reference/image/functions/imagecolorallocatealpha.xml
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<refsect1 role="description">
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&reftitle.description;
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<methodsynopsis>
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<type>int</type><methodname>imagecolorallocatealpha</methodname>
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<methodparam><type>resource</type><parameter>image</parameter></methodparam>
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<type class="union"><type>int</type><type>false</type></type><methodname>imagecolorallocatealpha</methodname>
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<methodparam><type>GdImage</type><parameter>image</parameter></methodparam>
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<methodparam><type>int</type><parameter>red</parameter></methodparam>
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<methodparam><type>int</type><parameter>green</parameter></methodparam>
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<methodparam><type>int</type><parameter>blue</parameter></methodparam>
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</para>
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&return.falseproblem;
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</refsect1>
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<refsect1 role="changelog">
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&reftitle.changelog;
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<para>
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<informaltable>
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<tgroup cols="2">
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<thead>
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<row>
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<entry>&Version;</entry>
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<entry>&Description;</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry>5.1.3</entry>
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<entry>
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Returns &false; if the allocation failed. Previously
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<literal>-1</literal> was returned.
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</entry>
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</row>
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</tbody>
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</tgroup>
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</informaltable>
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</para>
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<informaltable>
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<tgroup cols="2">
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<thead>
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<row>
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<entry>&Version;</entry>
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<entry>&Description;</entry>
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</row>
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</thead>
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<tbody>
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&gd.changelog.image-param;
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</tbody>
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</tgroup>
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</informaltable>
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</refsect1>
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<refsect1 role="examples">
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&reftitle.examples;
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<para>
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<example>
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<title>Example of using <function>imagecolorallocatealpha</function></title>
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<programlisting role="php">
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<example>
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<title>Example of using <function>imagecolorallocatealpha</function></title>
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<programlisting role="php">
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<![CDATA[
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<?php
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$size = 300;
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imagedestroy($image);
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?>
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]]>
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</programlisting>
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&example.outputs.similar;
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<mediaobject>
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<alt>Output of example : Example of using imagecolorallocatealpha()</alt>
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<imageobject>
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<imagedata fileref="en/reference/image/figures/imagecolorallocatealpha.png"/>
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</imageobject>
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</mediaobject>
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</example>
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</para>
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</programlisting>
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&example.outputs.similar;
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<mediaobject>
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<alt>Output of example : Example of using imagecolorallocatealpha()</alt>
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<imageobject>
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<imagedata fileref="en/reference/image/figures/imagecolorallocatealpha.png"/>
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</imageobject>
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</mediaobject>
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</example>
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<example xml:id="imagecolorallocatealpha.example.convert">
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<title>Convert typical alpha values for use with <function>imagecolorallocatealpha</function></title>
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<para>
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Usually alpha values of <literal>0</literal> designate fully transparent pixels,
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and the alpha channel has 8 bits. To convert such alpha values to be compatible
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with <function>imagecolorallocatealpha</function>, some simple arithmetic is
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sufficient:
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</para>
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<programlisting role="php">
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<![CDATA[
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<?php
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$alpha8 = 0; // fully transparent
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var_dump(127 - ($alpha8 >> 1));
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$alpha8 = 255; // fully opaque
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var_dump(127 - ($alpha8 >> 1));
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?>
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]]>
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</programlisting>
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&example.outputs;
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<screen>
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<![CDATA[
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int(127)
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int(0)
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]]>
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</screen>
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</example>
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</refsect1>
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<refsect1 role="seealso">
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&reftitle.seealso;
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<para>
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<simplelist>
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<member><function>imagecolorallocate</function></member>
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<member><function>imagecolordeallocate</function></member>
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</simplelist>
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</para>
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<simplelist>
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<member><function>imagecolorallocate</function></member>
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<member><function>imagecolordeallocate</function></member>
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</simplelist>
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</refsect1>
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</refentry>
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<!-- Keep this comment at the end of the file
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Local variables:
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mode: sgml
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