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Document Magick::Enum class
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.typetable {
padding-bottom: 1em;
}
</style>
</style>
</head>
<body>
<div class="header">RMagick User's Guide and Reference</div>
<div class="header">
RMagick User's Guide and Reference
</div>
<table align="right" class="nav" cellpadding="3">
<tr>
<td style="text-align: left"><a href="info.html">&lt;-
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<li><a href="#StretchType">StretchType</a></li>
<li><a href="#StyleType">StyleType</a></li>
<li><a href="#WeightType">WeightType</a></li>
<li><a href="#RMagick_Enums">RMagick Enums: Implementation
details</a></li>
</ul>
<table>
<tr class="typetable">
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quantum is one of the red, green, blue, or opacity
elements of a pixel in the RGB colorspace, or cyan,
yellow, magenta, or black elements in the CYMK
colorspace.
colorspace.</td>
</tr>
<tr valign="top">
<td>QuantumDepth</td>
<td>The number of bits in a quantum.
<div align="center">
<table border="1">
<caption>
<b>How MaxRGB and QuantumDepth are related</b>
</caption>
<tr>
<td>
<b>QuantumDepth</b>
</td>
<td><b>MaxRGB</b></td>
</tr>
<tr><td>8</td><td>255</td></tr>
<tr><td>16</td><td>65535</td></tr>
<tr><td>32</td><td>4294967295</td></tr>
</table>
</div>
<td>
The number of bits in a quantum.
<div align="center">
<table border="1">
<caption>
<b>How MaxRGB and QuantumDepth are
related</b>
</caption>
<tr>
<td><b>QuantumDepth</b></td>
<td><b>MaxRGB</b></td>
</tr>
<tr>
<td>8</td>
<td>255</td>
</tr>
<tr>
<td>16</td>
<td>65535</td>
</tr>
<tr>
<td>32</td>
<td>4294967295</td>
</tr>
</table>
</div>
</td>
</tr>
<tr valign="top">
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<td colspan="2">
<a name="ClassType"><b>ClassType</b></a> - The
ClassType constants specify the image storage
class.
class.
<p>See <a href=
"imageattrs.html#Image.class_type">Image#class_type</a></p>
</td>
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available compression types. If the compression
type specified is incompatable with the image,
&times;Magick selects a compression type
compatable with the image type.</span>
compatable with the image type.</span>
<p>See <a href=
"imageattrs.html#Image.compression">Image#compression</a>.</p>
</td>
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TriangleFilter) may execute much faster but may
show artifacts when the image is re-sized or
around diagonal lines. The only way to be sure is
to test the filter with sample images.</span>
to test the filter with sample images.</span>
<p>See <a href=
"image.html#Image.resize">Image#resize</a>.</p>
</td>
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region, in other words, you don't need to provide
absolute coordinates in order to position an
object. A common default for gravity is
<i>NorthWestGravity</i>.</span>
<i>NorthWestGravity</i>.</span>
<p>See <a href=
"draw.html#Draw.annotate">Draw#annotate</a> and
<a href=
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<a name="ImageType"><b>ImageType</b></a> - The
ImageType constants indicate <span class=
"imquote">the type classification of the
image.</span>
image.</span>
<p>See <a href=
"imageattrs.html#Image.image_type">Image#image_type</a>
and <a href=
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For example, interlacing allows images on the Web
to be recognizable sooner and satellite images to
accumulate/render with image resolution
increasing over time.</span>
increasing over time.</span>
<div class="imquote">
Use <i>LineInterlace</i> or
<i>PlaneInterlace</i> to create an interlaced
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<a name="NoiseType"><b>NoiseType</b></a> - The
NoiseType constants <span class="imquote">select
the type of noise to be added to the
image.</span>
image.</span>
<p>See <a href=
"image.html#Image.add_noise">Image#add_noise</a>.</p>
</td>
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<a name="PaintMethod"><b>PaintMethod</b></a> -
The PaintMethod constants <span class=
"imquote">specify how pixel colors are to be
replaced in the image.</span>
replaced in the image.</span>
<p>See <a href=
"image.html#Image.matte_floodfill">Image#matte_floodfill</a>
and <a href=
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concept defined by ICC Spec ICC.1:1998-09, "File
Format for Color Profiles". &times;Magick uses
RenderingIntent in order to support ICC Color
Profiles.</span>
Profiles.</span>
<p class="imquote">From the specification:
"Rendering intent specifies the style of
reproduction to be used during the evaluation of
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<span class="imquote">By default, &times;Magick
defines resolutions in pixels per inch.
ResolutionType provides a means to adjust
this.</span>
this.</span>
<p>See <a href=
"imageattrs.html#Image.units">Image#units</a>.</p>
</td>
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</td>
</tr>
</table>
<h3>RMagick Enums: Implementation details</h3>
<div style="font-size: small">
<p><a name="RMagick_Enums">With the exception of the</a> <a
href="#Miscellaneous_constants">miscellaneous constants</a>,
the constants listed on this page are references to instances
of subclasses of the <code>Magick::Enum</code> class. This
class is based on Paul Brannon's Ruby implementation of
type-safe enums in <a href=
"http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/79041">
ruby-talk:79401</a>. Credit should go to Mr. Brannon for the
design, but any faults in the RMagick implementation are my
own.</p>
<p>If you don't need to know the details of how these
constants are implemented you don't need to read the rest of
this section.</p>
<p>Although the actual Magick::Enum class is written in C,
the Ruby equivalent code is:</p>
<pre>
module Magick
class Enum
def initialize(sym, value)
@sym = sym
@value = value
end
def to_s
return sym.to_s
end
def to_i
return value
end
def &lt;=&gt;(other)
r = to_i &lt;=&gt; other.to_i
return r unless r == 0
return class &lt;=&gt; other.class
end
def ===(other)
if class == other.class
return to_i == other.to_i
end
return false
end
end
end

</pre>
Each &times;Magick enumeration type is a separate subclass of
<code>Enum</code>. For example, the AlignType enumeration is
defined as:
<pre>
class AlignType &lt; Enum
end

</pre>
The AlignType constants are then created by the code:
<pre>
UndefinedAlign = AlignType.new(:UndefinedAlign, 0)
LeftAlign = AlignType.new(:LeftAlign, 1)
CenterAlign = AlignType.new(:CenterAlign, 2)
RightAlign = AlignType.new(:RightAlign, 3)

</pre>
<p>The other enumeration types and values are created in an
equivalent manner.</p>
<p>The benefit of this implementation is that a method that
expects an argument to be a value of a specific enumeration
type can check for that type and raise an exception if the
wrong type was used. For example, the <a href=
"imageattrs.html#Image.units">units=</a> attribute will not
accept a value of any type except
<code>ResolutionType</code>:</p>
<pre>
img.units=Magick::RedChannel # Buzz! Wrong! &raquo;
TypeError: wrong enumeration type - expected Magick::ResolutionType, got Magick::ChannelType

</pre>
</div>
<table align="right" class="nav" cellpadding="3">
<tr>
<td style="text-align: left"><a href="info.html">&lt;-
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