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<h6 id="header">RMagick User's Guide and Reference</h6>
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« <a href="image1.html">Prev</a> | <a href=
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<h1>class Image <span class="superclass">< Object</span>
(class and instance methods, part 2)<br />
<span class="mixin">mixes in Comparable</span></h1>
<div id="toc">
<h2>Table of Contents</h2>
<h3>instance methods</h3>
<div>
<div class="toccol">
<ul>
<li><a href="#enhance">enhance</a></li>
<li><a href="#equalize">equalize</a></li>
<li><a href="#erase_bang">erase!</a></li>
<li><a href="#export_pixels">export_pixels</a></li>
<li><a href=
"#export_pixels_to_str">export_pixels_to_str</a></li>
<li><a href="#flip">flip</a></li>
<li><a href="#flip_bang">flip!</a></li>
<li><a href="#flop">flop</a></li>
<li><a href="#flop_bang">flop!</a></li>
<li><a href="#frame">frame</a></li>
<li><a href="#gamma_channel">gamma_channel</a></li>
<li><a href="#gamma_correct">gamma_correct</a></li>
<li><a href="#gaussian_blur">gaussian_blur</a></li>
<li><a href=
"#gaussian_blur_channel">gaussian_blur_channel</a></li>
<li><a href=
"#get_exif_by_entry">get_exif_by_entry</a></li>
<li><a href=
"#get_exif_by_number">get_exif_by_number</a></li>
</ul>
</div>
<div class="toccol">
<ul>
<li><a href="#get_pixels">get_pixels</a></li>
<li><a href="#gray_q">gray?</a></li>
<li><a href=
"#grayscale_pseudo_class">grayscale_pseudo_class</a></li>
<li><a href="#grey_q">grey?</a></li>
<li><a href="#implode">implode</a></li>
<li><a href="#import_pixels">import_pixels</a></li>
<li><a href="#inspect">inspect</a></li>
<li><a href="#level">level</a></li>
<li><a href="#level_channel">level_channel</a></li>
<li><a href="#magnify">magnify</a></li>
<li><a href="#magnify_bang">magnify!</a></li>
<li><a href="#map">map</a></li>
<li><a href=
"#matte_fill_to_border">matte_fill_to_border</a></li>
<li><a href="#matte_floodfill">matte_floodfill</a></li>
<li><a href="#matte_point">matte_point</a></li>
<li><a href="#matte_replace">matte_replace</a></li>
<li><a href="#matte_reset_bang">matte_reset!</a></li>
</ul>
</div>
<div class="toccol">
<ul>
<li><a href="#median_filter">median_filter</a></li>
<li><a href="#minify">minify</a></li>
<li><a href="#minify_bang">minify!</a></li>
<li><a href="#modulate">modulate</a></li>
<li><a href="#monochrome_q">monochrome?</a></li>
<li><a href="#motion_blur">motion_blur</a></li>
<li><a href="#negate">negate</a></li>
<li><a href="#negate_channel">negate_channel</a></li>
<li><a href="#normalize">normalize</a></li>
<li><a href=
"#normalize_channel">normalize_channel</a></li>
<li><a href="#oil_paint">oil_paint</a></li>
<li><a href="#opaque">opaque</a></li>
<li><a href="#opaque_q">opaque?</a></li>
<li><a href="#ordered_dither">ordered_dither</a></li>
<li><a href="#palette_q">palette?</a></li>
<li><a href="#pixel_color">pixel_color</a></li>
<li><a href="#posterize">posterize</a></li>
</ul>
</div>
</div>
</div>
<h2 class="methods">instance methods</h2>
<div class="sig">
<h3 id="enhance">enhance</h3>
<p><span class="arg">image</span>.enhance ->
<em>anImage</em></p>
</div>
<div class="desc">
<h4>Description</h4>
<p class="imquote">Applies a digital filter that improves the
quality of a noisy image.</p>
<h4>Returns</h4>
<p>A new image</p>
<h4>Example</h4>
<p>The left-hand side has had noise added by <code><a href=
"#add_noise">add_noise</a></code>. The right-hand side is the
result after using <code>enhance</code>.</p>
<p><a href="javascript:popup('enhance.rb.html')"><img src=
"ex/enhance.jpg" alt="enhance example" title=
"Click to see the example script" /></a></p>
<h4>See also</h4>
<p><a href="image2.html#median_filter">median_filter</a>,
<a href="image2.html#reduce_noise">reduce_noise</a>, <a href=
"image3.html#unsharp_mask">unsharp_mask</a></p>
<h4>Magick API</h4>
<p>EnhanceImage</p>
</div>
<div class="sig">
<h3 id="equalize">equalize</h3>
<p><span class="arg">image</span>.equalize ->
<em>anImage</em></p>
</div>
<div class="desc">
<h4>Description</h4>
<p class="imquote">Applies a histogram equalization to the
image.</p>
<h4>Returns</h4>
<p>A new image</p>
<h4>Example</h4>
<p class="rollover"><a href=
"javascript:popup('equalize.rb.html')"><img onmouseover=
"this.src='ex/images/Flower_Hat.jpg'" onmouseout=
"this.src='ex/equalize.jpg'" src="ex/equalize.jpg" alt=
"equalize example" title=
"Click to see the example script" /></a> <img src=
"ex/images/spin.gif" alt="" class="spin" title=
"Mouse over the example to see the original image" /></p>
<h4>Magick API</h4>
<p>EqualizeImage</p>
</div>
<div class="sig">
<h3 id="erase_bang">erase!</h3>
<p><span class="arg">image</span>.erase! ->
<em>image</em></p>
</div>
<div class="desc">
<h4>Description</h4>
<p>Sets the entire image to the <a href=
"imageattrs.html#background_color">background color</a>.</p>
<h4>Returns</h4>self
<h4>See also</h4>
<p><a href="image1.html#color_reset_bang">color_reset!</a></p>
<h4>Magick API</h4>
<p>SetImage</p>
</div>
<div class="sig">
<h3 id="export_pixels">export_pixels</h3>
<p><span class="arg">image</span>.export_pixels(<span class=
"arg">x</span>=0, <span class="arg">y</span>=0, <span class=
"arg">columns</span>=<span class="arg">image</span>.columns,
<span class="arg">rows</span>=<span class=
"arg">image</span>.rows, <span class="arg">map</span>="RGB")
-> <em>anArray</em></p>
</div>
<div class="desc">
<h4>Description</h4>
<p>Extracts the pixel data from the specified rectangle and
returns it as an array of <code>Integer</code> values.</p>
<p>The array returned by <code>export_pixels</code> is suitable
for use as an argument to <code>import_pixels</code>.</p>
<h4>Arguments</h4>
<dl>
<dt>x, y</dt>
<dd>The offset of the rectangle from the upper-left corner of
the image.</dd>
<dt>columns, rows</dt>
<dd>The width and height of the rectangle.</dd>
<dt>map</dt>
<dd>A string that describes which pixel channel data is
desired and the order in which it should be stored.
<span class="imquote">It can be any combination or order of R
= red, G = green, B = blue, A = alpha, C = cyan, Y = yellow,
M = magenta, K = black, I = intensity (for grayscale), or P =
pad.</span></dd>
</dl>
<h4>Returns</h4>An array
<h4>Example</h4>
<pre>
# Export the r'th scanline from an image in red-green-blue order
scanline = img.export_pixels(0, r, img.columns, 1, "RGB");
</pre>
<h4>See also</h4>
<p><a href="image1.html#dispatch">dispatch</a>, <a href=
"#export_pixels_to_str">export_pixels_to_str</a>, <a href=
"#import_pixels">import_pixels</a>, <a href=
"#get_pixels">get_pixels</a></p>
<h4>Magick API</h4>
<p>ExportImagePixels</p>
<h4>Note</h4>
<p>This method replaces the <code>dispatch</code> method.</p>
</div>
<div class="sig">
<h3 id="export_pixels_to_str">export_pixels_to_str</h3>
<p><span class=
"arg">image</span>.export_pixels_to_str(<span class=
"arg">x</span>=0, <span class="arg">y</span>=0, <span class=
"arg">columns</span>=<span class="arg">image</span>.columns,
<span class="arg">rows</span>=<span class=
"arg">image</span>.rows, <span class="arg">map</span>="RGB",
<span class="arg">type</span>=<code>Magick::CharPixel</code>)
-> <em>aString</em></p>
</div>
<div class="desc">
<h4>Description</h4>
<p>Extracts the pixel data from the specified rectangle and
returns it as a string. If you need to get the pixel data in a
memory buffer (as input to another application, for example),
this method is much, much faster than <a href=
"#export_pixels">export_pixels</a> or <a href=
"#get_pixels">get_pixels</a>.</p>
<p>The string returned by <code>export_pixels_to_str</code> is
suitable for use as an argument to
<code>import_pixels</code>.</p>
<p><strong>Note:</strong> You can also use <a href=
"image3.html#to_blob">to_blob</a> to convert an image into a
string.</p>
<h4>Arguments</h4>
<dl>
<dt>x, y</dt>
<dd>The offset of the rectangle from the upper-left corner of
the image.</dd>
<dt>columns, rows</dt>
<dd>The width and height of the rectangle.</dd>
<dt>map</dt>
<dd>A string that describes which pixel channel data is
desired and the order in which it should be stored.
<span class="imquote">It can be any combination or order of R
= red, G = green, B = blue, A = alpha, C = cyan, Y = yellow,
M = magenta, K = black, I = intensity (for grayscale), or P =
pad.</span></dd>
<dt>type</dt>
<dd>A <a href="constants.html#StorageType">StorageType</a>
value that specifies the C datatype to which the pixel data
will be converted. The default is <code>CharPixel</code>,
which means that the pixel values will be stored as C
<code>unsigned char</code>s.</dd>
</dl>
<h4>Returns</h4>A string
<h4>See also</h4>
<p><a href="image1.html#dispatch">dispatch</a>, <a href=
"#export_pixels">export_pixels</a>, <a href=
"#import_pixels">import_pixels</a>, <a href=
"#get_pixels">get_pixels</a></p>
<h4>Magick API</h4>
<p>ExportImagePixels</p>
</div>
<div class="sig">
<h3 id="flip">flip</h3>
<p><span class="arg">image</span>.flip ->
<em>anImage</em></p>
</div>
<div class="desc">
<h4>Description</h4>
<p>Create a vertical mirror image of the receiver.</p>
<h4>Returns</h4>
<p>A new image</p>
<h4>Example</h4>
<p class="rollover"><a href=
"javascript:popup('flip.rb.html')"><img onmouseover=
"this.src='ex/images/Flower_Hat.jpg'" onmouseout=
"this.src='ex/flip.jpg'" src="ex/flip.jpg" alt="flip example"
title="Click to see the example script" /></a> <img src=
"ex/images/spin.gif" alt="" class="spin" title=
"Mouse over the example to see the original image" /></p>
<h4>See also</h4>
<p><a href="#flip_bang">flip!</a>, <a href="#flop">flop</a>,
<a href="image1.html#affine_transform">affine_transform</a></p>
<h4>Magick API</h4>
<p>FlipImage</p>
</div>
<div class="sig">
<h3 id="flip_bang">flip!</h3>
<p><span class="arg">image</span>.flip! ->
<em>image</em></p>
</div>
<div class="desc">
<h4>Description</h4>
<p>In-place form of <a href="image1.html#flip">flip</a>.</p>
<h4>Returns</h4>
<p>self</p>
</div>
<div class="sig">
<h3 id="flop">flop</h3>
<p><span class="arg">image</span>.flop ->
<em>anImage</em></p>
</div>
<div class="desc">
<h4>Description</h4>
<p>Create a horizontal mirror image of the receiver.</p>
<h4>Returns</h4>
<p>A new image</p>
<h4>Example</h4>
<p class="rollover"><a href=
"javascript:popup('flop.rb.html')"><img onmouseover=
"this.src='ex/images/Flower_Hat.jpg'" onmouseout=
"this.src='ex/flop.jpg'" src="ex/flop.jpg" alt="flop example"
title="Click to see the example script" /></a> <img src=
"ex/images/spin.gif" alt="" class="spin" title=
"Mouse over the example to see the original image" /></p>
<h4>See also</h4>
<p><a href="#flop_bang">flop!</a>, <a href="#flip">flip</a>,
<a href="image1.html#affine_transform">affine_transform</a></p>
<h4>Magick API</h4>
<p>FlopImage</p>
</div>
<div class="sig">
<h3 id="flop_bang">flop!</h3>
<p><span class="arg">image</span>.flop! ->
<em>image</em></p>
</div>
<div class="desc">
<h4>Description</h4>
<p>In-place form of <a href="image1.html#flop">flop</a>.</p>
<h4>Returns</h4>
<p>self</p>
</div>
<div class="sig">
<h3 id="frame">frame</h3>
<p><span class="arg">image</span>.frame(<span class=
"arg">width</span>=25, <span class="arg">height</span>=25,
<span class="arg">x</span>=25, <span class="arg">y</span>=25,
<span class="arg">inner_bevel</span>=6, <span class=
"arg">outer_bevel</span>=6, <span class=
"arg">color</span>=<code><a href=
"imageattrs.html#matte_color">matte_color</a></code>) ->
<em>anImage</em></p>
</div>
<div class="desc">
<h4>Description</h4>
<p>Adds a simulated 3D border.</p>
<h4>Arguments</h4>
<dl>
<dt>width</dt>
<dd>The width of the left and right sides.</dd>
<dt>height</dt>
<dd>The height of the top and bottom sides.</dd>
<dt>x, y</dt>
<dd>The image does not have to be centered in the border.
These two arguments specify the offset of the image from the
upper-left outside corner of the border.</dd>
<dt>inner_bevel, outer_bevel</dt>
<dd>The width of the inner and outer shadows of the border.
These values should be much smaller than the width and height
and cannot be greater than 1/2 the lesser of the width or
height.</dd>
<dt>color</dt>
<dd>The border color. By default the color is the <a href=
"imageattrs.html#matte_color">matte color</a>.</dd>
</dl>
<h4>Returns</h4>
<p>A new image</p>
<h4>Example</h4>
<p class="rollover"><a href=
"javascript:popup('frame.rb.html')">
<!-- This img tag displays the original image when the mouse is over -->
<img style="padding:25px; display:none" id="frameless"
onmouseout="this.style.display='none';framed.style.display='';"
src="ex/images/Flower_Hat.jpg" alt="frame example" title=
"Click to see the example script" /><!--
This img tag displays the framed image when the mouse is not over
--><img id="framed"
onmouseover=
"this.style.display='none';frameless.style.display='';" src=
"ex/frame.jpg" alt="frame example" /></a>
<img src="ex/images/spin.gif" alt="" style=
"margin-bottom: 280px" title=
"Mouse over the example to see the original image" /></p>
<h4>See also</h4>
<p><a href="image1.html#border">border</a></p>
<h4>Magick API</h4>
<p>FrameImage</p>
</div>
<div class="sig">
<h3 id="gamma_channel">gamma_channel</h3>
<p><span class="arg">image</span>.gamma_channel(<span class=
"arg">gamma</span>, [<span class="arg">channel</span>...]) =
<em>anImage</em></p>
</div>
<div class="desc">
<h4>Description</h4>
<p class="imquote">Gamma-correct a particular image channel.
The same image viewed on different devices will have perceptual
differences in the way the image's intensities are represented
on the screen.</p>
<h4>Arguments</h4>
<dl>
<dt>gamma</dt>
<dd class="imquote">Values typically range from 0.8 to 2.3.
You can also reduce the influence of a particular channel
with a gamma value of 0.</dd>
<dt>channel...</dt>
<dd>0 or more <a href=
"constants.html#ChannelType">ChannelType</a> arguments. If no
channels are specified, all the channels are corrected using
the <span class="arg">gamma</span> value.</dd>
</dl>
<h4>Returns</h4>
<p>A new image</p>
<h4>See also</h4>
<p>The older <a href="#gamma_correct">gamma_correct</a> method
is implemented in terms of <code>gamma_channel</code>.</p>
<h4>Magick API</h4>
<p>GammaImageChannel</p>
</div>
<div class="sig">
<h3 id="gamma_correct">gamma_correct</h3>
<p><span class="arg">image</span>.gamma_correct(<span class=
"arg">red_gamma</span>[,<span class="arg">green_gamma</span>[,
<span class="arg">blue_gamma</span>[, <span class=
"arg">opacity_gamma</span>]]]) -> <em>anImage</em></p>
</div>
<div class="desc">
<h4>Description</h4>
<p>Gamma-correct an image. The same image viewed on different
devices will have perceptual differences in the way the image's
intensities are represented on the screen.</p>
<h4>Arguments</h4>
<p>You must specify at least <code>red_gamma</code>. Omitted
arguments take on the value of the last specified argument.
<span class="imquote">Values typically range from 0.8 to
2.3.</span></p>
<h4>Returns</h4>
<p>A new image</p>
<h4>See also</h4>
<p><a href="#gamma_channel">gamma_channel</a></p>
<h4>Magick API</h4>
<p>GammaImage</p>
</div>
<div class="sig">
<h3 id="gaussian_blur">gaussian_blur</h3>
<p><span class="arg">image</span>.gaussian_blur(<span class=
"arg">radius</span>=0.0, <span class="arg">sigma</span>=1.0)
-> <em>anImage</em></p>
</div>
<div class="desc">
<h4>Description</h4>
<p class="imquote">Blurs an image. We convolve the image with a
Gaussian operator of the given radius and standard deviation
(sigma).</p>
<h4>Arguments</h4>
<dl>
<dt>radius</dt>
<dd>A <code>Float</code> value representing <span class=
"imquote">the radius of the Gaussian, in pixels, not counting
the center pixel.</span></dd>
<dt>sigma</dt>
<dd>A <code>Float</code> value representing the standard
deviation of the Gaussian operator, in pixels. This argument
must be > 0.0.</dd>
</dl>
<h4>Returns</h4>
<p>A new image</p>
<h4>Example</h4>
<p><code>gaussian_blur(0.0, 3.0)</code></p>
<p class="rollover"><a href=
"javascript:popup('gaussian_blur.rb.html')"><img onmouseover=
"this.src='ex/images/Flower_Hat.jpg'" onmouseout=
"this.src='ex/gaussian_blur.jpg'" src="ex/gaussian_blur.jpg"
alt="gaussian_blur example" title=
"Click to see the example script" /></a> <img src=
"ex/images/spin.gif" alt="" class="spin" title=
"Mouse over the example to see the original image" /></p>
<h4>See also</h4>
<p><a href="image1.html#blur_image">blur_image</a>, <a href=
"#motion_blur">motion_blur</a>, <a href=
"image3.html#radial_blur">radial_blur</a></p>
<h4>Magick API</h4>
<p>GaussianBlurImage</p>
</div>
<div class="sig">
<h3 id="gaussian_blur_channel">gaussian_blur_channel</h3>
<p><span class=
"arg">image</span>.gaussian_blur_channel(<span class=
"arg">radius</span>=0.0, <span class="arg">sigma</span>=1.0[,
<span class="arg">channel</span>...]) ->
<em>anImage</em></p>
</div>
<div class="desc">
<h4>Description</h4>
<p>Blurs the selected channel or channels using a Gaussian
operator of the specified radius and standard deviation.</p>
<h4>Arguments</h4>
<dl>
<dt>radius</dt>
<dd>A <code>Float</code> value representing <span class=
"imquote">the radius of the Gaussian, in pixels, not counting
the center pixel.</span></dd>
<dt>sigma</dt>
<dd>A <code>Float</code> value representing the standard
deviation of the Gaussian operator, in pixels. This argument
must be > 0.0.</dd>
<dt>channel...</dt>
<dd>0 or more <a href=
"constants.html#ChannelType">ChannelType</a> arguments. If no
channels are specified, all the channels are blurred. This is
the same as using <a href=
"#gaussian_blur">gaussian_blur</a>.</dd>
</dl>
<h4>Returns</h4>
<p>A new image</p>
<h4>See also</h4>
<p><a href="image1.html#blur_channel">blur_channel</a></p>
<h4>Magick API</h4>GaussianBlurImageChannel (available in
ImageMagick 6.0.0)
</div>
<div class="sig">
<h3 id="get_exif_by_entry">get_exif_by_entry</h3>
<p><span class=
"arg">image</span>.get_exif_by_entry(<span class="arg">[name]*</span>)
-> <em>anArray</em></p>
</div>
<div class="desc">
<h4>Description</h4>
<p>Returns the value associated with the specified EXIF entry
name or names. If no names are specified, returns all the
entries. The return value is an array containing one or more
[name, value] elements.</p>
<h4>Arguments</h4>
<p>Zero or more EXIF entry names.</p>
<h4>Returns</h4>
<p>The elements in the returned array are 2-element arrays in
the form [name, value]. If ×Magick does not know the name
for an entry it uses "unknown." There may be more than one
entry for "unknown" in the returned array. If there is no entry
with the specified name the value is set to
<code>nil</code>.</p>
<h4>Example</h4>
<pre>
image.get_exif_by_entry('Make') » [["Make", "Canon"]]
image.get_exif_by_entry("ShutterSpeedValue") »
[["ShutterSpeedValue", "189/32"]]
image.get_exif_by_entry() »
[["Make", "Canon"], ["ShutterSpeedValue", "189/32"] ...]
</pre>
<h4>See also</h4>
<p><a href="#get_exif_by_number">get_exif_by_number</a></p>
</div>
<div class="sig">
<h3 id="get_exif_by_number">get_exif_by_number</h3>
<p><span class=
"arg">image</span>.get_exif_by_number(<span class=
"arg">[tag]*</span>) -> <em>aHash</em></p>
</div>
<div class="desc">
<h4>Description</h4>
<p>Returns the value associated with the specified EXIF tag
number or numbers. If no numbers are specified, returns all the
tags. The return value is a hash. The hash keys are EXIF tag
numbers. The values are the values associated with the
tags.</p>
<h4>Arguments</h4>
<p>Zero or more EXIF tag numbers.</p>
<h4>Returns</h4>
<p>A hash. If there is no tag with the specified number the
value is set to <code>nil</code>.</p>
<h4>Example</h4>
<pre>
image.get_exif_by_number(271) » {271=>"Canon"}
image.get_exif_by_number(37377) » {37377=>"189/32"}
image.get_exif_by_number() »
{271=>"Canon", 37377=>"189/32" ...}
</pre>
<h4>See also</h4>
<p><a href="#get_exif_by_entry">get_exif_by_entry</a></p>
</div>
<div class="sig">
<h3 id="get_pixels">get_pixels</h3>
<p><span class="arg">image</span>.get_pixels(<span class=
"arg">x</span>, <span class="arg">y</span>, <span class=
"arg">columns</span>, <span class="arg">rows</span>) ->
<em>anArray</em></p>
</div>
<div class="desc">
<h4>Description</h4>
<p>Gets the pixels from the specified rectangle within the
image.</p>
<h4>Arguments</h4>
<dl>
<dt>x, y</dt>
<dd>The x- and y-offset of the rectangle within the
image.</dd>
<dt>columns, rows</dt>
<dd>The width and height of the rectangle.</dd>
</dl>
<h4>Returns</h4>
<p>An array of <a href="struct.html#Pixel">pixels</a>. There
will be <code>columns*rows</code> elements in the array.</p>
<h4>Example</h4>
<p>This example <a href="image1.html#composite">composites</a>
a black-and-white version of an image over the same image in
its original colors. It uses <code>get_pixels</code> and
<a href="image3.html#store_pixels">store_pixels</a> to make
each column of pixels in the black-and-white image slightly
more opaque than the column on its left, so that the resulting
composite changes smoothly from color on the left to
black-and-white on the right.</p><!--
Reduce the size of the original image by specifying
the size of the example image.
-->
<p class="rollover"><a href=
"javascript:popup('get_pixels.rb.html')"><img width="384"
height="249" onmouseover="this.src='ex/images/Red_Rocks.jpg'"
onmouseout="this.src='ex/get_pixels.jpg'" src=
"ex/get_pixels.jpg" title="Click to see the example script"
alt="get_pixels example" /></a> <img src="ex/images/spin.gif"
alt="" class="spin" style="left:388px" title=
"Mouse over the example to see the original image" /></p>
<h4>See also</h4>
<p><a href="image3.html#store_pixels">store_pixels</a>,
<a href="image3.html#view">view</a></p>
<h4>Magick API</h4>
<p>AcquireImagePixels</p>
</div>
<div class="sig">
<h3 id="gray_q">gray?</h3>
<p><span class="arg">image</span>.gray? -> <code>true</code>
or <code>false</code></p>
</div>
<div class="desc">
<h4>Description</h4>
<p>Returns <code>true</code> if all the pixels in the image
have the same red, green, and blue intensities.</p>
<h4>Returns</h4>
<p><code>true</code> or <code>false</code></p>
<h4>See also</h4>
<p><a href="#monochrome_q">monochrome?</a></p>
<h4>Magick API</h4>
<p>IsGrayImage</p>
</div>
<div class="sig">
<h3 id="grayscale_pseudo_class">grayscale_pseudo_class</h3>
<p><span class=
"arg">image</span>.grayscale_pseudo_class(<span class=
"arg">optimize</span>=<code>true</code>) ->
<em>anImage</em></p>
</div>
<div class="desc">
<h4>Description</h4>
<p><span class="imquote">Converts an image to a PseudoClass
grayscale representation with an optionally compressed and
sorted colormap..</span> This method is only available in
GraphicsMagick 1.1 and later.</p>
<h4>Arguments</h4>
<dl>
<dt>optimize</dt>
<dd>If true, compress and sort the colormap by increasing
intensity.</dd>
</dl>
<h4>Returns</h4>
<p>A new image</p>
<h4>Magick API</h4>
<p>GrayscalePseudoClass</p>
</div>
<div class="sig">
<h3 id="grey_q">grey?</h3>
<p><span class="arg">image</span>.qrey? -> <code>true</code>
or <code>false</code></p>
</div>
<div class="desc">
<h4>Description</h4>
<p>Synonym for <a href="#gray_q">gray?</a></p>
</div>
<div class="sig">
<h3 id="implode">implode</h3>
<p><span class="arg">image</span>.implode(<span class=
"arg">amount</span>=0.50) -> <em>anImage</em></p>
</div>
<div class="desc">
<h4>Description</h4>
<p>A funhouse mirror effect. See the example below.</p>
<h4>Arguments</h4>
<p>A <code>Float</code> value. Increasing the absolute value of
the argument increases the effect. The value may be positive
for implosion, or negative for explosion. The default is
0.50.</p>
<h4>Returns</h4>
<p>A new image</p>
<h4>Example</h4>
<p>This example is an animated image. Mouse over the image to
start the animation.</p>
<p class="rollover"><a href=
"javascript:popup('implode.rb.html')"><img onmouseover=
"this.src='ex/implode.gif'" onmouseout=
"this.src='ex/images/Flower_Hat.jpg'" src=
"ex/images/Flower_Hat.jpg" alt="implode example" title=
"Click the image to see the example script" /></a><img src=
"ex/images/spin.gif" alt="" class="spin" title=
"Mouse over the example to see the animation" /></p>
<h4>Magick API</h4>
<p>ImplodeImage</p>
</div>
<div class="sig">
<h3 id="import_pixels">import_pixels</h3>
<p><span class="arg">image</span>.import_pixels(<span class=
"arg">x</span>, <span class="arg">y</span>, <span class=
"arg">columns</span>, <span class="arg">rows</span>,
<span class="arg">map</span>, <span class="arg">pixels</span>,
<span class="arg">type</span>=Magick::CharPixel) ->
<em>image</em></p>
</div>
<div class="desc">
<h4>Description</h4>
<p>Replaces the pixels in the specified rectangle with pixel
data from the supplied array or string. When the <span class=
"arg">pixels</span> argument is an array of pixel data, this
method is the reverse of <code>export_pixels</code>. When the
<span class="arg">pixels</span> argument is a string,
<code>import_pixels</code> is ideal for loading very large
amounts of binary pixel data.</p>
<h4>Arguments</h4>
<dl>
<dt>x, y</dt>
<dd>The offset of the rectangle from the upper-left corner of
the image</dd>
<dt>columns, rows</dt>
<dd>The width and height of the rectangle</dd>
<dt>map</dt>
<dd>A string describing <span class="imquote">the expected
ordering of the pixel array. It can be any combination or
order of R = red, G = green, B = blue, A = alpha, C = cyan, Y
= yellow, M = magenta, K = black, or I = intensity (for
grayscale).</span></dd>
<dt>pixels</dt>
<dd>
The pixel data. Pixel data can be supplied as an array or
as a string.
<dl>
<dt>If <span class="arg">pixels</span> responds to
<code>:to_str</code></dt>
<dd><code>import_pixels</code> assumes that <span class=
"arg">pixels</span> can be converted to a string by
<code>to_str</code> and that the result is a C array of
the type specified by <span class="arg">type</span>
containing binary pixel data in the order specified by
<span class="arg">map</span>. The elements in the buffer
must be in the range specified by <span class=
"arg">type</span>.</dd>
<dt>Otherwise</dt>
<dd><code>import_pixels</code> assumes that <span class=
"arg">pixels</span> is an array or an object that can be
converted to an array by the <code>Kernel::Array</code>
method. The elements in the array must be
<code>Numeric</code> values in the range [0..MaxRGB]. In
either case, the pixel data must be stored in scanline
order: left-to-right and top-to-bottom.</dd>
</dl>
</dd>
<dt>type</dt>
<dd>A <a href="constants.html#StorageType">StorageType</a>
value that specifies the type and range of the pixel data
when <span class="arg">pixels</span> is a string.</dd>
</dl>
<h4>Returns</h4>
<p>The image as transformed by the pixel data.</p>
<h4>Example</h4>
<pre>
# Replace the r'th scanline of the image using
# pixel data stored in red-green-blue order.
img.import_pixels(0, r, img.columns, 1, "RGB", scanline);
</pre>
<h4>Example</h4>
<p>This example is contrived since there's no need to convert
the <code>pixels</code> array into a string by calling
<code>pack</code>, but it does demonstrate the use of a string
<span class="arg">pixels</span> argument. Note that this
example assumes that ×Magick is configured with
QuantumDepth=8.</p>
<pre>
hat = Magick::Image.read("Flower_Hat.jpg").first
pixels = hat.export_pixels(0, 0, hat.columns, hat.rows, "RGB")
char_buffer = pixels.pack("C*")
img = Magick::Image.new(hat.columns, hat.rows)
img.import_pixels(0, 0, hat.columns, hat.rows, "RGB", char_buffer, Magick::CharPixel)
</pre>
<h4>See also</h4>
<p><a href="image1.html#constitute">constitute</a>, <a href=
"image2.html#export_pixels">export_pixels</a>, <a href=
"image3.html#store_pixels">store_pixels</a></p>
<h4>Magick API</h4>
<p>ImportImagePixels</p>
<h4>Note</h4>
<p>This method replaces the <code>constitute</code> method.</p>
</div>
<div class="sig">
<h3 id="inspect">inspect</h3>
<p><span class="arg">image</span>.inspect ->
<em>aString</em></p>
</div>
<div class="desc">
<h4>Description</h4>
<p>Constructs a description of the image as a string. The
string contains some or all of the following fields:</p>
<dl>
<dt>original_filename=></dt>
<dd>if different from the current filename.</dd>
<dt>filename</dt>
<dd>the current filename</dd>
<dt>[scene]</dt>
<dd>the scene number, if the image is part of an image
sequence</dd>
<dt>format</dt>
<dd>the image format (GIF or JPEG, for example)</dd>
<dt>original width x height</dt>
<dd>if different from the current width x height</dd>
<dt>page width x height + x-offset + y-offset</dt>
<dd>if any of these fields is non-zero</dd>
<dt>storage class</dt>
<dd><em>DirectClass</em> or <em>PseudoClass</em></dd>
<dt>number of colors</dt>
<dd>total number of colors used in the image</dd>
<dt>mean error per pixel/normalized mean error/normalized
maximum error</dt>
<dd>for PseudoClass images, if present</dd>
<dt><em>N</em>-bit</dt>
<dd>bit depth</dd>
<dt>blob size</dt>
<dd>if present</dd>
</dl>
<h4>Example</h4>
<pre>
f.inspect » "images/Flower_Hat.jpg JPEG 200x250 DirectClass 8-bit 9kb"
</pre>
</div>
<div class="sig">
<h3 id="level">level</h3>
<p><span class="arg">image</span>.level(<span class=
"arg">black_point</span>=<code>0.0</code>, <span class=
"arg">white_point</span>=<code>MaxRGB</code>, <span class=
"arg">gamma</span>=<code>1.0</code>) -> <em>anImage</em></p>
</div>
<div class="desc">
<h4>Description</h4>
<p class="imquote">Adjusts the levels of an image by scaling
the colors falling between specified white and black points to
the full available quantum range. The parameters provided
represent the black, mid, and white points. The black point
specifies the darkest color in the image. Colors darker than
the black point are set to zero. Gamma specifies a gamma
correction to apply to the image. White point specifies the
lightest color in the image. Colors brighter than the white
point are set to the maximum quantum value</p>
<h4>Arguments</h4>
<dl>
<dt>black_point</dt>
<dd>The black point level. The default is 0.0.</dd>
<dt>mid_point</dt>
<dd>The white point level. The default is <a href=
"constants.html#Miscellaneous_constants">MaxRGB</a> -
<span class="arg">black_point</span>.</dd>
<dt>gamma</dt>
<dd>The gamma correction. The default is 1.0.</dd>
</dl>
<h4>Returns</h4>
<p>A new image</p>
<h4>Example</h4>
<p><code>level(0,1.50)</code></p>
<p class="rollover"><a href=
"javascript:popup('level.rb.html')"><img onmouseover=
"this.src='ex/images/Flower_Hat.jpg'" onmouseout=
"this.src='ex/level.jpg'" src="ex/level.jpg" title=
"Click to see the example script" alt="level example" /></a>
<img src="ex/images/spin.gif" alt="" class="spin" title=
"Mouse over the image to see the original image" /></p>
<h4>See also</h4>
<p><a href="#level_channel">level_channel</a></p>
<h4>Magick API</h4>
<p>LevelImage</p>
</div>
<div class="sig">
<h3 id="level_channel">level_channel</h3>
<p><span class="arg">image</span>.level_channel(<span class=
"arg">channel</span>, <span class=
"arg">black_point</span>=<code>0</code>, <span class=
"arg">white_point</span>=<code>MaxRGB</code>-<code>black_point</code>,
<span class="arg">gamma</span>=<code>1.0</code>) ->
<em>anImage</em></p>
</div>
<div class="desc">
<h4>Description</h4>Same as <code>level</code> but operates
only on the specified channel.
<h4>Arguments</h4>
<dl>
<dt>channel</dt>
<dd>A <a href="constants.html#ChannelType">ChannelType</a>
value.</dd>
<dt>black_point</dt>
<dd>The black point level. The default is 0.0.</dd>
<dt>mid_point</dt>
<dd>The white point level. The default is <a href=
"constants.html#Miscellaneous_constants">MaxRGB</a> -
<span class="arg">black_point</span>.</dd>
<dt>gamma</dt>
<dd>The gamma correction. The default is 1.0.</dd>
</dl>
<h4>Returns</h4>
<p>A new image</p>
<h4>Example</h4>
<p class="rollover"><a href=
"javascript:popup('level_channel.rb.html')"><img onmouseover=
"this.src='ex/images/Flower_Hat.jpg'" onmouseout=
"this.src='ex/level_channel.jpg'" src="ex/level_channel.jpg"
title="Click to see the example script" alt=
"level_channel example" /></a> <img src="ex/images/spin.gif"
alt="" class="spin" title=
"Mouse over the example to see the original image" /></p>
<h4>See also</h4>
<p><a href="#level">level</a></p>
<h4>Magick API</h4>
<p>LevelImageChannel</p>
</div>
<div class="sig">
<h3 id="magnify">magnify</h3>
<p><span class="arg">image</span>.magnify ->
<em>anImage</em></p>
</div>
<div class="desc">
<h4>Description</h4>
<p>A convenience method that scales the receiver to twice its
size.</p>
<h4>Returns</h4>
<p>A new image</p>
<h4>See also</h4>
<p><a href="#magnify_bang">magnify!</a>, <a href=
"#minify">minify</a>, <a href="image3.html#resize">resize</a>,
<a href="image3.html#scale">scale</a>, <a href=
"image3.html#sample">sample</a>, <a href=
"image3.html#thumbnail">thumbnail</a></p>
<h4>Magick API</h4>
<p>MagnifyImage</p>
</div>
<div class="sig">
<h3 id="magnify_bang">magnify!</h3>
<p><span class="arg">image</span>.magnify! ->
<em>image</em></p>
</div>
<div class="desc">
<h4>Description</h4>
<p>In-place form of <a href="#magnify">magnify</a></p>
<h4>Returns</h4>self
</div>
<div class="sig">
<h3 id="map">map</h3>
<p><span class="arg">image</span>.map(<span class=
"arg">img</span>, <span class=
"arg">dither</span>=<code>false</code>) ->
<em>anImage</em></p>
</div>
<div class="desc">
<h4>Description</h4>
<p class="imquote">Replaces the colors of an image with the
closest color from a reference image.</p>
<h4>Arguments</h4>
<dl>
<dt>img</dt>
<dd>The reference image. May be either another image or an
<code>Image</code> object.</dd>
<dt>dither</dt>
<dd>If <code>true</code>, dithers the mapped image.</dd>
</dl>
<h4>Returns</h4>
<p>A new image</p>
<h4>Example</h4>
<p>This image has been mapped to the Netscape 216-color
cube.</p>
<p class="rollover"><a href=
"javascript:popup('map_f.rb.html')"><img onmouseover=
"this.src='ex/images/Flower_Hat.jpg'" onmouseout=
"this.src='ex/map_f.jpg'" src="ex/map_f.jpg" alt=
"map_f example" title="Click to see the example script" /></a>
<img src="ex/images/spin.gif" alt="" class="spin" title=
"Mouse over the image to see the original image" /></p>
<h4>See also</h4>
<p><a href="ilist.html#map">ImageList#map</a></p>
<h4>Magick API</h4>
<p>MapImage</p>
</div>
<div class="sig">
<h3 id="matte_fill_to_border">matte_fill_to_border</h3>
<p><span class=
"arg">image</span>.matte_fill_to_border(<span class=
"arg">x</span>, <span class="arg">y</span>) ->
<em>anImage</em></p>
</div>
<div class="desc">
<h4>Description</h4>
<p>Makes transparent all the pixels that are neighbors of the
pixel at <span class="arg">x</span>,<span class="arg">y</span>
and are not the border color.</p>
<h4>Arguments</h4>
<p>The x- and y- coordinates of the target pixel.</p>
<h4>Returns</h4>
<p>A new image</p>
<h4>Example</h4>
<p>In this example the border color is black. The fill starts
in the center and makes all the pixels transparent until it
reaches a black pixel. The resulting image has been composited
over a plasma background, which shows through the transparent
pixels.</p>
<p class="rollover"><a href=
"javascript:popup('matte_fill_to_border.rb.html')"><img src=
"ex/matte_fill_to_border_after.gif" onmouseover=
"this.src='ex/matte_fill_to_border_before.gif'" onmouseout=
"this.src='ex/matte_fill_to_border_after.gif'" alt=
"matte_fill_to_border example" title=
"Click to see the example script" /></a> <img src=
"ex/images/spin.gif" alt="" class="spin" title=
"Mouse over the image to see the original image" /></p>
<h4>See also</h4>
<p><a href="#matte_floodfill">matte_floodfill</a>, <a href=
"draw.html#matte">Draw#matte</a></p>
<h4>Magick API</h4>
<p>MatteFloodfillImage</p>
</div>
<div class="sig">
<h3 id="matte_floodfill">matte_floodfill</h3>
<p><span class="arg">image</span>.matte_floodfill(<span class=
"arg">x</span>, <span class="arg">y</span>) ->
<em>anImage</em></p>
</div>
<div class="desc">
<h4>Description</h4>
<p>Makes transparent all the pixels that are the same color as
the pixel at <span class="arg">x</span>, <span class=
"arg">y</span>, and are neighbors.</p>
<h4>Arguments</h4>
<p>The x- and y-coordinates of the target pixel.</p>
<h4>Returns</h4>
<p>A new image</p>
<h4>Example</h4>
<p>In this example the fill starts at the center pixel and
replaces all the yellow pixels - the color of the center pixel.
The resulting image has been composited over a plasma
background, which shows through the transparent pixels.</p>
<p class="rollover"><a href=
"javascript:popup('matte_floodfill.rb.html')"><img src=
"ex/matte_floodfill_after.gif" onmouseover=
"this.src='ex/matte_floodfill_before.gif'" onmouseout=
"this.src='ex/matte_floodfill_after.gif'" alt=
"matte_floodfill example" title=
"Click to see the example script" /></a> <img src=
"ex/images/spin.gif" alt="" class="spin" title=
"Mouse over the image to see the original image" /></p>
<h4>See also</h4>
<p><a href="#matte_replace">matte_replace</a>, <a href=
"draw.html#matte">Draw#matte</a></p>
<h4>Magick API</h4>
<p>MatteFloodfilImage</p>
</div>
<div class="sig">
<h3 id="matte_point">matte_point</h3>
<p><span class="arg">image</span>.matte_point(<span class=
"arg">x</span>, <span class="arg">y</span>) ->
<em>anImage</em></p>
</div>
<div class="desc">
<h4>Description</h4>
<p>Makes the pixel at <span class="arg">x</span>, <span class=
"arg">y</span> transparent. This method makes a copy of the
image, just to make one pixel transparent. I recommend using
the <code>Draw#matte</code> method instead.</p>
<h4>Arguments</h4>
<p>The x- and y-coordinates of the target pixel.</p>
<h4>Returns</h4>
<p>A new image</p>
<h4>See also</h4>
<p><a href="draw.html#Draw.matte">Draw#matte</a></p>
</div>
<div class="sig">
<h3 id="matte_replace">matte_replace</h3>
<p><span class="arg">image</span>.matte_replace(<span class=
"arg">x</span>, <span class="arg">y</span>) ->
<em>anImage</em></p>
</div>
<div class="desc">
<h4>Description</h4>
<p>Makes transparent all the pixels that are the same color as
the pixel at <span class="arg">x</span>, <span class=
"arg">y</span>.</p>
<h4>Arguments</h4>The x- and y-coordinates of the target pixel.
<h4>Returns</h4>
<p>A new image</p>
<h4>Example</h4>
<p>In this example the target pixel is a black pixel in the
center of the uppermost circle. The <code>matte_replace</code>
method makes all the black pixels in the image transparent. The
resulting image has been composited over a plasma background,
which shows through the transparent pixels.</p>
<p class="rollover"><a href=
"javascript:popup('matte_replace.rb.html')"><img onmouseover=
"this.src='ex/matte_replace_before.gif'" onmouseout=
"this.src='ex/matte_replace_after.gif'" src=
"ex/matte_replace_after.gif" alt="matte_replace example" title=
"Click to see the example script" /></a> <img src=
"ex/images/spin.gif" alt="" class="spin" title=
"Mouse over the image to see the original image" /></p>
<h4>See also</h4>
<p><a href="image3.html#transparent">transparent</a>, <a href=
"draw.html#matte">Draw#matte</a></p>
<h4>Magick API</h4>
<p>TransparentImage</p>
</div>
<div class="sig">
<h3 id="matte_reset_bang">matte_reset!</h3>
<p><span class="arg">image</span>.matte_reset! ->
<em>image</em></p>
</div>
<div class="desc">
<h4>Description</h4>
<p>Makes all the pixels in the image transparent.</p>
<h4>Returns</h4>
<p>self</p>
<h4>See also</h4>
<p><a href="imageattrs.html#opacity_eq">opacity=</a></p>
<h4>Magick API</h4>SetImageOpacity
</div>
<div class="sig">
<h3 id="median_filter">median_filter</h3>
<p><span class="arg">image</span>.median_filter(<span class=
"arg">radius</span>=1.0) -> <em>anImage</em></p>
</div>
<div class="desc">
<h4>Description</h4>
<p class="imquote">Applies a digital filter that improves the
quality of a noisy image. Each pixel is replaced by the median
in a set of neighboring pixels as defined by radius.</p>
<h4>Arguments</h4>
<p>The filter radius. The larger the value, the longer it takes
to render. Values larger than 8 or 9 may take longer than you
want to wait, and will not have significantly better results
than much smaller values.</p>
<h4>Returns</h4>
<p>A new image</p>
<h4>Example</h4>
<p>The left side of the image has been modified by <a href=
"image1.html#add_noise"><code>add_noise</code></a>. The right
side has been filtered by
<code>median_filter(0.05).</code></p><a href=
"javascript:popup('median_filter.rb.html')"><img src=
"ex/median_filter.jpg" alt="median_filter example" /></a>
<h4>See also</h4>
<p><a href="#enhance">enhance</a>, <a href=
"image3.html#reduce_noise">reduce_noise</a>, <a href=
"image3.html#unsharp_mask">unsharp_mask</a></p>
<h4>Magick API</h4>
<p>MedianFilterImage</p>
</div>
<div class="sig">
<h3 id="minify">minify</h3>
<p><span class="arg">image</span>.minify ->
<em>anImage</em></p>
</div>
<div class="desc">
<h4>Description</h4>
<p>A convenience method that scales the receiver to half its
size.</p>
<h4>Returns</h4>
<p>A new image</p>
<h4>See also</h4>
<p><a href="#minify_bang">minify!</a> <a href=
"#magnify">magnify</a>, <a href=
"image3.html#resize">resize</a>, <a href=
"image3.html#sample">sample</a>, <a href=
"image3.html#scale">scale</a>, <a href=
"image3.html#thumbnail">thumbnail</a></p>
<h4>Magick API</h4>
<p>MinifyImage</p>
</div>
<div class="sig">
<h3 id="minify_bang">minify!</h3>
<p><span class="arg">image</span>.minify! ->
<em>image</em></p>
</div>
<div class="desc">
<h4>Description</h4>
<p>In-place form of <a href="#Image.minify">minify</a>.</p>
<h4>Returns</h4>
<p>self</p>
</div>
<div class="sig">
<h3 id="modulate">modulate</h3>
<p><span class="arg">image</span>.modulate(<span class=
"arg">brightness</span>=1.0, <span class=
"arg">saturation</span>=1.0, <span class="arg">hue</span>=1.0)
-> <em>anImage</em></p>
</div>
<div class="desc">
<h4>Description</h4>
<p>Changes the brightness, saturation, and hue.</p>
<h4>Arguments</h4>
<p>The percent change in the brightness, saturation, and hue,
represented as <code>Float</code> numbers. For example, 0.25
means "25%". All three arguments may be omitted. The default
value of each argument is 1.0, that is, 100%.</p>
<h4>Returns</h4>
<p>A new image</p>
<h4>Example</h4>
<p><code>modulate(0.85)</code></p>
<p class="rollover"><a href=
"javascript:popup('modulate.rb.html')"><img src=
"ex/modulate.jpg" alt="modulate example" onmouseover=
"this.src='ex/images/Flower_Hat.jpg'" onmouseout=
"this.src='ex/modulate.jpg'" title=
"Click to see the example script" /></a> <img src=
"ex/images/spin.gif" alt="" class="spin" title=
"Mouse over the example to see the original image" /></p>
<h4>Magick API</h4>
<p>ModulateImage</p>
</div>
<div class="sig">
<h3 id="monochrome_q">monochrome?</h3>
<p><span class="arg">image</span>.monochrome? ->
<code>true</code> or <code>false</code></p>
</div>
<div class="desc">
<h4>Description</h4>
<p>Returns <code>true</code> if all the pixels have the same
red, green, and blue values and the values are either 0 or
MaxRGB. That is, the image is black-and-white.</p>
<h4>See also</h4>
<p><a href="#gray_q">gray?</a></p>
<h4>Magick API</h4>
<p>IsMonochromeImage</p>
</div>
<div class="sig">
<h3 id="motion_blur">motion_blur</h3>
<p><span class="arg">image</span>.motion_blur(<span class=
"arg">radius</span>, <span class="arg">sigma</span>,
<span class="arg">angle</span>) -> <em>anImage</em></p>
</div>
<div class="desc">
<h4>Description</h4>
<p class="imquote">Simulates motion blur. We convolve the image
with a Gaussian operator of the given <span class=
"arg">radius</span> and standard deviation (<span class=
"arg">sigma</span>). Use a radius of 0 and
<code>motion_blur</code> selects a suitable radius for you.
<span class="arg">Angle</span> gives the angle of the blurring
motion.</p>
<h4>Arguments</h4>
<dl>
<dt>radius</dt>
<dd>The radius of the Gaussian operator.</dd>
<dt>sigma</dt>
<dd>The standard deviation of the Gaussian operator. Must be
non-0.</dd>
<dt>angle</dt>
<dd>The angle (in degrees) of the blurring motion.</dd>
</dl>
<h4>Returns</h4>
<p>A new image</p>
<h4>Example</h4>
<p class="rollover"><a href=
"javascript:popup('motion_blur.rb.html')"><img src=
"ex/motion_blur.jpg" alt="motion_blur example" title=
"Click to see the example script" onmouseover=
"this.src='ex/images/Flower_Hat.jpg'" onmouseout=
"this.src='ex/motion_blur.jpg'" /></a> <img src=
"ex/images/spin.gif" alt="" class="spin" title=
"Mouse over the example to see the original image" /></p>
<h4>See also</h4>
<p><a href="image1.html#blur_image">blur_image</a>, <a href=
"#gaussian_blur">gaussian_blur</a></p>
<h4>Magick API</h4>
<p>MotionBlurImage</p>
</div>
<div class="sig">
<h3 id="negate">negate</h3>
<p><span class="arg">image</span>.negate(<span class=
"arg">grayscale</span>=<code>false</code>) ->
<em>anImage</em></p>
</div>
<div class="desc">
<h4>Description</h4>
<p>Negates the colors in the receiver.</p>
<h4>Arguments</h4>If the <span class="arg">grayscale</span>
argument is true, only the grayscale values are negated.
<h4>Returns</h4>
<p>A new image</p>
<h4>Example</h4>
<p class="rollover"><a href=
"javascript:popup('negate.rb.html')"><img src="ex/negate.jpg"
alt="negate example" onmouseover=
"this.src='ex/images/Flower_Hat.jpg'" onmouseout=
"this.src='ex/negate.jpg'" title=
"Click to see the example script" /></a> <img src=
"ex/images/spin.gif" alt="" class="spin" title=
"Mouse over the example to see the original image" /></p>
<h4>See also</h4>
<p><a href="#negate_channel">negate_channel</a></p>
<h4>Magick API</h4>
<p>NegateImage</p>
</div>
<div class="sig">
<h3 id="negate_channel">negate_channel</h3>
<p><span class="arg">image</span>.negate_channel(<span class=
"arg">grayscale</span>=<code>false</code>, [<span class=
"arg">channel</span>...]) = <em>anImage</em></p>
</div>
<div class="desc">
<h4>Description</h4>
<p>Negate a particular image channel or channels.</p>
<h4>Arguments</h4>
<dl>
<dt>grayscale</dt>
<dd class="imquote">if <code>true</code>, only negate
grayscale pixels within the image</dd>
<dt>channel...</dt>
<dd>0 or more <a href=
"constants.html#ChannelType">ChannelType</a> arguments. If no
channels are specified, all the channels are negated.
Specifying no channel arguments has the same effect as the
<code>negate</code> method, above.</dd>
</dl>
<h4>Returns</h4>
<p>A new image</p>
<h4>Example</h4>
<p><code>negate_channel(false, GreenChannel)</code></p>
<p class="rollover"><a href=
"javascript:popup('negate_channel.rb.html')"><img src=
"ex/negate_channel.jpg" alt="negate_channel example"
onmouseover="this.src='ex/images/Flower_Hat.jpg'" onmouseout=
"this.src='ex/negate_channel.jpg'" title=
"Click to see the example script" /></a> <img src=
"ex/images/spin.gif" alt="" class="spin" title=
"Mouse over the example to see the original image" /></p>
<h4>See also</h4>
<p><a href="#negate">negate</a></p>.
<h4>Magick API</h4>
<p>NegateImageChannel</p>
</div>
<div class="sig">
<h3 id="normalize">normalize</h3>
<p><span class="arg">image</span>.normalize ->
<em>anImage</em></p>
</div>
<div class="desc">
<h4>Description</h4>
<p class="imquote">Enhances the contrast of a color image by
adjusting the pixel color to span the entire range of colors
available.</p>
<h4>Returns</h4>
<p>A new image</p>
<h4>Example</h4>
<p class="rollover"><a href=
"javascript:popup('normalize.rb.html')"><img src=
"ex/normalize.jpg" alt="normalize example" title=
"Click to see the example script" onmouseover=
"this.src='ex/images/Hot_Air_Balloons.jpg'" onmouseout=
"this.src='ex/normalize.jpg'" /></a> <img src=
"ex/images/spin.gif" alt="" class="spin" style="left: 191px;"
title="Mouse over the example to see the original image" /></p>
<h4>Magick API</h4>
<p>NormalizeImage</p>
<h4>See also</h4>
<p><a href="#normalize_channel">normalize_channel</a></p>
</div>
<div class="sig">
<h3 id="normalize_channel">normalize_channel</h3>
<p><span class=
"arg">image</span>.normalize_channel([<span class=
"arg">channel</span>...]) = <em>anImage</em></p>
</div>
<div class="desc">
<h4>Description</h4>
<p><span class="imquote">Enhances the contrast of a color image
by adjusting the pixel color to span the entire range of colors
available.</span> Only the specified channels are
normalized.</p>
<h4>Arguments</h4>
<dl>
<dt>channel...</dt>
<dd>0 or more <a href=
"constants.html#ChannelType">ChannelType</a> arguments. If no
channels are specified, all the channels are normalized.
Specifying no channel arguments has the same effect as the
<code>normalize</code> method, above.</dd>
</dl>
<h4>Returns</h4>
<p>A new image</p>
<h4>Magick API</h4>
<p>NormalizeImageChannel (available in ImageMagick 6.1.0)</p>
<h4>See also</h4>
<p><a href="#normalize">normalize</a></p>
</div>
<div class="sig">
<h3 id="oil_paint">oil_paint</h3>
<p><span class="arg">image</span>.oil_paint(<span class=
"arg">radius</span>=3.0) -> <em>anImage</em></p>
</div>
<div class="desc">
<h4>Description</h4>
<p class="imquote">Applies a special effect filter that
simulates an oil painting. Each pixel is replaced by the most
frequent color occurring in a circular region defined by
<span class="arg">radius</span>.</p>
<h4>Returns</h4>
<p>A new image</p>
<h4>Example</h4>
<p class="rollover"><a href=
"javascript:('oil_paint.rb.html')"><img src="ex/oil_paint.jpg"
title="Click to see the example script" onmouseover=
"this.src='ex/images/Flower_Hat.jpg'" onmouseout=
"this.src='ex/oil_paint.jpg'" alt="oil_paint example" /></a>
<img src="ex/images/spin.gif" alt="" class="spin" title=
"Mouse over the example to see the original image" /></p>
<h4>Magick API</h4>
<p>OilPaintImage</p>
</div>
<div class="sig">
<h3 id="opaque">opaque</h3>
<p><span class="arg">image</span>.opaque(<span class=
"arg">target</span>, <span class="arg">fill</span>) ->
<em>anImage</em></p>
</div>
<div class="desc">
<h4>Description</h4>
<p>Changes all pixels having the target color to the fill
color.</p>
<h4>Arguments</h4>
<dl>
<dt>target</dt>
<dd>The color to be replaced. May be a color name or a
<code><a href="struct.html#Pixel">Pixel</a></code></dd>
<dt>fill</dt>
<dd>The replacement color. May be a color name or a
<code><a href="struct.html#Pixel">Pixel</a></code></dd>
</dl>
<h4>Returns</h4>
<p>A new image</p>
<h4>Example</h4>
<p>This example replaces white pixels with red pixels. Set the
<code>fuzz</code> attribute to specify how closely the target
pixels must match.</p>
<p class="rollover"><a href=
"javascript:popup('opaque.rb.html')"><img src="ex/opaque.jpg"
alt="opaque example" onmouseover=
"this.src='ex/images/Flower_Hat.jpg'" onmouseout=
"this.src='ex/opaque.jpg'" title=
"Click to see the example script" /></a> <img src=
"ex/images/spin.gif" alt="" class="spin" title=
"Mouse over the example to see the original image" /></p>
<h4>See also</h4>
<p><a href="#color_floodfill">color_floodfill</a></p>
<h4>Magick API</h4>
<p>OpaqueImage</p>
</div>
<div class="sig">
<h3 id="opaque_q">opaque?</h3>
<p><span class="arg">image</span>.opaque? ->
<code>true</code> or <code>false</code></p>
</div>
<div class="desc">
<h4>Description</h4>
<p>Returns <code>true</code> if all of the pixels in the
receiver have an opacity value of <a href=
"constants.html#Opacity">OpaqueOpacity</a>.</p>
<h4>Returns</h4>
<p><code>true</code> or <code>false</code></p>
<h4>Magick API</h4>
<p>IsOpaqueImage</p>
</div>
<div class="sig">
<h3 id="ordered_dither">ordered_dither</h3>
<p><span class="arg">image</span>.ordered_dither(<span class=
"arg">order</span>=2) -> <em>anImage</em></p>
</div>
<div class="desc">
<h4>Description</h4>
<p class="imquote">Uses the ordered dithering technique of
reducing color images to monochrome using positional
information to retain as much information as possible.</p>
<h4>Arguments</h4>
<dl>
<dt>order</dt>
<dd>The dither order. Must be one of the integers 2, 3, or
4.</dd>
</dl>
<h4>Returns</h4>
<p>A new image</p>
<h4>Example</h4>
<p class="rollover"><a href=
"javascript:popup('ordered_dither.rb.html')"><img src=
"ex/ordered_dither.jpg" alt="ordered_dither example"
onmouseover="this.src='ex/images/Flower_Hat.jpg'" onmouseout=
"this.src='ex/ordered_dither.jpg'" title=
"Click to see the example script" /></a> <img src=
"ex/images/spin.gif" alt="" class="spin" title=
"Mouse over the example to see the original image" /></p>
<h4>See also</h4>
<p><a href="#posterize">posterize</a>, <a href=
"image3.html#quantize">quantize</a></p>
<h4>Magick API</h4>
<p>RandomThresholdImageChannel</p>
</div>
<div class="sig">
<h3 id="palette_q">palette?</h3>
<p><span class="arg">image</span>.palette? ->
<code>true</code> or <code>false</code></p>
</div>
<div class="desc">
<h4>Description</h4>
<p class="imquote">Returns true if the image is <a href=
"constants.html#ClassType"><code>PseudoClass</code></a> and has
256 unique colors or less.</p>
<h4>Returns</h4>
<p><code>true</code> or <code>false</code></p>
<h4>Magick API</h4>
<p>IsPaletteImage</p>
</div>
<div class="sig">
<h3 id="pixel_color">pixel_color</h3>
<p><span class="arg">image</span>.pixel_color(<span class=
"arg">x</span>, <span class="arg">y</span>[, <span class=
"arg">new_color</span>]) -> <em>aPixel</em></p>
</div>
<div class="desc">
<h4>Description</h4>
<p>Returns the color of the pixel at <span class=
"arg">x</span>, <span class="arg">y</span>. Optionally, changes
the color of the pixel to a new color.</p>
<p>If <code>new_color</code> is specified,
<code>pixel_color</code> changes the image type to
<code>DirectClass</code> if necessary.</p>
<h4>Arguments</h4>
<dl>
<dt>x, y</dt>
<dd>The x- and y-coordinates of the pixel.</dd>
<dt>new_color</dt>
<dd>If specified, the pixel is set to this color. May be
either a color name or a <a href=
"struct.html#Pixel">Pixel</a>.</dd>
</dl>
<h4>Returns</h4>A <a href="struct.html#Pixel">Pixel</a> having
the RGB values of the specified pixel.
<h4>Example</h4>
<pre>
old = image.pixel_color(20,40,"white")
</pre>
<h4>Magick API</h4>
<p>AcquireImagePixels</p>
</div>
<div class="sig">
<h3 id="posterize">posterize</h3>
<p><span class="arg">image</span>.posterize(<span class=
"arg">levels</span>=4, <span class=
"arg">dither</span>=<code>false</code>) ->
<em>anImage</em></p>
</div>
<div class="desc">
<h4>Description</h4>
<p class="imquote">Reduces the image to a limited number of
colors for a "poster" effect.</p>
<h4>Arguments</h4>
<dl>
<dt>levels</dt>
<dd><span class="imquote">Number of color levels allowed in
each channel. Very low values (2, 3, or 4) have the most
visible effect.</span> The default is 4.</dd>
<dt>dither</dt>
<dd>If <code>true</code>, dither the image. The default is
<code>false</code>.</dd>
</dl>
<h4>Returns</h4>
<p>A new image</p>
<h4>Example</h4>
<p class="rollover"><a href=
"javascript:popup('posterize.rb.html')"><img src=
"ex/posterize.jpg" alt="posterize example" onmouseover=
"this.src='ex/images/Flower_Hat.jpg'" onmouseout=
"this.src='ex/posterize.jpg'" title=
"Click to see the example script" /></a> <img src=
"ex/images/spin.gif" alt="" class="spin" title=
"Mouse over the example to see the original image" /></p>
<h4>See also</h4>
<p><a href="#ordered_dither">ordered_dither</a>, <a href=
"image3.html#quantize">quantize</a></p>
<h4>Magick API</h4>
<p>PosterizeImage</p>
</div>
<p class="spacer"> </p>
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