Graphics Programming with Perl

Jul 23, 2002 by Simon Cozens

I recently received Martien Verbruggen’s long-awaited “Graphics Programming in Perl,” and I wasn’t quite sure what to make of it. As he notes himself, “I didn’t think there would be enough coherent material to write such a book, and I wasn’t entirely certain there would be much room for one.” Sure, you can write a chapter or so on business graphing – something on GraphViz – and a few chapters on GD, Imager and Image::Magick. But an entire book?

Like Martien, the more I look at this topic, the more there is to say, and the more comfortable I am with the way Martien says it. The book seems to concentrate primarily on Image::Magick, with some examples of GD.

All technical books seem to begin with a certain amount of introductory waffle; in “Graphics Programming in Perl,” the waffle is at least to some degree relevant - there’s a fundamental introduction to such things as color spaces, including some relatively fearsome equations converting between the various color systems. The introduction is carried on through chapter 2, a review of graphics file formats. I can’t really categorize this as waffle, though, since a thorough understanding of these things are fundamental to graphics programming.

The real Perl meat starts around the middle of chapter 2, with sections on finding the size of an image and converting between images. Unfortunately, there’s more introductory material again in chapter 3, with sections on the CPAN and descriptions on the modules that will be used in the rest of the book. Hence, I wouldn’t really say this was the fastest-starting book around, and most people will be able to happily skip the first 30 or 35 pages without much loss of continuity.

Chapter 4 is where we actually start using Perl to draw things, the stated purpose of the book. We begin with drawing simple objects in GD, which is adequately explained, but unfortunately, there’s no mention of how to save the images yet, so we can’t check them or play with the examples and examine the results!

Next, the same examples are implemented using Image::Magick, a good comparison of the two modules; there’s also another good comparison in the middle of an ill-fitting chapter on module interface design. In the middle, there’s precisely the sort of thing you’d expect for a book of this nature: font handling, business graphs, 3D rendering, (although a little more detail on this topic would have been nice) and so on. The section on designing graphics for the Web is, if you’ll allow a slight exaggeration, flawless.

I find the “bullet-point annotated code” style of explanation gets the important points across well, and Martien has achieved a nice balance of explanatory prose and demonstration code. The material occasionally seems to be let down by the odd bug or two in Image::Magick, but we can hardly blame the author for that.

What really disappointed me about this book was the glaring and complete omission of the Imager module; this is another module for doing programmatic graphics creation, and I personally favor it above Image::Magick and GD, which both require an intermediary external C library on top of the various libraries for handling graphics formats.

Similarly, much more could have been made of the interaction between Perl and the Gimp - there were a few pages on creating animated GIFs, but nothing about using Gimp plug-ins and the like.

Hence, in conclusion, I think if you take this book as being a complete reference to everything you can do with graphics and Perl, you’re going to be disappointed. However, if you have certain tasks in mind and need to know how to do them, or you’re particularly interested in what you can do with the Image::Magick module, then this book is for you.

Graphics Programming With Perl is available from Manning and all good computer bookshops.