The Definitive Guide to ImageMagick

Michael J. Ross writes "To modify a digital image, most computer users turn to a GUI-based image processing application, such as Photoshop. However, while Photoshop and many other similar programs can process multiple images in batch mode, they still require manual usage, and thus typically are unable to process images via a command line or within a second application. Those capabilities call for a programmatic digital image manipulation tool such as ImageMagick, which is explored in a relatively new book, The Definitive Guide to ImageMagick." Read the rest of Michael's review.

The Definitive Guide to ImageMagick
author	Michael Still
pages	335
publisher	Apress
rating	7
reviewer	Michael J. Ross
ISBN	1590595904
summary	An introduction to using ImageMagick for digital image manipulation.

The author of this title is Michael Still, a programmer who gained experience with ImageMagick during his eight years of working on imaging applications, as well as writing articles on ImageMagick for IBM DeveloperWorks. Apress maintains a Web page for the title, where a visitor can purchase the electronic version of the book, read its table of contents, or download its source code or a sample chapter (Chapter 4 — Using Other ImageMagick Tools) in PDF format. They also have a link where readers can submit errata — and apparently be the first to do so, as there are no existing errata listed on the Web page.

The book's 335 pages are organized into a dozen chapters, following an introduction and a few other standard sections, including a forward written by ImageMagick's principal architect, Christy, who briefly explains the product's 20 years of history, development, and lack of decent documentation. That is where this book is intended to fill the gap, and Christy notes that most future questions about ImageMagick will be answered by pointing people to this book, as is also noted on ImageMagick's homepage.

The first chapter of the book explains how to install and configure ImageMagick, for several Linux distros, as well as Microsoft Windows — using the precompiled versions, or by compiling from ImageMagick's source code. The chapter is wrapped up with a brief description of ImageMagick's online help, debug output, verbose output, and version information. The next ten chapters fall into two categories: ImageMagick usage as a standalone, and from within other applications. The first category of chapters covers basic image manipulation, compression, other metadata, ImageMagick tools, artistic transformations, other image transformations, and drawing commands. The second category discusses how to utilize ImageMagick from within programs written in Perl, C, Ruby, and PHP. The 12th and final chapter is quite brief, and describes where to find online help (Web sites, blogs, mailing lists, and forums) and where to report any apparent bug in ImageMagick.

For Windows users, the first chapter may begin badly, as the author fails to explain which precompiled version the reader should select if they wish to install ImageMagick on a Windows PC. For each version, there are four flavors to choose from. But which one is right for the reader? "static" vs. "dll?" "Q16" vs. "Q8?" What are the differences? The ImageMagick Web site and FTP file listings appear to have no README file or installation help file to explain which flavor you should download. The book should provide some assistance here, but does not. The former topic, static versus DLL, is mentioned only in reference to compiling ImageMagick from source — information which the reader will probably never see, should they choose to install the precompiled binaries and get started on ImageMagick as quickly as possible.

The latter topic is not covered at all — not even in the index, where a "quantum depth" entry would be useful. For those readers who are interested, "Q8" indicates 8 bits-per-pixel components, and "Q16" means 16 bits-per-pixel. The latter allows one to read or write 16-bit images without losing precision, but requires twice as much resources as Q8. Apparently Q16 is the best choice for medical or scientific images, or those with limited contrast. Otherwise, Q8 should be sufficient, and offers greater performance.

The material most likely to be read, referenced, and valued in this book, is the chapters devoted to explaining how to use ImageMagick for resizing, compressing, transforming, and drawing digital images. Most of these first-category chapters begin with a concise summary of the theory put into practice throughout the rest of the respective chapter — a wise inclusion in each case, since even the most experienced computer programmers and other users have had no instruction or experience in image theory. All of these chapters do a competent job of explaining what each ImageMagick command is used for, and then illustrating it with a straightforward example.

The most glaring deficiency in these chapters, and the book as a whole, is that far too many of the book's figures (digital images, naturally) fail to reflect what is intended to be conveyed by each figure. This is primarily because they are all in black-and-white, and in many cases do not offer the size and resolution necessary. In other words, there are many cases where the "before" and "after" images look almost identical. In the cases of color manipulation, most of those black-and-white images are of little value — occasionally laughably so.

The second-category chapters, covering ImageMagick usage with Perl, C, Ruby, and PHP, proved disappointing, primarily due to their narrow focus, and lack of tips, recommendations, and coverage of the APIs' capabilities. The details are presented in the form of a single example for each language. For instance, the Perl chapter devotes too many pages to source code listings of a Perl program written by the author, that few readers would probably download from the publisher's Web site, much less read.

Nonetheless, this book should be useful to any programmer interested in making the most of ImageMagick's capabilities, and that is not just because it is the only ImageMagick book on the market. Michael Still certainly had his work cut out for him when he agreed to document the bulk of what ImageMagick can do. It is unfortunate that the color images that he created for the book cannot be seen by the reader, and that the Windows binary versions and ImageMagick APIs, were given short shrift. We can hope that future editions of this book will be significantly strengthened, such as including color and higher resolution images where needed — even if it requires grouping them together within the book, if that reduces production costs.

Lastly, it should be mentioned that, as a smaller technical publisher, Apress is not resting on its laurels, and is not only scheduled to release an impressive variety of programming books this year, but their customer support — at least in my experience — was outstanding, as there was a problem with the shipping of this title, and they bent over backwards to make it right.

Michael J. Ross is a freelance writer, computer consultant, and the editor of the free newsletter of PristinePlanet.com."

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You can purchase The Definitive Guide to ImageMagick from bn.com. Slashdot welcomes readers' book reviews -- to see your own review here, read the book review guidelines, then visit the submission page.

yes, you can command line photoshop

Just create an action which does what you want, then you can export an "EXE" which takes as command line argument the file you want to process, and optionally, the output. Works like a charm.

Re:yes, you can command line photoshop

Oh, yes, that's much easier than

for img in `ls *.jpg`
do
  convert -sample 25%x25% $img thumb-$img
done

And the million other things you can do from the command line without making task-specific exes.

Re:yes, you can command line photoshop

don't be a dummy

for i in *jpg; do
  convert -sample 25%x25% "$i" "thumb-$i"
done

works perfectly with any special characters, including spaces and newlines, in the filename

Re:yes, you can command line photoshop

works perfectly with any special characters, including spaces and newlines, in the filename

Wow. Anyone who puts newlines in a filename should be beaten publically.

Re:yes, you can command line photoshop

for img in `ls *.jpg`

Am I the only person who laughed out loud?

Re:yes, you can command line photoshop

Am I the only person who laughed out loud?

Probably not, but I think it's kinda silly. If you're on a machine where you're worried about spawning off one more process, I feel sorry for you. :)

Remember, there's More Than One Way To Do It. That's kinda the beauty of Unix. I do like that 'for i in *.jpg' takes a lot fewer keystrokes, mind, but just because it uses fewer keystrokes and doesn't exec ls doesn't make it the Only Right Way.

Indeed, for some things, it may not be the Right Way at all. Ferinstance:

for i in `ls fullsize`
do
convert -scale 800x800 fullsize/$i $i
convert -scale 150x150 fullsize/$i thumbnails/$i
done

It's cheaper to exec ls here than it is to crunch $i each time to strip 'fullsize/' off the front. If you really wanted to streamline it (and if you're that worried about it, why the heck are you writing a shell script?) you could throw $PWD at a temporary variable, cd into fullsize, run your converts, but why bother with the extra typing or lines of code when this runs correctly, makes sense, and is only exec'ing the ls once?

But really what it boils down to, to me, is if exec'ing ls once instead of using the shell builtin * is causing problems on your system, you've got bigger problems than your shellscript-fu.

-F

Re:yes, you can command line photoshop

Just create an action which does what you want, then you can export an "EXE" which takes as command line argument the file you want to process, and optionally, the output. Works like a charm.

Maybe the author should have said 'useful commmand line processing' or similar.

1) Exes are not very useful for osx or linux users.

2) You need a copy of photoshop for every server you wish to run your exported exe on.

3) You have to create a different 'exe' for each action.

Photoshop is not even slightly useful for the sort of areas that imagemagick excels in.

Re:yes, you can command line photoshop

Just create an action which does what you want, then you can export an "EXE" which takes as command line argument the file you want to process, and optionally, the output. Works like a charm.

I've batch-processed sets comprising about 2,500–4,000 images (greyscale GIFs) both with command-line tools and with Photoshop CS. On each occasion, Photoshop took several hours longer than the specialized CLI apps to complete the jobs. The difference is even more dramatic when executing Photoshop Actions from within Photoshop, since the screen updates further increase processing time (an effect only slightly mitigated by hiding subwindows).

Manual vs. Automatic

Why would one need batch-sized automatic image editing? Although I can see one wanting to edit many pictures at a time, I think that you would still need to manually specify what you want done, and where. Unless you wanted to do almost identical edits to many different pictures (read: destalinization), then the application seems not to have much use.

Re:Manual vs. Automatic

As an example, in my previous job for a weather company, we'd generate large images of geographic data for a certain area of interest, and separately generate radar or satellite or lightning maps over the same area. We'd then use ImageMagick to combine all the separate images together, along with further generated warning areas, icons, and forecasts representing weather phenomena of interest (tornadoes, mesocyclones, hurricanes) and usually some sort of written annotation (time of image, source). ImageMagick was/is really useful.

Re:Manual vs. Automatic

Why would one need batch-sized automatic image editing?

Examples of edits that don't need to be manual: Thumbnails. Resizing. Addition of timestamps/watermarks/copyright info. Conversion to other formats. Motion detection. Mosaics. Proof sheets.

Gentle readers: just because something doesn't seem useful or make sense to you does not mean that it is categorically useless or senseless for everyone.

Re:Manual vs. Automatic

Why would one need batch-sized automatic image editing?

How do you think flickr makes perfect square thumbnails automatically?

convert in.jpg -thumbnail x200 -resize '200x' -resize 50% -gravity center -crop 100x100+0+0 +repage out.jpg

Any website that takes a user-uploaded photo needs to do something to it. From thumbnails to capping the image size.

Re:Manual vs. Automatic

If you're doing multiple transformations to the same file, PerlMagick is much faster than ImageMagick, since you only have to load and convert to internal format once for each file. One project I worked on thrashed badly as a BASH-ImageMagick script, but could be run in the background while the computer scanned (300 DPI, legal size, with a document feeder, 4ppm) as a PerlMagick script.

Re:Manual vs. Automatic

We use it for "normalizing" images. We have a device with a fixed resolution and some pretty severe limitations on the sizes, resolutions, formats, etc., of images we can send to it.

The original developer had his "submit image here" web page load the image into some Windows "object" format, and then do a bunch of tests, like 'reject if is it > 500 pixels wide' and 'warn if color depth > 2' and 'reject if not .BMP format'. But this is horrible for the users -- they may not have the image in the required format, and some won't have the knowledge to get it into the format we require.

I told him to just inline imagemagick's convert function, and output the exact format he requires. The sanitization is now very simple: if imagemagick can read it and successfully convert it to the desired format, it's good. That means we don't even have to tell our users to use .BMP or .GIF or .whatever -- if they can get us an image in a format recognized by imagemagick, we can use it. We've published guidelines that say "if you make your image conform to such-and-such attributes, our output will be as good as we can possibly make it." We're not promising an image that is horribly tortured by Imagemagick will print as well as they desire, but at least our app won't crash if they try to feed us garbage, or try to blow us up with a 10MB .TIFF or .WMF.

OS X Automator

OS X's Automator [apple.com] lets you do much of the same thing with apps like Photoshop.

ImageMagick is good stuff.

Imagemagick is good stuff, ive used it for a while now. Although I didn't buy a book to learn how, i just went here, for some great samples of uses:
http://www.cit.gu.edu.au/~anthony/graphics/imagick 6/ [gu.edu.au]
PIL isn't too shabby either http://www.pythonware.com/library/pil/handbook/ind ex.htm [pythonware.com]
Powerful stuff, maybe the book is not that great i don't know, but imagemagick and PIL are!

Better image examples online

In other words, there are many cases where the "before" and "after" images look almost identical. In the cases of color manipulation, most of those black-and-white images are of little value -- occasionally laughably so.

Haha, that was funny...well if you need to see what it actually does, their examples site [imagemagick.org] has some better images.

GraphicConverter

GraphicConverter on the Mac has some fairly powerful built-in scripting/workflows you can specify for a whole bunch of photos at once. And, it's shareware too. Such as I've used it to all at one time for 100+ photos, perform an "auto levels", reduce the file size so they're easier to e-mail, and create a basic thumbnail Web-ready batch. You can do probably 100 or more tasks this way.

ImageMagick + Rails == good

I did some nice charts [blogs.com] for the indi [getindi.com] admin pages; worked out really nicely thanks to Gruff + RMagick.

I did have a spot of trouble getting the fonts working at first, but once that was fixed, it was easy to create some nice charts with very little code.

Wikipedia uses it

For what it's worth, Wikipedia uses ImageMagick to automatically resize png/jpeg/gif images for articles (eg. photos uploaded at 1920x1080 can be displayed at 300x169 in an article). So it's good enough to run on a high-traffic website (and is pretty flexible for ad-hoc command-line use too).

Re:Wikipedia uses it

Just to clarify, ImageMagick is not called everytime someone views that smaller thumbnail everytime they view the Wikipedia article, ImageMagick is called upon only when the orginal article was edited, the output is saved by MediaWiki as a totally new image into an images folder. From then on, it's a straight HTML img tag.

I just wanted to make sure people didn't think ImageMagick is being called upon the MediaWiki software every time the image got a page hit.

Not just for command line use!

ImageMagick's function library is also accessible through a variety of APIs for your favorite language [imagemagick.org] -- scripting or otherwise. If you haven't used it, try it . . . it's GPL and it Rawks (with a capital "r"). ;-)

Flickr Hacks

My book, Flickr Hacks [amazon.com], contains a number of examples of using ImageMagick (via the Perl API) with Flickr. This is one area where it really shines. I used ImageMagick to create these mosaic posters [krazydad.com], the Flickr Colr Pickr [krazydad.com] and other cool things.

Photoshop Not!

I have been an imageMajick user for some years now I while I find it great for simple tasks and great for batch conversions it is no Photoshop. I think there is room for both. For simple image conversion or batch processing I use an Apple Automator action to call a do shell script. For others I drop into the terminal. For retouching or other tasks, it is Photoshop only.

check out netpbm too

those interested in command line image processing, should check out netpbm [sourceforge.net] too. it's really neat

instead of a single image processing program, netpbm is a massive collection of programs all using a small set of proprietery formats (they are all compatible with each other). you use pipes for communication between them, giving you some more flexibility.

for example:

pngtopnm foo.png | pnmscale -xsize=600 ysize=400 | pnmtojpeg > foo.jpg

the other advantage is, their proprietery formats were designed to be easy to use, so coding your own netpbm programs is much easier than rewriting imagemagick for a specific task.

Nconvert

ImageMagick is great, but if you work with less common formats or even those such as Maya's IFF, it doesn't help much (which is odd seeing as how Maya even installs ImageMagick's convert command renamed as imconvert).

There is another program called Nconvert that will handle pretty much any format you throw at it (about 400 in and 40 out). It can do much of what can be done with ImageMagick too, and is available for more than a dozen operating systems.

Unfortunately it's only free for non-commercial use, and 100 (or an agreement) otherwise.

http://perso.wanadoo.fr/pierre.g/xnview/en_ncdownl oad.html [wanadoo.fr]

Which Precompiled Windows Version?

"The ImageMagick Web site and FTP file listings appear to have no README file or installation help file to explain which flavor you should download."

From http://www.imagemagick.com/www/binary-releases.htm l [imagemagick.com] :

"The Windows version of ImageMagick is self-installing. Simply click on the appropriate version below and it will launch itself and ask you a few installation questions. Versions with Q8 in the name are 8 bits-per-pixel component, whereas, Q16 in the filename are 16 bits-per-pixel component. A Q16 version permits you to read or write 16-bit images without losing precision but requires twice as much resources as the Q8 version. Versions with dynamic in the filename include ImageMagick libraries as dynamic link libraries. If you are not sure which version is appropriate, choose ImageMagick-6.2.6-3-Q16-windows-dll.exe."

I know that its not a readme file but the website seems pretty explainatory. You are right about the FTP site, however.

Batch processing

For doing batch processing of photos I have been using Bibble Pro [bibblelabs.com] for Linux lately. I like it since it has good support for the raw format of my SLR and has a lot of batch processing features. For example, it's easy to select a group of 50 photos and adjust the white balance, or use the one click lens distortion fix on all my photos. Best of all, it runs under Linux. It gives me the best of both worlds. It gives me batch processing as well as the ability to individually make changes to each picture. I.e. I can bring out the shadows in a group of pictures, then straighten a couple of them if the camera was crooked and crop them as needed. It also does everything at 16 bits per color.

Now, granted, it does not run on the command line, but it easily lets me select a source and target directory to batch process as well as letting me select individual pictures. I can't really compare it with ImageMagick since I haven't used it directly.

-Aaron

NetPBM

Hmm, I tend to find the approach of NetPBM [sourceforge.net] easier to work with: having lots of separate utilities each doing a single simple thing and making it easy to use them together by piping the output of one to the next. Besides, reading/writing PBM files is trivial so you can very easily use these tools from your programs (by piping your image through them) or you can very easily create new filters that integrate well with the rest. I recommend you check out NetPBM.

If you need automatic processing of many images (the sort of thing ImageMagick is being praised for), I recommend you check it out.

Does eBook have color images?

Does the eBook version have color images? http://www.apress.com/book/bookDisplay.html?bID=10 052 [apress.com]

Irfanview

Irfanview [irfanview.com] is good for batch conversions, I used it all last summer to resize and greyscale hundreds of photographseach week. At 1.24mb for the whole program folder, and the ability to read almost any type of image file and use photoshop filters I haven't found anything better for quick edits.

A word before...

The book's 335 pages are organized into a dozen chapters, following an introduction and a few other standard sections, including a forward written by ImageMagick's principal architect, Christy, who briefly explains the...

Please, the word is Foreword, not "Forward". I don't want to be a grammar nazi, but I've seen this particular word substitution so often that Im afraid we're getting near the point where the sheer quantity of errors is going to confuse everybody. Heck, sometimes I think I'm wrong about this...I've actually seen books that have a section in front called "Forward".

ImageMagick is excellent

My company uses image magick to resize and add watermarks to tens of thousands of website classified images. We created several wrapper methods to access it in our app.

Poor Example:
myImage1 = imageMagickResize(thisImage.jpg,destImage.jpg,300, 200);

AFAIK it is more extensive than alot of the native image manipulation libs that come with certain languages (java?). Comparing imageMagick to photoshop or other apps is apples to oranges. We have this running on headless FreeBSD and CentOS boxes with no X. Can't do that with photoshop!

Matlab

Its called matlab

jpgs to movies

What I've really wanted, but not yet found, is some way to programmatically (or from command line) take a series of JPGs (1,000 to 50,000) and create a movie out of them. I've got Quicktime Pro, but it doesn't have command line ways of doing this (and it bogs down horribly when manually loading an image series and saving out a movie).

I do use ImageMagick (actually GraphicsMagick I think) to watermark/timestamp each of the JPGs before I make the movie, but surely there's a way to fully automate what I'm doing...

ImageMagick doesn't scale as well as Gimp?

I like using ImageMagick...but its scale feature doesn't look as good as when I use Gimp (or Photoshop for that matter). Why is that? There is a huge quality difference to my eyes when I put a picture scaled with Gimp next to one with ImageMagick. Am I doing something wrong? =/ Random_Amber

Doug Henning would be impressed

It's ImageMaaagick!!!!

ImageMacgick > Photoshop

Two words: UNSTABLE API

ImageMagick's API is notoriously unstable and new releases don't even bother with backwards compatibility. Once in a while, even the command line options change between releases breaking existing scripts (such as ImageIndex [edwinh.org], for example).

If you wish to write your own programs using a powerful image-processing library, you will, most likely, prefer the fork of ImageMagick called GraphicsMagick [graphicsmagick.org].

Disagree...

Batch processing images via the commandline isn't really a mainstream activity. ImageMagick is (ASAIK) widely used by the people and applications that need such a tool. I use it professionally and personally when I need such a tool.
You might as well say that weblog analysis tools are sliding towards obscurity because they aren't featured on the cover of LinuxNewbie Magazine.