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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "https://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" lang="en">
<head>
<meta name="generator" content="HTML Tidy for Linux/x86 (vers 7 December 2008), see www.w3.org" />
<title>RMagick 6.0.1: Constants</title>
<meta http-equiv="Content-Type" content="text/html; charset=us-ascii" />
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<meta name="Copyright" content="Copyright (C) 2006 by Timothy P. Hunter" />
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<body>
<h6 id="header">RMagick 6.0.1 User's Guide and Reference</h6>
<div class="nav">« <a href="info.html">Prev</a> | <a href="index.html">Contents</a> | <a href="rvgtut.html">Next</a> »</div>
<h1>Constants</h1>
<div id="toc">
<h2>Table of Contents</h2>
<h3>Constants</h3>
<div class="toccol">
<ul>
<li><a href="#Miscellaneous_constants">Miscellaneous constants</a></li>
<li><a href="#AlignType">AlignType</a></li>
<li><a href="#AlphaChannelOption">AlphaChannelOption</a></li>
<li><a href="#AnchorType">AnchorType</a></li>
<li><a href="#ChannelType">ChannelType</a></li>
<li><a href="#ClassType">ClassType</a></li>
<li><a href="#ColorspaceType">ColorspaceType</a></li>
<li><a href="#ComplianceType">ComplianceType</a></li>
<li><a href="#CompositeOperator">CompositeOperator</a></li>
<li><a href="#CompressionType">CompressionType</a></li>
<li><a href="#DecorationType">DecorationType</a></li>
<li><a href="#DisposeType">DisposeType</a></li>
<li><a href="#DistortMethod">DistortMethod</a></li>
</ul>
</div>
<div class="toccol">
<ul>
<li><a href="#DitherMethod">DitherMethod</a></li>
<li><a href="#EndianType">EndianType</a></li>
<li><a href="#FilterType">FilterType</a></li>
<li><a href="#GeometryFlags">GeometryFlags</a></li>
<li><a href="#GravityType">GravityType</a></li>
<li><a href="#ImageType">ImageType</a></li>
<li><a href="#InterlaceType">InterlaceType</a></li>
<li><a href="#KernelInfoType">KernelInfoType</a></li>
<li><a href="#MagickFunction">MagickFunction</a></li>
<li><a href="#MetricType">MetricType</a></li>
<li><a href="#MorphologyMethod">MorphologyMethod</a></li>
<li><a href="#NoiseType">NoiseType</a></li>
<li><a href="#Opacity">Opacity</a></li>
</ul>
</div>
<div class="toccol">
<ul>
<li><a href="#OrientationType">OrientationType</a></li>
<li><a href="#PaintMethod">PaintMethod</a></li>
<li><a href="#PixelInterpolateMethod">PixelInterpolateMethod</a></li>
<li><a href="#PreviewType">PreviewType</a></li>
<li><a href="#QuantumExpressionOperator">QuantumExpressionOperator</a></li>
<li><a href="#RenderingIntent">RenderingIntent</a></li>
<li><a href="#ResolutionType">ResolutionType</a></li>
<li><a href="#SparseColorMethod">SparseColorMethod</a></li>
<li><a href="#SpreadMethod">SpreadMethod</a></li>
<li><a href="#StretchType">StretchType</a></li>
<li><a href="#StorageType">StorageType</a></li>
<li><a href="#StyleType">StyleType</a></li>
<li><a href="#VirtualPixelMethod">VirtualPixelMethod</a></li>
<li><a href="#WeightType">WeightType</a></li>
</ul>
</div>
</div>
<h2 class="methods">Constants</h2>
<h3 class="const" style="margin-top: 0" id="Miscellaneous_constants">Miscellaneous constants</h3>
<dl>
<dt>Long_version</dt>
<dd>
An extended form of the <code>Version</code> constant with the format shown here:<br />
<code
>This is RMagick 5.2.0 ($Date: 2009/12/20 02:33:33 $) Copyright (C) 2009 by Timothy P. Hunter<br />
Built with ImageMagick 7.1.1-8 Q16-HDRI x86_64 21129 https://imagemagick.org<br />
Built for ruby 3.2.2<br />
Web page: https://rmagick.github.io/</code
>
</dd>
<dt>Magick_version</dt>
<dd>
The ImageMagick version string. This has the form:<br />
<code>@(#)ImageMagick X.Y.Z MM/DD/YY Q:16 https://www.imagemagick.org</code>
</dd>
<dt>MANAGED_MEMORY</dt>
<dd>
If <code>true</code>, RMagick is using Ruby managed memory for all allocations. If <code>false</code>, RMagick allocates memory for objects directly
from the operating system. You can enable RMagick to use Ruby managed memory (when built with ImageMagick 6.4.0-11 and later) by setting
<pre class="language-ruby">RMAGICK_ENABLE_MANAGED_MEMORY = true</pre>
<em>before</em> requiring RMagick.
</dd>
<dt>QuantumRange</dt>
<dd>
The maximum value of a <em>Quantum</em>. A 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.
</dd>
<dt>QuantumDepth</dt>
<dd>
The number of bits in a quantum. The relationship between QuantumDepth and QuantumRange is summarized in this table.
<table summary="number of bits in a quantum" id="maxrgb">
<tr>
<th>QuantumDepth</th>
<th>QuantumRange</th>
</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>
</dd>
<dt>Version</dt>
<dd>
The RMagick version string. This has the form:<br />
<code>RMagick 2.0.0</code>
</dd>
</dl>
<h3 class="const" id="AlignType">AlignType</h3>
<p>Specify text alignment. See <a href="draw.html#align_eq">align=</a>, <a href="draw.html#text_align">text_align</a>.</p>
<dl>
<dt>UndefinedAlign</dt>
<dd>No alignment specified. Equivalent to LeftAlign.</dd>
<dt>LeftAlign</dt>
<dd>Align the leftmost part of the text to the starting point.</dd>
<dt>CenterAlign</dt>
<dd>Center the text around the starting point.</dd>
<dt>RightAlign</dt>
<dd>Align the rightmost part of the text to the starting point.</dd>
</dl>
<h3 class="const" id="AlphaChannelOption">AlphaChannelOption</h3>
<p>Specify alpha channel option. See <a href="image1.html#alpha">Image#alpha</a>.</p>
<dl>
<dt>UndefinedAlphaChannel</dt>
<dt>ActivateAlphaChannel</dt>
<dt>DeactivateAlphaChannel</dt>
<dt>SetAlphaChannel</dt>
<dt>RemoveAlphaChannel</dt>
<dt>CopyAlphaChannel</dt>
<dt>ExtractAlphaChannel</dt>
<dt>OpaqueAlphaChannel</dt>
<dt>ShapeAlphaChannel</dt>
<dt>TransparentAlphaChannel</dt>
<dt>BackgroundAlphaChannel</dt>
<dt>AssociateAlphaChannel</dt>
<dt>DisassociateAlphaChannel</dt>
<dt>OnAlphaChannel</dt>
<dt>OffAlphaChannel</dt>
</dl>
<h3 class="const" id="AnchorType">AnchorType</h3>
<p>Specify text anchor. See <a href="draw.html#text_anchor">Draw#text_anchor</a>.</p>
<dl>
<dt>StartAnchor</dt>
<dt>MiddleAnchor</dt>
<dt>EndAnchor</dt>
</dl>
<h3 class="const" id="ChannelType">ChannelType</h3>
<p>
Specify an image channel. A channel is a color component of a pixel. In the RGB colorspace the channels are red, green, and blue. There may also be an
alpha (transparency/opacity) channel. In the CMYK colorspace the channels area cyan, magenta, yellow, and black. In the HSL colorspace the channels are
hue, saturation, and lightness. In the Gray colorspace the only channel is gray. See
<a href="image1.html#channel">Image#channel</a> and <a href="info.html#channel">Image::Info#channel</a>.
</p>
<dl>
<dt>UndefinedChannel</dt>
<dt>RedChannel</dt>
<dt>GreenChannel</dt>
<dt>BlueChannel</dt>
<dt>CyanChannel</dt>
<dt>MagentaChannel</dt>
<dt>YellowChannel</dt>
<dt>BlackChannel</dt>
<dt>OpacityChannel</dt>
<dt>AllChannels</dt>
<dd>In the RGB colorspace, the red, blue, green, and alpha channels. In the CMYK colorspace, the cyan, magenta, yellow, and black channels.</dd>
<dt>GrayChannel</dt>
<dt>CompositeChannels</dt>
<dt>TrueAlphaChannel</dt>
<dt>RGBChannels</dt>
<dt>GrayChannels</dt>
<dt>SyncChannels</dt>
<dt>AlphaChannel</dt>
<dd>Same as OpacityChannel</dd>
<dt>DefaultChannels</dt>
<dd>Same as AllChannels, excluding OpacityChannel</dd>
<dt>HueChannel</dt>
<dt>LuminosityChannel</dt>
<dt>SaturationChannel</dt>
<dt>IndexChannel</dt>
</dl>
<h3 class="const" id="ClassType">ClassType</h3>
<p>
Specify the image storage class. See
<a href="imageattrs.html#class_type">class_type</a>.
</p>
<dl>
<dt>UndefinedClass</dt>
<dd>No storage class has been specified.</dd>
<dt>DirectClass</dt>
<dd class="imquote">Image is composed of pixels which represent literal color values.</dd>
<dt>PseudoClass</dt>
<dd class="imquote">Image is composed of pixels which specify an index in a color palette.</dd>
</dl>
<h3 class="const" id="ColorspaceType">ColorspaceType</h3>
<p class="imquote">
Specify the colorspace that quantization (color reduction and mapping) is done under or to specify the colorspace when encoding an output image. Color
spaces are ways of describing colors to fit the requirements of a particular application (e.g. Television, offset printing, color monitors). Color
reduction, by default, takes place in the RGBColorspace. Empirical evidence suggests that distances in color spaces such as YUVColorspace or YIQColorspace
correspond to perceptual color differences more closely than do distances in RGB space. These color spaces may give better results when color reducing an
image.
</p>
<p>
<span class="imquote"
>When encoding an output image, the color spaces RGBColorspace, CMYKColorspace, and GRAYColorspace may be specified. The CMYKColorspace option is only
applicable when writing TIFF, JPEG, and Adobe Photoshop bitmap (PSD) files.</span
>
See <a href="imageattrs.html#colorspace">colorspace</a>.
</p>
<p>Each version of ImageMagick defines a subset of the color spaces listed below. To list the subset supported by your version, issue the command:</p>
<pre class="example language-ruby">ruby -r rmagick -e"Magick::ColorspaceType.values {|cs| puts cs}"</pre>
<dl>
<dt>UndefinedColorspace</dt>
<dd>No colorspace has been specified.</dd>
<dt>CMYColorspace</dt>
<dt>CMYKColorspace</dt>
<dd class="imquote">
Cyan-Magenta-Yellow-Black colorspace. CYMK is a subtractive color system used by printers and photographers for the rendering of colors with ink or
emulsion, normally on a white surface.
</dd>
<dt>GRAYColorspace</dt>
<dd>Full-range grayscale</dd>
<dt>HSBColorspace</dt>
<dt>HSLColorspace</dt>
<dd>Hue, saturation, luminosity</dd>
<dt>HWBColorspace</dt>
<dd>Hue, whiteness, blackness</dd>
<dt>LABColorspace</dt>
<dt>LogColorspace</dt>
<dt>OHTAColorspace</dt>
<dt>RGBColorspace</dt>
<dd class="imquote">Red-Green-Blue colorspace</dd>
<dt>SRGBColorspace</dt>
<dd>
Kodak PhotoCD sRGB. In ImageMagick, this constant is named sRGBColorspace, but since Ruby constants must start with an uppercase letter, I had to change
it.
</dd>
<dt>TransparentColorspace</dt>
<dd class="imquote">The Transparent color space behaves uniquely in that it preserves the matte channel of the image if it exists.</dd>
<dt>XYZColorspace</dt>
<dd>CIE XYZ</dd>
<dt>YCbCrColorspace</dt>
<dt>YCCColorspace</dt>
<dd>Kodak PhotoCD PhotoYCC</dd>
<dt>YIQColorspace</dt>
<dt>YPbPrColorspace</dt>
<dt>YUVColorspace</dt>
<dd class="imquote">Y-signal, U-signal, and V-signal colorspace. YUV is most widely used to encode color for use in television transmission.</dd>
</dl>
<p>The color spaces in this group are typically associated with the DPX and Cineon image formats used in the motion picture industry.</p>
<dl>
<dt>Rec601LumaColorspace</dt>
<dd>Luma (Y) according to ITU-R 601</dd>
<dt>Rec601YCbCrColorspace</dt>
<dd>YCbCr according to ITU-R 601</dd>
<dt>Rec709LumaColorspace</dt>
<dd>Luma (Y) according to ITU-R 709</dd>
<dt>Rec709YCbCrColorspace</dt>
<dd>YCbCr according to ITU-R 709</dd>
<dt>LuvColorspace</dt>
<dt>HCLColorspace</dt>
<dt>LCHColorspace</dt>
<dt>LMSColorspace</dt>
<dt>LCHabColorspace</dt>
<dt>LCHuvColorspace</dt>
<dt>ScRGBColorspace</dt>
<dt>HSIColorspace</dt>
<dt>HSVColorspace</dt>
<dt>HCLpColorspace</dt>
<dt>YDbDrColorspace</dt>
<dt>XyYColorspace</dt>
<dt>LinearGRAYColorspace</dt>
<dt>JzazbzColorspace</dt>
</dl>
<h3 class="const" id="ComplianceType">ComplianceType</h3>
<p>
Specify the color standard from which color names are chosen. See
<a href="struct.html#Pixel">to_color</a>.
</p>
<dl>
<dt>SVGCompliance</dt>
<dd>Adhere to SVG color standard.</dd>
<dt>X11Compliance</dt>
<dd>Adhere to X11 color standard.</dd>
<dt>XPMCompliance</dt>
<dd>Adhere to XPM color standard.</dd>
<dt>AllCompliance</dt>
<dd>The union of the 3 color standards.</dd>
<dt>UndefinedCompliance</dt>
<dt>NoCompliance</dt>
</dl>
<h3 class="const" id="CompositeOperator">CompositeOperator</h3>
<p>
<span class="imquote"
>Select the image composition algorithm used to compose a <code>composite image</code> with a <code>image</code>. By default, each of the
<code>composite image</code> pixels are replaced by the corresponding <code>image</code> tile pixel. Specify <code>CompositeOperator</code> to select a
different algorithm.</span
>
See <a href="image1.html#composite">composite</a>.
</p>
<dl>
<dt>UndefinedCompositeOp</dt>
<dd>No composite operator has been specified.</dd>
<dt>AddCompositeOp</dt>
<dd class="imquote">The result of <code>composite image</code> + <code>image</code>, with overflow wrapping around (mod 256).</dd>
<dt>AtopCompositeOp</dt>
<dd class="imquote">
The result is the same shape as <code>image</code>, with <code>composite image</code> obscuring <code>image</code> where the image shapes overlap. Note
that this differs from OverCompositeOp because the portion of <code>composite image</code> outside of <code>image</code>'s shape does not appear in the
result.
</dd>
<dt>BlendCompositeOp</dt>
<dt>BlurCompositeOp</dt>
<dd>?</dd>
<dt>BumpmapCompositeOp</dt>
<dd class="imquote">The result <code>image</code> shaded by <code>composite image</code>.</dd>
<dt>ChangeMaskCompositeOp</dt>
<dd class="imquote">
Replace any destination pixel that is the similar to the source image's pixel (as defined by the current fuzz factor), with transparency.
</dd>
<dt>ClearCompositeOp</dt>
<dd>Make the target image transparent. The composite image is ignored.</dd>
<dt>ColorBurnCompositeOp</dt>
<dd class="imquote">Darkens the destination color to reflect the source color. Painting with white produces no change.</dd>
<dt>ColorDodgeCompositeOp</dt>
<dd class="imquote">Brightens the destination color to reflect the source color. Painting with black produces no change.</dd>
<dt>ColorizeCompositeOp</dt>
<dd class="imquote">
Each pixel in the result image is the combination of the brightness of the target image and the saturation and hue of the composite image. This is the
<em>opposite</em> of LuminizeCompositeOp.
</dd>
<dt>CopyAlphaCompositeOp</dt>
<dd>
If the composite image's
<a href="image1.html#alpha_q">alpha?</a> is <code>true</code>, copy the opacity channel from the composite image to the target image. Otherwise, set the
target image pixel's opacity to the intensity of the corresponding pixel in the composite image.
</dd>
<dt>CopyCompositeOp</dt>
<dd>Replace the target image with the composite image.</dd>
<dt>CopyBlackCompositeOp</dt>
<dd>Copy the black channel from the composite image to the target image.</dd>
<dt>CopyBlueCompositeOp</dt>
<dd>Copy the blue channel from the composite image to the target image.</dd>
<dt>CopyCyanCompositeOp</dt>
<dd>Copy the cyan channel from the composite image to the target image.</dd>
<dt>CopyGreenCompositeOp</dt>
<dd>Copy the green channel from the composite image to the target image.</dd>
<dt>CopyMagentaCompositeOp</dt>
<dd>Copy the magenta channel from the composite image to the target image.</dd>
<dt>CopyRedCompositeOp</dt>
<dd>Copy the red channel from the composite image to the target image.</dd>
<dt>CopyYellowCompositeOp</dt>
<dd>Copy the yellow channel from the composite image to the target image.</dd>
<dt>DarkenCompositeOp</dt>
<dd>Replace target image pixels with darker pixels from the composite image.</dd>
<dt>DarkenIntensityCompositeOp</dt>
<dt>DifferenceCompositeOp</dt>
<dd class="imquote">The result of abs(<code>composite image</code> - <code>image</code>). This is useful for comparing two very similar images.</dd>
<dt>DisplaceCompositeOp</dt>
<dd>Displace target image pixels as defined by a displacement map. The operator used by the <a href="image1.html#displace">displace</a> method.</dd>
<dt>DissolveCompositeOp</dt>
<dd>
The operator used in the
<a href="image1.html#dissolve">dissolve</a> method.
</dd>
<dt>DistortCompositeOp</dt>
<dd>?</dd>
<dt>DivideDstCompositeOp</dt>
<dt>DivideSrcCompositeOp</dt>
<dt>DstCompositeOp</dt>
<dd class="imquote">The destination is left untouched.</dd>
<dt>DstAtopCompositeOp</dt>
<dd class="imquote">The part of the destination lying inside of the source is composited over the source and replaces the destination.</dd>
<dt>DstInCompositeOp</dt>
<dd class="imquote">The part of the destination lying inside of the source replaces the destination.</dd>
<dt>DstOutCompositeOp</dt>
<dd class="imquote">The part of the destination lying outside of the source replaces the destination.</dd>
<dt>DstOverCompositeOp</dt>
<dd class="imquote">The destination is composited over the source and the result replaces the destination.</dd>
<dt>ExclusionCompositeOp</dt>
<dd class="imquote">
Produces an effect similar to that of 'difference', but appears as lower contrast. Painting with white inverts the destination color. Painting with
black produces no change.
</dd>
<dt>HardLightCompositeOp</dt>
<dd class="imquote">
Multiplies or screens the colors, dependent on the source color value. If the source color is lighter than 0.5, the destination is lightened as if it
were screened. If the source color is darker than 0.5, the destination is darkened, as if it were multiplied. The degree of lightening or darkening is
proportional to the difference between the source color and 0.5. If it is equal to 0.5 the destination is unchanged. Painting with pure black or white
produces black or white.
</dd>
<dt>HardMixCompositeOp</dt>
<dt>HueCompositeOp</dt>
<dd class="imquote">
Each pixel in the result image is the combination of the hue of the target image and the saturation and brightness of the composite image.
</dd>
<dt>InCompositeOp</dt>
<dd class="imquote">
The result is simply <code>composite image</code> cut by the shape of <code>image</code>. None of the image data of <code>image</code> is included in
the result.
</dd>
<dt>LightenCompositeOp</dt>
<dd>Replace target image pixels with lighter pixels from the composite image.</dd>
<dt>LightenIntensityCompositeOp</dt>
<dt>LinearBurnCompositeOp</dt>
<dd>Same as <code>LinearDodgeCompositeOp</code>, but also subtract one from the result. Sort of a additive 'Screen' of the images.</dd>
<dt>LinearDodgeCompositeOp</dt>
<dd class="imquote">
This is equivalent to <code>PlusCompositeOp</code> in that the color channels are simply added, however it does not "plus" the alpha channel, but uses
the normal <code>OverCompositeOp</code> alpha blending, which transparencies are involved. Produces a sort of additive multiply-like result.
</dd>
<dt>LinearLightCompositeOp</dt>
<dd class="imquote">Increase contrast slightly with an impact on the foreground's tonal values.</dd>
<dt>LuminizeCompositeOp</dt>
<dd class="imquote">
Each pixel in the result image is the combination of the brightness of the composite image and the saturation and hue of the target image. This is the
<em>opposite</em> of ColorizeCompositeOp.
</dd>
<dt>MathematicsCompositeOp</dt>
<dt>MinusDstCompositeOp</dt>
<dt>MinusSrcCompositeOp</dt>
<dt>ModulateCompositeOp</dt>
<dd>Used by the <a href="image3.html#watermark">watermark</a> method.</dd>
<dt>ModulusAddCompositeOp</dt>
<dt>ModulusSubtractCompositeOp</dt>
<dt>MultiplyCompositeOp</dt>
<dd class="imquote">
Multiplies the color of each target image pixel by the color of the corresponding composite image pixel. The result color is always darker.
</dd>
<dt>NoCompositeOp</dt>
<dd>No composite operator has been specified.</dd>
<dt>OutCompositeOp</dt>
<dd class="imquote">The resulting image is <code>composite image</code> with the shape of <code>image</code> cut out.</dd>
<dt>OverCompositeOp</dt>
<dd>
<span class="imquote"
>The result is the union of the the two image shapes with <code>composite image</code> obscuring <code>image</code> in the region of overlap.</span
>
The matte channel of the composite image is respected, so that if the composite pixel is part or all transparent, the corresponding image pixel will
show through.
</dd>
<dt>OverlayCompositeOp</dt>
<dd class="imquote">
Multiplies or screens the colors, dependent on the destination color. Source colors overlay the destination whilst preserving its highlights and
shadows. The destination color is not replaced, but is mixed with the source color to reflect the lightness or darkness of the destination.
</dd>
<dt>PegtopLightCompositeOp</dt>
<dd class="imquote">
Almost equivalent to <code>SoftLightCompositeOp</code>, but using a continuious mathematical formula rather than two conditionally selected formulae.
</dd>
<dt>PinLightCompositeOp</dt>
<dd class="imquote">
Similar to <code>HardLightCompositeOp</code>, but using sharp linear shadings, to simulate the effects of a strong 'pinhole' light source.
</dd>
<dt>PlusCompositeOp</dt>
<dd class="imquote">
The result is just the sum of the image data. Output values are cropped to 255 (no overflow). This operation is independent of the matte channels.
</dd>
<dt>ReplaceCompositeOp</dt>
<dd class="imquote">The resulting image is image replaced with composite image. Here the matte information is ignored.</dd>
<dt>SaturateCompositeOp</dt>
<dd>Each pixel in the result image is the combination of the saturation of the target image and the hue and brightness of the composite image.</dd>
<dt>ScreenCompositeOp</dt>
<dd>Multiplies the inverse of each image's color information.</dd>
<dt>SoftLightCompositeOp</dt>
<dd class="imquote">
Darkens or lightens the colors, dependent on the source color value. If the source color is lighter than 0.5, the destination is lightened. If the
source color is darker than 0.5, the destination is darkened, as if it were burned in. The degree of darkening or lightening is proportional to the
difference between the source color and 0.5. If it is equal to 0.5, the destination is unchanged. Painting with pure black or white produces a
distinctly darker or lighter area, but does not result in pure black or white.
</dd>
<dt>SrcAtopCompositeOp</dt>
<dd class="imquote">The part of the source lying inside of the destination is composited onto the destination.</dd>
<dt>SrcCompositeOp</dt>
<dd class="imquote">The source is copied to the destination. The destination is not used as input.</dd>
<dt>SrcInCompositeOp</dt>
<dd class="imquote">he part of the source lying inside of the destination replaces the destination.</dd>
<dt>SrcOutCompositeOp</dt>
<dd class="imquote">The part of the source lying outside of the destination replaces the destination.</dd>
<dt>SrcOverCompositeOp</dt>
<dd class="imquote">The source is composited over the destination.</dd>
<dt>SubtractCompositeOp</dt>
<dd class="imquote">
The result of <code>composite image</code> - <code>image</code>, with underflow wrapping around (mod 256). The add and subtract operators can be used to
perform reversible transformations.
</dd>
<dt>ThresholdCompositeOp</dt>
<dd>?</dd>
<dt>VividLightCompositeOp</dt>
<dd class="imquote">A modified <code>LinearLightCompositeOp</code> designed to preserve very strong primary and secondary colors in the image.</dd>
<dt>XorCompositeOp</dt>
<dd class="imquote">
The result is the image data from both <code>composite image</code> and <code>image</code> that is outside the overlap region. The overlap region will
be blank.
</dd>
</dl>
<h3 class="const" id="CompressionType">CompressionType</h3>
<p>
<span class="imquote"
>Express the desired compression type when encoding an image. Be aware that most image types only support a sub-set of the available compression types.
If the compression type specified is incompatible with the image, ImageMagick selects a compression type compatible with the image type.</span
>
See <a href="imageattrs.html#compression">compression</a>.
</p>
<dl>
<dt>UndefinedCompression</dt>
<dd>No compression type has been specified.</dd>
<dt>NoCompression</dt>
<dd>The default for most formats.</dd>
<dt>B44Compression</dt>
<dd>Available in ImageMagick 6.5.5-4 and later.</dd>
<dt>B44ACompression</dt>
<dd>Available in ImageMagick 6.5.5-4 and later.</dd>
<dt>BZipCompression</dt>
<dd class="imquote">BZip (Burrows-Wheeler block-sorting text compression algorithm and Huffman coding) as used by bzip2 utilities</dd>
<dt>DXT1Compression</dt>
<dd>Available in ImageMagick 6.3.9-3 and later.</dd>
<dt>DXT3Compression</dt>
<dd>Available in ImageMagick 6.3.9-3 and later.</dd>
<dt>DXT5Compression</dt>
<dd>Available in ImageMagick 6.3.9-3 and later.</dd>
<dt>FaxCompression</dt>
<dd class="imquote">CCITT Group 3 FAX compression</dd>
<dt>Group4Compression</dt>
<dd class="imquote">CCITT Group 4 FAX compression (used only for TIFF)</dd>
<dt>JPEGCompression</dt>
<dd>
JPEG compression. See
<a href="http://www.faqs.org/faqs/jpeg-faq/part1/">The JPEG image compression FAQ</a>.
</dd>
<dt>JPEG2000Compression</dt>
<dd>JPEG2000 compression for compressed PDF images.</dd>
<dt>LosslessJPEGCompression</dt>
<dd>This compression format is almost never used.</dd>
<dt>LZWCompression</dt>
<dd class="imquote">Lempel-Ziv-Welch (LZW) compression</dd>
<dt>PizCompression</dt>
<dd>Available in ImageMagick 6.5.5-4 and later.</dd>
<dt>Pxr24Compression</dt>
<dd>Available in ImageMagick 6.5.5-4 and later.</dd>
<dt>RLECompression</dt>
<dd>
See the Wikipedia page for
<a href="https://en.wikipedia.org/wiki/Run_length_encoding">Run-length encoding</a>.
</dd>
<dt>ZipCompression</dt>
<dd class="imquote">Lempel-Ziv compression (LZ77) as used in PKZIP and GNU gzip.</dd>
<dt>ZipSCompression</dt>
<dd>Available in ImageMagick 6.5.5-4 and later.</dd>
<dt>LZMACompression</dt>