Another addendum to the seventh installment: imagemagick as a resource for the budget-constrained researcher continued

Continuing on the theme of the last couple of entries, the budet-contrained researcher may own or wish to acquire a piece of hardware that can aid him in obtaining needed materials from research libraries. For example he may need but a single article or perhaps a chapter from a book. Or maybe a bibliography. Obtaining limited segments of larger works such as those mentioned may be more difficult through inter-library loan channels, especially in the case of works that may contain more than one item of potential interest. It can happen that the researcher will need to go in person to inspect the work to decide which part is actually required.

Suppose the researcher is already on the premises of the local academic library and has located target material. Should he not wish to check out a book, he is left with the option of himself scanning the material. Of course these libraries often have scanners that they make available to patrons, so that is one possible option. Yet another option is for the researcher to use his own scanner, and this is where highly portable hardware such as the Magic Wand portable scanner comes in.

I invested in one of these a few years ago and it has proved quite useful. One of the problems with using it, though, is that, for the bulk of books and journals (i.e., those of more standard size) it seems to work best to scan pages sideways--horizontally, rather than vertically. In other words, it works best to start from the spine and to scan toward page edges. This, obviously, entails that roughly every other page will have been scanned in a different orientation from the page preceding.

Once all pages are scanned, they can be easily rotated in bulk to the desired orientation--by 90 or 270 degrees, as the case may be--using imagemagick's mogrify switch, like so; mogrify -rotate 90 *.JPG (a command like convert -rotate 270 PTDC0001.JPG PTDC0001-270rotate.jpg would perform much the same function while preserving the original file). In my case, it seemed best to first copy all odd, the all even, image files to separate directories prior to rotating them.

At this point, I needed to name all files with either odd or even numbers. My bash scripting skills being modest at best, I began scouring the internet for a solution that would aid me in doing this sort of bulk renaming. I found such a script at http://www.linuxquestions.org/questions/programming-9/bash-script-for-renaming-files-all-odd-617011/ and a bit of testing proved it to be a solution that would work for me.

I modified the script into 2 variants and named one rename-all_odd.sh and rename-all_even.sh. The scripts look as follows:

#!/bin/bash # rename all files having .JPG extension in current directory with an odd 4-digit numeral series # found at http://www.linuxquestions.org/questions/programming-9/bash-script-for-renaming-files-all-odd-617011/ # num=1 for file in *.JPG; do mv "$file" "$(printf "%04u" $num).jpg" let num=num+2 done
and

#!/bin/bash # rename all files having .JPG extension in current directory with an even 4-digit numeral series # for use with image files created using Magic Wand handheld scanner # found at http://www.linuxquestions.org/questions/programming-9/bash-script-for-renaming-files-all-odd-617011/ # num=2 for file in *.JPG; do mv "$file" "$(printf "%04u" $num).jpg" let num=num+2 done
It was then a simple matter of copying all the renamed files into a separate directory and concatenating them into a pdf, as was covered in a previous installment.

Seventh installment: imagemagick trick 1 of (?)

During a recent vacation, I needed to convert some digital images taken by a relative's camera from a raw format into something that would display better on my laptop. As usual, imagemagick came to the rescue. Details are included below.

imagemagick has been called something like "the swiss army knife of image manipulation utilities." I've utilized this application on many occasions over my years as a GNU/Linux user and been amazed to have as yet found nothing that it cannot do. Moreover, it's a CLI-friendly tool, which makes it doubly appealing for someone like me who favors using the least resource-intensive application for any given job.

I should mention that, not only was I converting these images to a different format with which my laptop could better deal, desirable, but resizing them was needed as well. You see, each photo taken by this fairly high-end camera came in at about 25 megabytes, and the dimensions of each image were probably in thousands of pixels. So I wanted to both resize and convert them; but, based on past experience with imagemagick, I was sure it would be up to the job.

I was surprised, after some initial searching on how to accomplish this task, at how simple this task would turn out to be. After mounting the Secure Digital card on my laptop, I copied over all the images--which had the .CR2 extension, by the way--to a temporary directory on my laptop.

The incantation I then used, after cd'ing to the temporary directory where the images resided, was mogrify -format jpg -geometry 1024x768 *.CR2. It should be fairly obvious what this does, but just in case it's not, let me explain. The mogrify command is part of imagemagick's image manipulating routines and can be invoked to do a number of things with an image, but in this case the -format switch, followed by the jpg extension, tells it to convert from one format to another.

Though most readers of this blog are likely to know this already, it will be worth mentioning that the asterisk preceding the file extension is the wildcard symbol. Thus, all files in that directory with the designated extension get converted. Incidentally, they are given the same prefix as the raw .CR2 files, but after conversion have the .jpg extension instead of the .CR2 extension.

I should mention here that, although raw formats are not especially new, I did run across some indications while researching how to do this, that older versions of imagemagick might not be able to operate on such formats. But I believe any version that's come out in the last 2 or 3 years should understand and be able to manipulate these raw formats.

The -geometry switch tells imagemagick to resize the image from something in the thousands of pixels down to a size that displays better, and takes up a whole lot less disk space, on this laptop. The switch does also have a somewhat undesirable effect on photos taken in vertical rather than horizontal orientation, since, as written to disk, these are taller than they are wide (whereas photos taken in horizontal orientation are wider than they are tall): the program thus makes the height of the photo 768 pixels, while the width, being kept proportional, turns out to be quite a bit less than that. But for my purposes--which was simply being able to view quickly these fresh photos on my laptop--these somewhat under-sized photos did not pose any particular problem.

The process of converting many photos this way can be lengthy, but, as you have seen, it is quite simple. I would simply start the process, then either do some other task in another desktop while awaiting completion, or just set the laptop aside while it was running the process. After about a half hour or so, I was ready to view photos.

Above is a sample of one of the converted images. Oh, and by the way, the "(?)" in the title of this entry is meant to indicate the multitude of other imagemagick tricks, as yet unknown to a relatively casual user such as myself, there are likely to be.