<?xml version="1.0" encoding="UTF-8"?>
<article id="Compare_images">
  <?target dbhh topicname="IDH_Compare_images" topicid ="003"?>

  <title>Comparing image files</title>

  <indexterm>
    <primary>comparing files</primary>
    <secondary>images</secondary>
  </indexterm>

  <para>This topic describes how to compare images using the Image
  Compare window.</para>

  <section id="Compare_images_starting">
    <title>Starting a image compare operation</title>

    <para>You can start an image compare operation from either the WinMerge window
    or a Command Prompt window.</para>

    <variablelist>
      <varlistentry>
        <term>From the WinMerge window</term>

        <listitem>
          <para>Click <menuchoice>
              <guimenu>File</guimenu>

              <guimenuitem>Open</guimenuitem>
            </menuchoice>. Use the Select Files or Folders dialog to specify the
          left and right source images to compare. For more details about the
          Select Files or Folder dialog, see <xref
          linkend="Open_paths" />.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>From a Command Prompt window</term>

        <listitem>
          <para>Run <command>WinMergeU.exe</command>, which is in your WinMerge
          install directory. In your command arguments, include the left and
          right images to compare. For more information about using the command
          line, see <xref linkend="Command_line" />.</para>
        </listitem>
      </varlistentry>
    </variablelist>
  </section>

  <section id="Compare_images_window">
    <title>Image Compare window</title>

    <para>WinMerge support many types of images and can highlight the differences
    with blocks. Overlaying of the pictures is also possible.</para>

    <mediaobject>
      <imageobject>
        <imagedata fileref="screenshots/imgcmp1.png" format="PNG" />
      </imageobject>

      <textobject>
        <phrase>Image Compare Window</phrase>
      </textobject>
    </mediaobject>

    <para>You can set the most options in the <guilabel>Location Pane</guilabel>:</para>

    <section>
      <title>Difference<indexterm>
        <primary>Diff</primary>
      </indexterm></title>

      <variablelist>
        <varlistentry>
          <term>Highlight</term>
          <listitem>
            <para>With the check box <guilabel>Highlight</guilabel> you can enable or
            disable the highlighting of the image differences.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>Blink</term>
          <listitem>
            <para>If the highlighting is enabled you can even make it blinking by checking
            the check box <guilabel>Blink</guilabel>.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>Block Size</term>
          <listitem>
            <para>The slider <guilabel>Block Size</guilabel> defines the size of the blocks
            which highlighting the image differences.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>Block Alpha</term>
          <listitem>
            <para>The <guilabel>Block Alpha</guilabel> slider defines how strong the alpha
            blending of the blocks is.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>Color Distance Threshold</term>
          <listitem>
            <para>The slider <guilabel>CD</guilabel> sets the <emphasis>Color Distance
            Threshold</emphasis> which helps to ignore color differences.</para>
          </listitem>
        </varlistentry>
      </variablelist>
    </section>

    <section>
      <title>Overlaying<indexterm>
        <primary>Overlay</primary>
      </indexterm></title>

      <variablelist>
        <varlistentry>
          <term>Mode</term>
          <listitem>
            <para>Currently the following <emphasis>Overlay Modes</emphasis> are possible:</para>
            <itemizedlist>
              <listitem><guilabel>None</guilabel></listitem>
              <listitem><guilabel>XOR</guilabel></listitem>
              <listitem><guilabel>Alpha Blend</guilabel></listitem>
              <listitem><guilabel>Alpha Blend Animation</guilabel></listitem>
            </itemizedlist>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>Alpha</term>
          <listitem>
            <para>The <guilabel>Alpha</guilabel> slider defines how strong the alpha blending
            of the overlay nodes <guilabel>Alpha Blend</guilabel> or
            <guilabel>Alpha Blend Animation</guilabel> is.</para>
          </listitem>
        </varlistentry>
      </variablelist>
    </section>

    <section>
      <title>Zooming<indexterm>
        <primary>Zoom</primary>
      </indexterm></title>

      <variablelist>
        <varlistentry>
          <term>Zoom</term>
          <listitem>
            <para>With the <guilabel>Zoom</guilabel> slider you can zoom in or out of the images.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>Page</term>
          <listitem>
            <para>If the image format support multiple pages you can select the current page with
            the <guilabel>Page</guilabel> number box.</para>
          </listitem>
        </varlistentry>
      </variablelist>
    </section>

  </section>

</article>
