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<h3 class="section" id="Representing-Images-1"><span>32.3 Representing Images<a class="copiable-link" href="#Representing-Images-1"> ¶</a></span></h3>
<p>In general Octave supports four different kinds of images, grayscale
images, RGB images, binary images, and indexed images. A grayscale
image is represented with an M-by-N matrix in which each
element corresponds to the intensity of a pixel. An RGB image is
represented with an M-by-N-by-3 array where each
3-vector corresponds to the red, green, and blue intensities of each
pixel.
</p>
<p>The actual meaning of the value of a pixel in a grayscale or RGB
image depends on the class of the matrix. If the matrix is of class
<code class="code">double</code> pixel intensities are between 0 and 1, if it is of class
<code class="code">uint8</code> intensities are between 0 and 255, and if it is of class
<code class="code">uint16</code> intensities are between 0 and 65535.
</p>
<p>A binary image is an M-by-N matrix of class <code class="code">logical</code>.
A pixel in a binary image is black if it is <code class="code">false</code> and white
if it is <code class="code">true</code>.
</p>
<p>An indexed image consists of an M-by-N matrix of integers
and a C-by-3 color map. Each integer corresponds to an
index in the color map, and each row in the color map corresponds to
an RGB color. The color map must be of class <code class="code">double</code> with values
between 0 and 1.
</p>
<p>The following convenience functions are available for conversion between image
formats.
</p>
<a class="anchor" id="XREFim2double"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-im2double"><span><code class="def-type"><var class="var">dimg</var> =</code> <strong class="def-name">im2double</strong> <code class="def-code-arguments">(<var class="var">img</var>)</code><a class="copiable-link" href="#index-im2double"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-im2double-1"><span><code class="def-type"><var class="var">dimg</var> =</code> <strong class="def-name">im2double</strong> <code class="def-code-arguments">(<var class="var">img</var>, "indexed")</code><a class="copiable-link" href="#index-im2double-1"> ¶</a></span></dt>
<dd><p>Convert image to double precision.
</p>
<p>The conversion of <var class="var">img</var> to double precision, is dependent on the type of
input image. The following input classes are supported:
</p>
<dl class="table">
<dt>‘<samp class="samp">uint8, uint16, and int16</samp>’</dt>
<dd><p>The range of values from the class is scaled to the interval [0 1].
</p>
</dd>
<dt>‘<samp class="samp">logical</samp>’</dt>
<dd><p>True and false values are assigned a value of 1 and 0 respectively.
</p>
</dd>
<dt>‘<samp class="samp">single</samp>’</dt>
<dd><p>Values are cast to double.
</p>
</dd>
<dt>‘<samp class="samp">double</samp>’</dt>
<dd><p>Returns the same image.
</p>
</dd>
</dl>
<p>If <var class="var">img</var> is an indexed image, then the second argument should be the
string <code class="code">"indexed"</code>. If so, then <var class="var">img</var> must either be of floating
point class, or unsigned integer class and it will simply be cast to double.
If it is an integer class, an offset of +1 is applied.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="Numeric-Data-Types.html#XREFdouble">double</a>.
</p></dd></dl>
<a class="anchor" id="XREFgray2ind"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-gray2ind"><span><code class="def-type"><var class="var">img</var> =</code> <strong class="def-name">gray2ind</strong> <code class="def-code-arguments">(<var class="var">I</var>)</code><a class="copiable-link" href="#index-gray2ind"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-gray2ind-1"><span><code class="def-type"><var class="var">img</var> =</code> <strong class="def-name">gray2ind</strong> <code class="def-code-arguments">(<var class="var">I</var>, <var class="var">n</var>)</code><a class="copiable-link" href="#index-gray2ind-1"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-gray2ind-2"><span><code class="def-type"><var class="var">img</var> =</code> <strong class="def-name">gray2ind</strong> <code class="def-code-arguments">(<var class="var">BW</var>)</code><a class="copiable-link" href="#index-gray2ind-2"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-gray2ind-3"><span><code class="def-type"><var class="var">img</var> =</code> <strong class="def-name">gray2ind</strong> <code class="def-code-arguments">(<var class="var">BW</var>, <var class="var">n</var>)</code><a class="copiable-link" href="#index-gray2ind-3"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-gray2ind-4"><span><code class="def-type">[<var class="var">img</var>, <var class="var">map</var>] =</code> <strong class="def-name">gray2ind</strong> <code class="def-code-arguments">(…)</code><a class="copiable-link" href="#index-gray2ind-4"> ¶</a></span></dt>
<dd><p>Convert a grayscale or binary intensity image to an indexed image.
</p>
<p>The indexed image will consist of <var class="var">n</var> different intensity values.
If not given <var class="var">n</var> defaults to 64 for grayscale images or 2 for binary
black and white images.
</p>
<p>The output <var class="var">img</var> is of class uint8 if <var class="var">n</var> is less than or equal to
256; Otherwise the return class is uint16.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFind2gray">ind2gray</a>, <a class="ref" href="#XREFrgb2ind">rgb2ind</a>.
</p></dd></dl>
<a class="anchor" id="XREFind2gray"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-ind2gray"><span><code class="def-type"><var class="var">I</var> =</code> <strong class="def-name">ind2gray</strong> <code class="def-code-arguments">(<var class="var">x</var>, <var class="var">map</var>)</code><a class="copiable-link" href="#index-ind2gray"> ¶</a></span></dt>
<dd><p>Convert a color indexed image to a grayscale intensity image.
</p>
<p>The image <var class="var">x</var> must be an indexed image which will be converted using the
colormap <var class="var">map</var>. If <var class="var">map</var> does not contain enough colors for the
image, pixels in <var class="var">x</var> outside the range are mapped to the last color in
the map before conversion to grayscale.
</p>
<p>The output <var class="var">I</var> is of the same class as the input <var class="var">x</var> and may be
one of <code class="code">uint8</code>, <code class="code">uint16</code>, <code class="code">single</code>, or <code class="code">double</code>.
</p>
<p>Implementation Note: There are several ways of converting colors to
grayscale intensities. This functions uses the luminance value obtained
from <code class="code">rgb2gray</code> which is <code class="code">I = 0.299*R + 0.587*G + 0.114*B</code>.
Other possibilities include the value component from <code class="code">rgb2hsv</code> or
using a single color channel from <code class="code">ind2rgb</code>.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFgray2ind">gray2ind</a>, <a class="ref" href="#XREFind2rgb">ind2rgb</a>.
</p></dd></dl>
<a class="anchor" id="XREFrgb2ind"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-rgb2ind"><span><code class="def-type">[<var class="var">x</var>, <var class="var">map</var>] =</code> <strong class="def-name">rgb2ind</strong> <code class="def-code-arguments">(<var class="var">rgb</var>)</code><a class="copiable-link" href="#index-rgb2ind"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-rgb2ind-1"><span><code class="def-type">[<var class="var">x</var>, <var class="var">map</var>] =</code> <strong class="def-name">rgb2ind</strong> <code class="def-code-arguments">(<var class="var">R</var>, <var class="var">G</var>, <var class="var">B</var>)</code><a class="copiable-link" href="#index-rgb2ind-1"> ¶</a></span></dt>
<dd><p>Convert an image in red-green-blue (RGB) color space to an indexed image.
</p>
<p>The input image <var class="var">rgb</var> can be specified as a single matrix of size
MxNx3, or as three separate variables, <var class="var">R</var>, <var class="var">G</var>, and
<var class="var">B</var>, its three color channels, red, green, and blue.
</p>
<p>It outputs an indexed image <var class="var">x</var> and a colormap <var class="var">map</var> to interpret
an image exactly the same as the input. No dithering or other form of color
quantization is performed. The output class of the indexed image <var class="var">x</var>
can be uint8, uint16 or double, whichever is required to specify the
number of unique colors in the image (which will be equal to the number
of rows in <var class="var">map</var>) in order.
</p>
<p>Multi-dimensional indexed images (of size MxNx3xK) are also
supported, both via a single input (<var class="var">rgb</var>) or its three color channels
as separate variables.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFind2rgb">ind2rgb</a>, <a class="ref" href="Color-Conversion.html#XREFrgb2hsv">rgb2hsv</a>, <a class="ref" href="Color-Conversion.html#XREFrgb2gray">rgb2gray</a>.
</p></dd></dl>
<a class="anchor" id="XREFind2rgb"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-ind2rgb"><span><code class="def-type"><var class="var">rgb</var> =</code> <strong class="def-name">ind2rgb</strong> <code class="def-code-arguments">(<var class="var">x</var>, <var class="var">map</var>)</code><a class="copiable-link" href="#index-ind2rgb"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-ind2rgb-1"><span><code class="def-type">[<var class="var">R</var>, <var class="var">G</var>, <var class="var">B</var>] =</code> <strong class="def-name">ind2rgb</strong> <code class="def-code-arguments">(<var class="var">x</var>, <var class="var">map</var>)</code><a class="copiable-link" href="#index-ind2rgb-1"> ¶</a></span></dt>
<dd><p>Convert an indexed image to red, green, and blue color components.
</p>
<p>The image <var class="var">x</var> must be an indexed image which will be converted using the
colormap <var class="var">map</var>. If <var class="var">map</var> does not contain enough colors for the
image, pixels in <var class="var">x</var> outside the range are mapped to the last color in
the map.
</p>
<p>The output may be a single RGB image (MxNx3 matrix where M and N
are the original image <var class="var">x</var> dimensions, one for each of the red, green
and blue channels). Alternatively, the individual red, green, and blue
color matrices of size MxN may be returned.
</p>
<p>Multi-dimensional indexed images (of size MxNx1xK) are also
supported.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFrgb2ind">rgb2ind</a>, <a class="ref" href="#XREFind2gray">ind2gray</a>, <a class="ref" href="Color-Conversion.html#XREFhsv2rgb">hsv2rgb</a>.
</p></dd></dl>
<p>Octave also provides tools to produce and work with movie frame structures.
Those structures encapsulate the image data (<code class="code">"cdata"</code> field) together
with the corresponding colormap (<code class="code">"colormap"</code> field).
</p>
<a class="anchor" id="XREFgetframe"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-getframe"><span><code class="def-type"><var class="var">frame</var> =</code> <strong class="def-name">getframe</strong> <code class="def-code-arguments">()</code><a class="copiable-link" href="#index-getframe"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-getframe-1"><span><code class="def-type"><var class="var">frame</var> =</code> <strong class="def-name">getframe</strong> <code class="def-code-arguments">(<var class="var">hax</var>)</code><a class="copiable-link" href="#index-getframe-1"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-getframe-2"><span><code class="def-type"><var class="var">frame</var> =</code> <strong class="def-name">getframe</strong> <code class="def-code-arguments">(<var class="var">hfig</var>)</code><a class="copiable-link" href="#index-getframe-2"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-getframe-3"><span><code class="def-type"><var class="var">frame</var> =</code> <strong class="def-name">getframe</strong> <code class="def-code-arguments">(…, <var class="var">rect</var>)</code><a class="copiable-link" href="#index-getframe-3"> ¶</a></span></dt>
<dd>
<p>Capture a figure or axes as a movie frame structure.
</p>
<p>Without an argument, capture the current axes excluding ticklabels, title,
and x/y/zlabels. The returned structure <var class="var">frame</var> has a field
<code class="code">cdata</code>, which contains the actual image data in the form of an
NxMx3 (RGB) uint8 matrix in physical screen pixels, and a field
<code class="code">colormap</code> which is provided for <small class="sc">MATLAB</small> compatibility but is
always empty.
</p>
<p>If the first argument <var class="var">hax</var> is an axes handle, then capture this axes,
rather than the current axes returned by <code class="code">gca</code>.
</p>
<p>If the first argument <var class="var">hfig</var> is a figure handle then the entire
corresponding figure canvas is captured.
</p>
<p>Finally, if a second argument <var class="var">rect</var> is provided it must be a
four-element vector ([left bottom width height]) defining the region inside
the figure to be captured. Regardless of the figure <code class="code">"units"</code>
property, <var class="var">rect</var> must be defined in <strong class="strong">pixels</strong>.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFim2frame">im2frame</a>, <a class="ref" href="#XREFframe2im">frame2im</a>, <a class="ref" href="#XREFmovie">movie</a>.
</p></dd></dl>
<a class="anchor" id="XREFmovie"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-movie"><span><strong class="def-name">movie</strong> <code class="def-code-arguments">(<var class="var">mov</var>)</code><a class="copiable-link" href="#index-movie"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-movie-1"><span><strong class="def-name">movie</strong> <code class="def-code-arguments">(<var class="var">mov</var>, <var class="var">n</var>)</code><a class="copiable-link" href="#index-movie-1"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-movie-2"><span><strong class="def-name">movie</strong> <code class="def-code-arguments">(<var class="var">mov</var>, <var class="var">n</var>, <var class="var">fps</var>)</code><a class="copiable-link" href="#index-movie-2"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-movie-3"><span><strong class="def-name">movie</strong> <code class="def-code-arguments">(<var class="var">h</var>, …)</code><a class="copiable-link" href="#index-movie-3"> ¶</a></span></dt>
<dd><p>Play a movie defined by an array of frame structures.
</p>
<p>The movie <var class="var">mov</var> must be a struct array of frames with fields
<code class="code">"cdata"</code> and <code class="code">"colormap"</code>, as returned by the <code class="code">getframe</code>
function. By default all images are displayed once, at 12 fps, in the
current axes.
</p>
<p>The optional argument <var class="var">n</var> is a scalar or vector of integers that
controls the number of times the movie is displayed and which particular
frames are shown:
</p>
<dl class="table">
<dt>First element:</dt>
<dd>
<dl class="table">
<dt><var class="var">n</var>(1) > 0</dt>
<dd><p>Play the movie <var class="var">n</var>(1) times.
</p>
</dd>
<dt><var class="var">n</var>(1) < 0</dt>
<dd><p>Play the movie <code class="code">abs (<var class="var">n</var>(1)</code> times alternatively in forward and
backward order.
</p></dd>
</dl>
</dd>
<dt>Other elements (if any):</dt>
<dd><p>Indices of the frames in <var class="var">mov</var> that will be displayed.
</p></dd>
</dl>
<p>If the first argument is a handle to a figure or axes <var class="var">h</var>, the movie is
played in that figure or axes instead of the current axes.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFgetframe">getframe</a>, <a class="ref" href="#XREFim2frame">im2frame</a>, <a class="ref" href="#XREFframe2im">frame2im</a>.
</p></dd></dl>
<a class="anchor" id="XREFframe2im"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-frame2im"><span><code class="def-type">[<var class="var">x</var>, <var class="var">map</var>] =</code> <strong class="def-name">frame2im</strong> <code class="def-code-arguments">(<var class="var">frame</var>)</code><a class="copiable-link" href="#index-frame2im"> ¶</a></span></dt>
<dd><p>Convert movie frame to indexed image.
</p>
<p>A movie frame is simply a struct with the fields <code class="code">"cdata"</code> and
<code class="code">"colormap"</code>.
</p>
<p>Support for N-dimensional images or movies is given when <var class="var">frame</var> is a
struct array. In such cases, <var class="var">x</var> will be a MxNx1xK or MxNx3xK
for indexed and RGB movies respectively, with each frame concatenated
along the 4th dimension.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFim2frame">im2frame</a>, <a class="ref" href="#XREFgetframe">getframe</a>.
</p></dd></dl>
<a class="anchor" id="XREFim2frame"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-im2frame"><span><code class="def-type"><var class="var">frame</var> =</code> <strong class="def-name">im2frame</strong> <code class="def-code-arguments">(<var class="var">rgb</var>)</code><a class="copiable-link" href="#index-im2frame"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-im2frame-1"><span><code class="def-type"><var class="var">frame</var> =</code> <strong class="def-name">im2frame</strong> <code class="def-code-arguments">(<var class="var">x</var>, <var class="var">map</var>)</code><a class="copiable-link" href="#index-im2frame-1"> ¶</a></span></dt>
<dd><p>Convert image to movie frame.
</p>
<p>A movie frame is simply a struct with the fields <code class="code">"cdata"</code> and
<code class="code">"colormap"</code>.
</p>
<p>Support for N-dimensional images is given when each image projection,
matrix sizes of MxN and MxNx3 for RGB images, is concatenated
along the fourth dimension. In such cases, the returned value is a struct
array.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFframe2im">frame2im</a>.
</p></dd></dl>
<p>The <code class="code">colormap</code> function is used to change the colormap of the current
axes or figure.
</p>
<a class="anchor" id="XREFcolormap"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-colormap"><span><code class="def-type"><var class="var">cmap</var> =</code> <strong class="def-name">colormap</strong> <code class="def-code-arguments">()</code><a class="copiable-link" href="#index-colormap"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-colormap-1"><span><code class="def-type"><var class="var">cmap</var> =</code> <strong class="def-name">colormap</strong> <code class="def-code-arguments">(<var class="var">map</var>)</code><a class="copiable-link" href="#index-colormap-1"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-colormap-2"><span><code class="def-type"><var class="var">cmap</var> =</code> <strong class="def-name">colormap</strong> <code class="def-code-arguments">(<code class="code">"default"</code>)</code><a class="copiable-link" href="#index-colormap-2"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-colormap-3"><span><code class="def-type"><var class="var">cmap</var> =</code> <strong class="def-name">colormap</strong> <code class="def-code-arguments">(<var class="var">map_name</var>)</code><a class="copiable-link" href="#index-colormap-3"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-colormap-4"><span><code class="def-type"><var class="var">cmap</var> =</code> <strong class="def-name">colormap</strong> <code class="def-code-arguments">(<var class="var">hax</var>, …)</code><a class="copiable-link" href="#index-colormap-4"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-colormap-5"><span><code class="def-type"><var class="var">cmap</var> =</code> <strong class="def-name">colormap</strong> <code class="def-code-arguments">(<var class="var">hfig</var>, …)</code><a class="copiable-link" href="#index-colormap-5"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-colormap-6"><span><strong class="def-name">colormap</strong> <code class="def-code-arguments"><var class="var">map_name</var></code><a class="copiable-link" href="#index-colormap-6"> ¶</a></span></dt>
<dd><p>Query or set the current colormap.
</p>
<p>With no input arguments, <code class="code">colormap</code> returns the current color map. If
there is no current figure, a new figure will be opened and the default
color map will be returned.
</p>
<p><code class="code">colormap (<var class="var">map</var>)</code> sets the current colormap to <var class="var">map</var>. The
colormap should be an <var class="var">n</var> row by 3 column matrix. The columns
contain red, green, and blue intensities respectively. All entries
must be between 0 and 1 inclusive. The new colormap is returned.
</p>
<p><code class="code">colormap (<code class="code">"default"</code>)</code> restores the default colormap (the
<code class="code">viridis</code> map with 256 entries). The default colormap is returned.
</p>
<p>The map may also be specified by a string, <var class="var">map_name</var>, which
is the name of a function that returns a colormap.
</p>
<p>If the first argument <var class="var">hax</var> is an axes handle, then the colormap for
the specified axes is queried or set. If the first argument <var class="var">hfig</var> is a
figure handle, then the colormap for the specified figure is queried or set.
</p>
<p>For convenience, it is also possible to use this function with the
command form, <code class="code">colormap <var class="var">map_name</var></code>.
</p>
<p>The list of built-in colormaps is:
</p>
<table class="multitable">
<thead><tr><th width="15%">Map</th><th width="85%">Description</th></tr></thead>
<tbody><tr><td width="15%">viridis</td><td width="85%">default</td></tr>
<tr><td width="15%">turbo</td><td width="85%">colormap traversing blue, cyan, green, yellow, red; modern replacement for jet.</td></tr>
<tr><td width="15%">jet</td><td width="85%">colormap traversing blue, cyan, green, yellow, red.</td></tr>
<tr><td width="15%">cubehelix</td><td width="85%">colormap traversing black, blue, green, red, white with increasing intensity.</td></tr>
<tr><td width="15%">hsv</td><td width="85%">cyclic colormap traversing Hue, Saturation, Value space.</td></tr>
<tr><td width="15%">rainbow</td><td width="85%">colormap traversing red, yellow, blue, green, violet.</td></tr>
<tr><td width="15%">————-</td><td width="85%">———————————————————————————————</td></tr>
<tr><td width="15%">hot</td><td width="85%">colormap traversing black, red, orange, yellow, white.</td></tr>
<tr><td width="15%">cool</td><td width="85%">colormap traversing cyan, purple, magenta.</td></tr>
<tr><td width="15%">spring</td><td width="85%">colormap traversing magenta to yellow.</td></tr>
<tr><td width="15%">summer</td><td width="85%">colormap traversing green to yellow.</td></tr>
<tr><td width="15%">autumn</td><td width="85%">colormap traversing red, orange, yellow.</td></tr>
<tr><td width="15%">winter</td><td width="85%">colormap traversing blue to green.</td></tr>
<tr><td width="15%">————-</td><td width="85%">———————————————————————————————</td></tr>
<tr><td width="15%">gray</td><td width="85%">colormap traversing black to white in shades of gray.</td></tr>
<tr><td width="15%">bone</td><td width="85%">colormap traversing black, gray-blue, white.</td></tr>
<tr><td width="15%">copper</td><td width="85%">colormap traversing black to light copper.</td></tr>
<tr><td width="15%">pink</td><td width="85%">colormap traversing black, gray-pink, white.</td></tr>
<tr><td width="15%">ocean</td><td width="85%">colormap traversing black, dark-blue, white.</td></tr>
<tr><td width="15%">————-</td><td width="85%">———————————————————————————————</td></tr>
<tr><td width="15%">colorcube</td><td width="85%">equally spaced colors in RGB color space.</td></tr>
<tr><td width="15%">flag</td><td width="85%">cyclic 4-color map of red, white, blue, black.</td></tr>
<tr><td width="15%">lines</td><td width="85%">cyclic colormap with colors from axes <code class="code">"ColorOrder"</code> property.</td></tr>
<tr><td width="15%">prism</td><td width="85%">cyclic 6-color map of red, orange, yellow, green, blue, violet.</td></tr>
<tr><td width="15%">————-</td><td width="85%">———————————————————————————————</td></tr>
<tr><td width="15%">white</td><td width="85%">all white colormap (no colors).</td></tr>
</tbody>
</table>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFviridis">viridis</a>, <a class="ref" href="#XREFturbo">turbo</a>, <a class="ref" href="#XREFjet">jet</a>, <a class="ref" href="#XREFcubehelix">cubehelix</a>, <a class="ref" href="#XREFhsv">hsv</a>, <a class="ref" href="#XREFrainbow">rainbow</a>, <a class="ref" href="#XREFhot">hot</a>, <a class="ref" href="#XREFcool">cool</a>, <a class="ref" href="#XREFspring">spring</a>, <a class="ref" href="#XREFsummer">summer</a>, <a class="ref" href="#XREFautumn">autumn</a>, <a class="ref" href="#XREFwinter">winter</a>, <a class="ref" href="#XREFgray">gray</a>, <a class="ref" href="#XREFbone">bone</a>, <a class="ref" href="#XREFcopper">copper</a>, <a class="ref" href="#XREFpink">pink</a>, <a class="ref" href="#XREFocean">ocean</a>, <a class="ref" href="#XREFcolorcube">colorcube</a>, <a class="ref" href="#XREFflag">flag</a>, <a class="ref" href="#XREFlines">lines</a>, <a class="ref" href="#XREFprism">prism</a>, <a class="ref" href="#XREFwhite">white</a>.
</p></dd></dl>
<a class="anchor" id="XREFiscolormap"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-iscolormap"><span><code class="def-type"><var class="var">tf</var> =</code> <strong class="def-name">iscolormap</strong> <code class="def-code-arguments">(<var class="var">cmap</var>)</code><a class="copiable-link" href="#index-iscolormap"> ¶</a></span></dt>
<dd><p>Return true if <var class="var">cmap</var> is a colormap.
</p>
<p>A colormap is a real matrix, of class single or double, with 3 columns.
Each row represents a single color. The 3 columns contain red, green,
and blue intensities respectively.
</p>
<p>All values in a colormap should be in the [0 1] range but this is not
enforced. Each function must decide what to do for values outside this
range.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFcolormap">colormap</a>, <a class="ref" href="#XREFrgbplot">rgbplot</a>.
</p></dd></dl>
<p>The following functions return predefined colormaps, the same that can be
requested by name using the <code class="code">colormap</code> function.
</p>
<a class="anchor" id="XREFrgbplot"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-rgbplot"><span><strong class="def-name">rgbplot</strong> <code class="def-code-arguments">(<var class="var">cmap</var>)</code><a class="copiable-link" href="#index-rgbplot"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-rgbplot-1"><span><strong class="def-name">rgbplot</strong> <code class="def-code-arguments">(<var class="var">cmap</var>, <var class="var">style</var>)</code><a class="copiable-link" href="#index-rgbplot-1"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-rgbplot-2"><span><code class="def-type"><var class="var">h</var> =</code> <strong class="def-name">rgbplot</strong> <code class="def-code-arguments">(…)</code><a class="copiable-link" href="#index-rgbplot-2"> ¶</a></span></dt>
<dd><p>Plot the components of a colormap.
</p>
<p>Two different <var class="var">style</var>s are available for displaying the <var class="var">cmap</var>:
</p>
<dl class="table">
<dt>profile (default)</dt>
<dd><p>Plot the RGB line profile of the colormap for each of the channels (red,
green and blue) with the plot lines colored appropriately. Each line
represents the intensity of an RGB component across the colormap.
</p>
</dd>
<dt>composite</dt>
<dd><p>Draw the colormap across the X-axis so that the actual index colors are
visible rather than the individual color components.
</p>
</dd>
</dl>
<p>The optional return value <var class="var">h</var> is a graphics handle to the created plot.
</p>
<p>Run <code class="code">demo rgbplot</code> to see an example of <code class="code">rgbplot</code> and each style
option.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFcolormap">colormap</a>.
</p></dd></dl>
<a class="anchor" id="XREFautumn"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-autumn"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">autumn</strong> <code class="def-code-arguments">()</code><a class="copiable-link" href="#index-autumn"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-autumn-1"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">autumn</strong> <code class="def-code-arguments">(<var class="var">n</var>)</code><a class="copiable-link" href="#index-autumn-1"> ¶</a></span></dt>
<dd><p>Create color colormap.
This colormap ranges from red through orange to yellow.
</p>
<p>The argument <var class="var">n</var> must be a scalar.
If <var class="var">n</var> is not specified the length of the current colormap is used. If
there is no current colormap the default value of 256 is used.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFcolormap">colormap</a>.
</p></dd></dl>
<a class="anchor" id="XREFbone"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-bone"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">bone</strong> <code class="def-code-arguments">()</code><a class="copiable-link" href="#index-bone"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-bone-1"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">bone</strong> <code class="def-code-arguments">(<var class="var">n</var>)</code><a class="copiable-link" href="#index-bone-1"> ¶</a></span></dt>
<dd><p>Create color colormap. This colormap varies from black to white with
gray-blue shades.
</p>
<p>The argument <var class="var">n</var> must be a scalar.
If <var class="var">n</var> is not specified the length of the current colormap is used. If
there is no current colormap the default value of 256 is used.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFcolormap">colormap</a>.
</p></dd></dl>
<a class="anchor" id="XREFcolorcube"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-colorcube"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">colorcube</strong> <code class="def-code-arguments">()</code><a class="copiable-link" href="#index-colorcube"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-colorcube-1"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">colorcube</strong> <code class="def-code-arguments">(<var class="var">n</var>)</code><a class="copiable-link" href="#index-colorcube-1"> ¶</a></span></dt>
<dd><p>Create color colormap. This colormap is composed of as many equally
spaced colors (not grays) in the RGB color space as possible.
</p>
<p>If there are not a perfect number <var class="var">n</var> of regularly spaced colors then
the remaining entries in the colormap are gradients of pure red, green,
blue, and gray.
</p>
<p>The argument <var class="var">n</var> must be a scalar.
If <var class="var">n</var> is not specified the length of the current colormap is used. If
there is no current colormap the default value of 256 is used.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFcolormap">colormap</a>.
</p></dd></dl>
<a class="anchor" id="XREFcool"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-cool"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">cool</strong> <code class="def-code-arguments">()</code><a class="copiable-link" href="#index-cool"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-cool-1"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">cool</strong> <code class="def-code-arguments">(<var class="var">n</var>)</code><a class="copiable-link" href="#index-cool-1"> ¶</a></span></dt>
<dd><p>Create color colormap. The colormap varies from cyan to magenta.
</p>
<p>The argument <var class="var">n</var> must be a scalar.
If <var class="var">n</var> is not specified the length of the current colormap is used. If
there is no current colormap the default value of 256 is used.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFcolormap">colormap</a>.
</p></dd></dl>
<a class="anchor" id="XREFcopper"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-copper"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">copper</strong> <code class="def-code-arguments">()</code><a class="copiable-link" href="#index-copper"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-copper-1"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">copper</strong> <code class="def-code-arguments">(<var class="var">n</var>)</code><a class="copiable-link" href="#index-copper-1"> ¶</a></span></dt>
<dd><p>Create color colormap. This colormap varies from black to a light copper
tone.
</p>
<p>The argument <var class="var">n</var> must be a scalar.
If <var class="var">n</var> is not specified the length of the current colormap is used. If
there is no current colormap the default value of 256 is used.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFcolormap">colormap</a>.
</p></dd></dl>
<a class="anchor" id="XREFcubehelix"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-cubehelix"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">cubehelix</strong> <code class="def-code-arguments">()</code><a class="copiable-link" href="#index-cubehelix"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-cubehelix-1"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">cubehelix</strong> <code class="def-code-arguments">(<var class="var">n</var>)</code><a class="copiable-link" href="#index-cubehelix-1"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-cubehelix-2"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">cubehelix</strong> <code class="def-code-arguments">(<var class="var">n</var>, <var class="var">start</var>, <var class="var">rots</var>, <var class="var">hue</var>, <var class="var">gamma</var>)</code><a class="copiable-link" href="#index-cubehelix-2"> ¶</a></span></dt>
<dd><p>Create cubehelix colormap.
</p>
<p>This colormap varies from black to white going though blue, green, and red
tones while maintaining a monotonically increasing perception of intensity.
This is achieved by traversing a color cube from black to white through
a helix, hence the name cubehelix, while taking into account the perceived
brightness of each channel according to the NTSC specifications from 1953.
</p>
<div class="example">
<pre class="example-preformatted">rgbplot (cubehelix (256))
</pre></div>
<p>The argument <var class="var">n</var> must be a scalar.
If <var class="var">n</var> is not specified the length of the current colormap is used. If
there is no current colormap the default value of 256 is used.
</p>
<p>Reference: Green, D. A., 2011,
<cite class="cite">A colour scheme for the display of astronomical intensity
images</cite>, Bulletin of the Astronomical Society of India, 39, 289.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFcolormap">colormap</a>.
</p></dd></dl>
<a class="anchor" id="XREFflag"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-flag"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">flag</strong> <code class="def-code-arguments">()</code><a class="copiable-link" href="#index-flag"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-flag-1"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">flag</strong> <code class="def-code-arguments">(<var class="var">n</var>)</code><a class="copiable-link" href="#index-flag-1"> ¶</a></span></dt>
<dd><p>Create color colormap. This colormap cycles through red, white, blue, and
black with each index change.
</p>
<p>The argument <var class="var">n</var> must be a scalar.
If <var class="var">n</var> is not specified the length of the current colormap is used. If
there is no current colormap the default value of 256 is used.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFcolormap">colormap</a>.
</p></dd></dl>
<a class="anchor" id="XREFgray"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-gray"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">gray</strong> <code class="def-code-arguments">()</code><a class="copiable-link" href="#index-gray"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-gray-1"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">gray</strong> <code class="def-code-arguments">(<var class="var">n</var>)</code><a class="copiable-link" href="#index-gray-1"> ¶</a></span></dt>
<dd><p>Create gray colormap. This colormap varies from black to white with shades
of gray.
</p>
<p>The argument <var class="var">n</var> must be a scalar.
If <var class="var">n</var> is not specified the length of the current colormap is used. If
there is no current colormap the default value of 256 is used.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFcolormap">colormap</a>.
</p></dd></dl>
<a class="anchor" id="XREFhot"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-hot"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">hot</strong> <code class="def-code-arguments">()</code><a class="copiable-link" href="#index-hot"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-hot-1"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">hot</strong> <code class="def-code-arguments">(<var class="var">n</var>)</code><a class="copiable-link" href="#index-hot-1"> ¶</a></span></dt>
<dd><p>Create color colormap. This colormap ranges from black through dark red,
red, orange, yellow, to white.
</p>
<p>The argument <var class="var">n</var> must be a scalar.
If <var class="var">n</var> is not specified the length of the current colormap is used. If
there is no current colormap the default value of 256 is used.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFcolormap">colormap</a>.
</p></dd></dl>
<a class="anchor" id="XREFhsv"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-hsv"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">hsv</strong> <code class="def-code-arguments">()</code><a class="copiable-link" href="#index-hsv"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-hsv-1"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">hsv</strong> <code class="def-code-arguments">(<var class="var">n</var>)</code><a class="copiable-link" href="#index-hsv-1"> ¶</a></span></dt>
<dd><p>Create color colormap. This colormap begins with red, changes through
yellow, green, cyan, blue, and magenta, before returning to red.
</p>
<p>It is useful for displaying periodic functions. The map is obtained by
linearly varying the hue through all possible values while keeping constant
maximum saturation and value. The equivalent code is
<code class="code">hsv2rgb ([(0:N-1)'/N, ones(N,2)])</code>.
</p>
<p>The argument <var class="var">n</var> must be a scalar.
If <var class="var">n</var> is not specified the length of the current colormap is used. If
there is no current colormap the default value of 256 is used.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFcolormap">colormap</a>.
</p></dd></dl>
<a class="anchor" id="XREFjet"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-jet"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">jet</strong> <code class="def-code-arguments">()</code><a class="copiable-link" href="#index-jet"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-jet-1"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">jet</strong> <code class="def-code-arguments">(<var class="var">n</var>)</code><a class="copiable-link" href="#index-jet-1"> ¶</a></span></dt>
<dd><p>Create color colormap. This colormap ranges from dark blue through blue,
cyan, green, yellow, red, to dark red.
</p>
<p>The argument <var class="var">n</var> must be a scalar.
If <var class="var">n</var> is not specified the length of the current colormap is used. If
there is no current colormap the default value of 256 is used.
</p>
<p>Programming Note: The <code class="code">jet</code> colormap is not perceptually uniform.
Try the <code class="code">viridis</code> colormap if that is important. For a drop-in
replacement for <code class="code">jet</code> with better perceptual characteristics try
the <code class="code">turbo</code> colormap.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFcolormap">colormap</a>, <a class="ref" href="#XREFturbo">turbo</a>.
</p></dd></dl>
<a class="anchor" id="XREFlines"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-lines"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">lines</strong> <code class="def-code-arguments">()</code><a class="copiable-link" href="#index-lines"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-lines-1"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">lines</strong> <code class="def-code-arguments">(<var class="var">n</var>)</code><a class="copiable-link" href="#index-lines-1"> ¶</a></span></dt>
<dd><p>Create color colormap. This colormap is composed of the list of colors
in the current axes <code class="code">"ColorOrder"</code> property. The default is blue,
orange, yellow, purple, green, light blue, and dark red.
</p>
<p>The argument <var class="var">n</var> must be a scalar.
If <var class="var">n</var> is not specified the length of the current colormap is used. If
there is no current colormap the default value of 256 is used.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFcolormap">colormap</a>.
</p></dd></dl>
<a class="anchor" id="XREFocean"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-ocean"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">ocean</strong> <code class="def-code-arguments">()</code><a class="copiable-link" href="#index-ocean"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-ocean-1"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">ocean</strong> <code class="def-code-arguments">(<var class="var">n</var>)</code><a class="copiable-link" href="#index-ocean-1"> ¶</a></span></dt>
<dd><p>Create color colormap. This colormap varies from black to white with shades
of blue.
</p>
<p>The argument <var class="var">n</var> must be a scalar.
If <var class="var">n</var> is not specified the length of the current colormap is used. If
there is no current colormap the default value of 256 is used.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFcolormap">colormap</a>.
</p></dd></dl>
<a class="anchor" id="XREFpink"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-pink"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">pink</strong> <code class="def-code-arguments">()</code><a class="copiable-link" href="#index-pink"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-pink-1"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">pink</strong> <code class="def-code-arguments">(<var class="var">n</var>)</code><a class="copiable-link" href="#index-pink-1"> ¶</a></span></dt>
<dd><p>Create color colormap. This colormap varies from black to white with
shades of gray-pink.
</p>
<p>This colormap gives a sepia tone when used on grayscale images.
</p>
<p>The argument <var class="var">n</var> must be a scalar.
If <var class="var">n</var> is not specified the length of the current colormap is used. If
there is no current colormap the default value of 256 is used.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFcolormap">colormap</a>.
</p></dd></dl>
<a class="anchor" id="XREFprism"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-prism"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">prism</strong> <code class="def-code-arguments">()</code><a class="copiable-link" href="#index-prism"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-prism-1"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">prism</strong> <code class="def-code-arguments">(<var class="var">n</var>)</code><a class="copiable-link" href="#index-prism-1"> ¶</a></span></dt>
<dd><p>Create color colormap. This colormap cycles through red, orange, yellow,
green, blue and violet with each index change.
</p>
<p>The argument <var class="var">n</var> must be a scalar.
If <var class="var">n</var> is not specified the length of the current colormap is used. If
there is no current colormap the default value of 256 is used.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFcolormap">colormap</a>.
</p></dd></dl>
<a class="anchor" id="XREFrainbow"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-rainbow"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">rainbow</strong> <code class="def-code-arguments">()</code><a class="copiable-link" href="#index-rainbow"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-rainbow-1"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">rainbow</strong> <code class="def-code-arguments">(<var class="var">n</var>)</code><a class="copiable-link" href="#index-rainbow-1"> ¶</a></span></dt>
<dd><p>Create color colormap. This colormap ranges from red through orange,
yellow, green, blue, to violet.
</p>
<p>The argument <var class="var">n</var> must be a scalar.
If <var class="var">n</var> is not specified the length of the current colormap is used. If
there is no current colormap the default value of 256 is used.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFcolormap">colormap</a>.
</p></dd></dl>
<a class="anchor" id="XREFspring"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-spring"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">spring</strong> <code class="def-code-arguments">()</code><a class="copiable-link" href="#index-spring"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-spring-1"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">spring</strong> <code class="def-code-arguments">(<var class="var">n</var>)</code><a class="copiable-link" href="#index-spring-1"> ¶</a></span></dt>
<dd><p>Create color colormap. This colormap varies from magenta to yellow.
</p>
<p>The argument <var class="var">n</var> must be a scalar.
If <var class="var">n</var> is not specified the length of the current colormap is used. If
there is no current colormap the default value of 256 is used.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFcolormap">colormap</a>.
</p></dd></dl>
<a class="anchor" id="XREFsummer"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-summer"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">summer</strong> <code class="def-code-arguments">()</code><a class="copiable-link" href="#index-summer"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-summer-1"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">summer</strong> <code class="def-code-arguments">(<var class="var">n</var>)</code><a class="copiable-link" href="#index-summer-1"> ¶</a></span></dt>
<dd><p>Create color colormap. This colormap varies from green to yellow.
</p>
<p>The argument <var class="var">n</var> must be a scalar.
If <var class="var">n</var> is not specified the length of the current colormap is used. If
there is no current colormap the default value of 256 is used.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFcolormap">colormap</a>.
</p></dd></dl>
<a class="anchor" id="XREFturbo"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-turbo"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">turbo</strong> <code class="def-code-arguments">()</code><a class="copiable-link" href="#index-turbo"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-turbo-1"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">turbo</strong> <code class="def-code-arguments">(<var class="var">n</var>)</code><a class="copiable-link" href="#index-turbo-1"> ¶</a></span></dt>
<dd><p>Create color colormap. This colormap ranges from dark blue through green
to dark red; similar to the outdated <code class="code">jet</code> colormap but perceptually
uniform.
</p>
<p>The argument <var class="var">n</var> must be a scalar.
If <var class="var">n</var> is not specified the length of the current colormap is used. If
there is no current colormap the default value of 256 is used.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFcolormap">colormap</a>.
</p></dd></dl>
<a class="anchor" id="XREFviridis"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-viridis"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">viridis</strong> <code class="def-code-arguments">()</code><a class="copiable-link" href="#index-viridis"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-viridis-1"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">viridis</strong> <code class="def-code-arguments">(<var class="var">n</var>)</code><a class="copiable-link" href="#index-viridis-1"> ¶</a></span></dt>
<dd><p>Create color colormap. This colormap ranges from dark purplish-blue through
blue, green, to yellow.
</p>
<p>The argument <var class="var">n</var> must be a scalar.
If <var class="var">n</var> is not specified the length of the current colormap is used. If
there is no current colormap the default value of 256 is used.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFcolormap">colormap</a>.
</p></dd></dl>
<a class="anchor" id="XREFwhite"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-white"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">white</strong> <code class="def-code-arguments">()</code><a class="copiable-link" href="#index-white"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-white-1"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">white</strong> <code class="def-code-arguments">(<var class="var">n</var>)</code><a class="copiable-link" href="#index-white-1"> ¶</a></span></dt>
<dd><p>Create color colormap. This colormap is completely white.
</p>
<p>The argument <var class="var">n</var> must be a scalar.
If <var class="var">n</var> is not specified the length of the current colormap is used. If
there is no current colormap the default value of 256 is used.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFcolormap">colormap</a>.
</p></dd></dl>
<a class="anchor" id="XREFwinter"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-winter"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">winter</strong> <code class="def-code-arguments">()</code><a class="copiable-link" href="#index-winter"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-winter-1"><span><code class="def-type"><var class="var">map</var> =</code> <strong class="def-name">winter</strong> <code class="def-code-arguments">(<var class="var">n</var>)</code><a class="copiable-link" href="#index-winter-1"> ¶</a></span></dt>
<dd><p>Create color colormap. This colormap varies from blue to green.
</p>
<p>The argument <var class="var">n</var> must be a scalar.
If <var class="var">n</var> is not specified the length of the current colormap is used. If
there is no current colormap the default value of 256 is used.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFcolormap">colormap</a>.
</p></dd></dl>
<a class="anchor" id="XREFcontrast"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-contrast"><span><code class="def-type"><var class="var">cmap</var> =</code> <strong class="def-name">contrast</strong> <code class="def-code-arguments">(<var class="var">x</var>)</code><a class="copiable-link" href="#index-contrast"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-contrast-1"><span><code class="def-type"><var class="var">cmap</var> =</code> <strong class="def-name">contrast</strong> <code class="def-code-arguments">(<var class="var">x</var>, <var class="var">n</var>)</code><a class="copiable-link" href="#index-contrast-1"> ¶</a></span></dt>
<dd><p>Return a gray colormap that maximizes the contrast in an image.
</p>
<p>The returned colormap will have <var class="var">n</var> rows. If <var class="var">n</var> is not defined
then the size of the current colormap is used.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFcolormap">colormap</a>, <a class="ref" href="#XREFbrighten">brighten</a>.
</p></dd></dl>
<p>The following three functions modify the existing colormap rather than
replace it.
</p>
<a class="anchor" id="XREFbrighten"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-brighten"><span><code class="def-type"><var class="var">map_out</var> =</code> <strong class="def-name">brighten</strong> <code class="def-code-arguments">(<var class="var">beta</var>)</code><a class="copiable-link" href="#index-brighten"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-brighten-1"><span><code class="def-type"><var class="var">map_out</var> =</code> <strong class="def-name">brighten</strong> <code class="def-code-arguments">(<var class="var">map</var>, <var class="var">beta</var>)</code><a class="copiable-link" href="#index-brighten-1"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-brighten-2"><span><code class="def-type"><var class="var">map_out</var> =</code> <strong class="def-name">brighten</strong> <code class="def-code-arguments">(<var class="var">h</var>, <var class="var">beta</var>)</code><a class="copiable-link" href="#index-brighten-2"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-brighten-3"><span><strong class="def-name">brighten</strong> <code class="def-code-arguments">(…)</code><a class="copiable-link" href="#index-brighten-3"> ¶</a></span></dt>
<dd><p>Brighten or darken a colormap.
</p>
<p>The argument <var class="var">beta</var> must be a scalar between -1 and 1, where a negative
value darkens and a positive value brightens the colormap.
</p>
<p>If the <var class="var">map</var> argument is omitted, the function is applied to the current
colormap.
</p>
<p>The first argument can also be a valid graphics handle <var class="var">h</var>, in which
case <code class="code">brighten</code> is applied to the colormap associated with this handle.
</p>
<p>If no output is specified then the result is written to the current
colormap.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFcolormap">colormap</a>, <a class="ref" href="#XREFcontrast">contrast</a>.
</p></dd></dl>
<a class="anchor" id="XREFspinmap"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-spinmap"><span><strong class="def-name">spinmap</strong> <code class="def-code-arguments">()</code><a class="copiable-link" href="#index-spinmap"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-spinmap-1"><span><strong class="def-name">spinmap</strong> <code class="def-code-arguments">(<var class="var">t</var>)</code><a class="copiable-link" href="#index-spinmap-1"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-spinmap-2"><span><strong class="def-name">spinmap</strong> <code class="def-code-arguments">(<var class="var">t</var>, <var class="var">inc</var>)</code><a class="copiable-link" href="#index-spinmap-2"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-spinmap-3"><span><strong class="def-name">spinmap</strong> <code class="def-code-arguments">("inf")</code><a class="copiable-link" href="#index-spinmap-3"> ¶</a></span></dt>
<dd><p>Cycle the colormap for <var class="var">t</var> seconds with a color increment of <var class="var">inc</var>.
</p>
<p>Both parameters are optional. The default cycle time is 5 seconds and the
default increment is 2. If the option <code class="code">"inf"</code> is given then cycle
continuously until <kbd class="kbd">Control-C</kbd> is pressed.
</p>
<p>When rotating, the original color 1 becomes color 2, color 2 becomes
color 3, etc. A positive or negative increment is allowed and a higher
value of <var class="var">inc</var> will cause faster cycling through the colormap.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFcolormap">colormap</a>.
</p></dd></dl>
<a class="anchor" id="XREFwhitebg"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-whitebg"><span><strong class="def-name">whitebg</strong> <code class="def-code-arguments">()</code><a class="copiable-link" href="#index-whitebg"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-whitebg-1"><span><strong class="def-name">whitebg</strong> <code class="def-code-arguments">(<var class="var">color</var>)</code><a class="copiable-link" href="#index-whitebg-1"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-whitebg-2"><span><strong class="def-name">whitebg</strong> <code class="def-code-arguments">("none")</code><a class="copiable-link" href="#index-whitebg-2"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-whitebg-3"><span><strong class="def-name">whitebg</strong> <code class="def-code-arguments">(<var class="var">hfig</var>)</code><a class="copiable-link" href="#index-whitebg-3"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-whitebg-4"><span><strong class="def-name">whitebg</strong> <code class="def-code-arguments">(<var class="var">hfig</var>, <var class="var">color</var>)</code><a class="copiable-link" href="#index-whitebg-4"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-whitebg-5"><span><strong class="def-name">whitebg</strong> <code class="def-code-arguments">(<var class="var">hfig</var>, "none")</code><a class="copiable-link" href="#index-whitebg-5"> ¶</a></span></dt>
<dd><p>Invert the colors in the current color scheme.
</p>
<p>The root properties are also inverted such that all subsequent plots will
use the new color scheme.
</p>
<p>If the optional argument <var class="var">color</var> is present then the background color
is set to <var class="var">color</var> rather than inverted. <var class="var">color</var> may be a string
representing one of the eight known colors or an RGB triplet. The special
string argument <code class="code">"none"</code> restores the plot to the factory default
colors.
</p>
<p>If the first argument <var class="var">hfig</var> is a figure handle or list of figure
handles, then operate on these figures rather than the current figure
returned by <code class="code">gcf</code>. The root properties will not be changed unless 0
is in the list of figures.
</p>
<p>Programming Note: <code class="code">whitebg</code> operates by changing the color properties
of the children of the specified figures. Only objects with a single color
are affected. For example, a patch with a single <code class="code">"FaceColor"</code> will
be changed, but a patch with shading (<code class="code">"interp"</code>) will not be
modified. For inversion, the new color is simply the inversion in RGB
space: <code class="code"><var class="var">cnew</var> = [1-<var class="var">R</var> 1-<var class="var">G</var> 1-<var class="var">B</var>]</code>. When a color
is specified, the axes and figure are set to the new color, and the color
of child objects are then adjusted to have some contrast (visibility)
against the new background.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="Managing-Default-Properties.html#XREFreset">reset</a>, <a class="ref" href="Handle-Functions.html#XREFget">get</a>, <a class="ref" href="Handle-Functions.html#XREFset">set</a>.
</p></dd></dl>
<p>The following functions can be used to manipulate colormaps.
</p>
<a class="anchor" id="XREFcmunique"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-cmunique"><span><code class="def-type">[<var class="var">Y</var>, <var class="var">newmap</var>] =</code> <strong class="def-name">cmunique</strong> <code class="def-code-arguments">(<var class="var">X</var>, <var class="var">map</var>)</code><a class="copiable-link" href="#index-cmunique"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-cmunique-1"><span><code class="def-type">[<var class="var">Y</var>, <var class="var">newmap</var>] =</code> <strong class="def-name">cmunique</strong> <code class="def-code-arguments">(<var class="var">RGB</var>)</code><a class="copiable-link" href="#index-cmunique-1"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-cmunique-2"><span><code class="def-type">[<var class="var">Y</var>, <var class="var">newmap</var>] =</code> <strong class="def-name">cmunique</strong> <code class="def-code-arguments">(<var class="var">I</var>)</code><a class="copiable-link" href="#index-cmunique-2"> ¶</a></span></dt>
<dd><p>Convert an input image <var class="var">X</var> to an output indexed image <var class="var">Y</var> which uses
the smallest colormap possible <var class="var">newmap</var>.
</p>
<p>When the input is an indexed image (<var class="var">X</var> with colormap <var class="var">map</var>) the
output is a colormap <var class="var">newmap</var> from which any repeated rows have been
eliminated. The output image, <var class="var">Y</var>, is the original input image with
the indices adjusted to match the new, possibly smaller, colormap.
</p>
<p>When the input is an RGB image (an MxNx3 array), the output
colormap will contain one entry for every unique color in the original
image. In the worst case the new map could have as many rows as the
number of pixels in the original image.
</p>
<p>When the input is a grayscale image <var class="var">I</var>, the output colormap will
contain one entry for every unique intensity value in the original image.
In the worst case the new map could have as many rows as the number of
pixels in the original image.
</p>
<p>Implementation Details:
</p>
<p><var class="var">newmap</var> is always an Mx3 matrix, even if the input image is
an intensity grayscale image <var class="var">I</var> (all three RGB planes are
assigned the same value).
</p>
<p>The output image is of class uint8 if the size of the new colormap is
less than or equal to 256. Otherwise, the output image is of class double.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFrgb2ind">rgb2ind</a>, <a class="ref" href="#XREFgray2ind">gray2ind</a>.
</p></dd></dl>
<a class="anchor" id="XREFcmpermute"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-cmpermute"><span><code class="def-type">[<var class="var">Y</var>, <var class="var">newmap</var>] =</code> <strong class="def-name">cmpermute</strong> <code class="def-code-arguments">(<var class="var">X</var>, <var class="var">map</var>)</code><a class="copiable-link" href="#index-cmpermute"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-cmpermute-1"><span><code class="def-type">[<var class="var">Y</var>, <var class="var">newmap</var>] =</code> <strong class="def-name">cmpermute</strong> <code class="def-code-arguments">(<var class="var">X</var>, <var class="var">map</var>, <var class="var">index</var>)</code><a class="copiable-link" href="#index-cmpermute-1"> ¶</a></span></dt>
<dd><p>Reorder colors in a colormap.
</p>
<p>When called with only two arguments, <code class="code">cmpermute</code> randomly rearranges
the colormap <var class="var">map</var> and returns a new colormap <var class="var">newmap</var>. It also
returns the indexed image <var class="var">Y</var> which is the equivalent of the original
input image <var class="var">X</var> when displayed using <var class="var">newmap</var>.
</p>
<p>When called with an optional third argument the order of colors in the new
colormap is defined by <var class="var">index</var>.
</p>
<p><strong class="strong">Caution:</strong> <var class="var">index</var> should not have repeated elements or the
function will fail.
</p>
</dd></dl>
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