<!DOCTYPE sect2 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
               "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
                <!ENTITY % darktable_dtd SYSTEM "../../dtd/darktable.dtd">
                %darktable_dtd;
                ]>
<sect2 status="final" id="histogram">

  <title>Histogram</title>

  <indexterm>
    <primary>darkroom panels</primary>
    <secondary>histogram</secondary>
  </indexterm>

  <indexterm>
    <primary>histogram</primary>
  </indexterm>

  <informaltable frame="none">
    <tgroup cols="2" colsep="0" rowsep="0">
      <colspec colwidth="6*"/>
      <colspec colwidth="4*"/>
      <tbody>
        <row>
          <entry>
            <para>
              This shows a histogram of the developed image's light levels. In its default state
              curves for all three RGB color channels are displayed. You can toggle the colored
              squares to enable or disable specific color channels. A curve button is also
              provided to toggle between linear view, logarithmic view and waveform view.
            </para>

            <para>
              The histogram is directly linked to the <emphasis>exposure</emphasis> module
              described in <xref linkend="exposure"/>, and you can operate some of the exposure
              module's controls from the histogram. You can left-click towards the right hand
              side of the histogram and then drag right to increase or drag left to decrease the
              exposure. In a similar manner you can control the black level by clicking and
              dragging in the left hand side. Double-clicking in the histogram resets the
              exposure module's parameters to their defaults.
            </para>
          </entry>
          <entry>
            <graphic fileref="darkroom/images/panel_histogram.png" scalefit="1" width="80%" align="center" />
          </entry>
        </row>
      </tbody>
    </tgroup>
  </informaltable>

</sect2>