Shallow Thoughts : : Dec

Akkana's Musings on Open Source Computing, Science, and Nature.

Sat, 25 Dec 2010

Happy Holidays to All!

[Happy holidays with a shroom] Happy holidays to everyone! Merry Christmas, if you celebrate it, and if you don't -- just go ahead and be merry anyway, okay?

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[ 16:18 Dec 25, 2010    More misc | permalink to this entry | comments ]

Thu, 23 Dec 2010

Editing Batches of Photos with GIMP and David's Batch Processor

[David's Batch Processor]

Have a lot of images to edit, but confused by command-line tools like ImageMagick? Try David's Batch Processor, a GIMP plug-in that lets you apply multiple operations like resize, rotate, or brightness/contrast to groups of photos.

The article is on Linux Planet: Editing Batches of Photos Easily on Linux.

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[ 10:07 Dec 23, 2010    More gimp | permalink to this entry | comments ]

Tue, 21 Dec 2010

Developing for Android

I wrote yesterday about my quest for an app for reading news feeds and other timely information from the web. And how existing ebook readers didn't meet that need. That meant I would have to write something.

Android development is done in Java, using Eclipse as an IDE. Let me just state up front that (a) I dislike Java (and have forgotten most of what I once knew about it) and (b) I hate IDEs -- they make you use their crippled editor instead of your own, they control what you can put where on the screen, and they're always popping up windows that get in your way.

Okay, not an auspicious beginning. But let's try to be open-minded, follow the instructions and see what happens.

I installed Eclipse from eclipse.org after being advised that the version on Ubuntu is out of date. Then I installed all the various Android plug-ins and SDKs and set them up (there is no single page that lists all the steps, so I did a lot of googling). It took maybe an hour or so to get it all installed to the point where it could produce its "Hello world".

And then ... wow! Hello world worked right off the bat, and the emulator worked for basic testing. Hmm, okay ... how about if we use HTML as a format ... is there a standard HTML display component? Sure enough -- I added a WebView to my app and right away I had a working HTML reader. Okay, how about a row of buttons and a status bar on top? Sure, no problem.

The standard Android online docs aren't great -- they're a wonderful example of how to write seemingly comprehensive documentation that somehow manages to tell you nothing of what you actually need to know. But that's not as bad as it sounds, because there are lots of forums and tutorials to fill in the gaps. Stack Overflow is particularly good for Android tips.

And yes, I did some swearing at Eclipse and spent too much time googling how to disable features, like the "Content Assist" that periodically freezes the whole UI for a minute or so in the middle of your typing a line of code, while it thinks about some unhelpful and irrelevant hints to offer you in a popup. Turn it off in the prefs under Java/Editor. (Eclipse's actual useful hints, like the ones you get when you hover over something that's red because of an error, will still work. I found them very helpful.)

More specifically: Java/Editor/Content Assist/Hovers, and turn off Combined Hover and maybe anything else that happens without a modifier key. You probably also want to turn off Enable Auto Activation under Java/Editor/Content Assist. And possibly others -- I kept turning things off until the popups and delays went away, and I haven't found anything explaining how all these parameters relate.

Okay, so there were snags, and it's frustrating how there are almost no open source apps for this open source OS. (Yes, my app will be.) But here's the thing: in about 4 days, starting from nothing, I had a little RSS reader that did everything I needed. I've been adding features since then. Android doesn't have a reasonable battery status monitor? Fine, my reader can show battery percentage in the status bar. Android doesn't dim the screen enough? Fine, I can dim it further inside the application (an idea borrowed from Aldiko).

After less than a week of work I have an RSS reader that's better than my Palms running Plucker ever were. And that says a lot about the ease of the Android programming environment. I'm impressed!

Update: The source, an apk, and a brief discussion of how I use my feed reader are now here: FeedViewer.

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[ 15:26 Dec 21, 2010    More programming | permalink to this entry | comments ]

Mon, 20 Dec 2010

Android tablet as an ebook/RSS reader

I reviewed my Archos 5 Android tablet last week, but I didn't talk much about my main use for it: offline reading of news, RSS feeds and ebooks.

I've been searching for years for something to replace the aging and unsupported Palm platform. I've been using Palms for many years to read daily news feeds; first on the proprietary Avantgo service, but mostly using the open source Plucker.

I don't normally have access to a network when I'm reading -- I might be a passenger in a car or train, in a restaurant, standing in line at the market, or in the middle of the Mojave desert. So I run a script once a day on a network-connected computer to gather up a list of feeds, package it up and transfer it to the mobile device, so I have something to read whenever I find spare time.

For years I used Sitescooper on the host end to translate HTML pages into a mobile format, and eventually became its primary maintainer. But that got cumbersome, and I wrote a simpler RSS feed reader, feedme.

But on the reader side, that still left me buying old PalmOS Clies on ebay. Surely there was a better option?

I've been keeping an eye on ebook readers and tablets for a while now. But the Plucker reader has several key features not available in most ebook reader apps:

  1. An easy, open-source way of automatically translating RSS and HTML pages into something the reader can understand;
  2. Delete documents after you've read them, without needing to switch to a separate application;
  3. Random access to document, e.g. jump to the beginning or end, or 60% in;
  4. Follow links: nearly all RSS sites, whether news sites or blogs, are set up as an index page with links to individual story pages;
  5. Save external links if you click on them while offline, so you can fetch them later.

Most modern apps seem to assume either (a) that you'll be reading only books packaged commercially, or (b) that you're reading web pages and always have a net connection. Which meant that I'd probably have to roll my own; and that pointed to Android tablets rather than dedicated ebook readers.

Android as a reader

All the reviews I read pointed to Aldiko as the best e-reader on Android, so I installed it first thing. And indeed, it's a wonderful reader. The font is beautiful, and you can adjust size and color easily, including a two-click transition between configurable "day" and "night" schemes. It's easy to turn pages (something surprisingly difficult in most Android apps, since the OS seems to have no concept of "Page down"). It's easy to import new documents and easy to delete them after reading them.

So how about those other requirements? Not so good. Aldiko uses epub format, and it's possible (after much research) to produce those using ebook-convert, a command-line script you can get as part of the huge Calibre package. Alas, Calibre requires all sorts of extraneous packages like Qt even if you're never going to use the GUI; but once you get past that, the ebook-convert script works pretty well.

Except that links don't work, much. Sometimes they do, but mostly they do nothing. I don't know if this is a problem with Calibre's ebook-convert, Aldiko's reader, or the epub format itself, but you can't rely on links from the index page actually jumping anywhere. Aldiko also doesn't have a way to jump to a set point, so once you're inside a story you can't easily go back to the title page (sometimes BACK works, sometimes it doesn't).

And of course there's no way to save external links for later.

So Aldiko is a good book reader, but it wouldn't solve my feed-reading problem.

And that meant I had to write my own reader, and it was time to delve into the world of Android development. And it was surprisingly easy ... which I'll cover in a separate post. For now, I'll skip ahead and ruin the punch line by saying I have a lovely little feed-reading app, and my Archos and Android are working out great.

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[ 14:14 Dec 20, 2010    More tech | permalink to this entry | comments ]

Wed, 15 Dec 2010

Archos 5 Android Tablet review

[Archos 5]

For the past couple weeks I've been using a small Android tablet, an Archos 5. I use it primarily as an ebook and RSS feed reader (more about that separately), though of course I've played with assorted games and other apps too.

I've been trying to wait for the slew of cheap Android tablets the media assure us is coming out any day now. Except "any day now" never turns into "now". And I wanted something suitable for reading: small enough to fit in a jacket pocket and hold in one hand, yet large enough to fit a reasonable amount of text on the screen. A 4-5-inch screen seemed ideal.

There's nothing in the current crop fitting that description, but there's a year-old model, the Archos 5. It has a 4.8-inch screen, plus some other nice hardware like GPS. And it seems to have a fair community behind it, at archosfans.com.

I have the 16G flash version. I've had it for a couple of weeks now and I'm very happy so far. I'm not sure I'd recommend it to a newbie (due to the Android Marketplace's ban on tablets -- see below), but it's a lovely toy for someone fairly tech savvy.

My review turned out quite long, too long for a blog post. So if you're interested in the details of what's good and what's bad, you'll find the details in my Archos 5 Android Tablet review.

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[ 21:22 Dec 15, 2010    More tech | permalink to this entry | comments ]

Thu, 09 Dec 2010

Article: Troubleshooting, part II: /proc and Python

My article this week on Linux Planet concerns Advanced Linux Server Troubleshooting (part 2).

It's two loosely related topics: exploring the /proc filesystem, and how to use it to find information on a running process; and several ways to get stack traces from Python programs.

This (as well as Troubleshooting part I) arose from a problem we had at work, where we use Linux plug computers (ARM-based Linux appliances) running Python scripts. It's not uncommon for Python networking scripts to go into never-never-land, waiting forever on a network connection without timing out. Since plug computers tend not to be outfitted with the latest and greatest tools like gdb and debug versions of libraries, we've needed to find more creative ways of figuring out what processes are doing to make sure our programs are ready for anything.

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[ 10:44 Dec 09, 2010    More linux | permalink to this entry | comments ]

Tue, 07 Dec 2010

Android/Eclipse Spellchecker is a bit confused

I've been doing some Android development, using the standard Eclipse development tools. A few days ago, I pasted some code that included a comment about different Android versions, and got a surprise:

[The word 'Android' is not correctly spelled. Change to 'Undried'?]

What do you think -- should I change all the "Android" references to "Undried"?

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[ 10:09 Dec 07, 2010    More humor | permalink to this entry | comments ]

Wed, 01 Dec 2010

Escaping HTML characters in Emacs (and how to do replaces in elisp)

Last week I found myself writing another article that includes code snippets in HTML.

So what, you ask? The problem is, when you're writing articles in HTML, every time you include a code snippet inside a <pre> tag you invariably forget that special characters like < > & have special meanings in HTML, and must be escaped. Every < has to change to &lt;, and so forth, after you paste the code.

In vi/vim, replacing characters is straightforward. But I usually write longer articles in emacs, for various unimportant reasons, and although emacs has global replace, it only works from wherever you are now (called "point" in emacs lingo) to the end of the file. So if you're trying to fix something you pasted in the middle of the article, you can't do it with normal emacs replace.

Surely this is a wheel that has already been re-invented a thousand times, I thought! But googling and asking emacs experts turned up nothing. Looks like I'd have to write it.

And that turned out to be more difficult than I expected, for the same reason: emacs replace-string works the same way from a program as it does interactively, and replaces from point to the end of the file, and there's no way to restrict it to a more limited range.

Several helpful people on #emacs chimed in with ideas, but most of them didn't pan out. But ggole knew a way to do it that was both clean and reliable (thanks!).

Here's the elisp function I ended up with. It uses save-excursion to put the cursor back where it started before you ran the function, narrow-to-region to make replace-string work only on the region, and save-restriction get rid of that narrow-to-region after we're done. Nice!

(defun unhtml (start end)
  (interactive "r")
  (save-excursion
    (save-restriction
      (narrow-to-region start end)
      (goto-char (point-min))
      (replace-string "&" "&amp;")
      (goto-char (point-min))
      (replace-string "<" "&lt;")
      (goto-char (point-min))
      (replace-string ">" "&gt;")
      )))

And yes, I used it just now on that elisp snippet.

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[ 19:08 Dec 01, 2010    More linux/editors | permalink to this entry | comments ]

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