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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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                  <a href="#libvips-resample.description" class="shortcut">Description</a></span>
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<div class="refentry">
<a name="libvips-resample"></a><div class="titlepage"></div>
<div class="refnamediv"><table width="100%"><tr>
<td valign="top">
<h2><span class="refentrytitle"><a name="libvips-resample.top_of_page"></a>resample</span></h2>
<p>resample</p>
</td>
<td class="gallery_image" valign="top" align="right"></td>
</tr></table></div>
<div class="refsect1">
<a name="libvips-resample.functions"></a><h2>Functions</h2>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="functions_return">
<col class="functions_name">
</colgroup>
<tbody>
<tr>
<td class="function_type">
<span class="returnvalue">int</span>
</td>
<td class="function_name">
<a class="link" href="libvips-resample.html#vips-shrink" title="vips_shrink ()">vips_shrink</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">int</span>
</td>
<td class="function_name">
<a class="link" href="libvips-resample.html#vips-shrinkh" title="vips_shrinkh ()">vips_shrinkh</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">int</span>
</td>
<td class="function_name">
<a class="link" href="libvips-resample.html#vips-shrinkv" title="vips_shrinkv ()">vips_shrinkv</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">int</span>
</td>
<td class="function_name">
<a class="link" href="libvips-resample.html#vips-shrink2" title="vips_shrink2 ()">vips_shrink2</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">int</span>
</td>
<td class="function_name">
<a class="link" href="libvips-resample.html#vips-similarity" title="vips_similarity ()">vips_similarity</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">int</span>
</td>
<td class="function_name">
<a class="link" href="libvips-resample.html#vips-affine" title="vips_affine ()">vips_affine</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">int</span>
</td>
<td class="function_name">
<a class="link" href="libvips-resample.html#vips-resize" title="vips_resize ()">vips_resize</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">int</span>
</td>
<td class="function_name">
<a class="link" href="libvips-resample.html#vips-mapim" title="vips_mapim ()">vips_mapim</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">int</span>
</td>
<td class="function_name">
<a class="link" href="libvips-resample.html#vips-quadratic" title="vips_quadratic ()">vips_quadratic</a> <span class="c_punctuation">()</span>
</td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect1">
<a name="libvips-resample.description"></a><h2>Description</h2>
</div>
<div class="refsect1">
<a name="libvips-resample.functions_details"></a><h2>Functions</h2>
<div class="refsect2">
<a name="vips-shrink"></a><h3>vips_shrink ()</h3>
<pre class="programlisting"><span class="returnvalue">int</span>
vips_shrink (<em class="parameter"><code><span class="type">VipsImage</span> *in</code></em>,
             <em class="parameter"><code><span class="type">VipsImage</span> **out</code></em>,
             <em class="parameter"><code><span class="type">double</span> xshrink</code></em>,
             <em class="parameter"><code><span class="type">double</span> yshrink</code></em>,
             <em class="parameter"><code>...</code></em>);</pre>
<p>Shrink <em class="parameter"><code>in</code></em>
 by a pair of factors with a simple box filter. For non-integer
factors, <a class="link" href="libvips-resample.html#vips-shrink" title="vips_shrink ()"><code class="function">vips_shrink()</code></a> will first shrink by the integer part with a box
filter, then use <a class="link" href="libvips-resample.html#vips-affine" title="vips_affine ()"><code class="function">vips_affine()</code></a> plus bilinear interpolation to shrink by the
remaining fractional part. </p>
<p>This is a very low-level operation: see <a class="link" href="libvips-resample.html#vips-resize" title="vips_resize ()"><code class="function">vips_resize()</code></a> for a more
convenient way to resize images. </p>
<p>This operation does not change xres or yres. The image resolution needs to
be updated by the application. </p>
<p>See also: <a class="link" href="libvips-resample.html#vips-resize" title="vips_resize ()"><code class="function">vips_resize()</code></a>, <a class="link" href="libvips-resample.html#vips-affine" title="vips_affine ()"><code class="function">vips_affine()</code></a>.</p>
<div class="refsect3">
<a name="id-1.4.14.5.2.8"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>in</p></td>
<td class="parameter_description"><p>input image</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>out</p></td>
<td class="parameter_description"><p>output image</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>xshrink</p></td>
<td class="parameter_description"><p>horizontal shrink</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>yshrink</p></td>
<td class="parameter_description"><p>vertical shrink</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>...</p></td>
<td class="parameter_description"><p><code class="literal">NULL</code>-terminated list of optional named arguments</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect3">
<a name="id-1.4.14.5.2.9"></a><h4>Returns</h4>
<p> 0 on success, -1 on error</p>
</div>
</div>
<hr>
<div class="refsect2">
<a name="vips-shrinkh"></a><h3>vips_shrinkh ()</h3>
<pre class="programlisting"><span class="returnvalue">int</span>
vips_shrinkh (<em class="parameter"><code><span class="type">VipsImage</span> *in</code></em>,
              <em class="parameter"><code><span class="type">VipsImage</span> **out</code></em>,
              <em class="parameter"><code><span class="type">int</span> xshrink</code></em>,
              <em class="parameter"><code>...</code></em>);</pre>
<p>Shrink <em class="parameter"><code>in</code></em>
 horizontally by an integer factor. Each pixel in the output is
the average of the corresponding line of <em class="parameter"><code>xshrink</code></em>
 pixels in the input. </p>
<p>This is a very low-level operation: see <a class="link" href="libvips-resample.html#vips-resize" title="vips_resize ()"><code class="function">vips_resize()</code></a> for a more
convenient way to resize images. </p>
<p>This operation does not change xres or yres. The image resolution needs to
be updated by the application. </p>
<p>See also: <a class="link" href="libvips-resample.html#vips-shrinkv" title="vips_shrinkv ()"><code class="function">vips_shrinkv()</code></a>, <a class="link" href="libvips-resample.html#vips-shrink" title="vips_shrink ()"><code class="function">vips_shrink()</code></a>, <a class="link" href="libvips-resample.html#vips-resize" title="vips_resize ()"><code class="function">vips_resize()</code></a>, <a class="link" href="libvips-resample.html#vips-affine" title="vips_affine ()"><code class="function">vips_affine()</code></a>.</p>
<div class="refsect3">
<a name="id-1.4.14.5.3.8"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>in</p></td>
<td class="parameter_description"><p>input image</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>out</p></td>
<td class="parameter_description"><p>output image</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>xshrink</p></td>
<td class="parameter_description"><p>horizontal shrink</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>...</p></td>
<td class="parameter_description"><p><code class="literal">NULL</code>-terminated list of optional named arguments</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect3">
<a name="id-1.4.14.5.3.9"></a><h4>Returns</h4>
<p> 0 on success, -1 on error</p>
</div>
</div>
<hr>
<div class="refsect2">
<a name="vips-shrinkv"></a><h3>vips_shrinkv ()</h3>
<pre class="programlisting"><span class="returnvalue">int</span>
vips_shrinkv (<em class="parameter"><code><span class="type">VipsImage</span> *in</code></em>,
              <em class="parameter"><code><span class="type">VipsImage</span> **out</code></em>,
              <em class="parameter"><code><span class="type">int</span> yshrink</code></em>,
              <em class="parameter"><code>...</code></em>);</pre>
<p>Shrink <em class="parameter"><code>in</code></em>
 vertically by an integer factor. Each pixel in the output is
the average of the corresponding column of <em class="parameter"><code>yshrink</code></em>
 pixels in the input. </p>
<p>You will get aliasing for non-integer shrinks. In this case, shrink with
this function to the nearest integer size above the target shrink, then
downsample to the exact size with <a class="link" href="libvips-resample.html#vips-affine" title="vips_affine ()"><code class="function">vips_affine()</code></a> and your choice of
interpolator. See <a class="link" href="libvips-resample.html#vips-resize" title="vips_resize ()"><code class="function">vips_resize()</code></a> for a convenient way to do this.</p>
<p>This operation does not change xres or yres. The image resolution needs to
be updated by the application. </p>
<p>See also: <a class="link" href="libvips-resample.html#vips-shrinkh" title="vips_shrinkh ()"><code class="function">vips_shrinkh()</code></a>, <a class="link" href="libvips-resample.html#vips-shrink" title="vips_shrink ()"><code class="function">vips_shrink()</code></a>, <a class="link" href="libvips-resample.html#vips-resize" title="vips_resize ()"><code class="function">vips_resize()</code></a>, <a class="link" href="libvips-resample.html#vips-affine" title="vips_affine ()"><code class="function">vips_affine()</code></a>.</p>
<div class="refsect3">
<a name="id-1.4.14.5.4.8"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>in</p></td>
<td class="parameter_description"><p>input image</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>out</p></td>
<td class="parameter_description"><p>output image</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>yshrink</p></td>
<td class="parameter_description"><p>vertical shrink</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>...</p></td>
<td class="parameter_description"><p><code class="literal">NULL</code>-terminated list of optional named arguments</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect3">
<a name="id-1.4.14.5.4.9"></a><h4>Returns</h4>
<p> 0 on success, -1 on error</p>
</div>
</div>
<hr>
<div class="refsect2">
<a name="vips-shrink2"></a><h3>vips_shrink2 ()</h3>
<pre class="programlisting"><span class="returnvalue">int</span>
vips_shrink2 (<em class="parameter"><code><span class="type">VipsImage</span> *in</code></em>,
              <em class="parameter"><code><span class="type">VipsImage</span> **out</code></em>,
              <em class="parameter"><code><span class="type">double</span> xshrink</code></em>,
              <em class="parameter"><code><span class="type">double</span> yshrink</code></em>,
              <em class="parameter"><code>...</code></em>);</pre>
<p>Shrink <em class="parameter"><code>in</code></em>
 by a pair of factors with a simple box filter. </p>
<p>This is an old version of <a class="link" href="libvips-resample.html#vips-shrink" title="vips_shrink ()"><code class="function">vips_shrink()</code></a> kept around for testing. Use
<a class="link" href="libvips-resample.html#vips-shrink" title="vips_shrink ()"><code class="function">vips_shrink()</code></a> in preference. </p>
<p>See also: <a class="link" href="libvips-resample.html#vips-resize" title="vips_resize ()"><code class="function">vips_resize()</code></a>, <a class="link" href="libvips-resample.html#vips-affine" title="vips_affine ()"><code class="function">vips_affine()</code></a>.</p>
<div class="refsect3">
<a name="id-1.4.14.5.5.7"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>in</p></td>
<td class="parameter_description"><p>input image</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>out</p></td>
<td class="parameter_description"><p>output image</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>xshrink</p></td>
<td class="parameter_description"><p>horizontal shrink</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>yshrink</p></td>
<td class="parameter_description"><p>vertical shrink</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>...</p></td>
<td class="parameter_description"><p><code class="literal">NULL</code>-terminated list of optional named arguments</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect3">
<a name="id-1.4.14.5.5.8"></a><h4>Returns</h4>
<p> 0 on success, -1 on error</p>
</div>
</div>
<hr>
<div class="refsect2">
<a name="vips-similarity"></a><h3>vips_similarity ()</h3>
<pre class="programlisting"><span class="returnvalue">int</span>
vips_similarity (<em class="parameter"><code><span class="type">VipsImage</span> *in</code></em>,
                 <em class="parameter"><code><span class="type">VipsImage</span> **out</code></em>,
                 <em class="parameter"><code>...</code></em>);</pre>
<p>Optional arguments:</p>
<p><em class="parameter"><code>scale</code></em>
: scale by this factor
<em class="parameter"><code>angle</code></em>
: rotate by this many degrees anticlockwise
<em class="parameter"><code>interpolate</code></em>
: interpolate pixels with this
<em class="parameter"><code>idx</code></em>
: input horizontal offset
<em class="parameter"><code>idy</code></em>
: input vertical offset
<em class="parameter"><code>odx</code></em>
: output horizontal offset
<em class="parameter"><code>ody</code></em>
: output vertical offset</p>
<p>This operator calls <a class="link" href="libvips-resample.html#vips-affine" title="vips_affine ()"><code class="function">vips_affine()</code></a> for you, calculating the matrix for the
affine transform from <em class="parameter"><code>scale</code></em>
 and <em class="parameter"><code>angle</code></em>
. Other parameters are passed on to
<a class="link" href="libvips-resample.html#vips-affine" title="vips_affine ()"><code class="function">vips_affine()</code></a> unaltered. </p>
<p>See also: <a class="link" href="libvips-resample.html#vips-affine" title="vips_affine ()"><code class="function">vips_affine()</code></a>, <span class="type">VipsInterpolate</span>.</p>
<div class="refsect3">
<a name="id-1.4.14.5.6.8"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>in</p></td>
<td class="parameter_description"><p>input image</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>out</p></td>
<td class="parameter_description"><p>output image</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>...</p></td>
<td class="parameter_description"><p><code class="literal">NULL</code>-terminated list of optional named arguments</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect3">
<a name="id-1.4.14.5.6.9"></a><h4>Returns</h4>
<p> 0 on success, -1 on error</p>
</div>
</div>
<hr>
<div class="refsect2">
<a name="vips-affine"></a><h3>vips_affine ()</h3>
<pre class="programlisting"><span class="returnvalue">int</span>
vips_affine (<em class="parameter"><code><span class="type">VipsImage</span> *in</code></em>,
             <em class="parameter"><code><span class="type">VipsImage</span> **out</code></em>,
             <em class="parameter"><code><span class="type">double</span> a</code></em>,
             <em class="parameter"><code><span class="type">double</span> b</code></em>,
             <em class="parameter"><code><span class="type">double</span> c</code></em>,
             <em class="parameter"><code><span class="type">double</span> d</code></em>,
             <em class="parameter"><code>...</code></em>);</pre>
<p>Optional arguments:</p>
<p><em class="parameter"><code>interpolate</code></em>
: interpolate pixels with this
<em class="parameter"><code>oarea</code></em>
: output rectangle
<em class="parameter"><code>idx</code></em>
: input horizontal offset
<em class="parameter"><code>idy</code></em>
: input vertical offset
<em class="parameter"><code>odx</code></em>
: output horizontal offset
<em class="parameter"><code>ody</code></em>
: output vertical offset</p>
<p>This operator performs an affine transform on an image using <em class="parameter"><code>interpolate</code></em>
.</p>
<p>The transform is:</p>
<p>  X = <em class="parameter"><code>a</code></em>
 * (x + <em class="parameter"><code>idx</code></em>
) + <em class="parameter"><code>b</code></em>
 * (y + <em class="parameter"><code>idy</code></em>
) + <em class="parameter"><code>odx</code></em>

  Y = <em class="parameter"><code>c</code></em>
 * (x + <em class="parameter"><code>idx</code></em>
) + <em class="parameter"><code>d</code></em>
 * (y + <em class="parameter"><code>idy</code></em>
) + <em class="parameter"><code>doy</code></em>
</p>
<p>  x and y are the coordinates in input image.  
  X and Y are the coordinates in output image.
  (0,0) is the upper left corner.</p>
<p>The section of the output space defined by <em class="parameter"><code>oarea</code></em>
 is written to
<em class="parameter"><code>out</code></em>
. <em class="parameter"><code>oarea</code></em>
 is a four-element int array of left, top, width, height. 
By default <em class="parameter"><code>oarea</code></em>
 is just large enough to cover the whole of the 
transformed input image.</p>
<p><em class="parameter"><code>interpolate</code></em>
 defaults to bilinear. </p>
<p><em class="parameter"><code>idx</code></em>
, <em class="parameter"><code>idy</code></em>
, <em class="parameter"><code>odx</code></em>
, <em class="parameter"><code>ody</code></em>
 default to zero.</p>
<p>This operation does not change xres or yres. The image resolution needs to
be updated by the application. </p>
<p>See also: <a class="link" href="libvips-resample.html#vips-shrink" title="vips_shrink ()"><code class="function">vips_shrink()</code></a>, <a class="link" href="libvips-resample.html#vips-resize" title="vips_resize ()"><code class="function">vips_resize()</code></a>, <span class="type">VipsInterpolate</span>.</p>
<div class="refsect3">
<a name="id-1.4.14.5.7.15"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>in</p></td>
<td class="parameter_description"><p>input image</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>out</p></td>
<td class="parameter_description"><p>output image</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>a</p></td>
<td class="parameter_description"><p>transformation matrix coefficient</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>b</p></td>
<td class="parameter_description"><p>transformation matrix coefficient</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>c</p></td>
<td class="parameter_description"><p>transformation matrix coefficient</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>d</p></td>
<td class="parameter_description"><p>transformation matrix coefficient</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>...</p></td>
<td class="parameter_description"><p><code class="literal">NULL</code>-terminated list of optional named arguments</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect3">
<a name="id-1.4.14.5.7.16"></a><h4>Returns</h4>
<p> 0 on success, -1 on error</p>
</div>
</div>
<hr>
<div class="refsect2">
<a name="vips-resize"></a><h3>vips_resize ()</h3>
<pre class="programlisting"><span class="returnvalue">int</span>
vips_resize (<em class="parameter"><code><span class="type">VipsImage</span> *in</code></em>,
             <em class="parameter"><code><span class="type">VipsImage</span> **out</code></em>,
             <em class="parameter"><code><span class="type">double</span> scale</code></em>,
             <em class="parameter"><code>...</code></em>);</pre>
<p>Optional arguments:</p>
<p><em class="parameter"><code>vscale</code></em>
: vertical scale factor
<em class="parameter"><code>interpolate</code></em>
: interpolate pixels with this
<em class="parameter"><code>idx</code></em>
: input horizontal offset
<em class="parameter"><code>idy</code></em>
: input vertical offset</p>
<p>Resize an image. When upsizing (<em class="parameter"><code>scale</code></em>
 &gt; 1), the image is simply resized
with <a class="link" href="libvips-resample.html#vips-affine" title="vips_affine ()"><code class="function">vips_affine()</code></a> and the supplied <em class="parameter"><code>interpolate</code></em>
. When downsizing, the
image is block-shrunk with <a class="link" href="libvips-resample.html#vips-shrink" title="vips_shrink ()"><code class="function">vips_shrink()</code></a> to roughly half the interpolator
window size above the target size, then blurred with an anti-alias filter,
then resampled with <a class="link" href="libvips-resample.html#vips-affine" title="vips_affine ()"><code class="function">vips_affine()</code></a> and the supplied interpolator, then
sharpened. </p>
<p>vips_resize() normally maintains the image apect ratio. If you set
<em class="parameter"><code>vscale</code></em>
, that factor is used for the vertical scale and <em class="parameter"><code>scale</code></em>
 for the
horizontal.</p>
<p><em class="parameter"><code>interpolate</code></em>
 defaults to bicubic.</p>
<p><em class="parameter"><code>idx</code></em>
, <em class="parameter"><code>idy</code></em>
 default to zero. Set them to 0.5 to get pixel-centre sampling. </p>
<p>This operation does not change xres or yres. The image resolution needs to
be updated by the application. </p>
<p>See also: <a class="link" href="libvips-resample.html#vips-shrink" title="vips_shrink ()"><code class="function">vips_shrink()</code></a>, <a class="link" href="libvips-resample.html#vips-affine" title="vips_affine ()"><code class="function">vips_affine()</code></a>, <span class="type">VipsInterpolate</span>.</p>
<div class="refsect3">
<a name="id-1.4.14.5.8.12"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>in</p></td>
<td class="parameter_description"><p>input image</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>out</p></td>
<td class="parameter_description"><p>output image</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>scale</p></td>
<td class="parameter_description"><p>scale factor</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>...</p></td>
<td class="parameter_description"><p><code class="literal">NULL</code>-terminated list of optional named arguments</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect3">
<a name="id-1.4.14.5.8.13"></a><h4>Returns</h4>
<p> 0 on success, -1 on error</p>
</div>
</div>
<hr>
<div class="refsect2">
<a name="vips-mapim"></a><h3>vips_mapim ()</h3>
<pre class="programlisting"><span class="returnvalue">int</span>
vips_mapim (<em class="parameter"><code><span class="type">VipsImage</span> *in</code></em>,
            <em class="parameter"><code><span class="type">VipsImage</span> **out</code></em>,
            <em class="parameter"><code><span class="type">VipsImage</span> *index</code></em>,
            <em class="parameter"><code>...</code></em>);</pre>
<p>Optional arguments:</p>
<p><em class="parameter"><code>interpolate</code></em>
: interpolate pixels with this</p>
<p>This operator resamples <em class="parameter"><code>in</code></em>
 using <em class="parameter"><code>index</code></em>
 to look up pixels. <em class="parameter"><code>out</code></em>
 is
the same size as <em class="parameter"><code>index</code></em>
, with each pixel being fetched from that position in
<em class="parameter"><code>in</code></em>
. That is:</p>
<div class="informalexample"><pre class="programlisting">
out[x, y] = in[index[x, y]]
</pre></div>
<p></p>
<p>If <em class="parameter"><code>index</code></em>
 has one band, that band must be complex. Otherwise, <em class="parameter"><code>index</code></em>
 must
have two bands of any format. 
Coordinates in <em class="parameter"><code>index</code></em>
 are in pixels, with (0, 0) being the top-left corner 
of <em class="parameter"><code>in</code></em>
, and with y increasing down the image. Use <a class="link" href="libvips-create.html#vips-xyz" title="vips_xyz ()"><code class="function">vips_xyz()</code></a> to build index
images. </p>
<p><em class="parameter"><code>interpolate</code></em>
 defaults to bilinear. </p>
<p>This operation does not change xres or yres. The image resolution needs to
be updated by the application. </p>
<p>See <a class="link" href="libvips-histogram.html#vips-maplut" title="vips_maplut ()"><code class="function">vips_maplut()</code></a> for a 1D equivalent of this operation. </p>
<p>See also: <a class="link" href="libvips-create.html#vips-xyz" title="vips_xyz ()"><code class="function">vips_xyz()</code></a>, <a class="link" href="libvips-resample.html#vips-affine" title="vips_affine ()"><code class="function">vips_affine()</code></a>, <a class="link" href="libvips-resample.html#vips-resize" title="vips_resize ()"><code class="function">vips_resize()</code></a>, 
<a class="link" href="libvips-histogram.html#vips-maplut" title="vips_maplut ()"><code class="function">vips_maplut()</code></a>, <span class="type">VipsInterpolate</span>.</p>
<div class="refsect3">
<a name="id-1.4.14.5.9.14"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>in</p></td>
<td class="parameter_description"><p>input image</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>out</p></td>
<td class="parameter_description"><p>output image</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>index</p></td>
<td class="parameter_description"><p>index image</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>...</p></td>
<td class="parameter_description"><p><code class="literal">NULL</code>-terminated list of optional named arguments</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect3">
<a name="id-1.4.14.5.9.15"></a><h4>Returns</h4>
<p> 0 on success, -1 on error</p>
</div>
</div>
<hr>
<div class="refsect2">
<a name="vips-quadratic"></a><h3>vips_quadratic ()</h3>
<pre class="programlisting"><span class="returnvalue">int</span>
vips_quadratic (<em class="parameter"><code><span class="type">VipsImage</span> *in</code></em>,
                <em class="parameter"><code><span class="type">VipsImage</span> **out</code></em>,
                <em class="parameter"><code><span class="type">VipsImage</span> *coeff</code></em>,
                <em class="parameter"><code>...</code></em>);</pre>
<p>Optional arguments:</p>
<p><em class="parameter"><code>interpolate</code></em>
: use this interpolator (default bilinear)</p>
<p>This operation is unfinished and unusable, sorry. </p>
<p>See also: <a class="link" href="libvips-resample.html#vips-affine" title="vips_affine ()"><code class="function">vips_affine()</code></a>.</p>
<div class="refsect3">
<a name="id-1.4.14.5.10.8"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>in</p></td>
<td class="parameter_description"><p>input image</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>out</p></td>
<td class="parameter_description"><p>output image</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>coeff</p></td>
<td class="parameter_description"><p>horizontal quadratic</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>...</p></td>
<td class="parameter_description"><p><code class="literal">NULL</code>-terminated list of optional named arguments</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect3">
<a name="id-1.4.14.5.10.9"></a><h4>Returns</h4>
<p> 0 on success, -1 on error</p>
</div>
</div>
</div>
<div class="refsect1">
<a name="libvips-resample.other_details"></a><h2>Types and Values</h2>
</div>
</div>
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