imagealphablending.xml

<?xml version="1.0" encoding="utf-8"?>
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<refentry xml:id="function.imagealphablending" xmlns="http://docbook.org/ns/docbook">
 <refnamediv>
  <refname>imagealphablending</refname>
  <refpurpose>设定图像的混色模式</refpurpose>
 </refnamediv>
 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type>bool</type><methodname>imagealphablending</methodname>
   <methodparam><type>GdImage</type><parameter>image</parameter></methodparam>
   <methodparam><type>bool</type><parameter>enable</parameter></methodparam>
  </methodsynopsis>
  <para>
   <function>imagealphablending</function>
   允许在真彩色图像上使用两种不同的绘画模式。在混色（blending）模式下，alpha
   通道色彩成分提供给所有的绘画函数，例如 <function>imagesetpixel</function>
   决定底层的颜色应在何种程度上被允许照射透过。作为结果，GD
   自动将该点现有的颜色和画笔颜色混合，并将结果储存在图像中。结果的像素是不透明的。在非混色模式下，画笔颜色连同其
   alpha 通道信息一起被拷贝，替换掉目标像素。混色模式在画调色板图像时不可用。如果
   <parameter>blendmode</parameter> 为 &true;，则启用混色模式，否则关闭。&return.success;
  </para>
 </refsect1>
 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    &gd.image.description;
    <varlistentry>
     <term><parameter>enable</parameter></term>
     <listitem>
      <para>
       是否启用混合模式。在真彩色图像上，默认值为 &true;，否则默认值为 &false;
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>
 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   &return.success;
  </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;
    </tbody>
   </tgroup>
  </informaltable>
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <example>
   <title><function>imagealphablending</function> 用法示例</title>
   <programlisting role="php">
<![CDATA[
<?php
// Create image
$im = imagecreatetruecolor(100, 100);

// Set alphablending to on
imagealphablending($im, true);

// Draw a square
imagefilledrectangle($im, 30, 30, 70, 70, imagecolorallocate($im, 255, 0, 0));

// Output
header('Content-Type: image/png');

imagepng($im);
imagedestroy($im);
?>
]]>
   </programlisting>
  </example>
 </refsect1>
</refentry>
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