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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<tr><td colspan="5" class="shortcuts">
<a href="#VipsInterpolate.synopsis" class="shortcut">Top</a>
                   | 
                  <a href="#VipsInterpolate.description" class="shortcut">Description</a>
                   | 
                  <a href="#VipsInterpolate.object-hierarchy" class="shortcut">Object Hierarchy</a>
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<div class="refentry">
<a name="VipsInterpolate"></a><div class="titlepage"></div>
<div class="refnamediv"><table width="100%"><tr>
<td valign="top">
<h2><span class="refentrytitle"><a name="VipsInterpolate.top_of_page"></a>VipsInterpolate</span></h2>
<p>VipsInterpolate — various interpolators: nearest, bilinear, and
some non-linear</p>
</td>
<td valign="top" align="right"></td>
</tr></table></div>
<div class="refsect1">
<a name="VipsInterpolate.stability-level"></a><h2>Stability Level</h2>
Stable, unless otherwise indicated
</div>
<div class="refsynopsisdiv">
<a name="VipsInterpolate.synopsis"></a><h2>Synopsis</h2>
<pre class="synopsis">
#include &lt;vips/vips.h&gt;

                    <a class="link" href="VipsInterpolate.html#VipsInterpolate-struct" title="VipsInterpolate">VipsInterpolate</a>;
<span class="returnvalue">void</span>                (<a class="link" href="VipsInterpolate.html#VipsInterpolateMethod" title="VipsInterpolateMethod ()">*VipsInterpolateMethod</a>)            (<em class="parameter"><code><a class="link" href="VipsInterpolate.html" title="VipsInterpolate"><span class="type">VipsInterpolate</span></a> *interpolate</code></em>,
                                                         <em class="parameter"><code><span class="type">void</span> *out</code></em>,
                                                         <em class="parameter"><code><a class="link" href="VipsRegion.html" title="VipsRegion"><span class="type">VipsRegion</span></a> *in</code></em>,
                                                         <em class="parameter"><code><span class="type">double</span> x</code></em>,
                                                         <em class="parameter"><code><span class="type">double</span> y</code></em>);
                    <a class="link" href="VipsInterpolate.html#VipsInterpolateClass" title="VipsInterpolateClass">VipsInterpolateClass</a>;
<span class="returnvalue">void</span>                <a class="link" href="VipsInterpolate.html#vips-interpolate" title="vips_interpolate ()">vips_interpolate</a>                    (<em class="parameter"><code><a class="link" href="VipsInterpolate.html" title="VipsInterpolate"><span class="type">VipsInterpolate</span></a> *interpolate</code></em>,
                                                         <em class="parameter"><code><span class="type">void</span> *out</code></em>,
                                                         <em class="parameter"><code><a class="link" href="VipsRegion.html" title="VipsRegion"><span class="type">VipsRegion</span></a> *in</code></em>,
                                                         <em class="parameter"><code><span class="type">double</span> x</code></em>,
                                                         <em class="parameter"><code><span class="type">double</span> y</code></em>);
<a class="link" href="VipsInterpolate.html#VipsInterpolateMethod" title="VipsInterpolateMethod ()"><span class="returnvalue">VipsInterpolateMethod</span></a> <a class="link" href="VipsInterpolate.html#vips-interpolate-get-method" title="vips_interpolate_get_method ()">vips_interpolate_get_method</a>       (<em class="parameter"><code><a class="link" href="VipsInterpolate.html" title="VipsInterpolate"><span class="type">VipsInterpolate</span></a> *interpolate</code></em>);
<span class="returnvalue">int</span>                 <a class="link" href="VipsInterpolate.html#vips-interpolate-get-window-size" title="vips_interpolate_get_window_size ()">vips_interpolate_get_window_size</a>    (<em class="parameter"><code><a class="link" href="VipsInterpolate.html" title="VipsInterpolate"><span class="type">VipsInterpolate</span></a> *interpolate</code></em>);
<span class="returnvalue">int</span>                 <a class="link" href="VipsInterpolate.html#vips-interpolate-get-window-offset" title="vips_interpolate_get_window_offset ()">vips_interpolate_get_window_offset</a>  (<em class="parameter"><code><a class="link" href="VipsInterpolate.html" title="VipsInterpolate"><span class="type">VipsInterpolate</span></a> *interpolate</code></em>);
#define             <a class="link" href="VipsInterpolate.html#VIPS-TRANSFORM-SHIFT:CAPS" title="VIPS_TRANSFORM_SHIFT">VIPS_TRANSFORM_SHIFT</a>
#define             <a class="link" href="VipsInterpolate.html#VIPS-TRANSFORM-SCALE:CAPS" title="VIPS_TRANSFORM_SCALE">VIPS_TRANSFORM_SCALE</a>
#define             <a class="link" href="VipsInterpolate.html#VIPS-INTERPOLATE-SHIFT:CAPS" title="VIPS_INTERPOLATE_SHIFT">VIPS_INTERPOLATE_SHIFT</a>
#define             <a class="link" href="VipsInterpolate.html#VIPS-INTERPOLATE-SCALE:CAPS" title="VIPS_INTERPOLATE_SCALE">VIPS_INTERPOLATE_SCALE</a>
<a class="link" href="VipsInterpolate.html" title="VipsInterpolate"><span class="returnvalue">VipsInterpolate</span></a> *   <a class="link" href="VipsInterpolate.html#vips-interpolate-nearest-static" title="vips_interpolate_nearest_static ()">vips_interpolate_nearest_static</a>     (<em class="parameter"><code><span class="type">void</span></code></em>);
<a class="link" href="VipsInterpolate.html" title="VipsInterpolate"><span class="returnvalue">VipsInterpolate</span></a> *   <a class="link" href="VipsInterpolate.html#vips-interpolate-bilinear-static" title="vips_interpolate_bilinear_static ()">vips_interpolate_bilinear_static</a>    (<em class="parameter"><code><span class="type">void</span></code></em>);
<a class="link" href="VipsInterpolate.html" title="VipsInterpolate"><span class="returnvalue">VipsInterpolate</span></a> *   <a class="link" href="VipsInterpolate.html#vips-interpolate-new" title="vips_interpolate_new ()">vips_interpolate_new</a>                (<em class="parameter"><code>const <span class="type">char</span> *nickname</code></em>);
</pre>
</div>
<div class="refsect1">
<a name="VipsInterpolate.object-hierarchy"></a><h2>Object Hierarchy</h2>
<pre class="synopsis">
  GObject
   +----<a class="link" href="libvips-VipsArgument.html#VipsObject">VipsObject</a>
         +----VipsInterpolate
</pre>
</div>
<div class="refsect1">
<a name="VipsInterpolate.description"></a><h2>Description</h2>
<p>
A number of image interpolators.
</p>
</div>
<div class="refsect1">
<a name="VipsInterpolate.details"></a><h2>Details</h2>
<div class="refsect2">
<a name="VipsInterpolate-struct"></a><h3>VipsInterpolate</h3>
<pre class="programlisting">typedef struct _VipsInterpolate VipsInterpolate;</pre>
<p>
</p>
</div>
<hr>
<div class="refsect2">
<a name="VipsInterpolateMethod"></a><h3>VipsInterpolateMethod ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>                (*VipsInterpolateMethod)            (<em class="parameter"><code><a class="link" href="VipsInterpolate.html" title="VipsInterpolate"><span class="type">VipsInterpolate</span></a> *interpolate</code></em>,
                                                         <em class="parameter"><code><span class="type">void</span> *out</code></em>,
                                                         <em class="parameter"><code><a class="link" href="VipsRegion.html" title="VipsRegion"><span class="type">VipsRegion</span></a> *in</code></em>,
                                                         <em class="parameter"><code><span class="type">double</span> x</code></em>,
                                                         <em class="parameter"><code><span class="type">double</span> y</code></em>);</pre>
<p>
An interpolation function. It should read source pixels from <em class="parameter"><code>in</code></em> with
<a class="link" href="VipsRegion.html#VIPS-REGION-ADDR:CAPS" title="VIPS_REGION_ADDR()"><code class="function">VIPS_REGION_ADDR()</code></a>, it can look left and up from (x, y) by <em class="parameter"><code>window_offset</code></em>
pixels and it can access pixels in a window of size <em class="parameter"><code>window_size</code></em>.
</p>
<p>
The interpolated value should be written to the pixel pointed to by <em class="parameter"><code>out</code></em>.
</p>
<p>
See also: <a class="link" href="VipsInterpolate.html#VipsInterpolateClass" title="VipsInterpolateClass"><span class="type">VipsInterpolateClass</span></a>.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>interpolate</code></em> :</span></p></td>
<td>the interpolator</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>out</code></em> :</span></p></td>
<td>write the interpolated pixel here</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>in</code></em> :</span></p></td>
<td>read source pixels from here</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>x</code></em> :</span></p></td>
<td>interpolate value at this position</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>y</code></em> :</span></p></td>
<td>interpolate value at this position</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="VipsInterpolateClass"></a><h3>VipsInterpolateClass</h3>
<pre class="programlisting">typedef struct {
	VipsObjectClass parent_class;

	/* Write to pixel out(x,y), interpolating from in(x,y). The caller has
	 * to set the regions up.
	 */
	VipsInterpolateMethod interpolate;

	/* This interpolator needs a window this many pixels across and down.
	 */
	int (*get_window_size)( VipsInterpolate * );

	/* Or just set this if you want a constant.
	 */
	int window_size;

	/* Stencils are offset by this much. Default to window_size / 2 - 1
	 * (centering) if get_window_offset is NULL and window_offset is -1.
	 */
	int (*get_window_offset)( VipsInterpolate * );
	int window_offset;
} VipsInterpolateClass;
</pre>
<p>
The abstract base class for the various VIPS interpolation functions. 
Use "vips --list classes" to see all the interpolators available.
</p>
<p>
An interpolator consists of a function to perform the interpolation, plus
some extra data fields which tell vips how to call the function and what
data it needs.
</p>
<p>
<em class="parameter"><code>window_size</code></em> is the size of the window that the interpolator needs. For
example, a bicubic interpolator needs to see a window of 4x4 pixels to be
able to interpolate a value. 
</p>
<p>
You can either have a function in <em class="parameter"><code>get_window_size</code></em> which returns the window
that a specific interpolator needs, or you can leave <em class="parameter"><code>get_window_size</code></em> <code class="literal">NULL</code>
and set a constant value in <em class="parameter"><code>window_size</code></em>.
</p>
<p>
<em class="parameter"><code>window_offset</code></em> is how much to offset the window up and left of (x, y). For
example, a bicubic interpolator will want a <em class="parameter"><code>window_offset</code></em> of 1.
</p>
<p>
You can either have a function in <em class="parameter"><code>get_window_offset</code></em> which returns the
offset that a specific interpolator needs, or you can leave
<em class="parameter"><code>get_window_offset</code></em> <code class="literal">NULL</code> and set a constant value in <em class="parameter"><code>window_offset</code></em>.
</p>
<p>
You also need to set <em class="parameter"><code>nickname</code></em> and <em class="parameter"><code>description</code></em> in <a class="link" href="libvips-VipsArgument.html#VipsObject"><span class="type">VipsObject</span></a>.
</p>
<p>
See also: <a class="link" href="VipsInterpolate.html#VipsInterpolateMethod" title="VipsInterpolateMethod ()"><span class="type">VipsInterpolateMethod</span></a>, <a class="link" href="libvips-VipsArgument.html#VipsObject"><span class="type">VipsObject</span></a>, 
<a class="link" href="VipsInterpolate.html#vips-interpolate-bilinear-static" title="vips_interpolate_bilinear_static ()"><code class="function">vips_interpolate_bilinear_static()</code></a>.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><a class="link" href="libvips-VipsArgument.html#VipsObjectClass" title="struct VipsObjectClass"><span class="type">VipsObjectClass</span></a> <em class="structfield"><code><a name="VipsInterpolateClass.parent-class"></a>parent_class</code></em>;</span></p></td>
<td></td>
</tr>
<tr>
<td><p><span class="term"><a class="link" href="VipsInterpolate.html#VipsInterpolateMethod" title="VipsInterpolateMethod ()"><span class="type">VipsInterpolateMethod</span></a> <em class="structfield"><code><a name="VipsInterpolateClass.interpolate"></a>interpolate</code></em>;</span></p></td>
<td>the interpolation method</td>
</tr>
<tr>
<td><p><span class="term"><em class="structfield"><code><a name="VipsInterpolateClass.get-window-size"></a>get_window_size</code></em> ()</span></p></td>
<td>return the size of the window needed by this method</td>
</tr>
<tr>
<td><p><span class="term"><span class="type">int</span> <em class="structfield"><code><a name="VipsInterpolateClass.window-size"></a>window_size</code></em>;</span></p></td>
<td>or just set this for a constant window size</td>
</tr>
<tr>
<td><p><span class="term"><em class="structfield"><code><a name="VipsInterpolateClass.get-window-offset"></a>get_window_offset</code></em> ()</span></p></td>
<td>return the window offset for this method</td>
</tr>
<tr>
<td><p><span class="term"><span class="type">int</span> <em class="structfield"><code><a name="VipsInterpolateClass.window-offset"></a>window_offset</code></em>;</span></p></td>
<td>or just set this for a constant window offset</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="vips-interpolate"></a><h3>vips_interpolate ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>                vips_interpolate                    (<em class="parameter"><code><a class="link" href="VipsInterpolate.html" title="VipsInterpolate"><span class="type">VipsInterpolate</span></a> *interpolate</code></em>,
                                                         <em class="parameter"><code><span class="type">void</span> *out</code></em>,
                                                         <em class="parameter"><code><a class="link" href="VipsRegion.html" title="VipsRegion"><span class="type">VipsRegion</span></a> *in</code></em>,
                                                         <em class="parameter"><code><span class="type">double</span> x</code></em>,
                                                         <em class="parameter"><code><span class="type">double</span> y</code></em>);</pre>
<p>
Look up the <em class="parameter"><code>interpolate</code></em> method in the class and call it. Use
<a class="link" href="VipsInterpolate.html#vips-interpolate-get-method" title="vips_interpolate_get_method ()"><code class="function">vips_interpolate_get_method()</code></a> to get a direct pointer to the function and
avoid the lookup overhead.
</p>
<p>
You need to set <em class="parameter"><code>in</code></em> and <em class="parameter"><code>out</code></em> up correctly.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>interpolate</code></em> :</span></p></td>
<td>interpolator to use</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>out</code></em> :</span></p></td>
<td>write result here</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>in</code></em> :</span></p></td>
<td>read source data from here</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>x</code></em> :</span></p></td>
<td>interpolate value at this position</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>y</code></em> :</span></p></td>
<td>interpolate value at this position</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="vips-interpolate-get-method"></a><h3>vips_interpolate_get_method ()</h3>
<pre class="programlisting"><a class="link" href="VipsInterpolate.html#VipsInterpolateMethod" title="VipsInterpolateMethod ()"><span class="returnvalue">VipsInterpolateMethod</span></a> vips_interpolate_get_method       (<em class="parameter"><code><a class="link" href="VipsInterpolate.html" title="VipsInterpolate"><span class="type">VipsInterpolate</span></a> *interpolate</code></em>);</pre>
<p>
Look up the <em class="parameter"><code>interpolate</code></em> method in the class and return it. Use this
instead of <a class="link" href="VipsInterpolate.html#vips-interpolate" title="vips_interpolate ()"><code class="function">vips_interpolate()</code></a> to cache method dispatch.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>interpolate</code></em> :</span></p></td>
<td>interpolator to use</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>a pointer to the interpolation function</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="vips-interpolate-get-window-size"></a><h3>vips_interpolate_get_window_size ()</h3>
<pre class="programlisting"><span class="returnvalue">int</span>                 vips_interpolate_get_window_size    (<em class="parameter"><code><a class="link" href="VipsInterpolate.html" title="VipsInterpolate"><span class="type">VipsInterpolate</span></a> *interpolate</code></em>);</pre>
<p>
Look up an interpolators desired window size.
</p>
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<td><p><span class="term"><em class="parameter"><code>interpolate</code></em> :</span></p></td>
<td>interpolator to use</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>the interpolators required window size</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="vips-interpolate-get-window-offset"></a><h3>vips_interpolate_get_window_offset ()</h3>
<pre class="programlisting"><span class="returnvalue">int</span>                 vips_interpolate_get_window_offset  (<em class="parameter"><code><a class="link" href="VipsInterpolate.html" title="VipsInterpolate"><span class="type">VipsInterpolate</span></a> *interpolate</code></em>);</pre>
<p>
Look up an interpolators desired window offset.
</p>
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<td><p><span class="term"><em class="parameter"><code>interpolate</code></em> :</span></p></td>
<td>interpolator to use</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>the interpolators required window offset</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="VIPS-TRANSFORM-SHIFT:CAPS"></a><h3>VIPS_TRANSFORM_SHIFT</h3>
<pre class="programlisting">#define VIPS_TRANSFORM_SHIFT (6)
</pre>
<p>
Many of the vips interpolators use fixed-point arithmetic for coordinate
calculation. This is how many bits of precision they use.
</p>
</div>
<hr>
<div class="refsect2">
<a name="VIPS-TRANSFORM-SCALE:CAPS"></a><h3>VIPS_TRANSFORM_SCALE</h3>
<pre class="programlisting">#define VIPS_TRANSFORM_SCALE (1 &lt;&lt; VIPS_TRANSFORM_SHIFT)
</pre>
<p>
<a class="link" href="VipsInterpolate.html#VIPS-TRANSFORM-SHIFT:CAPS" title="VIPS_TRANSFORM_SHIFT"><span class="type">VIPS_TRANSFORM_SHIFT</span></a> as a multiplicative constant.
</p>
</div>
<hr>
<div class="refsect2">
<a name="VIPS-INTERPOLATE-SHIFT:CAPS"></a><h3>VIPS_INTERPOLATE_SHIFT</h3>
<pre class="programlisting">#define VIPS_INTERPOLATE_SHIFT (12)
</pre>
<p>
Many of the vips interpolators use fixed-point arithmetic for value
calcualtion. This is how many bits of precision they use.
</p>
</div>
<hr>
<div class="refsect2">
<a name="VIPS-INTERPOLATE-SCALE:CAPS"></a><h3>VIPS_INTERPOLATE_SCALE</h3>
<pre class="programlisting">#define VIPS_INTERPOLATE_SCALE (1 &lt;&lt; VIPS_INTERPOLATE_SHIFT)
</pre>
<p>
<a class="link" href="VipsInterpolate.html#VIPS-INTERPOLATE-SHIFT:CAPS" title="VIPS_INTERPOLATE_SHIFT"><span class="type">VIPS_INTERPOLATE_SHIFT</span></a> as a multiplicative constant.
</p>
</div>
<hr>
<div class="refsect2">
<a name="vips-interpolate-nearest-static"></a><h3>vips_interpolate_nearest_static ()</h3>
<pre class="programlisting"><a class="link" href="VipsInterpolate.html" title="VipsInterpolate"><span class="returnvalue">VipsInterpolate</span></a> *   vips_interpolate_nearest_static     (<em class="parameter"><code><span class="type">void</span></code></em>);</pre>
<p>
A convenience function that returns a nearest-neighbour interpolator you 
don't need to free.
</p>
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<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>a nearest-neighbour interpolator. <span class="annotation">[<acronym title="Don't free data after the code is done."><span class="acronym">transfer none</span></acronym>]</span>
</td>
</tr></tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="vips-interpolate-bilinear-static"></a><h3>vips_interpolate_bilinear_static ()</h3>
<pre class="programlisting"><a class="link" href="VipsInterpolate.html" title="VipsInterpolate"><span class="returnvalue">VipsInterpolate</span></a> *   vips_interpolate_bilinear_static    (<em class="parameter"><code><span class="type">void</span></code></em>);</pre>
<p>
A convenience function that returns a bilinear interpolator you 
don't need to free.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody><tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>a bilinear interpolator. <span class="annotation">[<acronym title="Don't free data after the code is done."><span class="acronym">transfer none</span></acronym>]</span>
</td>
</tr></tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="vips-interpolate-new"></a><h3>vips_interpolate_new ()</h3>
<pre class="programlisting"><a class="link" href="VipsInterpolate.html" title="VipsInterpolate"><span class="returnvalue">VipsInterpolate</span></a> *   vips_interpolate_new                (<em class="parameter"><code>const <span class="type">char</span> *nickname</code></em>);</pre>
<p>
Look up an interpolator from a nickname and make one. You need to free the
result with <code class="function">g_object_unref()</code> when you're done with it.
</p>
<p>
See also: <a class="link" href="libvips-VipsArgument.html#vips-type-find" title="vips_type_find ()"><code class="function">vips_type_find()</code></a>.
</p>
<div class="variablelist"><table border="0" class="variablelist">
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<td><p><span class="term"><em class="parameter"><code>nickname</code></em> :</span></p></td>
<td>nickname for interpolator</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>an interpolator, or <code class="literal">NULL</code> on error.</td>
</tr>
</tbody>
</table></div>
</div>
</div>
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