXIF metadata in some JPEG photographs, I’m posting my method here for future reference.

The first thing I needed to do was geoencode/geotag the images with a GPS location tag. I did this with the perl module Image::ExifTool::Location (script here).

The second thing I needed to do was examine what metadata was in the JPEG and reduct some of it. I used `exifprobe` and `exiftool -v` to examine the metadata. I ended up using this command on each image:

exiftool -overwrite_original -scanForXMP \
 -MakerNotes:SerialNumber='0' -MakerNotes:OwnerName='' -MakerNotes:InternalSerialNumber="0" -XMP:SerialNumber= \
 -XMP:OwnerName="Andrew Harvey <andrew.harvey4@gmail.com>" \
 -XMP-cc:AttributionName='Andrew Harvey' -XMP-cc:License='http://creativecommons.org/licenses/by/3.0/' -XMP-cc:attributionURL="http://www.flickr.com/photos/andrewharvey4/"\
"file_name.jpg"

http://www.sno.phy.queensu.ca/~phil/exiftool/TagNames/Canon.html was a good reference to find out about the MakerNotes tags. Also it took me a little experimenting and research before finding out that “MakerNotes tags may be edited, but not created or deleted individually.” This is why the SerialNumber tag is set to zero, and not removed. I tried to remove the camera serial numbers, but who knows, Canon probably secretly embed the serial number into the image pixel values as well…

http://wiki.creativecommons.org/XMP also provided me with some hints on how best to embed these JPEGs with at least some form of machine readable tagging as CC BY licensed.

Categories: computing Tags: ,

A Great Gnome Panel Applet + A UPnP Enabled Router

July 26, 2010 Leave a comment

I have just discovered that my ADSL router supports UPnP, and that this provides an interface to access 3 important bits of information from the router (external IP address, total bytes sent and total bytes received). I had previously been scraping the router’s web interface to grab the external IP. As for the bytes sent and received, I didn’t even know the router had a method of reporting these.

My first instinct was to look for a Perl library for UPnP, I found two. One in the Ubuntu repositories (and in CPAN) http://search.cpan.org/perldoc?Net::UPnP::GW::Gateway and another which appears to be in neither, http://perlupnp.sourceforge.net/.

I tried out the first one and after some fiddling get it working (though I haven’t yet been able to eliminate the 2 seconds it spends blocked, ie. not executing on the CPU but still not complete).

Next I found a great program that allows you to place an arbitrary command’s output in the Gnome Panel, http://code.google.com/p/compa/. Which resulted in,

Compa Gnome panel applet showing total bytes recieved and sent by the router.

The Perl script I use to provide the output to the Compa applet is at http://github.com/andrewharvey/perlmisc/blob/master/upnp_router_inoutbytes_to_compa.pl

Categories: computing Tags: ,

The URL shown in Firefox’s status bar isn’t always where you end up.

June 27, 2010 Leave a comment

Unless you are aware of the more technical details of web browsing its reasonable for the average web user to assume that if you hover your mouse over a link and Firefox tells you in the status bar that the link is to http://foobar.com/, then clicking on the link will actually take you to http://foorbar.com/. But sadly this is not the case for out of the box Firefox.

Take a look at a Google search results pages. Hovering your mouse over the links gives one URL in the status bar, yet clicking the link actually takes you somewhere else.

Here is a sample of the HTML for the link,

<a href="http://www.example.com/page1.html" onmousedown="return rwt(this,'','','res','1','$ID1','&amp;sig2=$ID2','$ID3')">Page Title</a>

Hovering over the link, you see in the status bar http://www.example.com/page1.html, but as soon as you mousedown javascript goes ahead and changes the href to something else (keep in mind that Firefox only goes to the new link on mouserelease), so that when you release the mouse your browser takes you to the replacement URL.

The problem I see with this is what if some unsuspecting user checks the link in the status bar, clicks the link thinking they are going one place then get taken somewhere else. This becomes even more of a problem if that site is susceptible to certain kinds of XSS attacks. So you can think your going to https://paypal.com/, and the URL bar after clicking the link goes to https://paypal.com/ but yet you’ve actually got some malicious js or html injected in the paypal.com/ page that you have loaded in your browser window.

I originally thought this was clickjacking, but the Wikipedia article describes that as when a transparent layer on top of the page provides the concealed URL.

Categories: computing Tags: ,

Australian States Map/Graph API

February 19, 2010 Leave a comment

I’ve managed to do a couple things all in one here. I’ve made use of some Geoscience Australia Creative Commons licensed material, in a nice little program with a web API, and I’ve aggregated some data from the myschool scraper and parser. Putting them all together gives some nice images like this.

The program for generating these images basically takes an SVG template file with placeholder markers and then fills these values based on the CGI parameters. The API is fairly simple so one should be able to work out how to use it from the example in the README file. Here are the files I used to make the graphs (and the svg versions as WordPress.com won’t let me upload them to here).

ps. This gets cut off when viewing it from the default web interface of this blog, use print preview or even better look at the RSS feed to see the cut off parts. Also I tried to ensure the accuracy of the data, but I cannot be 100% sure that there are no bugs, in fact there are discrepancies with the averages I get from my scrape of myschool and the averages provided in the report on the NPLAN website. The numbers I get seem to be consistent (ie. the state rankings seem mostly the same), but nonetheless not exactly the same as those reported in the report. Although I would be very surprised if all the numbers I got were exactly the same as in the report. I mainly did this to use map/graph code I wrote, so if you really care about how certain state averages compare in these tests look at the reports on the NPLAN website.

The lighter the colour the higher the number.

Primary

2008 2009
Literacy
Numeracy
All

Secondary

2008 2009
Literacy
Numeracy
All
Categories: computing Tags: , ,

anonymous FTP

January 22, 2010 Leave a comment

So I’ve started reading a book about networks, and to complement this I’ve been taking a closer look at my network traffic in Wireshark (really great tool, by the way.).

So I pick an ftp site that I know, ftp://download.nvidia.com/ and see what happens in Wireshark when I visit it in Firefox. At the FTP application level this is what happens,

ftpsite to me: 220 spftp/1.0.0000 Server [69.31.121.43]\r\n
me to ftpsite: USER anonymous\r\n
ftpsite to me: 331 Password required for USER.\r\n
me to ftpsite: PASS mozilla@example.com\r\n
ftpsite to me: 230- \r\n
               230- ---------------------------------------------------------------------------\r\n
               230- WARNING:  This is a restricted access system.  If you do not have explicit\r\n
               230-           permission to access this system, please disconnect immediately!\r\n
               230 ----------------------------------------------------------------------------\r\n

But Firefox does not disconnect. So I did some more research and I found no references to “anonymous” users in either RFC 959 (FTP) or RFC 3659 (extensions to FTP). (Though there are references in latter RFCs, see RFC 2228).

The thing I find disconcerting is that I don’t think I have “explicit permission” to access this system. I (or rather Firefox) just guessed a username and password and they happened to let me in (what if I guessed a different username and password that wasn’t anonymous and it let me in?). If the RFC specified that a user of anonymous requires no password, or any password, then I would assume that the FTP server is granting me permission, but I assume rather people just started using anonymous as the user and it caught on…

The real problem here is that there are laws which govern such areas, and it doesn’t help that that I don’t understand what PART 6 – COMPUTER OFFENCES of the CRIMES ACT 1900 (NSW) is saying.


								
Categories: computing, law Tags: ,

To fix broken audio, unplug faulty USB device.

January 19, 2010 Leave a comment

How weird is this, just recently when I started up my computer lots of stuff was broken, no audio (and /proc/asound/cards was empty, normally it has “0 [Intel          ]: HDA-Intel – HDA Intel\nHDA Intel at 0xfa100000 irq 22”), libsensors weren’t reporting any values (eg. no CPU temp reported), eth0 dissapeared from NetworkManager, and probably a host of other things that I didn’t notice. Restarting didn’t fix it.

Well long story short, it turns out that everything magically fixed when I unplugged a USB hard drive that was plugged in. I had seen a lot of concerning messages sent to /var/log/messages from the kernel about it,

Jan 19 09:45:00 host kernel: [  564.100026] usb 1-3: reset high speed USB device using ehci_hcd and address 2
Jan 19 09:45:00 host kernel: [  564.237716] sd 8:0:0:0: [sdd] Unhandled error code
Jan 19 09:45:00 host kernel: [  564.237719] sd 8:0:0:0: [sdd] Result: hostbyte=DID_ABORT driverbyte=DRIVER_OK

that repeated every so often, but I never thought that a dodgy USB device would break the kernel from doing some of its job.

Categories: computing Tags:

An Idea for a Media-Centreish Interface for a UNIX terminal/shell

December 18, 2009 Leave a comment

Back in July or August this year when I was going through the notes on unix shells for COMP2041 I came up with idea of doing a shell/terminal interface that looked like an interface for a media centre ie. rather than looking like this,

manual page for man in xtermit would look “like” this (obvious not exactly the same but similar feel),

The key principles I had in mind were,

  • nice aesthetics
  • interface similar to a game or media centre
  • features easily discoverable for new users

My original motives were that I was just learning all these core-utils commands (ls, cat, mkdir, cp, mv…) and I found that although the shell had tab completion and apropos, it didn’t categorise these or give them in a list of common commands. Then I came up with more abstract ideas,

  • categorise common commands and give help on them. eg. File System: ls, cd, cd .., mkdir. Filters: cat, wc, grep…
  • parse commands and their argument list based on common styles (eg. GNU style, short -las and long -l –all –size) and provide contextual information (eg hovering over an –argument gives a one line message about what that argument does (perhaps parse the man file to get this info)) also auto-layout the command line as per the argument style.
  • it could also parse the pipe lines and display these much more visually so its easier to see what’s piping into what and allow the user to easily change the order/flow of the pipeline.
  • process management. don’t force the user to remember Ctrl+C and Ctrl+Z and bg and fg commands, show these as pause and stop icons.
  • redirection of output should be easily changed in the interface rather than just adding a < or > to the command line (and allow one to redirect STDOUT to a file AFTER the command has already run (because currently you would need to run the command again, or copy and paste and put up the with new lines that gnome-terminal puts in))
  • bookmarking commands (including argmunts) so that those common ones you use that you haven’t remembered yet are quick and easy to use.
  • colour STDERR in red.

I haven’t really thought about it on a technical level, but it may not be so portable as say gnome-terminal. I don’t know the really differences among different shells out there so I don’t know how dependent this is on bash or even if it ties bash and the terminal together, but from a beginner user perspective I don’t care about this.

The cloudy idea I have in my mind is basically a GUI/CLI hybrid but I think such a program would need to be careful not to go too far, because it could be made so that after doing an ls -la you could click on a file in the list and rename it, but then we are turning into a file manager in list mode (like Dolphin or Nautilus) which is unnecessary as those tools already exist.

I’m aiming to do come up with a list and more detailed list of requirements and a set of activity and use case scenarios, along with some wire-frame prototypes for such an interface soon. But for now I just needed to get it all out of my head an onto paper (and also public (in case someone tries to patent a concept)).

Categories: computing Tags: , ,