RMagick User's Guide and Reference
module Magick

Table Of Contents

module methods

colors Magick.colors { |color| block } -> Magick
Magick.colors -> anArray
Description Lists the named colors. If the optional block is present, calls the block once for each color, passing a Magick::Color object. Otherwise, returns an array of Magick::Color objects, one for each color.

The Magick::Color class is a Struct class with the following attributes:

Attribute Value
name The color name. For example, "red".
compliance A ComplianceType value such as X11Compliance.
color A Pixel object containing the RGB values.
Arguments None
Returns If no block is associated with the call, returns an array of Magick::Color objects.
Example
This is a small sample of colors.miff, the complete image created by the example program. .
Magick::colors example
×Magick API GetColorInfo
fonts Magick.fonts { |font| block } -> Magick
Magick.fonts -> anArray
Description Lists the fonts that ×Magick knows about. If the optional block is present, calls the block once for each font, passing a Magick::Font object. Otherwise, returns an array of Magick::Font objects, one for each font.

The Magick::Font class is a Struct class with the following attributes:

Attribute Value
name The font name. For example, "Palatino-Roman".
description The font description. For example, "Palatino Roman".
family The font family. For example, "Palatino", "Helvetica", or "Courier".
style A StyleType value such as NormalStyle.
stretch A StretchType value such as NormalStretch.
weight The font weight, one of 100, 200, 300, 400, 500, 600, 700, 800, or 900.
encoding The font encoding, such as "AppleRoman". May be nil.
foundry The font foundry. "URW", for example. May be nil.
format If the font is a Type1 font, has the value "type1", otherwise nil.
Arguments None
Returns If no block is associated with the call, returns an array of Magick::Font objects.
Example fonts.rb
×Magick API GetFontInfo
formats Magick.formats { |f,v| block } -> Magick
Magick.formats -> aHash
Description Describes the supported image formats (and therefore RMagick). If the optional block is present, calls the block once for each image format. The first argument, f, is the format name. The second argument, v, is the properties string described below.
Arguments None
Returns A hash of image formats and their properties. Each key in the returned hash is the name of a supported image format. Each value is a string in the form "BRWA", where
B is "*" if the format has native blob support, and "-" otherwise.
R is "r" if ×Magick can read the format, and "-" otherwise.
W is "w" if ×Magick can write the format, and "-" otherwise.
A is "+" if the format supports multi-image files, and "-" otherwise.
Example
p Magick.formats »
   {"TIF"=>"*rw+",
   "H"=>"*rw-",
   "MNG"=>"*rw+",
   "NULL"=>"*rw-",
   ...
   "G"=>"*rw+",
   "GIF"=>"*rw+",
   "PDB"=>"*rw+"}
×Magick notes http://www.imagemagick.org/www/formats.html
Advanced ×Magick depends on external programs for some formats. Depending on how ×Magick was installed on your system, some formats may not be available. If you have questions, ask your system administrator.
set_cache_threshold Magick.set_cache_threshold(n)
Description Sets the amount of free memory allocated for the pixel cache.
Arguments An integer number of megabytes.
Example
# set the cache threshold to 10Mb
Magick.set_cache_threshold(10)
×Magick notes Once this threshold is exceeded, all subsequent pixels cache operations are to/from disk.
 
set_monitor Magick.set_monitor(aProc)
Description

Establish a monitor exit block. Some (see below) RMagick methods will call the monitor event block, passing parameters that describe how much work there is to be done and how much of that work has already been accomplished.

There can be at most one monitor block defined at a time. To turn off monitoring, call Magick.set_monitor(nil).

The argument is a block. The block should accept 3 arguments:

text
a String that describes the operation being monitored.
quantum
a value between 0 and span that represents the number of events that have been performed, images that have been processed, etc.
span
The total number of events to be performed, images to be processed, etc.
Arguments A Proc object.
Example
#! /usr/local/bin/ruby -w
require 'RMagick'
img = Magick::Image.read("images/Cheetah.jpg").first
monitor = Proc.new { |text, quantum, span|
    printf("%s %3.0f%% complete\n", text, ((quantum/span.to_f)*100.0))
    }
Magick.set_monitor(monitor)
img.resize!(.50)
exit

produces:

  Resize image...     0% complete
  Resize image...    29% complete
  Resize image...    57% complete
  Resize image...    86% complete
  Resize image...   100% complete


×Magick notes The list of methods which call the monitor block is difficult to determine. The only sure way to find out is to read the source code. In the Image class the list includes add_noise, blur_image, channel, chop, colorize, crop, colors, despeckle, enhance, equalize, flip, flop, frame, gamma_correct, implode, level, magnify, median_filter, minify, modulate, morph, negate, normalize, oil_paint, opaque, raise, reduce_noise, resize, roll, rotate, sample, scale, segment, shade, sharpen, shear, solarize, spread, stegano, stereo, swirl, texture threshold, transparent, and wave. In the ImageList class, the list includes append, average, and montage.