<?xml version="1.0" encoding="utf-8"?>
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<refentry xml:id="function.imagecolortransparent" xmlns="http://docbook.org/ns/docbook">
 <refnamediv>
  <refname>imagecolortransparent</refname>
  <refpurpose>Define a color as transparent</refpurpose>
 </refnamediv>
 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type>int</type><methodname>imagecolortransparent</methodname>
   <methodparam><type>GdImage</type><parameter>image</parameter></methodparam>
   <methodparam choice="opt"><type class="union"><type>int</type><type>null</type></type><parameter>color</parameter><initializer>&null;</initializer></methodparam>
  </methodsynopsis>
  <para>
   Gets or sets the transparent color in the given <parameter>image</parameter>.
  </para>
 </refsect1>
 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    &gd.image.description;
    <varlistentry>
     <term><parameter>color</parameter></term>
     <listitem>
      <para>
       &gd.identifier.color;
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>
 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   The identifier of the new (or current, if none is specified)
   transparent color is returned. If <parameter>color</parameter>
   is &null;, and the image has no transparent color, the
   returned identifier will be <literal>-1</literal>.
  </para>
 </refsect1>

 <refsect1 role="changelog">
  &reftitle.changelog;
  <informaltable>
   <tgroup cols="2">
    <thead>
     <row>
      <entry>&Version;</entry>
      <entry>&Description;</entry>
     </row>
    </thead>
    <tbody>
     &gd.changelog.image-param;
     <row>
      <entry>8.0.0</entry>
      <entry>
       <parameter>color</parameter> is now nullable.
      </entry>
     </row>
    </tbody>
   </tgroup>
  </informaltable>
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title><function>imagecolortransparent</function> example</title>
    <programlisting role="php">
<![CDATA[
<?php
// Create a 55x30 image
$im = imagecreatetruecolor(55, 30);
$red = imagecolorallocate($im, 255, 0, 0);
$black = imagecolorallocate($im, 0, 0, 0);

// Make the background transparent
imagecolortransparent($im, $black);

// Draw a red rectangle
imagefilledrectangle($im, 4, 4, 50, 25, $red);

// Save the image
imagepng($im, './imagecolortransparent.png');
imagedestroy($im);
?>
]]>
    </programlisting>
    &example.outputs.similar;
    <mediaobject>
     <alt>Output of example : imagecolortransparent()</alt>
     <imageobject>
      <imagedata fileref="en/reference/image/figures/imagecolortransparent.png"/>
     </imageobject>
    </mediaobject>
   </example>
  </para>
 </refsect1>
 <refsect1 role="notes">
  &reftitle.notes;
  <note>
   <para>
    Transparency is copied only with <function>imagecopymerge</function> and
    true color images, not with <function>imagecopy</function> or pallete images.
   </para>
  </note>
  <note>
   <para>
    The transparent color is a property of the image, transparency is not a
    property of the color. Once you have set a color to be the transparent
    color, any regions of the image in that color that were drawn previously
    will be transparent.
   </para>
  </note>
 </refsect1>
</refentry>
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