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<refentry xml:id="function.imagefilter" xmlns="http://docbook.org/ns/docbook">
 <refnamediv>
  <refname>imagefilter</refname>
  <refpurpose>Applies a filter to an image</refpurpose>
 </refnamediv>
 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type>bool</type><methodname>imagefilter</methodname>
   <methodparam><type>resource</type><parameter>image</parameter></methodparam>
   <methodparam><type>int</type><parameter>filtertype</parameter></methodparam>
   <methodparam choice="opt"><type>int</type><parameter>arg1</parameter></methodparam>
   <methodparam choice="opt"><type>int</type><parameter>arg2</parameter></methodparam>
   <methodparam choice="opt"><type>int</type><parameter>arg3</parameter></methodparam>
   <methodparam choice="opt"><type>int</type><parameter>arg4</parameter></methodparam>
  </methodsynopsis>
  <para>
   <function>imagefilter</function> applies the given filter
   <parameter>filtertype</parameter> on the <parameter>image</parameter>.
  </para>
 </refsect1>
 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    &gd.image.description;
    <varlistentry>
     <term><parameter>filtertype</parameter></term>
     <listitem>
      <para>
       <parameter>filtertype</parameter> can be one of the following:
       <itemizedlist>
        <listitem>
         <simpara>
          <constant>IMG_FILTER_NEGATE</constant>: Reverses all colors of
          the image.
         </simpara>
        </listitem>
        <listitem>
         <simpara>
          <constant>IMG_FILTER_GRAYSCALE</constant>: Converts the image into
          grayscale.
         </simpara>
        </listitem>
        <listitem>
         <simpara>
          <constant>IMG_FILTER_BRIGHTNESS</constant>: Changes the brightness
          of the image. Use <parameter>arg1</parameter> to set the level of
          brightness.
         </simpara>
        </listitem>
        <listitem>
         <simpara>
          <constant>IMG_FILTER_CONTRAST</constant>: Changes the contrast of
          the image. Use <parameter>arg1</parameter> to set the level of
          contrast.
         </simpara>
        </listitem>
        <listitem>
         <simpara>
          <constant>IMG_FILTER_COLORIZE</constant>: Like
          <constant>IMG_FILTER_GRAYSCALE</constant>, except you can specify the
          color. Use <parameter>arg1</parameter>, <parameter>arg2</parameter> and
          <parameter>arg3</parameter> in the form of
          <parameter>red</parameter>, <parameter>blue</parameter>,
          <parameter>green</parameter> and <parameter>arg4</parameter> for the
          <parameter>alpha</parameter> channel. The range for each color is 0 to 255.
         </simpara>
        </listitem>
        <listitem>
         <simpara>
          <constant>IMG_FILTER_EDGEDETECT</constant>: Uses edge detection to
          highlight the edges in the image.
         </simpara>
        </listitem>
        <listitem>
         <simpara>
          <constant>IMG_FILTER_EMBOSS</constant>: Embosses the image.
         </simpara>
        </listitem>
        <listitem>
         <simpara>
          <constant>IMG_FILTER_GAUSSIAN_BLUR</constant>: Blurs the image using
          the Gaussian method.
         </simpara>
        </listitem>
        <listitem>
         <simpara>
          <constant>IMG_FILTER_SELECTIVE_BLUR</constant>: Blurs the image.
         </simpara>
        </listitem>
        <listitem>
         <simpara>
          <constant>IMG_FILTER_MEAN_REMOVAL</constant>: Uses mean removal to
          achieve a "sketchy" effect.
         </simpara>
        </listitem>
        <listitem>
         <simpara>
          <constant>IMG_FILTER_SMOOTH</constant>: Makes the image smoother.
          Use <parameter>arg1</parameter> to set the level of smoothness.
         </simpara>
        </listitem>
       </itemizedlist>
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>arg1</parameter></term>
     <listitem>
      <para>
       <itemizedlist>
        <listitem>
         <simpara>
          <constant>IMG_FILTER_BRIGHTNESS</constant>: Brightness level.
         </simpara>
        </listitem>
        <listitem>
         <simpara>
          <constant>IMG_FILTER_CONTRAST</constant>: Contrast level.
         </simpara>
        </listitem>
        <listitem>
         <simpara>
          <constant>IMG_FILTER_COLORIZE</constant>: Value of red component.
         </simpara>
        </listitem>
        <listitem>
         <simpara>
          <constant>IMG_FILTER_SMOOTH</constant>: Smoothness level.
         </simpara>
        </listitem>
       </itemizedlist>
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>arg2</parameter></term>
     <listitem>
      <para>
       <itemizedlist>
        <listitem>
         <simpara>
          <constant>IMG_FILTER_COLORIZE</constant>: Value of green component.
         </simpara>
        </listitem>
       </itemizedlist>
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>arg3</parameter></term>
     <listitem>
      <para>
       <itemizedlist>
        <listitem>
         <simpara>
          <constant>IMG_FILTER_COLORIZE</constant>: Value of blue component.
         </simpara>
        </listitem>
       </itemizedlist>
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>arg4</parameter></term>
     <listitem>
      <para>
       <itemizedlist>
        <listitem>
         <simpara>
          <constant>IMG_FILTER_COLORIZE</constant>: Alpha channel, A value 
          between 0 and 127. 0 indicates completely opaque while 127 indicates 
          completely transparent.
         </simpara>
        </listitem>
       </itemizedlist>
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>
 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   &return.success;
  </para>
 </refsect1>
 <refsect1 role="changelog">
  &reftitle.changelog;
  <para>
   <informaltable>
    <tgroup cols="2">
     <thead>
      <row>
       <entry>&Version;</entry>
       <entry>&Description;</entry>
      </row>
     </thead>
     <tbody>
      <row>
       <entry>5.2.5</entry>
       <entry>
        Alpha support for <constant>IMG_FILTER_COLORIZE</constant> was added.
       </entry>
      </row>
     </tbody>
    </tgroup>
   </informaltable>
  </para>
 </refsect1>
 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title><function>imagefilter</function> grayscale example</title>
    <programlisting role="php">
<![CDATA[
<?php
$im = imagecreatefrompng('dave.png');

if($im && imagefilter($im, IMG_FILTER_GRAYSCALE))
{
    echo 'Image converted to grayscale.';

    imagepng($im, 'dave.png');
}
else
{
    echo 'Conversion to grayscale failed.';
}

imagedestroy($im);
?>
]]>
    </programlisting>
   </example>
   <example>
    <title><function>imagefilter</function> brightness example</title>
    <programlisting role="php">
<![CDATA[
<?php
$im = imagecreatefrompng('sean.png');

if($im && imagefilter($im, IMG_FILTER_BRIGHTNESS, 20))
{
    echo 'Image brightness changed.';

    imagepng($im, 'sean.png');
    imagedestroy($im);
}
else
{
    echo 'Image brightness change failed.';
}
?>
]]>
    </programlisting>
   </example>
   <example>
    <title><function>imagefilter</function> colorize example</title>
    <programlisting role="php">
<![CDATA[
<?php
$im = imagecreatefrompng('philip.png');

/* R, G, B, so 0, 255, 0 is green */
if($im && imagefilter($im, IMG_FILTER_COLORIZE, 0, 255, 0))
{
    echo 'Image successfully shaded green.';

    imagepng($im, 'philip.png');
    imagedestroy($im);
}
else
{
    echo 'Green shading failed.';
}
?>
]]>
    </programlisting>
   </example>
   <example>
    <title><function>imagefilter</function> negate example</title>
    <programlisting role="php">
<![CDATA[
<?php
// Define our negate function so its portable for 
// php versions without imagefilter()
function negate($im)
{
    if(function_exists('imagefilter'))
    {
        return imagefilter($im, IMG_FILTER_NEGATE);
    }

    for($x = 0; $x < imagesx($im); ++$x)
    {
        for($y = 0; $y < imagesy($im); ++$y)
        {
            $index = imagecolorat($im, $x, $y);
            $rgb = imagecolorsforindex($index);
            $color = imagecolorallocate($im, 255 - $rgb['red'], 255 - $rgb['green'], 255 - $rgb['blue']);

            imagesetpixel($im, $x, $y, $color);
        }
    }

    return(true);
}

$im = imagecreatefromjpeg('kalle.jpg');

if($im && negate($im))
{
    echo 'Image successfully converted to negative colors.';

    imagejpeg($im, 'kalle.jpg', 100);
    imagedestroy($im);
}
else
{
    echo 'Converting to negative colors failed.';
}
?>
]]>
    </programlisting>
   </example>
  </para>
 </refsect1>
 <refsect1 role="notes">
  &reftitle.notes;
  &note.bundled.gd;
 </refsect1>
 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>imageconvolution</function></member>
   </simplelist>
  </para>
 </refsect1>
</refentry>

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