Ruby+ImageMagickTM
Ruby+GraphicsMagick
RMagick is a binding from Ruby to the ImageMagick TM and GraphicsMagick image manipulation libraries. Here's how the ImageMagick home page describes ImageMagick:
ImageMagickTM... is a free software suite to create, edit, and compose bitmap images. It can read, convert and write images in a large variety of formats. Images can be cropped, colors can be changed, various effects can be applied, images can be rotated and combined, and text, lines, polygons, ellipses and Bézier curves can be added to images and stretched and rotated.
GraphicsMagick is a branch from ImageMagick 5.5.2 and provides a nearly identical API. The GraphicsMagick web site says this about GraphicsMagick:
GraphicsMagick is the swiss army knife of image processing. It provides a robust collection of tools and libraries which support reading, writing, and manipulating an image in over 88 major formats including important formats like DPX, GIF, JPEG, JPEG-2000, PNG, PDF, SVG, and TIFF. GraphicsMagick supports huge images on systems that support large files, and has been tested with gigapixel-size images. GraphicsMagick can create new images on the fly, making it suitable for building dynamic Web applications. GraphicsMagick may be used to resize, rotate, sharpen, color reduce, or add special effects to an image and save the result in the same or differing image format
Both libraries offer a full range of image processing tools that provide the capability to:
RMagick is a complete interface to ImageMagick and GraphicsMagick. Version 1.0.0 was released in February, 2003. Within its four major classes and 30 minor classes RMagick defines over 600 methods and 225 constants. RMagick exploits Ruby idioms such as blocks and iterators, Struct classes, symbols, ?- and !-suffixed methods, and exceptions.
This document is divided into 4 parts. The first is this page. The second part is a usage guide covering both RMagick and ImageMagick/GraphicsMagick usage and conventions. The third part is a reference guide to the ImageList, Image, and Draw classes. This guide includes many examples.
The fourth part covers the newest addition to RMagick, Ruby Vector Graphics (RVG). RVG is a facade for Draw that provides a high-level API for scalable vector graphics. The RVG section includes a tutorial and complete reference documentation.
Accompanying the HTML documentation is a set of over 175 example RMagick programs. Each is a complete, stand-alone program that either creates an image from scratch or modifies an input image using one or more RMagick methods. The output images are used as illustrations in the HTML documentation. Throughout this document, click any example image to see the program that created it.
Names I've tried to follow existing Ruby
conventions in this document. A class is identified by its name,
which always starts with a capital letter. An object is referred
to by its class name, starting with a small letter. For example,
a generic ImageList object is referred to as an
imagelist. In the Reference section, when a method
signature identifies the type of an argument or return value, the
type is shown by preceding the class name by "a" or "an". For
example, anImage refers to an Image object, and
anImageList refers to an ImageList object. Class
methods are identified like this: Class.method.
Instance methods are identified like this:
Class#method.
RMagick is implemented in the Magick module, therefore
its constants are in the Magick namespace. However, for clarity
I've omitted the Magick:: prefix in most places in
this document. You can use the include Magick
statement to add the constants and methods to the Object
namespace.
References to ImageMagick and GraphicsMagick GraphicsMagick is a fork of ImageMagick and shares most of its APIs. When describing a feature, API, convention, component, or other element that is shared by both, I use the string ×Magick. For example, "×Magick supports over 89 major image formats" means that both ImageMagick and GraphicsMagick support over 89 formats.
×Magick documentation Text that looks like this is quoted from the ×Magick documentation.
Example programs and images All of the
example images on these pages were created by RMagick. Click the
image to see the progam code. (You may need to configure your
browser to allow JavaScript and popup windows.) All example
images show the result of applying the method. Many example
images show the "before" image as well. When the image is
accompanied by this symbol 
mouse over the image to
see the "before" version.
If you have a question that is not answered by these pages,
you can post it at the Support Request
Tracker or the Feature Request
Tracker on RubyForge, or email me at rmagick at
rubyforge.org.
Please report problems with RMagick installation and usage to
the Bug
Tracker at RubyForge, or email me at rmagick at
rubyforge.org.
For quickest results, include the RMagick, ×Magick and
Ruby version numbers, along with a thorough description of the
problem. RMagick will tell you both its version number and
×Magick's version number. Simply bring up irb and print the
Magick::Long_version constant:
irb(main):001:0> puts Magick::Long_version This is RMagick 1.7.0 ($Date: 2005/04/30 14:43:19 $) Copyright (C) 2004 by Timothy P. Hunter Built with GraphicsMagick 1.1.4 2004-11-13 Q8 http://www.GraphicsMagick.org/ Built for ruby 1.8.1 (2003-12-25) [i686-linux] Web page: http://rmagick.rubyforge.org Email: rmagick@rubyforge.org
It will help a lot if you supply a small Ruby program that reproduces the problem. (Don't forget to include any input image files!).
Please remember I can't help with Ruby or ×Magick
installation and configuration problems. For help with Ruby, post
your questions to comp.lang.ruby. For help with
ImageMagick or GraphicsMagick, join the ImageMagick or
GraphicsMagick mailing list. See the instructions at http://www.imagemagick.org/www/magick-list.html
or http://sourceforge.net/projects/graphicsmagick/.
I'm not an image processing guru, either, so I probably won't be able to help with questions about specific image formats and transformations. I will be glad, however, to translate between the RMagick API and the ×Magick C API to help you compose a question to the ×Magick developers.
If you have a script or an image using RMagick that you're
particularly proud of, let me know. I'd like to collect your
contributions, along with other users' contributions, and put
them in a contrib directory to distribute with
RMagick. I'm particularly interested in getting examples for the
RMagick methods that currently have no examples.