Writing Your Own Image Gallery Application with the UNIX Shell
Digital photography has become so ubiquitous today that even medium-range mobile phones can capture photographs. Once you transfer photos to the PC, you need to be able to share them with friends and relatives. Most digital cameras produce such high-resolution images that sending them directly to folks via e-mail is not always convenient.
This is when you need an on-line photo-sharing Web site, such as flickr.com, to help share photographs simply by uploading them. Of course, you also can do the heavy lifting with tools such as gallery2.
But, in this article, I discuss how to utilize the power of the Linux command line to create an image gallery.
All of you have heard of the GNU Image Manipulation Program (GIMP). It is useful for interactive image manipulation, photo retouching and other editing purposes, but I find it quite difficult to use. There are often much simpler alternatives that do a much better job for commonplace image editing. The nice thing about these alternatives is that you can run them directly from the almighty command line, which can save time and facilitate easy scripting. Here are some such tools that interest me:
qiv: this one is the fastest of the lot. It is lightweight, and it can handle a huge list of images on the command line. In fact, you can reproduce the “persistence of vision” effect of video by dumping the frames using MPlayer's -vo jpeg or -vo png driver and view them using qiv *. Pressing the spacebar gives the same effect of actually watching the video sans the audio.
xloadimage: xloadimage, or xli, is another application for viewing images.
xv: this one is rather outdated now, but it is worth taking a look at it. Some of its image processing algorithms are cool.
tgif: tgif, along with dia, xfig and friends, is most useful for creating technical drawings, block diagrams and the like. I find tgif to be really user-friendly and powerful when it comes to certain common image processing tasks, such as generating a collage or mosaic of images and annotating images with text.
Netpbm suite: this suite has more than 200 command-line utilities and is used for advanced image processing purposes that primarily are designed to be invoked from the Linux command line.
ImageMagick suite: this suite can be described as the be-all end-all of image processing. It has mind-boggling capabilities that can create animations, logos, convert file formats and, of course, do highly sophisticated image processing. Go to www.imagemagick.org/Usage for details on all it can do.
In this article, I focus primarily on using the ImageMagick toolkit for the purpose of creating an image gallery.
Obviously, you will want the gallery to be an HTML page for sharing with friends using the Web.
The first step involves generating thumbnails for all the images. These have to be linked to the images using HTML tags. But, before that, you need to take care of the images' varying orientations. Different photographs may have different dimensions, and you should be able to categorize the thumbnails based on that. This is no hard and fast rule, but I prefer it this way.
The next task is to annotate the images with relevant text, by watermarking either below or above the image. ImageMagick has a rich toolchest for achieving this task in an elegant manner.
You also will want to be able to retrieve, save and optionally display the EXIF data embedded in the photographs. After annotating the images, you may want to generate borders, frames or 3-D reliefs for better visual appeal. Usually, they look nice on Web pages with a white background.
Another nice-to-have feature is to be able to generate black-and-white photo equivalents. Of course, in addition to all this, if users want to download the original, untouched, pristine photo in full size, they should be able to do so. It might be worthwhile to provide a download link for all the photos in one single zip file.
For people who don't like clicking on each of the thumbnails, you can provide a slideshow. But, on Linux, you can do much better. You can create a full-fledged video with sound effects. I prefer a nice MIDI tune, appropriate for the occasion and mood of the snaps. This has a side benefit of being directly writable to DVD too.
But before this, it's a good idea to create vertical and horizontal mirror images of each of the photos. That way, the video has a better flow and visual appeal. It so happens that this is extremely easy to do with the Linux command line and ImageMagick.
You might have other requirements, such as correcting the exposure, brightness or contrast, cropping out certain parts of the image or doing photo retouching with more interesting effects. Again, ImageMagick can do the trick (as can qiv and other image display tools). To correct images, you might prefer an interactive tool, such as The GIMP or tgif.
Other possibilities exist, such as creating a mosaic of images annotated with nice fonts, but this does not make much sense in an image gallery application.
Now, let's get down to business.
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.
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