Magick with Images
While there are many packages available with some or all of the functions listed above, the real strength of ImageMagick lies in the ability to write programs using its library functions.
Included in the distribution is a simple program to demonstrate how to write your own image manipulation programs. It loads an image in JPEG format and creates a thumbnail in GIF format. I have changed the program slightly from its form in the distribution and presented it below. The thumbnail version will look something like the original image in Figure 1.
The C API to the ImageMagick library is documented through a set of web pages, which are also included in the distribution.
To compile the example code in Listing 1, you will need to give a command such as:
gcc -o example example.c -lMagick\ -lX11 -lXext -ltiff -lpng\<\n> -I/usr/include/X11/magick -L/usr/X11/lib
The exact number of libraries required and the location of the libraries and include files will depend on the configuration of your system. The example given here works on my Red Hat 4.2 system installed from the RPM ImageMagick distribution.
To use the program, create a file called image.jpg and run the program in the same directory. The result will be a thumbnail-sized version of the original image called image.gif.
Using the included documentation, it is easy to see how this example can be extended and modified to form the basis of a wide variety of different functions. The same calls may also be made from Perl using the PerlMagick interface. Since I am not a Perl programmer, I have not investigated this interface.
ImageMagick is a complex package to use to its full potential; it is also very powerful. It offers a wealth of features in a flexible manner. It is easy to use the basic features without worrying about the more esoteric options available. I suspect that many people will use the basic options combined with only one or two of the more advanced options according to their application.
I consider ImageMagick a package well worth investigating for anyone needing anything from a basic image viewer to a full-fledged custom image manipulation system.
Pictures of Alan Cox are courtesy of Justin Mitchell and the ray-traced background image in Figure 1 was produced by David Beynon.
Practical Task Scheduling Deployment
July 20, 2016 12:00 pm CDT
One of the best things about the UNIX environment (aside from being stable and efficient) is the vast array of software tools available to help you do your job. Traditionally, a UNIX tool does only one thing, but does that one thing very well. For example, grep is very easy to use and can search vast amounts of data quickly. The find tool can find a particular file or files based on all kinds of criteria. It's pretty easy to string these tools together to build even more powerful tools, such as a tool that finds all of the .log files in the /home directory and searches each one for a particular entry. This erector-set mentality allows UNIX system administrators to seem to always have the right tool for the job.
Cron traditionally has been considered another such a tool for job scheduling, but is it enough? This webinar considers that very question. The first part builds on a previous Geek Guide, Beyond Cron, and briefly describes how to know when it might be time to consider upgrading your job scheduling infrastructure. The second part presents an actual planning and implementation framework.
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With all the industry talk about the benefits of Linux on Power and all the performance advantages offered by its open architecture, you may be considering a move in that direction. If you are thinking about analytics, big data and cloud computing, you would be right to evaluate Power. The idea of using commodity x86 hardware and replacing it every three years is an outdated cost model. It doesn’t consider the total cost of ownership, and it doesn’t consider the advantage of real processing power, high-availability and multithreading like a demon.
This ebook takes a look at some of the practical applications of the Linux on Power platform and ways you might bring all the performance power of this open architecture to bear for your organization. There are no smoke and mirrors here—just hard, cold, empirical evidence provided by independent sources. I also consider some innovative ways Linux on Power will be used in the future.Get the Guide