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Next: <a rel="next" accesskey="n" href="Representing-Images.html#Representing-Images">Representing Images</a>,
Previous: <a rel="previous" accesskey="p" href="Loading-and-Saving-Images.html#Loading-and-Saving-Images">Loading and Saving Images</a>,
Up: <a rel="up" accesskey="u" href="Image-Processing.html#Image-Processing">Image Processing</a>
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<h3 class="section">32.2 Displaying Images</h3>
<p>A natural part of image processing is visualization of an image.
The most basic function for this is the <code>imshow</code> function that
shows the image given in the first input argument.
<!-- imshow scripts/image/imshow.m -->
<p><a name="doc_002dimshow"></a>
<div class="defun">
— Function File: <b>imshow</b> (<var>im</var>)<var><a name="index-imshow-2897"></a></var><br>
— Function File: <b>imshow</b> (<var>im, limits</var>)<var><a name="index-imshow-2898"></a></var><br>
— Function File: <b>imshow</b> (<var>im, map</var>)<var><a name="index-imshow-2899"></a></var><br>
— Function File: <b>imshow</b> (<var>rgb, <small class="dots">...</small></var>)<var><a name="index-imshow-2900"></a></var><br>
— Function File: <b>imshow</b> (<var>filename</var>)<var><a name="index-imshow-2901"></a></var><br>
— Function File: <b>imshow</b> (<var><small class="dots">...</small>, string_param1, value1, <small class="dots">...</small></var>)<var><a name="index-imshow-2902"></a></var><br>
— Function File: <var>h</var> = <b>imshow</b> (<var><small class="dots">...</small></var>)<var><a name="index-imshow-2903"></a></var><br>
<blockquote><p>Display the image <var>im</var>, where <var>im</var> can be a 2-dimensional
(gray-scale image) or a 3-dimensional (RGB image) matrix.
<p>If <var>limits</var> is a 2-element vector <code>[</code><var>low</var><code>, </code><var>high</var><code>]</code>,
the image is shown using a display range between <var>low</var> and
<var>high</var>. If an empty matrix is passed for <var>limits</var>, the
display range is computed as the range between the minimal and the
maximal value in the image.
<p>If <var>map</var> is a valid color map, the image will be shown as an indexed
image using the supplied color map.
<p>If a file name is given instead of an image, the file will be read and
shown.
<p>If given, the parameter <var>string_param1</var> has value
<var>value1</var>. <var>string_param1</var> can be any of the following:
<dl>
<dt>"displayrange"<dd><var>value1</var> is the display range as described above.
</dl>
<p>The optional return value <var>h</var> is a graphics handle to the image.
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<p class="noindent"><strong>See also:</strong> <a href="doc_002dimage.html#doc_002dimage">image</a>, <a href="doc_002dimagesc.html#doc_002dimagesc">imagesc</a>, <a href="doc_002dcolormap.html#doc_002dcolormap">colormap</a>, <a href="doc_002dgray2ind.html#doc_002dgray2ind">gray2ind</a>, <a href="doc_002drgb2ind.html#doc_002drgb2ind">rgb2ind</a>.
</p></blockquote></div>
<!-- image scripts/image/image.m -->
<p><a name="doc_002dimage"></a>
<div class="defun">
— Function File: <b>image</b> (<var>img</var>)<var><a name="index-image-2904"></a></var><br>
— Function File: <b>image</b> (<var>x, y, img</var>)<var><a name="index-image-2905"></a></var><br>
— Function File: <var>h</var> = <b>image</b> (<var><small class="dots">...</small></var>)<var><a name="index-image-2906"></a></var><br>
<blockquote><p>Display a matrix as a color image. The elements of <var>img</var> are indices
into the current colormap, and the colormap will be scaled so that the
extremes of <var>img</var> are mapped to the extremes of the colormap.
<p>The axis values corresponding to the matrix elements are specified in
<var>x</var> and <var>y</var>. If you're not using gnuplot 4.2 or later, these
variables are ignored.
<p>Implementation Note: The origin (0, 0) for images is located in the
upper left. For ordinary plots, the origin is located in the lower
left. Octave handles this inversion by plotting the data normally,
and then reversing the direction of the y-axis by setting the
<code>ydir</code> property to <code>"reverse"</code>. This has implications whenever
an image and an ordinary plot need to be overlaid. The recommended
solution is to display the image and then plot the reversed ydata
using, for example, <code>flipud (ydata,1)</code>.
<p>The optional return value <var>h</var> is a graphics handle to the image.
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<p class="noindent"><strong>See also:</strong> <a href="doc_002dimshow.html#doc_002dimshow">imshow</a>, <a href="doc_002dimagesc.html#doc_002dimagesc">imagesc</a>, <a href="doc_002dcolormap.html#doc_002dcolormap">colormap</a>.
</p></blockquote></div>
<!-- imagesc scripts/image/imagesc.m -->
<p><a name="doc_002dimagesc"></a>
<div class="defun">
— Function File: <b>imagesc</b> (<var>A</var>)<var><a name="index-imagesc-2907"></a></var><br>
— Function File: <b>imagesc</b> (<var>x, y, A</var>)<var><a name="index-imagesc-2908"></a></var><br>
— Function File: <b>imagesc</b> (<var><small class="dots">...</small>, limits</var>)<var><a name="index-imagesc-2909"></a></var><br>
— Function File: <b>imagesc</b> (<var>h, <small class="dots">...</small></var>)<var><a name="index-imagesc-2910"></a></var><br>
— Function File: <var>h</var> = <b>imagesc</b> (<var><small class="dots">...</small></var>)<var><a name="index-imagesc-2911"></a></var><br>
<blockquote><p>Display a scaled version of the matrix <var>A</var> as a color image. The
colormap is scaled so that the entries of the matrix occupy the entire
colormap. If <var>limits</var> = [<var>lo</var>, <var>hi</var>] are given, then that
range is set to the 'clim' of the current axes.
<p>The axis values corresponding to the matrix elements are specified in
<var>x</var> and <var>y</var>, either as pairs giving the minimum and maximum
values for the respective axes, or as values for each row and column
of the matrix <var>A</var>.
<p>The optional return value <var>h</var> is a graphics handle to the image.
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<p class="noindent"><strong>See also:</strong> <a href="doc_002dimage.html#doc_002dimage">image</a>, <a href="doc_002dimshow.html#doc_002dimshow">imshow</a>, <a href="doc_002dcaxis.html#doc_002dcaxis">caxis</a>.
</p></blockquote></div>
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