/usr/share/gtk-doc/html/libgwyprocess/libgwyprocess-simpleFFT.html is in libgwyddion20-doc 2.34-3ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 | <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Gwyddion Data Processing Library Reference Manual: simpleFFT</title>
<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
<link rel="home" href="index.html" title="Gwyddion Data Processing Library Reference Manual">
<link rel="up" href="index.html" title="Gwyddion Data Processing Library Reference Manual">
<link rel="prev" href="libgwyprocess-linestats.html" title="linestats">
<link rel="next" href="libgwyprocess-stats.html" title="stats">
<meta name="generator" content="GTK-Doc V1.19 (XML mode)">
<link rel="stylesheet" href="style.css" type="text/css">
</head>
<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
<table class="navigation" id="top" width="100%" summary="Navigation header" cellpadding="2" cellspacing="10"><tr valign="middle">
<td width="100%" align="left">
<a href="#" class="shortcut">Top</a>
|
<a href="#libgwyprocess-simpleFFT.description" class="shortcut">Description</a>
</td>
<td><a accesskey="h" href="index.html"><img src="home.png" width="16" height="16" border="0" alt="Home"></a></td>
<td><img src="up-insensitive.png" width="16" height="16" border="0"></td>
<td><a accesskey="p" href="libgwyprocess-linestats.html"><img src="left.png" width="16" height="16" border="0" alt="Prev"></a></td>
<td><a accesskey="n" href="libgwyprocess-stats.html"><img src="right.png" width="16" height="16" border="0" alt="Next"></a></td>
</tr></table>
<div class="refentry">
<a name="libgwyprocess-simpleFFT"></a><div class="titlepage"></div>
<div class="refnamediv"><table width="100%"><tr>
<td valign="top">
<h2><span class="refentrytitle"><a name="libgwyprocess-simpleFFT.top_of_page"></a>simpleFFT</span></h2>
<p>simpleFFT — Simple FFT algorithm</p>
</td>
<td valign="top" align="right"></td>
</tr></table></div>
<div class="refsynopsisdiv">
<a name="libgwyprocess-simpleFFT.synopsis"></a><h2>Synopsis</h2>
<pre class="synopsis">
#include <libprocess/gwyprocess.h>
<span class="returnvalue">void</span> <a class="link" href="libgwyprocess-simpleFFT.html#gwy-fft-simple" title="gwy_fft_simple ()">gwy_fft_simple</a> (<em class="parameter"><code><a class="link" href="libgwyprocess-gwyprocessenums.html#GwyTransformDirection" title="enum GwyTransformDirection"><span class="type">GwyTransformDirection</span></a> dir</code></em>,
<em class="parameter"><code><a href="http://developer.gnome.org/doc/API/2.0/glib/glib-Basic-Types.html#gint"><span class="type">gint</span></a> n</code></em>,
<em class="parameter"><code><a href="http://developer.gnome.org/doc/API/2.0/glib/glib-Basic-Types.html#gint"><span class="type">gint</span></a> istride</code></em>,
<em class="parameter"><code>const <a href="http://developer.gnome.org/doc/API/2.0/glib/glib-Basic-Types.html#gdouble"><span class="type">gdouble</span></a> *in_re</code></em>,
<em class="parameter"><code>const <a href="http://developer.gnome.org/doc/API/2.0/glib/glib-Basic-Types.html#gdouble"><span class="type">gdouble</span></a> *in_im</code></em>,
<em class="parameter"><code><a href="http://developer.gnome.org/doc/API/2.0/glib/glib-Basic-Types.html#gint"><span class="type">gint</span></a> ostride</code></em>,
<em class="parameter"><code><a href="http://developer.gnome.org/doc/API/2.0/glib/glib-Basic-Types.html#gdouble"><span class="type">gdouble</span></a> *out_re</code></em>,
<em class="parameter"><code><a href="http://developer.gnome.org/doc/API/2.0/glib/glib-Basic-Types.html#gdouble"><span class="type">gdouble</span></a> *out_im</code></em>);
<span class="returnvalue">void</span> <a class="link" href="libgwyprocess-simpleFFT.html#gwy-fft-window" title="gwy_fft_window ()">gwy_fft_window</a> (<em class="parameter"><code><a href="http://developer.gnome.org/doc/API/2.0/glib/glib-Basic-Types.html#gint"><span class="type">gint</span></a> n</code></em>,
<em class="parameter"><code><a href="http://developer.gnome.org/doc/API/2.0/glib/glib-Basic-Types.html#gdouble"><span class="type">gdouble</span></a> *data</code></em>,
<em class="parameter"><code><a class="link" href="libgwyprocess-gwyprocessenums.html#GwyWindowingType" title="enum GwyWindowingType"><span class="type">GwyWindowingType</span></a> windowing</code></em>);
<span class="returnvalue">void</span> <a class="link" href="libgwyprocess-simpleFFT.html#gwy-fft-window-data-field" title="gwy_fft_window_data_field ()">gwy_fft_window_data_field</a> (<em class="parameter"><code><a class="link" href="GwyDataField.html" title="GwyDataField"><span class="type">GwyDataField</span></a> *dfield</code></em>,
<em class="parameter"><code><a class="link" href="libgwyprocess-gwyprocessenums.html#GwyOrientation" title="enum GwyOrientation"><span class="type">GwyOrientation</span></a> orientation</code></em>,
<em class="parameter"><code><a class="link" href="libgwyprocess-gwyprocessenums.html#GwyWindowingType" title="enum GwyWindowingType"><span class="type">GwyWindowingType</span></a> windowing</code></em>);
</pre>
</div>
<div class="refsect1">
<a name="libgwyprocess-simpleFFT.description"></a><h2>Description</h2>
<p>
The simple one-dimensional FFT algorithm <a class="link" href="libgwyprocess-simpleFFT.html#gwy-fft-simple" title="gwy_fft_simple ()"><code class="function">gwy_fft_simple()</code></a> is used as
a fallback by other functions when a better implementation (FFTW3) is not
available.
</p>
<p>
You should not use it directly, as it is a waste of resources
if FFTW3 backed is in use, neither you should feel any need to, as
high-level functions such as <a class="link" href="libgwyprocess-inttrans.html#gwy-data-field-2dfft" title="gwy_data_field_2dfft ()"><code class="function">gwy_data_field_2dfft()</code></a> are available.
</p>
<p>
Up to version 2.7 simpleFFT works only with certain tranform sizes, mostly
powers of 2. Since 2.8 it can handle arbitrary tranform sizes, although
sizes with large prime factors can be quite slow (still O(n*log(n)) though).
</p>
</div>
<div class="refsect1">
<a name="libgwyprocess-simpleFFT.details"></a><h2>Details</h2>
<div class="refsect2">
<a name="gwy-fft-simple"></a><h3>gwy_fft_simple ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span> gwy_fft_simple (<em class="parameter"><code><a class="link" href="libgwyprocess-gwyprocessenums.html#GwyTransformDirection" title="enum GwyTransformDirection"><span class="type">GwyTransformDirection</span></a> dir</code></em>,
<em class="parameter"><code><a href="http://developer.gnome.org/doc/API/2.0/glib/glib-Basic-Types.html#gint"><span class="type">gint</span></a> n</code></em>,
<em class="parameter"><code><a href="http://developer.gnome.org/doc/API/2.0/glib/glib-Basic-Types.html#gint"><span class="type">gint</span></a> istride</code></em>,
<em class="parameter"><code>const <a href="http://developer.gnome.org/doc/API/2.0/glib/glib-Basic-Types.html#gdouble"><span class="type">gdouble</span></a> *in_re</code></em>,
<em class="parameter"><code>const <a href="http://developer.gnome.org/doc/API/2.0/glib/glib-Basic-Types.html#gdouble"><span class="type">gdouble</span></a> *in_im</code></em>,
<em class="parameter"><code><a href="http://developer.gnome.org/doc/API/2.0/glib/glib-Basic-Types.html#gint"><span class="type">gint</span></a> ostride</code></em>,
<em class="parameter"><code><a href="http://developer.gnome.org/doc/API/2.0/glib/glib-Basic-Types.html#gdouble"><span class="type">gdouble</span></a> *out_re</code></em>,
<em class="parameter"><code><a href="http://developer.gnome.org/doc/API/2.0/glib/glib-Basic-Types.html#gdouble"><span class="type">gdouble</span></a> *out_im</code></em>);</pre>
<p>
Performs a DFT algorithm.
</p>
<p>
This is a low-level function used by other FFT functions when no better
backend is available.
</p>
<p>
Strides are distances between samples in input and output arrays. Use 1
for normal `dense' arrays. To use <a class="link" href="libgwyprocess-simpleFFT.html#gwy-fft-simple" title="gwy_fft_simple ()"><code class="function">gwy_fft_simple()</code></a> with interleaved arrays,
that is with alternating real and imaginary data, call it with
<em class="parameter"><code>istride</code></em>=2, <em class="parameter"><code>in_re</code></em>=<em class="parameter"><code>complex_array</code></em>, <em class="parameter"><code>in_im</code></em>=<em class="parameter"><code>complex_array</code></em>+1 (and similarly
for output arrays).
</p>
<p>
The output is symmetrically normalized by square root of <em class="parameter"><code>n</code></em> for both
transform directions. By performing forward and then backward transform,
you will obtain the original array (up to rounding errors).
</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>dir</code></em> :</span></p></td>
<td>Transformation direction.</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>n</code></em> :</span></p></td>
<td>Number of data points. Note only certain transform sizes are
implemented. If <a class="link" href="libgwyprocess-simpleFFT.html#gwy-fft-simple" title="gwy_fft_simple ()"><code class="function">gwy_fft_simple()</code></a> is the current FFT backend, then
<a class="link" href="libgwyprocess-inttrans.html#gwy-fft-find-nice-size" title="gwy_fft_find_nice_size ()"><code class="function">gwy_fft_find_nice_size()</code></a> can provide accepted transform sizes.
If <a class="link" href="libgwyprocess-simpleFFT.html#gwy-fft-simple" title="gwy_fft_simple ()"><code class="function">gwy_fft_simple()</code></a> is not the current FFT backend, you should not
use it.</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>istride</code></em> :</span></p></td>
<td>Input data stride.</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>in_re</code></em> :</span></p></td>
<td>Real part of input data.</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>in_im</code></em> :</span></p></td>
<td>Imaginary part of input data.</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>ostride</code></em> :</span></p></td>
<td>Output data stride.</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>out_re</code></em> :</span></p></td>
<td>Real part of output data.</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>out_im</code></em> :</span></p></td>
<td>Imaginary part of output data.</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="gwy-fft-window"></a><h3>gwy_fft_window ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span> gwy_fft_window (<em class="parameter"><code><a href="/usr/share/gtk-doc/html/glib/glib-Basic-Types.html#gint"><span class="type">gint</span></a> n</code></em>,
<em class="parameter"><code><a href="/usr/share/gtk-doc/html/glib/glib-Basic-Types.html#gdouble"><span class="type">gdouble</span></a> *data</code></em>,
<em class="parameter"><code><a class="link" href="libgwyprocess-gwyprocessenums.html#GwyWindowingType" title="enum GwyWindowingType"><span class="type">GwyWindowingType</span></a> windowing</code></em>);</pre>
<p>
Multiplies data by given window.
</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>n</code></em> :</span></p></td>
<td>Number of data values.</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>data</code></em> :</span></p></td>
<td>Data values.</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>windowing</code></em> :</span></p></td>
<td>Method used for windowing.</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="gwy-fft-window-data-field"></a><h3>gwy_fft_window_data_field ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span> gwy_fft_window_data_field (<em class="parameter"><code><a class="link" href="GwyDataField.html" title="GwyDataField"><span class="type">GwyDataField</span></a> *dfield</code></em>,
<em class="parameter"><code><a class="link" href="libgwyprocess-gwyprocessenums.html#GwyOrientation" title="enum GwyOrientation"><span class="type">GwyOrientation</span></a> orientation</code></em>,
<em class="parameter"><code><a class="link" href="libgwyprocess-gwyprocessenums.html#GwyWindowingType" title="enum GwyWindowingType"><span class="type">GwyWindowingType</span></a> windowing</code></em>);</pre>
<p>
Performs windowing of a data field in given direction.
</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>dfield</code></em> :</span></p></td>
<td>A data field.</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>orientation</code></em> :</span></p></td>
<td>Windowing orientation (the same as corresponding FFT
orientation).</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>windowing</code></em> :</span></p></td>
<td>The windowing type to use.</td>
</tr>
</tbody>
</table></div>
</div>
</div>
<div class="refsect1">
<a name="libgwyprocess-simpleFFT.see-also"></a><h2>See Also</h2>
<a class="link" href="libgwyprocess-inttrans.html" title="inttrans">inttrans</a>
-- high-level integral transform functions
</div>
</div>
<div class="footer">
<hr>
Generated by GTK-Doc V1.19</div>
</body>
</html>
|