Tuesday, June 24, 2014

A Work in Progress: OwnCloud and CALDAV

Very very cool.

OwnCloud and Caldav Sync Free Beta, that is.

I wanted to get away from big data. This link gave me the inspiration. So I've installed OwnCloud

Avishek Kumar does an excellent job of providing a straight-forward overview of the installation process:

So now it works at http://localhost/owncloud/index.php/ but I want sync.

Well first we explored import/export of .vcf and .ics files. This is an interesting exercise, and I've learned a lot. In particular, 


is an excellent exposition on automating the download of .vcf and .ics files from OwnCloud. 

I worked these into a BASH script and quite happily now have the requisite files. And Evolution quite happily imports them.

But what about the 'droid?

Well, it turns out that there really is no happy way to import .ics files into the Android calendar.At least I couldn't find one.

So bite the bullet and start learning yet another something new: DAV.

Simply stated, in the beginning there was WebDAV, and then CardDAV and CalDAV. All are protocols for synchronizing data.

Well, it turns out that Konqueror (and a lot of other file managers) already have webdav support built in. So the first step (synchronizing, exchanging files) is a piece of cake. Enter the following (obviously changing the path to your OwnCloud's URL) in the address field of the file manager:


This will prompt y     ou for your OwnCloud username and password, and then present the OwnCloud file tree.

Easy when you know how.

Next: Synchronize Evolution:

But this is problematic. All our attempts fail.

On the other hand, the Android is a delight:


just works.

It's a little tricky, since it does not appear in the normal App Store. Go to 

     Settings →Accounts

and choose Add Account. Choose CalDav Sync Adapter and add the required information, e.g., 

     User:               andy
     Password:     **********

For Calendar:
You get the URL from the OwnCloud screen. Click the gear icon in the upper right corner. There are a number of icons. The second one is the link. Click on it and read the URL in the popup dialog. 

(There are also a number of greyed-out sub-icons, including a download arrow. Click it. it will download the current calendar as an ics, that then happily imports into Evolution.)

For Contacts there is no such gear icon. The URL is in the form:


But the calendar works great, so that is enough for now.

Easy When You Know How: Deskewing text scans under Linux


I've been scanning documents for ages, but more recently than before. Especially in large numbers. 

So I use the ADF (Automatic Document Feeder) on my HP-6400 scanner with XSane to direct the images to a Download directory.

But inevitably they are off by a fraction, no more than a fraction, like 0.5°, but my eye still catches it. And deems it unprofessional.

But if you have fifteen pages, opening each one to correct them is a royal PITA. And time consuming to boot.

So I cast about for ways to fix it: 
  • Looked for GIMP plugins. There was one once upon a time called Deskew but it seems to have evanesced.
  • Looked for options under Imagick. Its convert and mogrify scripts are very capable. There is a deskew option, but I did not find any simple description of how to use it.
  • Looked for other options...
And found the cited program deskew.  It is current, and has versions for Linux (both 32- and 64-bit), Mac, and Windows. You can recompile it if you really want to, but it comes with a Bin subdirectory containing precompiled versions for all three OS.

And it is a positive dream to use. Most of the parameters are precompiled with defaults. I changed the binary RRGGBB background (-b) parameter to white (fffff) from its default black (000000), but frankly haven't had the time to examine whether that was really necessary.

So the command at its simplest for me was

     deskew -o output.jpg -b ffffff input.jpg

Yes, you have to know what you're doing: unzip the download, move the entire resulting Deskew directory to somewhere useful, e.g., /data/graphics You also need to 

     chmod +x deskew

to make it executable and adjust your .bashrc to include that path, or simply prepend it to the deskew command:

     /data/graphics/Deskew/Bin/deskew ...

So, generally, a breeze.

A very elegant piece of work.

Well done.