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<title>GwySpline: Gwyddion Data Processing Library Reference Manual</title>
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<a name="libgwyprocess-GwySpline"></a><div class="titlepage"></div>
<div class="refnamediv"><table width="100%"><tr>
<td valign="top">
<h2><span class="refentrytitle"><a name="libgwyprocess-GwySpline.top_of_page"></a>GwySpline</span></h2>
<p>GwySpline — Sampling curves in plane</p>
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<td class="gallery_image" valign="top" align="right"></td>
</tr></table></div>
<div class="refsect1">
<a name="libgwyprocess-GwySpline.functions"></a><h2>Functions</h2>
<div class="informaltable"><table width="100%" border="0">
<colgroup>
<col width="150px" class="functions_return">
<col class="functions_name">
</colgroup>
<tbody>
<tr>
<td class="function_type">
<a class="link" href="libgwyprocess-GwySpline.html#GwySpline" title="GwySpline"><span class="returnvalue">GwySpline</span></a> *
</td>
<td class="function_name">
<a class="link" href="libgwyprocess-GwySpline.html#gwy-spline-new" title="gwy_spline_new ()">gwy_spline_new</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="libgwyprocess-GwySpline.html#gwy-spline-free" title="gwy_spline_free ()">gwy_spline_free</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a class="link" href="libgwyprocess-GwySpline.html#GwySpline" title="GwySpline"><span class="returnvalue">GwySpline</span></a> *
</td>
<td class="function_name">
<a class="link" href="libgwyprocess-GwySpline.html#gwy-spline-new-from-points" title="gwy_spline_new_from_points ()">gwy_spline_new_from_points</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a href="http://developer.gnome.org/doc/API/2.0/gtk/glibglib-Basic-Types.html#guint"><span class="returnvalue">guint</span></a>
</td>
<td class="function_name">
<a class="link" href="libgwyprocess-GwySpline.html#gwy-spline-get-npoints" title="gwy_spline_get_npoints ()">gwy_spline_get_npoints</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">const <span class="returnvalue">GwyXY</span> *
</td>
<td class="function_name">
<a class="link" href="libgwyprocess-GwySpline.html#gwy-spline-get-points" title="gwy_spline_get_points ()">gwy_spline_get_points</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">const <span class="returnvalue">GwyXY</span> *
</td>
<td class="function_name">
<a class="link" href="libgwyprocess-GwySpline.html#gwy-spline-get-tangents" title="gwy_spline_get_tangents ()">gwy_spline_get_tangents</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a href="http://developer.gnome.org/doc/API/2.0/gtk/glibglib-Basic-Types.html#gdouble"><span class="returnvalue">gdouble</span></a>
</td>
<td class="function_name">
<a class="link" href="libgwyprocess-GwySpline.html#gwy-spline-get-slackness" title="gwy_spline_get_slackness ()">gwy_spline_get_slackness</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a href="http://developer.gnome.org/doc/API/2.0/gtk/glibglib-Basic-Types.html#gboolean"><span class="returnvalue">gboolean</span></a>
</td>
<td class="function_name">
<a class="link" href="libgwyprocess-GwySpline.html#gwy-spline-get-closed" title="gwy_spline_get_closed ()">gwy_spline_get_closed</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="libgwyprocess-GwySpline.html#gwy-spline-set-points" title="gwy_spline_set_points ()">gwy_spline_set_points</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="libgwyprocess-GwySpline.html#gwy-spline-set-slackness" title="gwy_spline_set_slackness ()">gwy_spline_set_slackness</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="libgwyprocess-GwySpline.html#gwy-spline-set-closed" title="gwy_spline_set_closed ()">gwy_spline_set_closed</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a href="http://developer.gnome.org/doc/API/2.0/gtk/glibglib-Basic-Types.html#gdouble"><span class="returnvalue">gdouble</span></a>
</td>
<td class="function_name">
<a class="link" href="libgwyprocess-GwySpline.html#gwy-spline-length" title="gwy_spline_length ()">gwy_spline_length</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">const <span class="returnvalue">GwyXY</span> *
</td>
<td class="function_name">
<a class="link" href="libgwyprocess-GwySpline.html#gwy-spline-sample-naturally" title="gwy_spline_sample_naturally ()">gwy_spline_sample_naturally</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a href="http://developer.gnome.org/doc/API/2.0/gtk/glibglib-Basic-Types.html#gdouble"><span class="returnvalue">gdouble</span></a>
</td>
<td class="function_name">
<a class="link" href="libgwyprocess-GwySpline.html#gwy-spline-sample-uniformly" title="gwy_spline_sample_uniformly ()">gwy_spline_sample_uniformly</a> <span class="c_punctuation">()</span>
</td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect1">
<a name="libgwyprocess-GwySpline.other"></a><h2>Types and Values</h2>
<div class="informaltable"><table width="100%" border="0">
<colgroup>
<col width="150px" class="name">
<col class="description">
</colgroup>
<tbody><tr>
<td class="datatype_keyword"> </td>
<td class="function_name"><a class="link" href="libgwyprocess-GwySpline.html#GwySpline" title="GwySpline">GwySpline</a></td>
</tr></tbody>
</table></div>
</div>
<div class="refsect1">
<a name="libgwyprocess-GwySpline.includes"></a><h2>Includes</h2>
<pre class="synopsis">#include <libprocess/gwyprocess.h>
</pre>
</div>
<div class="refsect1">
<a name="libgwyprocess-GwySpline.description"></a><h2>Description</h2>
</div>
<div class="refsect1">
<a name="libgwyprocess-GwySpline.functions_details"></a><h2>Functions</h2>
<div class="refsect2">
<a name="gwy-spline-new"></a><h3>gwy_spline_new ()</h3>
<pre class="programlisting"><a class="link" href="libgwyprocess-GwySpline.html#GwySpline" title="GwySpline"><span class="returnvalue">GwySpline</span></a> *
gwy_spline_new (<em class="parameter"><code><span class="type">void</span></code></em>);</pre>
<p>Creates a new empty spline curve.</p>
<p>You need to set the curve points using <a class="link" href="libgwyprocess-GwySpline.html#gwy-spline-set-points" title="gwy_spline_set_points ()"><code class="function">gwy_spline_set_points()</code></a> before any
sampling along the curve. Alternatively, use <a class="link" href="libgwyprocess-GwySpline.html#gwy-spline-new-from-points" title="gwy_spline_new_from_points ()"><code class="function">gwy_spline_new_from_points()</code></a>
to construct the spline already with some points.</p>
<div class="refsect3">
<a name="gwy-spline-new.returns"></a><h4>Returns</h4>
<p> A newly created spline curve.</p>
</div>
<p class="since">Since: <a class="link" href="api-index-2-45.html#api-index-2.45">2.45</a></p>
</div>
<hr>
<div class="refsect2">
<a name="gwy-spline-free"></a><h3>gwy_spline_free ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
gwy_spline_free (<em class="parameter"><code><a class="link" href="libgwyprocess-GwySpline.html#GwySpline" title="GwySpline"><span class="type">GwySpline</span></a> *spline</code></em>);</pre>
<p>Frees a spline curve and all associated resources.</p>
<div class="refsect3">
<a name="gwy-spline-free.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table 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>spline</p></td>
<td class="parameter_description"><p>A spline curve.</p></td>
<td class="parameter_annotations"> </td>
</tr></tbody>
</table></div>
</div>
<p class="since">Since: <a class="link" href="api-index-2-45.html#api-index-2.45">2.45</a></p>
</div>
<hr>
<div class="refsect2">
<a name="gwy-spline-new-from-points"></a><h3>gwy_spline_new_from_points ()</h3>
<pre class="programlisting"><a class="link" href="libgwyprocess-GwySpline.html#GwySpline" title="GwySpline"><span class="returnvalue">GwySpline</span></a> *
gwy_spline_new_from_points (<em class="parameter"><code>const <span class="type">GwyXY</span> *xy</code></em>,
<em class="parameter"><code><a href="http://developer.gnome.org/doc/API/2.0/gtk/glibglib-Basic-Types.html#guint"><span class="type">guint</span></a> n</code></em>);</pre>
<p>Creates a new spline curve passing through given points.</p>
<p>See <a class="link" href="libgwyprocess-GwySpline.html#gwy-spline-set-points" title="gwy_spline_set_points ()"><code class="function">gwy_spline_set_points()</code></a> for discussion.</p>
<div class="refsect3">
<a name="gwy-spline-new-from-points.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table 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>xy</p></td>
<td class="parameter_description"><p>Array of points in plane the curve will pass through.</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>n</p></td>
<td class="parameter_description"><p>Number of points in <em class="parameter"><code>xy</code></em>
.</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect3">
<a name="gwy-spline-new-from-points.returns"></a><h4>Returns</h4>
<p> A newly created spline curve.</p>
</div>
<p class="since">Since: <a class="link" href="api-index-2-45.html#api-index-2.45">2.45</a></p>
</div>
<hr>
<div class="refsect2">
<a name="gwy-spline-get-npoints"></a><h3>gwy_spline_get_npoints ()</h3>
<pre class="programlisting"><a href="http://developer.gnome.org/doc/API/2.0/gtk/glibglib-Basic-Types.html#guint"><span class="returnvalue">guint</span></a>
gwy_spline_get_npoints (<em class="parameter"><code><a class="link" href="libgwyprocess-GwySpline.html#GwySpline" title="GwySpline"><span class="type">GwySpline</span></a> *spline</code></em>);</pre>
<p>Gets the number of points of a spline curve.</p>
<div class="refsect3">
<a name="gwy-spline-get-npoints.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table 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>spline</p></td>
<td class="parameter_description"><p>A spline curve.</p></td>
<td class="parameter_annotations"> </td>
</tr></tbody>
</table></div>
</div>
<div class="refsect3">
<a name="gwy-spline-get-npoints.returns"></a><h4>Returns</h4>
<p> The number of XY points defining the curve.</p>
</div>
<p class="since">Since: <a class="link" href="api-index-2-45.html#api-index-2.45">2.45</a></p>
</div>
<hr>
<div class="refsect2">
<a name="gwy-spline-get-points"></a><h3>gwy_spline_get_points ()</h3>
<pre class="programlisting">const <span class="returnvalue">GwyXY</span> *
gwy_spline_get_points (<em class="parameter"><code><a class="link" href="libgwyprocess-GwySpline.html#GwySpline" title="GwySpline"><span class="type">GwySpline</span></a> *spline</code></em>);</pre>
<p>Gets the coordinates of spline curve points.</p>
<p>If the spline is empty (there are no points) the function returns <a href="http://developer.gnome.org/doc/API/2.0/gtk/glibglib-Standard-Macros.html#NULL:CAPS"><code class="literal">NULL</code></a>.</p>
<div class="refsect3">
<a name="gwy-spline-get-points.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table 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>spline</p></td>
<td class="parameter_description"><p>A spline curve.</p></td>
<td class="parameter_annotations"> </td>
</tr></tbody>
</table></div>
</div>
<div class="refsect3">
<a name="gwy-spline-get-points.returns"></a><h4>Returns</h4>
<p> Coordinates of the XY points defining the curve. The returned
array is owned by <em class="parameter"><code>spline</code></em>
, must not be modified and is only
guaranteed to exist so long as the spline is not modified nor
destroyed.</p>
</div>
<p class="since">Since: <a class="link" href="api-index-2-45.html#api-index-2.45">2.45</a></p>
</div>
<hr>
<div class="refsect2">
<a name="gwy-spline-get-tangents"></a><h3>gwy_spline_get_tangents ()</h3>
<pre class="programlisting">const <span class="returnvalue">GwyXY</span> *
gwy_spline_get_tangents (<em class="parameter"><code><a class="link" href="libgwyprocess-GwySpline.html#GwySpline" title="GwySpline"><span class="type">GwySpline</span></a> *spline</code></em>);</pre>
<p>Gets tangents to the curve in its defining points.</p>
<p>See <a class="link" href="libgwyprocess-GwySpline.html#gwy-spline-sample-uniformly" title="gwy_spline_sample_uniformly ()"><code class="function">gwy_spline_sample_uniformly()</code></a> for discussion.</p>
<p>If the spline is empty (there are no points) the function returns <a href="http://developer.gnome.org/doc/API/2.0/gtk/glibglib-Standard-Macros.html#NULL:CAPS"><code class="literal">NULL</code></a>.</p>
<div class="refsect3">
<a name="gwy-spline-get-tangents.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table 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>spline</p></td>
<td class="parameter_description"><p>A spline curve.</p></td>
<td class="parameter_annotations"> </td>
</tr></tbody>
</table></div>
</div>
<div class="refsect3">
<a name="gwy-spline-get-tangents.returns"></a><h4>Returns</h4>
<p> Tangents to the spline in the XY points defining the curve. The
returned array is owned by <em class="parameter"><code>spline</code></em>
, must not be modified and is
only guaranteed to exist so long as the spline is not modified nor
destroyed.</p>
</div>
<p class="since">Since: <a class="link" href="api-index-2-45.html#api-index-2.45">2.45</a></p>
</div>
<hr>
<div class="refsect2">
<a name="gwy-spline-get-slackness"></a><h3>gwy_spline_get_slackness ()</h3>
<pre class="programlisting"><a href="http://developer.gnome.org/doc/API/2.0/gtk/glibglib-Basic-Types.html#gdouble"><span class="returnvalue">gdouble</span></a>
gwy_spline_get_slackness (<em class="parameter"><code><a class="link" href="libgwyprocess-GwySpline.html#GwySpline" title="GwySpline"><span class="type">GwySpline</span></a> *spline</code></em>);</pre>
<p>Gets the slackness parameter of a spline curve.</p>
<p>See <a class="link" href="libgwyprocess-GwySpline.html#gwy-spline-set-slackness" title="gwy_spline_set_slackness ()"><code class="function">gwy_spline_set_slackness()</code></a> for discussion.</p>
<div class="refsect3">
<a name="gwy-spline-get-slackness.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table 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>spline</p></td>
<td class="parameter_description"><p>A spline curve.</p></td>
<td class="parameter_annotations"> </td>
</tr></tbody>
</table></div>
</div>
<div class="refsect3">
<a name="gwy-spline-get-slackness.returns"></a><h4>Returns</h4>
<p> The slackness parameter value.</p>
</div>
<p class="since">Since: <a class="link" href="api-index-2-45.html#api-index-2.45">2.45</a></p>
</div>
<hr>
<div class="refsect2">
<a name="gwy-spline-get-closed"></a><h3>gwy_spline_get_closed ()</h3>
<pre class="programlisting"><a href="http://developer.gnome.org/doc/API/2.0/gtk/glibglib-Basic-Types.html#gboolean"><span class="returnvalue">gboolean</span></a>
gwy_spline_get_closed (<em class="parameter"><code><a class="link" href="libgwyprocess-GwySpline.html#GwySpline" title="GwySpline"><span class="type">GwySpline</span></a> *spline</code></em>);</pre>
<p>Reports whether a spline curve is closed or not.</p>
<p>See <a class="link" href="libgwyprocess-GwySpline.html#gwy-spline-set-closed" title="gwy_spline_set_closed ()"><code class="function">gwy_spline_set_closed()</code></a> for discussion.</p>
<div class="refsect3">
<a name="gwy-spline-get-closed.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table 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>spline</p></td>
<td class="parameter_description"><p>A spline curve.</p></td>
<td class="parameter_annotations"> </td>
</tr></tbody>
</table></div>
</div>
<div class="refsect3">
<a name="gwy-spline-get-closed.returns"></a><h4>Returns</h4>
<p> <a href="http://developer.gnome.org/doc/API/2.0/gtk/glibglib-Standard-Macros.html#TRUE:CAPS"><code class="literal">TRUE</code></a> if <em class="parameter"><code>spline</code></em>
is closed, <a href="http://developer.gnome.org/doc/API/2.0/gtk/glibglib-Standard-Macros.html#FALSE:CAPS"><code class="literal">FALSE</code></a> if it is open-ended.</p>
</div>
<p class="since">Since: <a class="link" href="api-index-2-45.html#api-index-2.45">2.45</a></p>
</div>
<hr>
<div class="refsect2">
<a name="gwy-spline-set-points"></a><h3>gwy_spline_set_points ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
gwy_spline_set_points (<em class="parameter"><code><a class="link" href="libgwyprocess-GwySpline.html#GwySpline" title="GwySpline"><span class="type">GwySpline</span></a> *spline</code></em>,
<em class="parameter"><code>const <span class="type">GwyXY</span> *xy</code></em>,
<em class="parameter"><code><a href="http://developer.gnome.org/doc/API/2.0/gtk/glibglib-Basic-Types.html#guint"><span class="type">guint</span></a> n</code></em>);</pre>
<p>Sets the coordinates of XY points a spline curve should pass through.</p>
<p>It is possible to pass <em class="parameter"><code>n</code></em>
=0 to make the spline empty (<em class="parameter"><code>xy</code></em>
can be <a href="http://developer.gnome.org/doc/API/2.0/gtk/glibglib-Standard-Macros.html#NULL:CAPS"><code class="literal">NULL</code></a> then)
but such spline may not be sampled using <a class="link" href="libgwyprocess-GwySpline.html#gwy-spline-sample-uniformly" title="gwy_spline_sample_uniformly ()"><code class="function">gwy_spline_sample_uniformly()</code></a>.</p>
<p>The coordinates should be device-scaled, i.e. they should data field rows
and columns, or screen or image pixels. Generally, the unit length should
be about the smallest distinguishable distance.</p>
<p>This is important namely for <a class="link" href="libgwyprocess-GwySpline.html#gwy-spline-sample-naturally" title="gwy_spline_sample_naturally ()"><code class="function">gwy_spline_sample_naturally()</code></a> that stops
refining the curve when the details become too tiny, even though there may
be sharp changes of direction. It is also important if the physical X and Y
scales differ.</p>
<p>Using unscaled physical coordinates may produce odd results.</p>
<div class="refsect3">
<a name="gwy-spline-set-points.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table 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>spline</p></td>
<td class="parameter_description"><p>A spline curve.</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>xy</p></td>
<td class="parameter_description"><p>Array of points in plane the curve will pass through.</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>n</p></td>
<td class="parameter_description"><p>Number of points in <em class="parameter"><code>xy</code></em>
.</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<p class="since">Since: <a class="link" href="api-index-2-45.html#api-index-2.45">2.45</a></p>
</div>
<hr>
<div class="refsect2">
<a name="gwy-spline-set-slackness"></a><h3>gwy_spline_set_slackness ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
gwy_spline_set_slackness (<em class="parameter"><code><a class="link" href="libgwyprocess-GwySpline.html#GwySpline" title="GwySpline"><span class="type">GwySpline</span></a> *spline</code></em>,
<em class="parameter"><code><a href="http://developer.gnome.org/doc/API/2.0/gtk/glibglib-Basic-Types.html#gdouble"><span class="type">gdouble</span></a> slackness</code></em>);</pre>
<p>Sets the slackness parameter of a spline curve.</p>
<p>The slackness parameter determines how taut or slack the curve is.</p>
<p>The curve always passes through the given XY points. For zero slackness
the curve is maximally taut, i.e. the shortest possible passing
through the points. Such curve is formed by straight segments. For
slackness of 1 the curve is a ‘free’ spline. Values smaller than 1 mean
tensile stress while values larger than 1 compressive stres. The default
value is 1/sqrt(2).</p>
<div class="refsect3">
<a name="gwy-spline-set-slackness.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table 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>spline</p></td>
<td class="parameter_description"><p>A spline curve.</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>slackness</p></td>
<td class="parameter_description"><p>New slackness parameter value from the range [0, <a href="/usr/share/gtk-doc/html/glibglib-Numerical-Definitions.html#G-SQRT2:CAPS"><code class="literal">G_SQRT2</code></a>].</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<p class="since">Since: <a class="link" href="api-index-2-45.html#api-index-2.45">2.45</a></p>
</div>
<hr>
<div class="refsect2">
<a name="gwy-spline-set-closed"></a><h3>gwy_spline_set_closed ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
gwy_spline_set_closed (<em class="parameter"><code><a class="link" href="libgwyprocess-GwySpline.html#GwySpline" title="GwySpline"><span class="type">GwySpline</span></a> *spline</code></em>,
<em class="parameter"><code><a href="/usr/share/gtk-doc/html/glibglib-Basic-Types.html#gboolean"><span class="type">gboolean</span></a> closed</code></em>);</pre>
<p>Sets whether a spline curve is closed or open.</p>
<p>In closed curve the last point is connected smoothly with the first point,
forming a cycle. Note you should not repeat the point in the <em class="parameter"><code>xy</code></em>
array.
When a closed curve is sampled, the sampling starts from the first point
and continues beyond the last point until it gets close to the first point
again.</p>
<p>An open curve begins with the first point and ends with the last point. It
has zero curvature at these two points.</p>
<div class="refsect3">
<a name="gwy-spline-set-closed.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table 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>spline</p></td>
<td class="parameter_description"><p>A spline curve.</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>closed</p></td>
<td class="parameter_description"><p><a href="/usr/share/gtk-doc/html/glibglib-Standard-Macros.html#TRUE:CAPS"><code class="literal">TRUE</code></a> to make <em class="parameter"><code>spline</code></em>
closed, <a href="/usr/share/gtk-doc/html/glibglib-Standard-Macros.html#FALSE:CAPS"><code class="literal">FALSE</code></a> to make it open-ended.</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<p class="since">Since: <a class="link" href="api-index-2-45.html#api-index-2.45">2.45</a></p>
</div>
<hr>
<div class="refsect2">
<a name="gwy-spline-length"></a><h3>gwy_spline_length ()</h3>
<pre class="programlisting"><a href="/usr/share/gtk-doc/html/glibglib-Basic-Types.html#gdouble"><span class="returnvalue">gdouble</span></a>
gwy_spline_length (<em class="parameter"><code><a class="link" href="libgwyprocess-GwySpline.html#GwySpline" title="GwySpline"><span class="type">GwySpline</span></a> *spline</code></em>);</pre>
<p>Calculates the length of a spline curve.</p>
<p>This is useful when you want to sample the curve with a specific step
(at least approximately).</p>
<p>Note <a class="link" href="libgwyprocess-GwySpline.html#gwy-spline-sample-uniformly" title="gwy_spline_sample_uniformly ()"><code class="function">gwy_spline_sample_uniformly()</code></a> also returns the length.</p>
<div class="refsect3">
<a name="gwy-spline-length.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table 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>spline</p></td>
<td class="parameter_description"><p>A spline curve.</p></td>
<td class="parameter_annotations"> </td>
</tr></tbody>
</table></div>
</div>
<div class="refsect3">
<a name="gwy-spline-length.returns"></a><h4>Returns</h4>
<p> The curve length.</p>
</div>
<p class="since">Since: <a class="link" href="api-index-2-45.html#api-index-2.45">2.45</a></p>
</div>
<hr>
<div class="refsect2">
<a name="gwy-spline-sample-naturally"></a><h3>gwy_spline_sample_naturally ()</h3>
<pre class="programlisting">const <span class="returnvalue">GwyXY</span> *
gwy_spline_sample_naturally (<em class="parameter"><code><a class="link" href="libgwyprocess-GwySpline.html#GwySpline" title="GwySpline"><span class="type">GwySpline</span></a> *spline</code></em>,
<em class="parameter"><code><a href="/usr/share/gtk-doc/html/glibglib-Basic-Types.html#guint"><span class="type">guint</span></a> *n</code></em>);</pre>
<p>Samples efficiently a spline curve.</p>
<p>This function calculates coordinates of points that lie on the spline curve
and are sufficient for a good approximation by straight lines. This is
particularly useful for drawing the curve.</p>
<p>See <a class="link" href="libgwyprocess-GwySpline.html#gwy-spline-sample-uniformly" title="gwy_spline_sample_uniformly ()"><code class="function">gwy_spline_sample_uniformly()</code></a> for some discussion of closed versus open
curves and corner case handling.</p>
<div class="refsect3">
<a name="gwy-spline-sample-naturally.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table 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>spline</p></td>
<td class="parameter_description"><p>A spline curve.</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>n</p></td>
<td class="parameter_description"><p>Location where to store the number of returned points.</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect3">
<a name="gwy-spline-sample-naturally.returns"></a><h4>Returns</h4>
<p> Coordinates of the XY points defining the sampled curve. The
returned array is owned by <em class="parameter"><code>spline</code></em>
, must not be modified and is
only guaranteed to exist so long as the spline is not modified nor
destroyed.</p>
</div>
<p class="since">Since: <a class="link" href="api-index-2-45.html#api-index-2.45">2.45</a></p>
</div>
<hr>
<div class="refsect2">
<a name="gwy-spline-sample-uniformly"></a><h3>gwy_spline_sample_uniformly ()</h3>
<pre class="programlisting"><a href="/usr/share/gtk-doc/html/glibglib-Basic-Types.html#gdouble"><span class="returnvalue">gdouble</span></a>
gwy_spline_sample_uniformly (<em class="parameter"><code><a class="link" href="libgwyprocess-GwySpline.html#GwySpline" title="GwySpline"><span class="type">GwySpline</span></a> *spline</code></em>,
<em class="parameter"><code><span class="type">GwyXY</span> *xy</code></em>,
<em class="parameter"><code><span class="type">GwyXY</span> *t</code></em>,
<em class="parameter"><code><a href="/usr/share/gtk-doc/html/glibglib-Basic-Types.html#guint"><span class="type">guint</span></a> n</code></em>);</pre>
<p>Samples uniformly a spline curve.</p>
<p>This function calculates coordinates of points that lie on the spline curve
and are equidistant along it. For open curves the first sampled point
coincides with the first given XY point and, similar, the last with the last.
For closed curves the first point again coincides with the first given XY
point but the last lies one sampling distance before the curve gets back
again to the first point.</p>
<p>If you want to specify the sampling step instead of the number of samples
use <a class="link" href="libgwyprocess-GwySpline.html#gwy-spline-length" title="gwy_spline_length ()"><code class="function">gwy_spline_length()</code></a> first to obtain the curve length and calculate <em class="parameter"><code>n</code></em>
accordingly.</p>
<p>A single-point curve always consists of a single point. Hence all samples
lie in this point. A two-point curve is always formed by straight segments,
in the case of a closed curve one going forward and the other back. A
meaningful sampling requires <em class="parameter"><code>n</code></em>
at least 2, nevertheless, the function
permits also <em class="parameter"><code>n</code></em>
of one or zero.</p>
<p>The tangents vectors stored in <em class="parameter"><code>t</code></em>
are normalised and oriented from the
beginning of the curve towards the end. If two or more consecutive given XY
points coincide or the curve has only a single point the vectors may be
(0,0).</p>
<div class="refsect3">
<a name="gwy-spline-sample-uniformly.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table 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>spline</p></td>
<td class="parameter_description"><p>A spline curve.</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>xy</p></td>
<td class="parameter_description"><p>Array where the sampled point coordinates should be stored in.
May be <a href="/usr/share/gtk-doc/html/glibglib-Standard-Macros.html#NULL:CAPS"><code class="literal">NULL</code></a> if you are only interested in the tangents.</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>t</p></td>
<td class="parameter_description"><p>Array where tangent vectors at the <em class="parameter"><code>xy</code></em>
coordinates should be stored in.
May be <a href="/usr/share/gtk-doc/html/glibglib-Standard-Macros.html#NULL:CAPS"><code class="literal">NULL</code></a> if you are only interested in the coordinates.</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>n</p></td>
<td class="parameter_description"><p>The number of samples to take.</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect3">
<a name="gwy-spline-sample-uniformly.returns"></a><h4>Returns</h4>
<p> The curve length.</p>
</div>
<p class="since">Since: <a class="link" href="api-index-2-45.html#api-index-2.45">2.45</a></p>
</div>
</div>
<div class="refsect1">
<a name="libgwyprocess-GwySpline.other_details"></a><h2>Types and Values</h2>
<div class="refsect2">
<a name="GwySpline"></a><h3>GwySpline</h3>
<pre class="programlisting">typedef struct _GwySpline GwySpline;</pre>
</div>
</div>
</div>
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