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Next: <a rel="next" accesskey="n" href="Plotting-on-top-of-Images.html#Plotting-on-top-of-Images">Plotting on top of Images</a>,
Previous: <a rel="previous" accesskey="p" href="Displaying-Images.html#Displaying-Images">Displaying Images</a>,
Up: <a rel="up" accesskey="u" href="Image-Processing.html#Image-Processing">Image Processing</a>
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<h3 class="section">32.3 Representing Images</h3>
<p>In general Octave supports four different kinds of images, gray-scale
images, RGB images, binary images, and indexed images. A gray-scale
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>The actual meaning of the value of a pixel in a gray-scale or RGB
image depends on the class of the matrix. If the matrix is of class
<code>double</code> pixel intensities are between 0 and 1, if it is of class
<code>uint8</code> intensities are between 0 and 255, and if it is of class
<code>uint16</code> intensities are between 0 and 65535.
<p>A binary image is an M-by-N matrix of class <code>logical</code>.
A pixel in a binary image is black if it is <code>false</code> and white
if it is <code>true</code>.
<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>double</code> with values
between 0 and 1.
<!-- gray2ind scripts/image/gray2ind.m -->
<p><a name="doc_002dgray2ind"></a>
<div class="defun">
— Function File: [<var>img</var>, <var>map</var>] = <b>gray2ind</b> (<var>I, n</var>)<var><a name="index-gray2ind-2912"></a></var><br>
<blockquote><p>Convert a gray scale intensity image to an Octave indexed image.
The indexed image will consist of <var>n</var> different intensity values. If not
given <var>n</var> will default to 64.
</p></blockquote></div>
<!-- ind2gray scripts/image/ind2gray.m -->
<p><a name="doc_002dind2gray"></a>
<div class="defun">
— Function File: <b>ind2gray</b> (<var>x, map</var>)<var><a name="index-ind2gray-2913"></a></var><br>
<blockquote><p>Convert an Octave indexed image to a gray scale intensity image.
If <var>map</var> is omitted, the current colormap is used to determine the
intensities.
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<p class="noindent"><strong>See also:</strong> <a href="doc_002dgray2ind.html#doc_002dgray2ind">gray2ind</a>, <a href="doc_002drgb2ntsc.html#doc_002drgb2ntsc">rgb2ntsc</a>, <a href="doc_002dimage.html#doc_002dimage">image</a>, <a href="doc_002dcolormap.html#doc_002dcolormap">colormap</a>.
</p></blockquote></div>
<!-- rgb2ind scripts/image/rgb2ind.m -->
<p><a name="doc_002drgb2ind"></a>
<div class="defun">
— Function File: [<var>x</var>, <var>map</var>] = <b>rgb2ind</b> (<var>rgb</var>)<var><a name="index-rgb2ind-2914"></a></var><br>
— Function File: [<var>x</var>, <var>map</var>] = <b>rgb2ind</b> (<var>R, G, B</var>)<var><a name="index-rgb2ind-2915"></a></var><br>
<blockquote><p>Convert an RGB image to an Octave indexed image.
<!-- Texinfo @sp should work but in practice produces ugly results for HTML. -->
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<p class="noindent"><strong>See also:</strong> <a href="doc_002dind2rgb.html#doc_002dind2rgb">ind2rgb</a>, <a href="doc_002drgb2ntsc.html#doc_002drgb2ntsc">rgb2ntsc</a>.
</p></blockquote></div>
<!-- ind2rgb scripts/image/ind2rgb.m -->
<p><a name="doc_002dind2rgb"></a>
<div class="defun">
— Function File: <var>rgb</var> = <b>ind2rgb</b> (<var>x, map</var>)<var><a name="index-ind2rgb-2916"></a></var><br>
— Function File: [<var>R</var>, <var>R</var>, <var>R</var>] = <b>ind2rgb</b> (<var>x, map</var>)<var><a name="index-ind2rgb-2917"></a></var><br>
<blockquote><p>Convert an indexed image to red, green, and blue color components.
If the colormap doesn't contain enough colors, pad it with the
last color in the map.
If <var>map</var> is omitted, the current colormap is used for the conversion.
<!-- Texinfo @sp should work but in practice produces ugly results for HTML. -->
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<p class="noindent"><strong>See also:</strong> <a href="doc_002drgb2ind.html#doc_002drgb2ind">rgb2ind</a>, <a href="doc_002dimage.html#doc_002dimage">image</a>, <a href="doc_002dimshow.html#doc_002dimshow">imshow</a>, <a href="doc_002dind2gray.html#doc_002dind2gray">ind2gray</a>, <a href="doc_002dgray2ind.html#doc_002dgray2ind">gray2ind</a>.
</p></blockquote></div>
<!-- colormap scripts/image/colormap.m -->
<p><a name="doc_002dcolormap"></a>
<div class="defun">
— Function File: <b>colormap</b> (<var>map</var>)<var><a name="index-colormap-2918"></a></var><br>
— Function File: <b>colormap</b> (<var>"default"</var>)<var><a name="index-colormap-2919"></a></var><br>
<blockquote><p>Set the current colormap.
<p><code>colormap (</code><var>map</var><code>)</code> sets the current colormap to <var>map</var>. The
color map should be an <var>n</var> row by 3 column matrix. The columns
contain red, green, and blue intensities respectively. All entries
should be between 0 and 1 inclusive. The new colormap is returned.
<p><code>colormap ("default")</code> restores the default colormap (the
<code>jet</code> map with 64 entries). The default colormap is returned.
<p>With no arguments, <code>colormap</code> returns the current color map.
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<p class="noindent"><strong>See also:</strong> <a href="doc_002djet.html#doc_002djet">jet</a>.
</p></blockquote></div>
<!-- autumn scripts/image/autumn.m -->
<p><a name="doc_002dautumn"></a>
<div class="defun">
— Function File: <var>map</var> = <b>autumn</b> ()<var><a name="index-autumn-2920"></a></var><br>
— Function File: <var>map</var> = <b>autumn</b> (<var>n</var>)<var><a name="index-autumn-2921"></a></var><br>
<blockquote><p>Create color colormap. This colormap ranges from red through orange
to yellow.
The argument <var>n</var> must be a scalar.
If unspecified, the length of the current colormap, or 64, is used.
<!-- Texinfo @sp should work but in practice produces ugly results for HTML. -->
<!-- A simple blank line produces the correct behavior. -->
<!-- @sp 1 -->
<p class="noindent"><strong>See also:</strong> <a href="doc_002dcolormap.html#doc_002dcolormap">colormap</a>.
</p></blockquote></div>
<!-- bone scripts/image/bone.m -->
<p><a name="doc_002dbone"></a>
<div class="defun">
— Function File: <var>map</var> = <b>bone</b> ()<var><a name="index-bone-2922"></a></var><br>
— Function File: <var>map</var> = <b>bone</b> (<var>n</var>)<var><a name="index-bone-2923"></a></var><br>
<blockquote><p>Create color colormap. This colormap varies from black to white with
gray-blue shades.
The argument <var>n</var> must be a scalar.
If unspecified, the length of the current colormap, or 64, is used.
<!-- Texinfo @sp should work but in practice produces ugly results for HTML. -->
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<!-- @sp 1 -->
<p class="noindent"><strong>See also:</strong> <a href="doc_002dcolormap.html#doc_002dcolormap">colormap</a>.
</p></blockquote></div>
<!-- cool scripts/image/cool.m -->
<p><a name="doc_002dcool"></a>
<div class="defun">
— Function File: <var>map</var> = <b>cool</b> ()<var><a name="index-cool-2924"></a></var><br>
— Function File: <var>map</var> = <b>cool</b> (<var>n</var>)<var><a name="index-cool-2925"></a></var><br>
<blockquote><p>Create color colormap. The colormap varies from cyan to magenta.
The argument <var>n</var> must be a scalar.
If unspecified, the length of the current colormap, or 64, is used.
<!-- Texinfo @sp should work but in practice produces ugly results for HTML. -->
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<p class="noindent"><strong>See also:</strong> <a href="doc_002dcolormap.html#doc_002dcolormap">colormap</a>.
</p></blockquote></div>
<!-- copper scripts/image/copper.m -->
<p><a name="doc_002dcopper"></a>
<div class="defun">
— Function File: <var>map</var> = <b>copper</b> ()<var><a name="index-copper-2926"></a></var><br>
— Function File: <var>map</var> = <b>copper</b> (<var>n</var>)<var><a name="index-copper-2927"></a></var><br>
<blockquote><p>Create color colormap. This colormap varies from black to
a light copper tone.
The argument <var>n</var> must be a scalar.
If unspecified, the length of the current colormap, or 64, is used.
<!-- Texinfo @sp should work but in practice produces ugly results for HTML. -->
<!-- A simple blank line produces the correct behavior. -->
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<p class="noindent"><strong>See also:</strong> <a href="doc_002dcolormap.html#doc_002dcolormap">colormap</a>.
</p></blockquote></div>
<!-- flag scripts/image/flag.m -->
<p><a name="doc_002dflag"></a>
<div class="defun">
— Function File: <var>map</var> = <b>flag</b> ()<var><a name="index-flag-2928"></a></var><br>
— Function File: <var>map</var> = <b>flag</b> (<var>n</var>)<var><a name="index-flag-2929"></a></var><br>
<blockquote><p>Create color colormap. This colormap cycles through red, white, blue
and black with each index change.
The argument <var>n</var> must be a scalar.
If unspecified, the length of the current colormap, or 64, is used.
<!-- Texinfo @sp should work but in practice produces ugly results for HTML. -->
<!-- A simple blank line produces the correct behavior. -->
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<p class="noindent"><strong>See also:</strong> <a href="doc_002dcolormap.html#doc_002dcolormap">colormap</a>.
</p></blockquote></div>
<!-- gray scripts/image/gray.m -->
<p><a name="doc_002dgray"></a>
<div class="defun">
— Function File: <var>map</var> = <b>gray</b> ()<var><a name="index-gray-2930"></a></var><br>
— Function File: <var>map</var> = <b>gray</b> (<var>n</var>)<var><a name="index-gray-2931"></a></var><br>
<blockquote><p>Create gray colormap. This colormap varies from black to white with
shades of gray.
The argument <var>n</var> must be a scalar.
If unspecified, the length of the current colormap, or 64, is used.
</p></blockquote></div>
<!-- hot scripts/image/hot.m -->
<p><a name="doc_002dhot"></a>
<div class="defun">
— Function File: <var>map</var> = <b>hot</b> ()<var><a name="index-hot-2932"></a></var><br>
— Function File: <var>map</var> = <b>hot</b> (<var>n</var>)<var><a name="index-hot-2933"></a></var><br>
<blockquote><p>Create color colormap. This colormap ranges from black through dark red,
red, orange, yellow, to white.
The argument <var>n</var> must be a scalar.
If unspecified, the length of the current colormap, or 64, is used.
<!-- Texinfo @sp should work but in practice produces ugly results for HTML. -->
<!-- A simple blank line produces the correct behavior. -->
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<p class="noindent"><strong>See also:</strong> <a href="doc_002dcolormap.html#doc_002dcolormap">colormap</a>.
</p></blockquote></div>
<!-- hsv scripts/image/hsv.m -->
<p><a name="doc_002dhsv"></a>
<div class="defun">
— Function File: <b>hsv</b> (<var>n</var>)<var><a name="index-hsv-2934"></a></var><br>
<blockquote><p>Create color colormap. This colormap begins with red, changes through
yellow, green, cyan, blue, and magenta, before returning to red.
It is useful for displaying periodic functions. It is obtained by linearly
varying the hue through all possible values while keeping constant maximum
saturation and value and is equivalent to
<code>hsv2rgb ([linspace(0,1,N)', ones(N,2)])</code>.
<p>The argument <var>n</var> must be a scalar.
If unspecified, the length of the current colormap, or 64, is used.
<!-- Texinfo @sp should work but in practice produces ugly results for HTML. -->
<!-- A simple blank line produces the correct behavior. -->
<!-- @sp 1 -->
<p class="noindent"><strong>See also:</strong> <a href="doc_002dcolormap.html#doc_002dcolormap">colormap</a>.
</p></blockquote></div>
<!-- jet scripts/image/jet.m -->
<p><a name="doc_002djet"></a>
<div class="defun">
— Function File: <var>map</var> = <b>jet</b> ()<var><a name="index-jet-2935"></a></var><br>
— Function File: <var>map</var> = <b>jet</b> (<var>n</var>)<var><a name="index-jet-2936"></a></var><br>
<blockquote><p>Create color colormap. This colormap ranges from dark blue through blue,
cyan, green, yellow, red, to dark red.
The argument <var>n</var> must be a scalar.
If unspecified, the length of the current colormap, or 64, is used.
<!-- Texinfo @sp should work but in practice produces ugly results for HTML. -->
<!-- A simple blank line produces the correct behavior. -->
<!-- @sp 1 -->
<p class="noindent"><strong>See also:</strong> <a href="doc_002dcolormap.html#doc_002dcolormap">colormap</a>.
</p></blockquote></div>
<!-- ocean scripts/image/ocean.m -->
<p><a name="doc_002docean"></a>
<div class="defun">
— Function File: <var>map</var> = <b>ocean</b> ()<var><a name="index-ocean-2937"></a></var><br>
— Function File: <var>map</var> = <b>ocean</b> (<var>n</var>)<var><a name="index-ocean-2938"></a></var><br>
<blockquote><p>Create color colormap. This colormap varies from black to white with shades
of blue.
The argument <var>n</var> must be a scalar.
If unspecified, the length of the current colormap, or 64, is used.
</p></blockquote></div>
<!-- pink scripts/image/pink.m -->
<p><a name="doc_002dpink"></a>
<div class="defun">
— Function File: <var>map</var> = <b>pink</b> ()<var><a name="index-pink-2939"></a></var><br>
— Function File: <var>map</var> = <b>pink</b> (<var>n</var>)<var><a name="index-pink-2940"></a></var><br>
<blockquote><p>Create color colormap. This colormap varies from black to white with
shades of gray-pink. It gives a sepia tone when used on grayscale images.
The argument <var>n</var> must be a scalar.
If unspecified, the length of the current colormap, or 64, is used.
<!-- Texinfo @sp should work but in practice produces ugly results for HTML. -->
<!-- A simple blank line produces the correct behavior. -->
<!-- @sp 1 -->
<p class="noindent"><strong>See also:</strong> <a href="doc_002dcolormap.html#doc_002dcolormap">colormap</a>.
</p></blockquote></div>
<!-- prism scripts/image/prism.m -->
<p><a name="doc_002dprism"></a>
<div class="defun">
— Function File: <var>map</var> = <b>prism</b> ()<var><a name="index-prism-2941"></a></var><br>
— Function File: <var>map</var> = <b>prism</b> (<var>n</var>)<var><a name="index-prism-2942"></a></var><br>
<blockquote><p>Create color colormap. This colormap cycles through red, orange, yellow,
green, blue and violet with each index change.
The argument <var>n</var> must be a scalar.
If unspecified, the length of the current colormap, or 64, is used.
<!-- Texinfo @sp should work but in practice produces ugly results for HTML. -->
<!-- A simple blank line produces the correct behavior. -->
<!-- @sp 1 -->
<p class="noindent"><strong>See also:</strong> <a href="doc_002dcolormap.html#doc_002dcolormap">colormap</a>.
</p></blockquote></div>
<!-- rainbow scripts/image/rainbow.m -->
<p><a name="doc_002drainbow"></a>
<div class="defun">
— Function File: <var>map</var> = <b>rainbow</b> ()<var><a name="index-rainbow-2943"></a></var><br>
— Function File: <var>map</var> = <b>rainbow</b> (<var>n</var>)<var><a name="index-rainbow-2944"></a></var><br>
<blockquote><p>Create color colormap. This colormap ranges from red through orange,
yellow, green, blue, to violet.
The argument <var>n</var> must be a scalar.
If unspecified, the length of the current colormap, or 64, is used.
<!-- Texinfo @sp should work but in practice produces ugly results for HTML. -->
<!-- A simple blank line produces the correct behavior. -->
<!-- @sp 1 -->
<p class="noindent"><strong>See also:</strong> <a href="doc_002dcolormap.html#doc_002dcolormap">colormap</a>.
</p></blockquote></div>
<!-- spring scripts/image/spring.m -->
<p><a name="doc_002dspring"></a>
<div class="defun">
— Function File: <var>map</var> = <b>spring</b> ()<var><a name="index-spring-2945"></a></var><br>
— Function File: <var>map</var> = <b>spring</b> (<var>n</var>)<var><a name="index-spring-2946"></a></var><br>
<blockquote><p>Create color colormap. This colormap varies from magenta to yellow.
The argument <var>n</var> must be a scalar.
If unspecified, the length of the current colormap, or 64, is used.
<!-- Texinfo @sp should work but in practice produces ugly results for HTML. -->
<!-- A simple blank line produces the correct behavior. -->
<!-- @sp 1 -->
<p class="noindent"><strong>See also:</strong> <a href="doc_002dcolormap.html#doc_002dcolormap">colormap</a>.
</p></blockquote></div>
<!-- summer scripts/image/summer.m -->
<p><a name="doc_002dsummer"></a>
<div class="defun">
— Function File: <var>map</var> = <b>summer</b> ()<var><a name="index-summer-2947"></a></var><br>
— Function File: <var>map</var> = <b>summer</b> (<var>n</var>)<var><a name="index-summer-2948"></a></var><br>
<blockquote><p>Create color colormap. This colormap varies from green to yellow.
The argument <var>n</var> must be a scalar.
If unspecified, the length of the current colormap, or 64, is used.
<!-- Texinfo @sp should work but in practice produces ugly results for HTML. -->
<!-- A simple blank line produces the correct behavior. -->
<!-- @sp 1 -->
<p class="noindent"><strong>See also:</strong> <a href="doc_002dcolormap.html#doc_002dcolormap">colormap</a>.
</p></blockquote></div>
<!-- white scripts/image/white.m -->
<p><a name="doc_002dwhite"></a>
<div class="defun">
— Function File: <var>map</var> = <b>white</b> ()<var><a name="index-white-2949"></a></var><br>
— Function File: <var>map</var> = <b>white</b> (<var>n</var>)<var><a name="index-white-2950"></a></var><br>
<blockquote><p>Create color colormap. This colormap is completely white.
The argument <var>n</var> should be a scalar. If it
is omitted, the length of the current colormap or 64 is assumed.
<!-- Texinfo @sp should work but in practice produces ugly results for HTML. -->
<!-- A simple blank line produces the correct behavior. -->
<!-- @sp 1 -->
<p class="noindent"><strong>See also:</strong> <a href="doc_002dcolormap.html#doc_002dcolormap">colormap</a>.
</p></blockquote></div>
<!-- winter scripts/image/winter.m -->
<p><a name="doc_002dwinter"></a>
<div class="defun">
— Function File: <var>map</var> = <b>winter</b> ()<var><a name="index-winter-2951"></a></var><br>
— Function File: <var>map</var> = <b>winter</b> (<var>n</var>)<var><a name="index-winter-2952"></a></var><br>
<blockquote><p>Create color colormap. This colormap varies from blue to green.
The argument <var>n</var> must be a scalar.
If unspecified, the length of the current colormap, or 64, is used.
<!-- Texinfo @sp should work but in practice produces ugly results for HTML. -->
<!-- A simple blank line produces the correct behavior. -->
<!-- @sp 1 -->
<p class="noindent"><strong>See also:</strong> <a href="doc_002dcolormap.html#doc_002dcolormap">colormap</a>.
</p></blockquote></div>
<!-- contrast scripts/image/contrast.m -->
<p><a name="doc_002dcontrast"></a>
<div class="defun">
— Function File: <b>contrast</b> (<var>x, n</var>)<var><a name="index-contrast-2953"></a></var><br>
<blockquote><p>Return a gray colormap that maximizes the contrast in an image. The
returned colormap will have <var>n</var> rows. If <var>n</var> is not defined
then the size of the current colormap is used instead.
<!-- Texinfo @sp should work but in practice produces ugly results for HTML. -->
<!-- A simple blank line produces the correct behavior. -->
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<p class="noindent"><strong>See also:</strong> <a href="doc_002dcolormap.html#doc_002dcolormap">colormap</a>.
</p></blockquote></div>
<p>An additional colormap is <code>gmap40</code>. This code map contains only
colors with integer values of the red, green and blue components. This
is a workaround for a limitation of gnuplot 4.0, that does not allow the color
of line or patch objects to be set, and so <code>gmap40</code> is useful for gnuplot
4.0 users, and in particular in conjunction with the <var>bar</var>,
<var>barh</var> or <var>contour</var> functions.
<!-- gmap40 scripts/image/gmap40.m -->
<p><a name="doc_002dgmap40"></a>
<div class="defun">
— Function File: <var>map</var> = <b>gmap40</b> ()<var><a name="index-gmap40-2954"></a></var><br>
— Function File: <var>map</var> = <b>gmap40</b> (<var>n</var>)<var><a name="index-gmap40-2955"></a></var><br>
<blockquote><p>Create color colormap. The colormap consists of red, green, blue, yellow,
magenta and cyan. This colormap is specifically designed for users of
gnuplot 4.0 where these 6 colors are the allowable ones for patch objects.
The argument <var>n</var> must be a scalar.
If unspecified, a length of 6 is assumed. Larger values
of <var>n</var> result in a repetition of the above colors.
<!-- Texinfo @sp should work but in practice produces ugly results for HTML. -->
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<p class="noindent"><strong>See also:</strong> <a href="doc_002dcolormap.html#doc_002dcolormap">colormap</a>.
</p></blockquote></div>
<p>The following three functions modify the existing colormap rather than
replace it.
<!-- brighten scripts/image/brighten.m -->
<p><a name="doc_002dbrighten"></a>
<div class="defun">
— Function File: <var>map_out</var> = <b>brighten</b> (<var>map, beta</var>)<var><a name="index-brighten-2956"></a></var><br>
— Function File: <var>map_out</var> = <b>brighten</b> (<var>h, beta</var>)<var><a name="index-brighten-2957"></a></var><br>
— Function File: <var>map_out</var> = <b>brighten</b> (<var>beta</var>)<var><a name="index-brighten-2958"></a></var><br>
<blockquote><p>Darken or brighten the given colormap. If the <var>map</var> argument
is omitted, the function is applied to the current colormap. The first
argument can also be a valid graphics handle <var>h</var>, in which case
<code>brighten</code> is applied to the colormap associated with this handle.
<p>Should the resulting colormap <var>map_out</var> not be assigned, it will be
written to the current colormap.
<p>The argument <var>beta</var> should be a scalar between -1 and 1,
where a negative value darkens and a positive value brightens
the colormap.
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<p class="noindent"><strong>See also:</strong> <a href="doc_002dcolormap.html#doc_002dcolormap">colormap</a>.
</p></blockquote></div>
<!-- spinmap scripts/plot/spinmap.m -->
<p><a name="doc_002dspinmap"></a>
<div class="defun">
— Function File: <b>spinmap</b> (<var>t, inc</var>)<var><a name="index-spinmap-2959"></a></var><br>
<blockquote><p>Cycle the colormap for <var>t</var> seconds with an increment
of <var>inc</var>. Both parameters are optional. The default cycle time
is 5 seconds and the default increment is 2.
<p>A higher value of <var>inc</var> causes a faster cycle through the
colormap.
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<p class="noindent"><strong>See also:</strong> <a href="doc_002dgca.html#doc_002dgca">gca</a>, <a href="doc_002dcolorbar.html#doc_002dcolorbar">colorbar</a>.
</p></blockquote></div>
<!-- whitebg scripts/plot/whitebg.m -->
<p><a name="doc_002dwhitebg"></a>
<div class="defun">
— Function File: <b>whitebg</b> ()<var><a name="index-whitebg-2960"></a></var><br>
— Function File: <b>whitebg</b> (<var>color</var>)<var><a name="index-whitebg-2961"></a></var><br>
— Function File: <b>whitebg</b> (<var>"none"</var>)<var><a name="index-whitebg-2962"></a></var><br>
— Function File: <b>whitebg</b> (<var>fig</var>)<var><a name="index-whitebg-2963"></a></var><br>
— Function File: <b>whitebg</b> (<var>fig, color</var>)<var><a name="index-whitebg-2964"></a></var><br>
— Function File: <b>whitebg</b> (<var>fig, "none"</var>)<var><a name="index-whitebg-2965"></a></var><br>
<blockquote><p>Invert the colors in the current color scheme. The root properties are
also inverted such that all subsequent plot use the new color scheme.
<p>If defined, <var>fig</var> is the handle to the figure to be inverted. In
this case only the specified figure has its color properties changed.
<p>If the optional argument <var>color</var> is present then the background color
is set to <var>color</var> rather than inverted. <var>color</var> may be a string
representing one of the eight known colors or an RGB triplet. The special
string argument "none" restores the plot to the default colors.
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<p class="noindent"><strong>See also:</strong> <a href="doc_002dreset.html#doc_002dreset">reset</a>.
</p></blockquote></div>
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