Friday, March 11, 2016


Over the next few weeks, I will be writing on topics related to my latest book, Data Simplification: Taming Information With Open Source Tools (release date March 23, 2016). I hope I can convince you that this is a book worth reading.

Blog readers can use the discount code: COMP315 for a 30% discount, at checkout.

In yesterday's blog, I discussed using system calls within your scripts. One of my examples called an ImageMagick. Today, I thought I'd describe ImageMagick, and some of its benefits.

ImageMagick is an open source utility that supports a huge selection of robust and sophisticated image editing methods. Its source code download site is:

Users may find it convenient to download the executable binaries, for their specific operating system, from:

Hundreds of ImageMagick methods are described in detail, and useful examples are provided, at:

There are several things you should know about ImageMagick:

1. Unlike the commercial image processing applications, ImageMagick has no graphic user interface. ImageMagick is intended to serve as a command line utility.

2. ImageMagick is powerful. There are hundreds of available methods for creating and modifying images.

3. ImageMagick can be called from Python, Perl, Ruby, and other scripting languages, via system calls or via language-specific ImageMagick interface modules (i.e., PerlMagick, PythonMagick, or RMagick)

Here are a few examples of ImageMagick command lines that can be launched from the system prompt (which happens to be sitting at the c:\ftp subdirectory on my home computer):

Converts an image in SVG format to JPEG format.
c:\ftp>convert mtor_pathway.svg mtor_pathway.jpg
Creates a thumbnail image from image.jpg and converts it to gif format.
c:\ftp>convert -size 600x800 image.jpg -thumbnail 120x160 image_thumb.gif
Applies contrast twice to an image, and produce a new file for the results.
c:\ftp>convert original.jpg -contrast -contrast result.png
Puts the contents of file words.txt into the comment section of tar1.jpg and keeps the same filename for the output file.
c:\ftp>convert -comment @words.txt tar1.jpg tar1.jpg
Displays a verbose description of an image, including the header contents.
c:\ftp>identify -verbose tar1.jpg
The real power of ImageMagick comes when it is inserted into scripts, allowing the programmer to perform batch operations of image collections.

Here is a Python script,, that creates a resized copy of every jpeg file in the current directory.
import sys, os, re 
filelist = os.listdir(".")
pattern = re.compile(".jpg$")
for filename in filelist:
    out_filename = pattern.sub('_small.jpg', filename)
    cmdstring = "convert " + filename + " -resize 400x267! " + out_filename
Here is a Perl script,, that reduces the size of every image in a subdirectory that exclusively contains image files. In this case, the all-image subdirectory is "c:\ftp\factth".
$newdir = "c\:\\ftp\\factth";
opendir (MYDIR, $newdir) || die ("Can't open directory");
chdir ($newdir);
while ($file = readdir (MYDIR))
  next if (-d $file);
  next if ($file eq "." || $file eq "..");
  system("convert $file -resize 30% $file");
closedir (MYFILE);

- Jules Berman

key words: computer science, data analysis, data repurposing, data simplification, data wrangling, information science, simplifying data, taming data, complexity, system calls, Perl, Python, open source tools, utility, Image Magick, ImageMagick, jules j berman

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