Graphics and Other File Formats

Hundreds of standards exist for storing structured data in text or binary files. Some of these are so popular that weve devoted entire chapters to them (Chapters 11 and 13). Some are so simple that you can process them with the ad hoc techniques listed in Chapters 1 and 6. This chapter is a grab bag that tries to cover the rest of the field.

We focus especially on graphics, probably the most common binary files. Ruby lacks a mature image manipulation library like the Python Imaging Library, but it does have bindings to ImageMagick and GraphicsMagick, popular and stable C libraries. The RMagick library provides the same interface against ImageMagick and GraphicsMagick, so it doesn matter which one you use.

You can get RMagick by installing the RMagick or Rmagick-win32 gem. Unfortunately, the C libraries themselves are difficult to install: they have a lot of dependencies, especially if you want to process image formats like GIF and PostScript. The installation FAQ can help (http://rmagick.rubyforge.org/install-faq.html). On Debian GNU/Linux, you can just install the imagemagick package and then the RMagick gem.

The first recipes in this chapter show how to use RMagick to manipulate and convert images (on the question of finding images, see Recipe 16.2). Then it gets miscellaneous: we cover encryption, archive formats, Excel spreadsheets, and music files. We don have space to cover every popular file format, but this chapter should give you an idea of whats out there. If this chapter lacks a recipe on your file format of choice, you may be able to find a Ruby library for it on the RAA, or by doing a web search for ruby [file format name].