KBibtex in Ubuntu Oneiric 11.10

KBibtex is a useful bibtex bibliography management tool for the KDE desktop.
However, it seems that the package is missing in the Ubuntu 11.10 repositories.

A quick remedy (as tweeted here) is to install the package from the Debian Sid distribution: kbibtex.
To install on the command line (check the exact name of the .deb file)
sudo dpkg -i kbibtex_0.4-1_amd64.deb

Alternatively .deb packages can be installed in the GUI (e.g. by opening the file in Dolphin).

The package should be compatible with Ubuntu 11.10, and seems to work fine.

The 0.4 version has improved a lot and has a very useful online search tool for acquiring bibtex files. Google scholar and other data bases can be used.
Other tools include a reference preview (though bibtex2html) and a PDF preview.

Autocrop images with imagemagick

Often one has to crop excess margins from an raster image. Common image graphical editors have autocrop tool, but if many files need to be processed, opening and saving files one by one quickly becomes tedious.

A better solution is to use convert tool that is a part of the powerful Imagemagick toolkit:

convert image.jpg -trim -bordercolor White -border 20x10 +repage cropped_image.jpg
This command reads the original file, removes (trims, crops) white borders, adds 20 pixel white borders horizontally and 10px vertically, and stores the file as cropped_image.jpg.

It is also possible to process all image files in the current directory with the following one line command:
for i in `ls *.jpg`; do convert $i -trim -bordercolor White -border 20x10 +repage cropped_`basename $i`; done

If you want to convert to another image format, it can be done conveniently at the same time (-quality option controls the jpg quality):
for i in `ls *.gif`; do convert $i -trim -bordercolor White -border 20x10 -quality 92 +repage cropped_`basename $i gif`jpg; done
Above basename utility is used for trimming suffix from the file name.

Extract images from a pdf file

In Linux pdfimages utility extracts raster images from a pdf file.

Extract all raster images from pdf file, save in jpg format (creates bar-000.jpg, bar-001.jpg, etc.):
pdfimages -j file.pdf image

The -j option is to convert the images to jpeg format if possible.
Other options can be found in the manual.

Use pdftk to edit pdf files

pdftk is a useful free utility for editing pdf files.

Split a pdf file to individual pages (generates: page01.pdf, page02.pdf, etc.)
pdftk original.pdf burst output page%02d.pdf

Split a pdf file to two parts:
pdftk original.pdf cat 1-3 output threeFirstPages.pdf
pdftk original.pdf cat 4-end output rest.pdf

Merge multiple pdf files to one:
pdftk first.pdf second.pdf third.pdf cat output 123.pdf

Many more examples can be found on pdflabs examples page.

Using wget to download multiple files from a website

The following command downloads all files pdf files from http://www.host.com/some/path/ to currenct directory
wget -r -l1 -nd -nc -A.pdf http://www.host.com/some/path/

The options are:
-r Makes it recursive for subfolders
-l1 set maximum recursion, 1 levels of subfolders
-nd no directories — copies all matching files to current directory, discards directory information
-nc Do not download it file already exists
-A.pdf Accept only certain files (with pdf suffix in this case). Specify comma-separated lists of file name suffixes or patterns.