Note the requirements of setting the background colour and fix example

git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@204359 c90b9560-bf6c-de11-be94-00142212c4b1

reference/image/functions/imagecolorallocate.xml

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="iso-8859-1"?>
-<!-- $Revision: 1.8 $ -->
+<!-- $Revision: 1.9 $ -->
 <!-- splitted from ./en/functions/image.xml, last change in rev 1.36 -->
  <refentry id="function.imagecolorallocate">
   <refnamediv>
@@ -18,9 +18,8 @@
    <para>
     <function>imagecolorallocate</function> returns a color
     identifier representing the color composed of the given
-    <acronym>RGB</acronym> components.  The <parameter>image</parameter>
-    argument is the return from the <function>imagecreatetruecolor</function>
-    function. <parameter>red</parameter>, <parameter>green</parameter> and
+    <acronym>RGB</acronym> components.
+    <parameter>red</parameter>, <parameter>green</parameter> and
     <parameter>blue</parameter> are the values of the red, green and blue
     component of the requested color respectively.  These parameters are
     integers between 0 and 255 or hexadecimals between 0x00 and 0xFF.
@@ -31,7 +30,8 @@
    <note>
     <para>
      The first call to <function>imagecolorallocate</function> fills
-     the background color.
+     the background color in palette-based images - images created using
+     <function>imagecreate</function>.
     </para>
    </note>
    <para>
@@ -40,9 +40,11 @@
 <![CDATA[
 <?php
 
-$im = imagecreatetruecolor('example.jpg');
+$im = imagecreatetruecolor('example.jpg', 100, 100);
+
 // sets background to red
-$background = imagecolorallocate($im, 255, 0, 0);
+$red = imagecolorallocate($im, 255, 0, 0);
+imagefill($im, 0, 0, $red);
 
 // sets some colors
 $white = imagecolorallocate($im, 255, 255, 255);