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<refentry version="5.0-subset Scilab" xml:id="Chtl" xml:lang="en"
          xmlns="http://docbook.org/ns/docbook"
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  <refnamediv>
    <refname>Chtl</refname>
	<refpurpose>Hough transform for detection of lines in images</refpurpose>
  </refnamediv>

<refsynopsisdiv>
   <title>Calling Sequence</title>
   <synopsis>
   [HT,RHO,THETA] = Chtl(IM)
   [HT,RHO,THETA] = Chtl(IM, M)
   [HT,RHO,THETA] = Chtl(IM, M, N)
   </synopsis>
</refsynopsisdiv>

<refsection>
   <title>Parameters</title>
   <variablelist>
   <varlistentry><term>IM    :</term>
      <listitem><para> image to be analyzed (size Xmax x Ymax).</para></listitem></varlistentry>
   <varlistentry><term>M     :</term>
      <listitem><para> desired number of samples along the radial axis   (default : Xmax).</para></listitem></varlistentry>
   <varlistentry><term>N     :</term>
      <listitem><para> desired number of samples along the azimutal (angle) axis   (default : Ymax).</para></listitem></varlistentry>
   <varlistentry><term>HT    :</term>
      <listitem><para> output matrix (MxN matrix).</para></listitem></varlistentry>
   <varlistentry><term>RHO   :</term>
      <listitem><para> sequence of samples along the radial axis.</para></listitem></varlistentry>
   <varlistentry><term>THETA :</term>
      <listitem><para> sequence of samples along the azimutal axis.</para></listitem></varlistentry>
   </variablelist>
</refsection>

<refsection>
   <title>Description</title>
   <para>
From an image IM, computes the integration of the values
of the image over all the lines. The lines are parametrized
using polar coordinates. The origin of the coordinates is fixed
at the center of the image, and theta is the angle between the
VERTICAL axis and the perpendicular (to the line) passing through
the origin.
</para>
</refsection>

<refsection>
   <title>Examples</title>
   <programlisting role="example"><![CDATA[
x = hilbert(sin(2*%pi*0.25*(1:128))+0.5*rand(1,128,'normal'));
tfr = Ctfrwv(x);
[HT,RHO,THETA] = Chtl(tfr);
grayplot(THETA, RHO, HT');
xlabel theta
ylabel rho
   ]]></programlisting>
</refsection>

<refsection role="see also">
   <title>See also</title>
   <simplelist type="inline">
   <member><link linkend="Ctfrsp">Ctfrsp</link></member>
   </simplelist>
</refsection>

<refsection>
   <title>Authors</title>
   <simplelist type="vert">
   <member>H. Nahrstaedt - Sep 2010</member>
   <member>Emmanuel Roy - 2000</member>
   <member>Manuel Davy - 2000</member>
   </simplelist>
</refsection>
</refentry>
